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  • Feedback on iterating over type-safe enums

    - by Sumant
    In response to the earlier SO question "Enumerate over an enum in C++", I came up with the following reusable solution that uses type-safe enum idiom. I'm just curious to see the community feedback on my solution. This solution makes use of a static array, which is populated using type-safe enum objects before first use. Iteration over enums is then simply reduced to iteration over the array. I'm aware of the fact that this solution won't work if the enumerators are not strictly increasing. template<typename def, typename inner = typename def::type> class safe_enum : public def { typedef typename def::type type; inner val; static safe_enum array[def::end - def::begin]; static bool init; static void initialize() { if(!init) // use double checked locking in case of multi-threading. { unsigned int size = def::end - def::begin; for(unsigned int i = 0, j = def::begin; i < size; ++i, ++j) array[i] = static_cast<typename def::type>(j); init = true; } } public: safe_enum(type v = def::begin) : val(v) {} inner underlying() const { return val; } static safe_enum * begin() { initialize(); return array; } static safe_enum * end() { initialize(); return array + (def::end - def::begin); } bool operator == (const safe_enum & s) const { return this->val == s.val; } bool operator != (const safe_enum & s) const { return this->val != s.val; } bool operator < (const safe_enum & s) const { return this->val < s.val; } bool operator <= (const safe_enum & s) const { return this->val <= s.val; } bool operator > (const safe_enum & s) const { return this->val > s.val; } bool operator >= (const safe_enum & s) const { return this->val >= s.val; } }; template <typename def, typename inner> safe_enum<def, inner> safe_enum<def, inner>::array[def::end - def::begin]; template <typename def, typename inner> bool safe_enum<def, inner>::init = false; struct color_def { enum type { begin, red = begin, green, blue, end }; }; typedef safe_enum<color_def> color; template <class Enum> void f(Enum e) { std::cout << static_cast<unsigned>(e.underlying()) << std::endl; } int main() { std::for_each(color::begin(), color::end(), &f<color>); color c = color::red; }

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  • Is this a right way to use NHibernate?

    - by Venemo
    I spent the rest of the evening reading StackOverflow questions and also some blog entries and links about the subject. All of them turned out to be very helpful, but I still feel that they don't really answer my question. So, I'm developing a simple web application. I'd like to create a reusable data access layer which I can later reuse in other solutions. 99% of these will be web applications. This seems to be a good excuse for me to learn NHibernate and some of the patterns around it. My goals are the following: I don't want the business logic layer to know ANYTHING about the inner workings of the database, nor NHibernate itself. I want the business logic layer to have the least possible number of assumptions about the data access layer. I want the data access layer as simplistic and easy-to-use as possible. This is going to be a simple project, so I don't want to overcomplicate anything. I want the data access layer to be as non-intrusive as possible. Will all this in mind, I decided to use the popular repository pattern. I read about this subject on this site and on various dev blogs, and I heard some stuff about the unit of work pattern. I also looked around and checked out various implementations. (Including FubuMVC contrib, and SharpArchitecture, and stuff on some blogs.) I found out that most of these operate with the same principle: They create a "unit of work" which is instantiated when a repository is instantiated, they start a transaction, do stuff, and commit, and then start all over again. So, only one ISession per Repository and that's it. Then the client code needs to instantiate a repository, do stuff with it, and then dispose. This usage pattern doesn't meet my need of being as simplistic as possible, so I began thinking about something else. I found out that NHibernate already has something which makes custom "unit of work" implementations unnecessary, and that is the CurrentSessionContext class. If I configure the session context correctly, and do the clean up when necessary, I'm good to go. So, I came up with this: I have a static class called NHibernateHelper. Firstly, it has a static property called CurrentSessionFactory, which upon first call, instantiates a session factory and stores it in a static field. (One ISessionFactory per one AppDomain is good enough.) Then, more importantly, it has a CurrentSession static property, which checks if there is an ISession bound to the current session context, and if not, creates one, and binds it, and it returns with the ISession bound to the current session context. Because it will be used mostly with WebSessionContext (so, one ISession per HttpRequest, although for the unit tests, I configured ThreadStaticSessionContext), it should work seamlessly. And after creating and binding an ISession, it hooks an event handler to the HttpContext.Current.ApplicationInstance.EndRequest event, which takes care of cleaning up the ISession after the request ends. (Of course, it only does this if it is really running in a web environment.) So, with all this set up, the NHibernateHelper will always be able to return a valid ISession, so there is no need to instantiate a Repository instance for the "unit of work" to operate properly. Instead, the Repository is a static class which operates with the ISession from the NHibernateHelper.CurrentSession property, and exposes some functionality through that. I'm curious, what do you think about this? Is it a valid way of thinking, or am I completely off track here?

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  • Generics and Performance question.

    - by Tarmon
    Hey Everyone, I was wondering if anyone could look over a class I wrote, I am receiving generic warnings in Eclipse and I am just wondering if it could be cleaned up at all. All of the warnings I received are surrounded in ** in my code below. The class takes a list of strings in the form of (hh:mm AM/PM) and converts them into HourMinute objects in order to find the first time in the list that comes after the current time. I am also curious about if there are more efficient ways to do this. This works fine but the student in me just wants to find out how I could do this better. public class FindTime { private String[] hourMinuteStringArray; public FindTime(String[] hourMinuteStringArray){ this.hourMinuteStringArray = hourMinuteStringArray; } public int findTime(){ HourMinuteList hourMinuteList = convertHMStringArrayToHMArray(hourMinuteStringArray); Calendar calendar = new GregorianCalendar(); int hour = calendar.get(Calendar.HOUR_OF_DAY); int minute = calendar.get(Calendar.MINUTE); HourMinute now = new HourMinute(hour,minute); int nearestTimeIndex = findNearestTimeIndex(hourMinuteList, now); return nearestTimeIndex; } private int findNearestTimeIndex(HourMinuteList hourMinuteList, HourMinute now){ HourMinute current; int position = 0; Iterator<HourMinute> iterator = **hourMinuteList.iterator()**; while(iterator.hasNext()){ current = (HourMinute) iterator.next(); if(now.compareTo(current) == -1){ return position; } position++; } return position; } private static HourMinuteList convertHMStringArrayToHMArray(String[] times){ FindTime s = new FindTime(new String[1]); HourMinuteList list = s.new HourMinuteList(); String[] splitTime = new String[3]; for(String time : times ){ String[] tempFirst = time.split(":"); String[] tempSecond = tempFirst[1].split(" "); splitTime[0] = tempFirst[0]; splitTime[1] = tempSecond[0]; splitTime[2] = tempSecond[1]; int hour = Integer.parseInt(splitTime[0]); int minute = Integer.parseInt(splitTime[1]); HourMinute hm; if(splitTime[2] == "AM"){ hm = s.new HourMinute(hour,minute); } else if((splitTime[2].equals("PM")) && (hour < 12)){ hm = s.new HourMinute(hour + 12,minute); } else{ hm = s.new HourMinute(hour,minute); } **list.add(hm);** } return list; } class **HourMinuteList** extends **ArrayList** implements RandomAccess{ } class HourMinute implements **Comparable** { int hour; int minute; public HourMinute(int hour, int minute) { setHour(hour); setMinute(minute); } int getMinute() { return this.minute; } String getMinuteString(){ if(this.minute < 10){ return "0" + this.minute; }else{ return "" + this.minute; } } int getHour() { return this.hour; } void setHour(int hour) { this.hour = hour; } void setMinute(int minute) { this.minute = minute; } @Override public int compareTo(Object aThat) { if (aThat instanceof HourMinute) { HourMinute that = (HourMinute) aThat; if (this.getHour() == that.getHour()) { if (this.getMinute() > that.getMinute()) { return 1; } else if (this.getMinute() < that.getMinute()) { return -1; } else { return 0; } } else if (this.getHour() > that.getHour()) { return 1; } else if (this.getHour() < that.getHour()) { return -1; } else { return 0; } } return 0; } } If you have any questions let me know. Thanks, Rob

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  • Android: HttpURLConnection not working properly

    - by giorgiline
    I'm trying to get the cookies from a website after sending user credentials through a POST Request an it seems that it doesn't work in android this way. ¿Am I doing something bad?. Please help. I've searched here in different posts but there's no useful answer. It's curious that this run in a desktop Java implementation it works perfect but it crashes in Android platform. And it is exactly the same code, specifically when calling HttpURLConnection.getHeaderFields(), it also happens with other member methods. It's a simple code and I don't know why the hell isn't working. DESKTOP CODE: This goes just in the main() HttpURLConnection connection = null; OutputStream out = null; try { URL url = new URL("http://www.XXXXXXXX.php"); String charset = "UTF-8"; String postback = "1"; String user = "XXXXXXXXX"; String password = "XXXXXXXX"; String rememberme = "on"; String query = String.format("postback=%s&user=%s&password=%s&rememberme=%s" , URLEncoder.encode(postback, charset) , URLEncoder.encode(user,charset) , URLEncoder.encode(password, charset) , URLEncoder.encode(rememberme, charset)); connection = (HttpURLConnection)url.openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Accept-Charset", charset); connection.setDoOutput(true); connection.setFixedLengthStreamingMode(query.length()); out = connection.getOutputStream (); out.write(query.getBytes(charset)); if (connection.getHeaderFields() == null){ System.out.println("Header null"); }else{ for (String cookie: connection.getHeaderFields().get("Set-Cookie")){ System.out.println(cookie.split(";", 2)[0]); } } } catch (IOException e){ e.printStackTrace(); } finally { try { out.close();} catch (IOException e) { e.printStackTrace();} connection.disconnect(); } So the output is: login_key=20ad8177db4eca3f057c14a64bafc2c9 FASID=cabf20cc471fcacacdc7dc7e83768880 track=30c8183e4ebbe8b3a57b583166326c77 client-data=%7B%22ism%22%3Afalse%2C%22showm%22%3Afalse%2C%22ts%22%3A1349189669%7D ANDROID CODE: This goes inside doInBackground AsyncTask body HttpURLConnection connection = null; OutputStream out = null; try { URL url = new URL("http://www.XXXXXXXXXXXXXX.php"); String charset = "UTF-8"; String postback = "1"; String user = "XXXXXXXXX"; String password = "XXXXXXXX"; String rememberme = "on"; String query = String.format("postback=%s&user=%s&password=%s&rememberme=%s" , URLEncoder.encode(postback, charset) , URLEncoder.encode(user,charset) , URLEncoder.encode(password, charset) , URLEncoder.encode(rememberme, charset)); connection = (HttpURLConnection)url.openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Accept-Charset", charset); connection.setDoOutput(true); connection.setFixedLengthStreamingMode(query.length()); out = connection.getOutputStream (); out.write(query.getBytes(charset)); if (connection.getHeaderFields() == null){ Log.v(TAG, "Header null"); }else{ for (String cookie: connection.getHeaderFields().get("Set-Cookie")){ Log.v(TAG, cookie.split(";", 2)[0]); } } } catch (IOException e){ e.printStackTrace(); } finally { try { out.close();} catch (IOException e) { e.printStackTrace();} connection.disconnect(); } And here there is no output, it seems that connection.getHeaderFields() doesn't return result. It takes al least 30 seconds to show the Log: 10-02 16:56:25.918: V/class com.giorgi.myproject.activities.HomeActivity(2596): Header null

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  • Why might a System.String object not cache its hash code?

    - by Dan Tao
    A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is implementation-dependent, so the question "is GetHashCode implemented in the form of X or Y?" is not really answerable. I'm just curious about a few things: If Reflector has disassembled the DLL correctly and this is the implementation of GetHashCode (in my environment), am I correct in interpreting this code to indicate that a string object, based on this particular implementation, would not cache its hash code? Assuming the answer is yes, why would this be? It seems to me that the memory cost would be minimal (one more 32-bit integer, a drop in the pond compared to the size of the string itself) whereas the savings would be significant, especially in cases where, e.g., strings are used as keys in a hashtable-based collection like a Dictionary<string, [...]>. And since the string class is immutable, it isn't like the value returned by GetHashCode will ever even change. What could I be missing? UPDATE: In response to Andras Zoltan's closing remark: There's also the point made in Tim's answer(+1 there). If he's right, and I think he is, then there's no guarantee that a string is actually immutable after construction, therefore to cache the result would be wrong. Whoa, whoa there! This is an interesting point to make (and yes it's very true), but I really doubt that this was taken into consideration in the implementation of GetHashCode. The statement "therefore to cache the result would be wrong" implies to me that the framework's attitude regarding strings is "Well, they're supposed to be immutable, but really if developers want to get sneaky they're mutable so we'll treat them as such." This is definitely not how the framework views strings. It fully relies on their immutability in so many ways (interning of string literals, assignment of all zero-length strings to string.Empty, etc.) that, basically, if you mutate a string, you're writing code whose behavior is entirely undefined and unpredictable. I guess my point is that for the author(s) of this implementation to worry, "What if this string instance is modified between calls, even though the class as it is publicly exposed is immutable?" would be like for someone planning a casual outdoor BBQ to think to him-/herself, "What if someone brings an atomic bomb to the party?" Look, if someone brings an atom bomb, party's over.

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  • IE7 is making my life miserable! Getting gaps between html table columns (w/ colspan) with css togg

    - by Art Peterson
    Copy/paste this html code snippet and try it out in IE7. When you toggle the hidden columns it leaves a gap between the columns. In Firefox it works fine, the columns touch when minimized. Haven't tried IE8 yet, would be curious to hear how it works there. Any ideas? I've tried a bunch of things in the CSS like table-layout:fixed but no luck. Note: Not looking for a different toggling method because the table I'm really dealing with is 50+ columns wide and 4000+ rows so looping/jquery techniques are too slow. Here's the code - if someone can re-post a working version of it I'll instantly give them the check and be forever in your debt! <DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <script> function toggle() { var tableobj = document.getElementById("mytable"); if (tableobj.className == "") { tableobj.className = "hide1 hide2"; } else { tableobj.className = ""; } } </script> <style> table { border-collapse: collapse; } td, th { border: 1px solid silver; } .hide1 .col1 { display: none; } .hide2 .col2 { display: none; } </style> </head> <body> <input type="button" value="toggle" onclick="toggle();" /> <table id="mytable"> <tr> <th>A</th> <th colspan="2">B</th> <th colspan="2" class="col1">B1</th> <th colspan="2">C</th> <th colspan="2" class="col2">C1</th> </tr> <tr> <td>123</td> <td>456</td> <td>789</td> <td class="col1">123</td> <td class="col1">456</td> <td>789</td> <td>123</td> <td class="col2">456</td> <td class="col2">789</td> </tr> </table> </body> </html>

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  • Is there a way to delay compilation of a stored procedure's execution plan?

    - by Ian Henry
    (At first glance this may look like a duplicate of http://stackoverflow.com/questions/421275 or http://stackoverflow.com/questions/414336, but my actual question is a bit different) Alright, this one's had me stumped for a few hours. My example here is ridiculously abstracted, so I doubt it will be possible to recreate locally, but it provides context for my question (Also, I'm running SQL Server 2005). I have a stored procedure with basically two steps, constructing a temp table, populating it with very few rows, and then querying a very large table joining against that temp table. It has multiple parameters, but the most relevant is a datetime "@MinDate." Essentially: create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @MinDate If I just execute this as a normal query, by declaring @MinDate as a local variable and running that, it produces an optimal execution plan that executes very quickly (first joins on #smallTable and then only considers a very small subset of rows from aGiantTable while doing other operations). It seems to realize that #smallTable is tiny, so it would be efficient to start with it. This is good. However, if I make that a stored procedure with @MinDate as a parameter, it produces a completely inefficient execution plan. (I am recompiling it each time, so it's not a bad cached plan...at least, I sure hope it's not) But here's where it gets weird. If I change the proc to the following: declare @LocalMinDate datetime set @LocalMinDate = @MinDate --where @MinDate is still a parameter create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @LocalMinDate Then it gives me the efficient plan! So my theory is this: when executing as a plain query (not as a stored procedure), it waits to construct the execution plan for the expensive query until the last minute, so the query optimizer knows that #smallTable is small and uses that information to give the efficient plan. But when executing as a stored procedure, it creates the entire execution plan at once, thus it can't use this bit of information to optimize the plan. But why does using the locally declared variables change this? Why does that delay the creation of the execution plan? Is that actually what's happening? If so, is there a way to force delayed compilation (if that indeed is what's going on here) even when not using local variables in this way? More generally, does anyone have sources on when the execution plan is created for each step of a stored procedure? Googling hasn't provided any helpful information, but I don't think I'm looking for the right thing. Or is my theory just completely unfounded? Edit: Since posting, I've learned of parameter sniffing, and I assume this is what's causing the execution plan to compile prematurely (unless stored procedures indeed compile all at once), so my question remains -- can you force the delay? Or disable the sniffing entirely? The question is academic, since I can force a more efficient plan by replacing the select * from aGiantTable with select * from (select * from aGiantTable where ID in (select ID from #smallTable)) as aGiantTable Or just sucking it up and masking the parameters, but still, this inconsistency has me pretty curious.

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  • Neo4j increasing latency as SKIP increases on Cypher query + REST API

    - by voldomazta
    My setup: Java(TM) SE Runtime Environment (build 1.7.0_45-b18) Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode) Neo4j 2.0.0-M06 Enterprise First I made sure I warmed up the cache by executing the following: START n=node(*) RETURN COUNT(n); START r=relationship(*) RETURN count(r); The size of the table is 63,677 nodes and 7,169,995 relationships Now I have the following query: START u1=node:node_auto_index('uid:39') MATCH (u1:user)-[w:WANTS]->(c:card)<-[h:HAS]-(u2:user) WHERE u2.uid <> 39 WITH u2.uid AS uid, (CASE WHEN w.qty < h.qty THEN w.qty ELSE h.qty END) AS have RETURN uid, SUM(have) AS total ORDER BY total DESC SKIP 0 LIMIT 25 This UID has about 40k+ results that I want to be able to put a pagination to. The initial skip was around 773ms. I tried page 2 (skip 25) and the latency was around the same even up to page 500 it only rose up to 900ms so I didn't really bother. Now I tried some fast forward paging and jumped by thousands so I did 1000, then 2000, then 3000. I was hoping the ORDER BY arrangement will already have been cached by Neo4j and using SKIP will just move to that index in the result and wont have to iterate through each one again. But for each thousand skip I made the latency increased by alot. It's not just cache warming because for one I already warmed up the cache and two, I tried the same skip a couple of times for each skip and it yielded the same results: SKIP 0: 773ms SKIP 1000: 1369ms SKIP 2000: 2491ms SKIP 3000: 3899ms SKIP 4000: 5686ms SKIP 5000: 7424ms Now who the hell would want to view 5000 pages of results? 40k even?! :) Good point! I will probably put a cap on the maximum results a user can view but I was just curious about this phenomenon. Will somebody please explain why Neo4j seems to be re-iterating through stuff which appears to be already known to it? Here is my profiling for the 0 skip: ==> ColumnFilter(symKeys=["uid", " INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14"], returnItemNames=["uid", "total"], _rows=25, _db_hits=0) ==> Slice(skip="Literal(0)", _rows=25, _db_hits=0) ==> Top(orderBy=["SortItem(Cached( INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14 of type Any),false)"], limit="Add(Literal(0),Literal(25))", _rows=25, _db_hits=0) ==> EagerAggregation(keys=["uid"], aggregates=["( INTERNAL_AGGREGATE65c4d6a2-1930-4f32-8fd9-5e4399ce6f14,Sum(have))"], _rows=41659, _db_hits=0) ==> ColumnFilter(symKeys=["have", "u1", "uid", "c", "h", "w", "u2"], returnItemNames=["uid", "have"], _rows=146826, _db_hits=0) ==> Extract(symKeys=["u1", "c", "h", "w", "u2"], exprKeys=["uid", "have"], _rows=146826, _db_hits=587304) ==> Filter(pred="((NOT(Product(u2,uid(0),true) == Literal(39)) AND hasLabel(u1:user(0))) AND hasLabel(u2:user(0)))", _rows=146826, _db_hits=146826) ==> TraversalMatcher(trail="(u1)-[w:WANTS WHERE (hasLabel(NodeIdentifier():card(1)) AND hasLabel(NodeIdentifier():card(1))) AND true]->(c)<-[h:HAS WHERE (NOT(Product(NodeIdentifier(),uid(0),true) == Literal(39)) AND hasLabel(NodeIdentifier():user(0))) AND true]-(u2)", _rows=146826, _db_hits=293696) And for the 5000 skip: ==> ColumnFilter(symKeys=["uid", " INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872"], returnItemNames=["uid", "total"], _rows=25, _db_hits=0) ==> Slice(skip="Literal(5000)", _rows=25, _db_hits=0) ==> Top(orderBy=["SortItem(Cached( INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872 of type Any),false)"], limit="Add(Literal(5000),Literal(25))", _rows=5025, _db_hits=0) ==> EagerAggregation(keys=["uid"], aggregates=["( INTERNAL_AGGREGATE99329ea5-03cd-4d53-a6bc-3ad554b47872,Sum(have))"], _rows=41659, _db_hits=0) ==> ColumnFilter(symKeys=["have", "u1", "uid", "c", "h", "w", "u2"], returnItemNames=["uid", "have"], _rows=146826, _db_hits=0) ==> Extract(symKeys=["u1", "c", "h", "w", "u2"], exprKeys=["uid", "have"], _rows=146826, _db_hits=587304) ==> Filter(pred="((NOT(Product(u2,uid(0),true) == Literal(39)) AND hasLabel(u1:user(0))) AND hasLabel(u2:user(0)))", _rows=146826, _db_hits=146826) ==> TraversalMatcher(trail="(u1)-[w:WANTS WHERE (hasLabel(NodeIdentifier():card(1)) AND hasLabel(NodeIdentifier():card(1))) AND true]->(c)<-[h:HAS WHERE (NOT(Product(NodeIdentifier(),uid(0),true) == Literal(39)) AND hasLabel(NodeIdentifier():user(0))) AND true]-(u2)", _rows=146826, _db_hits=293696) The only difference is the LIMIT clause on the Top function. I hope we can make this work as intended, I really don't want to delve into doing an embedded Neo4j + my own Jetty REST API for the web app.

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  • Use component id in Castle Windsor generic object configuration

    - by ChoccyButton
    2 questions in one, but very much related. Is it possible with Castle Windsor to resolve a configuration entry such as - Assembly.Namespace.Object1`2[[${ComponentId1}],[${ComponentId2}]], Assembly Where ComponentId1 and ComponentId2 are defined as components. Castle Windsor doesn't seem to be resolving the ComponentId, it is just looking for ComponentId1 in the Castle.Windsor assembly. The second question comes in to play if you can't do the first question. If you have to use a full assembly reference instead of a ComponentId, how can you pass any parameters to the object being created? eg to set ComponentId1.Field1 = "blah", or pass something to the constructor of ComponentId1 Hope that makes sense Update - Following the request for code I've knocked together the following - Objects public class Wrapper<T, T1> where T : ICollector where T1:IProcessor { private T _collector; private T1 _processor; public Wrapper(T collector, T1 processor) { _collector = collector; _processor = processor; } public void GetData() { _collector.CollectData(); _processor.ProcessData(); } } public class Collector1 : ICollector { public void CollectData() { Console.WriteLine("Collecting data from Collector1 ..."); } } public class Processor1 : IProcessor { public void ProcessData() { Console.WriteLine("Processing data from Processor1 ..."); } } repeated so 3 of each type of object in the example Config <components> <component id="Collector1" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector1, CastleWindsorPlay"/> <component id="Collector2" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector2, CastleWindsorPlay"/> <component id="Collector3" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector3, CastleWindsorPlay"/> <component id="Processor1" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor1, CastleWindsorPlay"/> <component id="Processor2" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor2, CastleWindsorPlay"/> <component id="Processor3" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor3, CastleWindsorPlay"/> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[[CastleWindsorPlay.Collector1, CastleWindsorPlay],[CastleWindsorPlay.Processor3, CastleWindsorPlay]], CastleWindsorPlay" /> </components> Instantiation var wrapper = (Wrapper<ICollector, IProcessor>) container.Resolve("Wrapper1"); wrapper.GetData(); This brief example errors with this error message though - Can't create component 'Wrapper1' as it has dependencies to be satisfied. Wrapper1 is waiting for the following dependencies: Services: - CastleWindsorPlay.Collector1 which was not registered. - CastleWindsorPlay.Processor3 which was not registered. The curious part about this is that I can get it to resolve Collector1 and Processor3 individually before the call to the wrapper, but the wrapper still can't see them. This is a basic example, the next thing I'd like to be able to do is when instantiating the Wrapper, set a property on the collector and/or processor. So it could be something like Collector.Id = 10, but set in the config where the wrapper is defined. Setting against the Collector component definition wouldn't work as I'd want to be able to instantiate multiple copies of each Collector, using different Id's Update 2 What I'm actually trying to do is have - <components> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=1)],[${Processor3}]], CastleWindsorPlay" /> <component id="Wrapper2" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=3)],[${Processor3}]], CastleWindsorPlay" /> </components> Then have another object defined as <component id="Manager" type="CastleWindsorPlay.Manager,CastleWindsorPlay"> <parameters> <wrappers> <array> <item>${Wrapper1}</item> <item>${Wrapper2}</item> </array> </wrappers> </parameters> Then finally in code just be able to call - var manager = (Manager)container.Resolve("Manager"); This should return the manager object, with an array of wrappers populated and the wrappers configured with the correct Collector and Convertor. I know there are errors in the Castle config here, that's why I'm asking the question, I don't know how to set the config up to do what I'm after, or even if it's possible to do it in Castle Windsor

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  • how to gzip-compress large Ajax responses (HTML only) in Coldfusion?

    - by frequent
    I'm running Coldfusion8 and jquery/jquery-mobile on the front-end. I'm playing around with an Ajax powered search engine trying to find the best tradeoff between data-volume and client-side processing time. Currently my AJAX search returns 40k of (JQM-enhanced markup), which avoids any client-side enhancement. This way I'm getting by without the page stalling for about 2-3 seconds, while JQM enhances all elements in the search results. What I'm curious is whether I can gzip Ajax responses sent from Coldfusion. If I check the header of my search right now, I'm having this: RESPONSE-header Connection Keep-Alive Content-Type text/html; charset=UTF-8 Date Sat, 01 Sep 2012 08:47:07 GMT Keep-Alive timeout=5, max=95 Server Apache/2.2.21 (Win32) mod_ssl/2.2.21 ... Transfer-Encoding chunked REQUEST-header Accept */* Accept-Encoding gzip, deflate Accept-Language de-de,de;q=0.8,en-us;q=0.5,en;q=0.3 Connection keep-alive Cookie CFID= ; CFTOKEN= ; resolution=1143 Host www.host.com Referer http://www.host.com/dev/users/index.cfm So, my request would accept gzip, deflate, but I'm getting back chunked. I'm generating the AJAX response in a cfsavecontent (called compressedHTML) and run this to eliminate whitespace <cfrscipt> compressedHTML = reReplace(renderedResults, "\>\s+\<", "> <", "ALL"); compressedHTML = reReplace(compressedHTML, "\s{2,}", chr(13), "ALL"); compressedHTML = reReplace(compressedHTML, "\s{2,}", chr(09), "ALL"); </cfscript> before sending the compressedHTML in a response object like this: {"SUCCESS":true,"DATA": compressedHTML } Question If I know I'm sending back HTML in my data object via Ajax, is there a way to gzip the response server-side before returning it vs sending chunked? If this is at all possible? If so, can I do this inside my response object or would I have to send back "pure" HTML? Thanks! EDIT: Found this on setting a 'web.config' for dynamic compression - doesn't seem to work EDIT2: Found thi snippet and am playing with it, although I'm not sure this will work. <cfscript> compressedHTML = reReplace(renderedResults, "\>\s+\<", "> <", "ALL"); compressedHTML = reReplace(compressedHTML, "\s{2,}", chr(13), "ALL"); compressedHTML = reReplace(compressedHTML, "\s{2,}", chr(09), "ALL"); if ( cgi.HTTP_ACCEPT_ENCODING contains "gzip" AND not showRaw ){ cfheader name="Content-Encoding" value="gzip"; bos = createObject("java","java.io.ByteArrayOutputStream").init(); gzipStream = createObject("java","java.util.zip.GZIPOutputStream"); gzipStream.init(bos); gzipStream.write(compressedHTML.getBytes("utf-8")); gzipStream.close(); bos.flush(); bos.close(); encoder = createObject("java","sun.misc. outStr= encoder.encode(bos.toByteArray()); compressedHTML = toString(bos.toByteArray()); } </cfscript> Probably need to try this on the response object and not the compressedTHML variable

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  • Make interchangeable class types via pointer casting only, without having to allocate any new objects?

    - by HostileFork
    UPDATE: I do appreciate "don't want that, want this instead" suggestions. They are useful, especially when provided in context of the motivating scenario. Still...regardless of goodness/badness, I've become curious to find a hard-and-fast "yes that can be done legally in C++11" vs "no it is not possible to do something like that". I want to "alias" an object pointer as another type, for the sole purpose of adding some helper methods. The alias cannot add data members to the underlying class (in fact, the more I can prevent that from happening the better!) All aliases are equally applicable to any object of this type...it's just helpful if the type system can hint which alias is likely the most appropriate. There should be no information about any specific alias that is ever encoded in the underlying object. Hence, I feel like you should be able to "cheat" the type system and just let it be an annotation...checked at compile time, but ultimately irrelevant to the runtime casting. Something along these lines: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Under the hood, the factory method is actually making a NodeBase class, and then using a similar reinterpret_cast to return it as a Node<AccessorFoo>*. The easy way to avoid this is to make these lightweight classes that wrap nodes and are passed around by value. Thus you don't need casting, just Accessor classes that take the node handle to wrap in their constructor: AccessorFoo foo (NodeBase::createViaFactory()); AccessorBar bar (foo.getNode()); But if I don't have to pay for all that, I don't want to. That would involve--for instance--making a special accessor type for each sort of wrapped pointer (AccessorFooShared, AccessorFooUnique, AccessorFooWeak, etc.) Having these typed pointers being aliased for one single pointer-based object identity is preferable, and provides a nice orthogonality. So back to that original question: Node<AccessorFoo>* fooPtr = Node<AccessorFoo>::createViaFactory(); Node<AccessorBar>* barPtr = reinterpret_cast< Node<AccessorBar>* >(fooPtr); Seems like there would be some way to do this that might be ugly but not "break the rules". According to ISO14882:2011(e) 5.2.10-7: An object pointer can be explicitly converted to an object pointer of a different type.70 When a prvalue v of type "pointer to T1" is converted to the type "pointer to cv T2", the result is static_cast(static_cast(v)) if both T1 and T2 are standard-layout types (3.9) and the alignment requirements of T2 are no stricter than those of T1, or if either type is void. Converting a prvalue of type "pointer to T1" to the type "pointer to T2" (where T1 and T2 are object types and where the alignment requirements of T2 are no stricter than those of T1) and back to its original type yields the original pointer value. The result of any other such pointer conversion is unspecified. Drilling into the definition of a "standard-layout class", we find: has no non-static data members of type non-standard-layout-class (or array of such types) or reference, and has no virtual functions (10.3) and no virtual base classes (10.1), and has the same access control (clause 11) for all non-static data members, and has no non-standard-layout base classes, and either has no non-static data member in the most-derived class and at most one base class with non-static data members, or has no base classes with non-static data members, and has no base classes of the same type as the first non-static data member. Sounds like working with something like this would tie my hands a bit with no virtual methods in the accessors or the node. Yet C++11 apparently has std::is_standard_layout to keep things checked. Can this be done safely? Appears to work in gcc-4.7, but I'd like to be sure I'm not invoking undefined behavior.

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  • Edit of self referencing HABTM in cakephp works, sometimes

    - by Odegard
    I'm using a self referencing HABTM model with Participants. You sign up for an event and when you log in to your reservation/profile you see a list of other participants and you can choose to add yourself and others into various groups; share hotel room, share transportation from airport etc. What I've managed so far: 1) In my profile I see the list of all other participants with checkboxes. Great so far. 2) Adding another participant works fine. Next time I edit, the participant I added is shown as checked. 3) Removing another participant works fine too as long as you still have checked participants before you submit! Again, with words: There are 3 participants. I'm logged in as one of them, and I see the 2 other people on the participants list. I choose to check both of them. This works fine (always). Later I choose to remove one of them (by unchecking the checkbox and hitting submit). This also works fine (always). If I want to remove the last checkbox... nothing is updated (always!). What's curious is that I can add and remove any odd combination of participants and it will always work UNLESS I choose to remove every participants in one go (removing a one and only participant is a special case of "remove all checked participants"). As far as I know, HABTMs work by first deleting all relations, then re-saving them. I can see that in my tables when I remove, add, remove, add the same participant over and over again - the id on the HABTM table is always increasing. When I deselect all participants at once, however, the relations are not updated. The ids stay the same, so it's like the save never happened. This behaviour is so specific and peculiar, I have a feeling I'm missing something obvious here. Anyway, here's the relevant code: Model class Participant extends AppModel { var $hasAndBelongsToMany = array( 'buddy' = array( 'className' = 'Participant', 'joinTable' = 'participants_participants', 'foreignKey' = 'participant_id', 'associationForeignKey' = 'buddy_id', 'unique' = true, ) ); Controller function edit($id = null) { if (!$id && empty($this-data)) { $this-Session-setFlash(__('Invalid Participant', true)); $this-redirect(array('action'='index')); } if (!empty($this-data)) { if ($this-Participant-saveAll($this-data)) { $this-Session-setFlash(__('The Participant has been saved', true)); $this-redirect(array('action'='index')); } else { $this-Session-setFlash(__('The Participant could not be saved. Please, try again.', true)); } } if (empty($this-data)) { $this-data = $this-Participant-read(null, $id); } // Fetching all participants except yourself $allParticipants = $this-Participant-find('list', array('conditions' = array('participant.id ' = $id))); // Fetching every participant that has added you to their list $allBuddies = $this-Participant-ParticipantsParticipant-find('list', array( 'conditions' = array('buddy_id' = $id), 'fields' = 'ParticipantsParticipant.participant_id', 'order' = 'ParticipantsParticipant.participant_id ASC' )); $this-set(compact('allParticipants','allBuddies')); } View echo $form-create('Participant'); echo $associations-habtmCheckBoxes($allParticipants, $this-data['buddy'], 'buddy', 'div', '\'border: 1px solid #000;\'', '\'border: 1px solid #000;\''); echo $form-end('Submit'); I'm using a slightly modified helper, habtmCheckBoxes, found here: http://cakeforge.org/snippet/detail.php?type=snippet&id=190 It works like this: function habtmCheckBoxes($rows=array(), $selectedArr=array(), $modelName, $wrapTag='p', $checkedDiv, $uncheckedDiv) {}

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  • Defend PHP; convince me it isn't horrible

    - by Jason L
    I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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  • Possible to set two values for two different nodes from user input in XForms?

    - by iHeartGreek
    Hi! I would like to set two values for two different nodes from user input in XForms. I am curious about how this is done, if at all possible. For example, if I have the following data model: <xf:instance id="criteria_data" xmlns=""> <criteria> <set> <root></root> <criterion></criterion> </set> </criteria> </xf:instance> <xf:instance id="choices" xmlns=""> <choices> <root label="The Choices">/AAA</root> <choice label="BBB">/@BBB</choice> </choices> </xf:instance> <xf:instance id="choices" xmlns=""> <choices> <root>/AAA</root> <choice label="BBB">/@BBB</choice> <choice label="CCC">/@CCC</choice> <choices> </xf:instance> <xf:bind id="data_criterion" nodeset="instance('criteria_data')/criteria/set/criterion"/> <xf:bind id="data_root" nodeset="instance('criteria_data')/criteria/set/root"/> <xf:bind id="choices_root" nodeset="instance('choices')/root"/> <xf:bind id="choices" nodeset="instance('choices')/choice"/> and my ui code looks like: <xf:select bind="data_criterion" appearance="full"> <xf:label>Your choices:</xf:label> <xf:itemset bind="choices"> <xf:label ref="@label"></xf:label> <xf:value ref="."></xf:value> </xf:itemset> </xf:select> But I essentially want it to be like this (though this is invalid and does not produce any xml at all): <xf:select appearance="full"> <xf:label>Your choices:</xf:label> <xf:itemset bind="choices"> <xf:label ref="@label"></xf:label> <xf:value bind="data_criterion" ref="."></xf:value> <xf:value bind="data_root" ref="instance('choices')/root"></xf:value> </xf:itemset> </xf:select> The XML output I want to achieve (if user checks "BBB"): <criteria> <set> <root>/AAA</root> <criterion>/@BBB</criterion> </set> </criteria> How can I achieve setting these two nodes for the one checkbox seletion? Hope that all made sense... Thanks! :)

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  • Javascript style objects in Objective-C

    - by awolf
    Background: I use a ton of NSDictionary objects in my iPhone and iPad code. I'm sick of the verbose way of getting/setting keys to these state dictionaries. So a little bit of an experiment: I just created a class I call Remap. Remap will take any arbitrary set[VariableName]:(NSObject *) obj selector and forward that message to a function that will insert obj into an internal NSMutableDictionary under the key [vairableName]. Remap will also take any (zero argument) arbitrary [variableName] selector and return the NSObject mapped in the NSMutableDictionary under the key [variableName]. e.g. Remap * remap = [[Remap alloc] init]; NSNumber * testNumber = [NSNumber numberWithInt:46]; [remap setTestNumber:testNumber]; testNumber = [remap testNumber]; [remap setTestString:@"test string"]; NSString * testString = [remap testString]; NSMutableDictionary * testDict = [NSMutableDictionary dictionaryWithObject:testNumber forKey:@"testNumber"]; [remap setTestDict:testDict]; testDict = [remap testDict]; where none of the properties testNumber, testString, or testDict are actually defined in Remap. The crazy thing? It works... My only question is how can I disable the "may not respond to " warnings for JUST accesses to Remap? P.S. : I'll probably end up scrapping this and going with macros since message forwarding is quite inefficient... but aside from that does anyone see other problems with Remap? Here's Remap's .m for those who are curious: #import "Remap.h" @interface Remap () @property (nonatomic, retain) NSMutableDictionary * _data; @end @implementation Remap @synthesize _data; - (void) dealloc { relnil(_data); [super dealloc]; } - (id) init { self = [super init]; if (self != nil) { NSMutableDictionary * dict = [[NSMutableDictionary alloc] init]; [self set_data:dict]; relnil(dict); } return self; } - (void)forwardInvocation:(NSInvocation *)anInvocation { NSString * selectorName = [NSString stringWithUTF8String: sel_getName([anInvocation selector])]; NSRange range = [selectorName rangeOfString:@"set"]; NSInteger numArguments = [[anInvocation methodSignature] numberOfArguments]; if (range.location == 0 && numArguments == 4) { //setter [anInvocation setSelector:@selector(setData:withKey:)]; [anInvocation setArgument:&selectorName atIndex:3]; [anInvocation invokeWithTarget:self]; } else if (numArguments == 3) { [anInvocation setSelector:@selector(getDataWithKey:)]; [anInvocation setArgument:&selectorName atIndex:2]; [anInvocation invokeWithTarget:self]; } } - (NSMethodSignature *) methodSignatureForSelector:(SEL) aSelector { NSString * selectorName = [NSString stringWithUTF8String: sel_getName(aSelector)]; NSMethodSignature * sig = [super methodSignatureForSelector:aSelector]; if (sig == nil) { NSRange range = [selectorName rangeOfString:@"set"]; if (range.location == 0) { sig = [self methodSignatureForSelector:@selector(setData:withKey:)]; } else { sig = [self methodSignatureForSelector:@selector(getDataWithKey:)]; } } return sig; } - (NSObject *) getDataWithKey: (NSString *) key { NSObject * returnValue = [[self _data] objectForKey:key]; return returnValue; } - (void) setData: (NSObject *) data withKey:(NSString *)key { if (key && [key length] >= 5 && data) { NSRange range; range.length = 1; range.location = 3; NSString * firstChar = [key substringWithRange:range]; firstChar = [firstChar lowercaseString]; range.length = [key length] - 5; // the 4 we have processed plus the training : range.location = 4; NSString * adjustedKey = [NSString stringWithFormat:@"%@%@", firstChar, [key substringWithRange:range]]; [[self _data] setObject:data forKey:adjustedKey]; } else { //assert? } } @end

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  • Trying to reinvent the wheel of StackOverflow to have a good learning experience. Need some suggesti

    - by Legend
    I want to learn and am not able to do it unless I have a real "mission" to complete. SO is my favorite and I can't imagine a better experience than actually recreating it but not in ASP. I'd like to use PHP+MySQL+jQuery. So far, I have been a self-taught programmer but I would like to master one paradigm that forces you to adhere to the standards. For instance, recently, jQuery forced me to use some "rules". The plugins were supposed to be written in a particular way and that's it. When I started off, everything seemed like Greek and Latin but when I finished a very small plugin, I felt really happy because it forced me to program in a certain way. I am looking for something like this only in a larger project. I've heard a lot about MVC and all but I am confused about the various frameworks out there. Zend seems awesome but looks heavy at the same time and also requires you to have a lot more control over the web-server whereas CakePHP is a good and a fast framework that needs only little control. Do I use one of these or just write my own MVC? I have the following goals: Goals: Site should be fast - I know this depends on my coding skills but I will learn on my way. The framework itself should not slow me down) Setting up the site should not require you to use command-line - This requirement is ok during development. But some frameworks like Symphony require you to initialize certain things through command-line Should support pluggable modules - For instance, if I want to be able to use the FCK editor, I should be able to organize things in a good way. Should be possible to extend - For instance, SO is mainly a Q&A site but I should be able to logically extend it into an Idea Management System (optional but I'm curious). This goes more into code re-usability I guess. I am comfortable with MySQL so I should be done with database design etc. with some serious effort. As for PHP, I can write code on my own but haven't really used any frameworks that much. jQuery, I started off recently and love it. I would be glad if someone can guide me during these initial steps. Precisely, when designing something like SO, I have the following questions: Do I use a framework? If yes, should it be MVC? If MVC, which one is a good and a scalable one? (I'd love something like jQuery that will not die anytime soon) How do I balance the functionality? The same logic can sometimes be made server centric or client centric. (more Ajax?). Is it a good idea to make a heavy javascript site considering the recent advances on client-side JS processing? Just in case anyone is wondering, I am not interested in commercializing any of this. I need a reason to learn something :)

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  • Suggestions for lightweight, thread-safe scheduler

    - by nirvanai
    I am trying to write a round-robin scheduler for lightweight threads (fibers). It must scale to handle as many concurrently-scheduled fibers as possible. I also need to be able to schedule fibers from threads other than the one the run loop is on, and preferably unschedule them from arbitrary threads as well (though I could live with only being able to unschedule them from the run loop). My current idea is to have a circular doubly-linked list, where each fiber is a node and the scheduler holds a reference to the current node. This is what I have so far: using Interlocked = System.Threading.Interlocked; public class Thread { internal Future current_fiber; public void RunLoop () { while (true) { var fiber = current_fiber; if (fiber == null) { // block the thread until a fiber is scheduled continue; } if (fiber.Fulfilled) fiber.Unschedule (); else fiber.Resume (); //if (current_fiber == fiber) current_fiber = fiber.next; Interlocked.CompareExchange<Future> (ref current_fiber, fiber.next, fiber); } } } public abstract class Future { public bool Fulfilled { get; protected set; } internal Future previous, next; // this must be thread-safe // it inserts this node before thread.current_fiber // (getting the exact position doesn't matter, as long as the // chosen nodes haven't been unscheduled) public void Schedule (Thread thread) { next = this; // maintain circularity, even if this is the only node previous = this; try_again: var current = Interlocked.CompareExchange<Future> (ref thread.current_fiber, this, null); if (current == null) return; var target = current.previous; while (target == null) { // current was unscheduled; negotiate for new current_fiber var potential = current.next; var actual = Interlocked.CompareExchange<Future> (ref thread.current_fiber, potential, current); current = (actual == current? potential : actual); if (current == null) goto try_again; target = current.previous; } // I would lock "current" and "target" at this point. // How can I do this w/o risk of deadlock? next = current; previous = target; target.next = this; current.previous = this; } // this would ideally be thread-safe public void Unschedule () { var prev = previous; if (prev == null) { // already unscheduled return; } previous = null; if (next == this) { next = null; return; } // Again, I would lock "prev" and "next" here // How can I do this w/o risk of deadlock? prev.next = next; next.previous = prev; } public abstract void Resume (); } As you can see, my sticking point is that I cannot ensure the order of locking, so I can't lock more than one node without risking deadlock. Or can I? I don't want to have a global lock on the Thread object, since the amount of lock contention would be extreme. Plus, I don't especially care about insertion position, so if I lock each node separately then Schedule() could use something like Monitor.TryEnter and just keep walking the list until it finds an unlocked node. Overall, I'm not invested in any particular implementation, as long as it meets the requirements I've mentioned. Any ideas would be greatly appreciated. Thanks! P.S- For the curious, this is for an open source project I'm starting at http://github.com/nirvanai/Cirrus

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  • about getadrrinfo() C++?

    - by Isavel
    I'm reading this book called beej's guide to network programming and there's a part in the book were it provide a sample code which illustrate the use of getaddrinfo(); the book state that the code below "will print the IP addresses for whatever host you specify on the command line" - beej's guide to network programming. now I'm curious and want to try it out and run the code, but I guess the code was develop in UNIX environment and I'm using visual studio 2012 windows 7 OS, and most of the headers was not supported so I did a bit of research and find out that I need to include the winsock.h and ws2_32.lib for windows, for it to get working, fortunately everything compiled no errors, but when I run it using the debugger and put in 'www.google.com' as command argument I was disappointed that it did not print any ipaddress, the output that I got from the console is "getaddrinfo: E" what does the letter E mean? Do I need to configure something out of the debugger? Interestingly I left the command argument blank and the output changed to "usage: showip hostname" Any help would be appreciated. #ifdef _WIN32 #endif #include <sys/types.h> #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> using namespace std; #include <stdio.h> #include <string.h> #include <sys/types.h> #include <winsock.h> #pragma comment(lib, "ws2_32.lib") int main(int argc, char *argv[]) { struct addrinfo hints, *res, *p; int status; char ipstr[INET6_ADDRSTRLEN]; if (argc != 2) { fprintf(stderr,"usage: showip hostname\n"); system("PAUSE"); return 1; } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version hints.ai_socktype = SOCK_STREAM; if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); system("PAUSE"); return 2; } printf("IP addresses for %s:\n\n", argv[1]); for(p = res;p != NULL; p = p->ai_next) { void *addr; char *ipver; // get the pointer to the address itself, // different fields in IPv4 and IPv6: if (p->ai_family == AF_INET) { // IPv4 struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr; addr = &(ipv4->sin_addr); ipver = "IPv4"; } else { // IPv6 struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr; addr = &(ipv6->sin6_addr); ipver = "IPv6"; } // convert the IP to a string and print it: inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr); printf(" %s: %s\n", ipver, ipstr); } freeaddrinfo(res); // free the linked list system("PAUSE"); return 0; }

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  • Real Excel Templates I

    - by Tim Dexter
    As promised, I'm starting to document the new Excel templates that I teased you all with a few weeks back. Leslie is buried in 11g documentation and will not get to officially documenting the templates for a while. I'll do my best to be professional and not ramble on about this and that, although the weather here has finally turned and its 'scorchio' here in Colorado today. Maybe our stand of Aspen will finally come into leaf ... but I digress. Preamble These templates are not actually that new, I helped in a small way to develop them a few years back with Excel 'meistress' Shirley for a company that was trying to use the Report Manager(RR) Excel FSG outputs under EBS 12. The functionality they needed was just not there in the RR FSG templates, the templates are actually XSL that is created from the the RR Excel template builder and fed to BIP for processing. Think of Excel from our RTF templates and you'll be there ie not really Excel but HTML masquerading as Excel. Although still under controlled release in EBS they have now made their way to the standlone release and are willing to share their Excel goodness. You get everything you have with hte Excel Analyzer Excel templates plus so much more. Therein lies a question, what will happen to the Analyzer templates? My understanding is that both will come together into a single Excel template format some time in the post-11g release world. The new XLSX format for Exce 2007/10 is also in the mix too so watch this space. What more do these templates offer? Well, you can structure data in the Excel output. Similar to RTF templates you can create sheets of data that have master-detail n relationships. Although the analyzer templates can do this, you have to get into macros whereas BIP will do this all for you. You can also use native XSL functions in your data to manipulate it prior to rendering. BP functions are not currently supported. The most impressive, for me at least, is the sheet 'bursting'. You can split your hierarchical data across multiple sheets and dynamically name those sheets. Finally, you of course, still get all the native Excel functionality. Pre-reqs You must be on 10.1.3.4.1 plus the latest rollup patch, 9546699. You can patch upa BIP instance running with OBIEE, no problem You need Excel 2000 or above to build the templates Some patience - there is no Excel template builder for these new templates. So its all going to have to be done by hand. Its not that tough but can get a little 'fiddly'. You can not test the template from Excel , it has to be deployed and then run. Limitations The new templates are definitely superior to the Analyzer templates but there are a few limitations. Re-grouping is not supported. You can only follow a data hierarchy not bend it to your will unless you want to get into macros. No support for BIP functions. The templates support native XSL functions only. No template builder Getting Started The templates make the use of named cells and groups of cells to allow BIP to find the insertion point for data points. It also uses a hidden sheet to store calculation mappings from named cells to XML data elements. To start with, in the great BIP tradition, we need some sample XML data. Becasue I wanted to show the master-detail output we need some hierarchical data. If you have not yet gotten into the data templates, now is a good time, I wrote a post a while back starting from the simple to more complex. They generate ideal data sets for these templates. Im working with the following data set: <EMPLOYEES> <LIST_G_DEPT> <G_DEPT> <DEPARTMENT_ID>10</DEPARTMENT_ID> <DEPARTMENT_NAME>Administration</DEPARTMENT_NAME> <LIST_G_EMP> <G_EMP> <EMPLOYEE_ID>200</EMPLOYEE_ID> <EMP_NAME>Jennifer Whalen</EMP_NAME> <EMAIL>JWHALEN</EMAIL> <PHONE_NUMBER>515.123.4444</PHONE_NUMBER> <HIRE_DATE>1987-09-17T00:00:00.000-06:00</HIRE_DATE> <SALARY>4400</SALARY> </G_EMP> </LIST_G_EMP> <TOTAL_EMPS>1</TOTAL_EMPS> <TOTAL_SALARY>4400</TOTAL_SALARY> <AVG_SALARY>4400</AVG_SALARY> <MAX_SALARY>4400</MAX_SALARY> <MIN_SALARY>4400</MIN_SALARY> </G_DEPT> ... <LIST_G_DEPT> <EMPLOYEES> Simple enough to follow and bread and butter stuff for an RTF template. Building the Template For an Excel template we need to start by thinking about how we want to render the data. Come up with a sample output in Excel. Its all dummy data, nothing marked up yet with one row of data for each level. I have the department name and then a repeating row for the employees. You can apply Excel formatting to the layout. The total is going to be derived from a data element. We'll get to Excel functions later. Marking Up Cells Next we need to start marking up the cells with custom names to map them to data elements. The cell names need to follow a specific format: For data grouping, XDO_GROUP_?group_name? For data elements, XDO_?element_name? Notice the question mark delimter, the group_name and element_name are case sensitive. The next step is to find how to name cells; the easiest method is to highlight the cell and then type in the name. You can also find the Name Manager dialog. I use 2007 and its available on the ribbon under the Formulas section Go thorugh the process of naming all the cells for the element values you have. Using my data set from above.You should end up with something like this in your 'Name Manager' dialog. You can update any mistakes you might have made through this dialog. Creating Groups In the image above you can see there are a couple of named group cells. To create these its a simple case of highlighting the cells that make up the group and then naming them. For the EMP group, highlight the employee row and then type in the name, XDO_GROUP?G_EMP? Notice the 10,000 total is outside of the G_EMP group. Its actually named, XDO_?TOTAL_SALARY?, a query calculated value. For the department group, we need to include the department name cell and the sub EMP grouping and name it, XDO_GROUP?G_DEPT? Notice, the 10,000 total is included in the G_DEPT group. This will ensure it repeats at the department level. Lastly, we do need to include a special sheet in the workbook. We will not have anything meaningful in there for now, but it needs to be present. Create a new sheet and name it XDO_METADATA. The name is important as the BIP rendering engine will looking for it. For our current example we do not need anything other than the required stuff in our XDO_METADATA sheet but, it must be present. Easy enough to hide it. Here's what I have: The only cell that is important is the 'Data Constraints:' cell. The rest is optional. To save curious users getting distracted, hide the metadata sheet. Deploying & Running Templates We should now have a usable Excel template. Loading it into a report is easy enough using the browser UI, just like an RTF template. Set the template type to Excel. You will now be able to run the report and hopefully get something like this. You will not get the red highlighting, thats just some conditional formatting I added to the template using Excel functionality. Your dates are probably going to look raw too. I got around this for now using an Excel function on the cell: =--REPLACE(SUBSTITUTE(E8,"T"," "),LEN(E8)-6,6,"") Google to the rescue on that one. Try some other stuff out. To avoid constantly loading the template through the UI. If you have BIP running locally or you can access the reports repository, once you have loaded the template the first time. Just save the template directly into the report folder. I have put together a sample report using a sample data set, available here. Just drop the xml data file, EmpbyDeptExcelData.xml into 'demo files' folder and you should be good to go. Thats the basics, next we'll start using some XSL functions in the template and move onto the 'bursting' across sheets.

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  • Pluralsight Meet the Author Podcast on Structuring JavaScript Code

    - by dwahlin
    I had the opportunity to talk with Fritz Onion from Pluralsight about one of my recent courses titled Structuring JavaScript Code for one of their Meet the Author podcasts. We talked about why JavaScript patterns are important for building more re-useable and maintainable apps, pros and cons of different patterns, and how to go about picking a pattern as a project is started. The course provides a solid walk-through of converting what I call “Function Spaghetti Code” into more modular code that’s easier to maintain, more re-useable, and less susceptible to naming conflicts. Patterns covered in the course include the Prototype Pattern, Revealing Module Pattern, and Revealing Prototype Pattern along with several other tips and techniques that can be used. Meet the Author:  Dan Wahlin on Structuring JavaScript Code   The transcript from the podcast is shown below: [Fritz]  Hello, this is Fritz Onion with another Pluralsight author interview. Today we’re talking with Dan Wahlin about his new course, Structuring JavaScript Code. Hi, Dan, it’s good to have you with us today. [Dan]  Thanks for having me, Fritz. [Fritz]  So, Dan, your new course, which came out in December of 2011 called Structuring JavaScript Code, goes into several patterns of usage in JavaScript as well as ways of organizing your code and what struck me about it was all the different techniques you described for encapsulating your code. I was wondering if you could give us just a little insight into what your motivation was for creating this course and sort of why you decided to write it and record it. [Dan]  Sure. So, I got started with JavaScript back in the mid 90s. In fact, back in the days when browsers that most people haven’t heard of were out and we had JavaScript but it wasn’t great. I was on a project in the late 90s that was heavy, heavy JavaScript and we pretty much did what I call in the course function spaghetti code where you just have function after function, there’s no rhyme or reason to how those functions are structured, they just kind of flow and it’s a little bit hard to do maintenance on it, you really don’t get a lot of reuse as far as from an object perspective. And so coming from an object-oriented background in JAVA and C#, I wanted to put something together that highlighted kind of the new way if you will of writing JavaScript because most people start out just writing functions and there’s nothing with that, it works, but it’s definitely not a real reusable solution. So the course is really all about how to move from just kind of function after function after function to the world of more encapsulated code and more reusable and hopefully better maintenance in the process. [Fritz]  So I am sure a lot of people have had similar experiences with their JavaScript code and will be looking forward to seeing what types of patterns you’ve put forth. Now, a couple I noticed in your course one is you start off with the prototype pattern. Do you want to describe sort of what problem that solves and how you go about using it within JavaScript? [Dan]  Sure. So, the patterns that are covered such as the prototype pattern and the revealing module pattern just as two examples, you know, show these kind of three things that I harp on throughout the course of encapsulation, better maintenance, reuse, those types of things. The prototype pattern specifically though has a couple kind of pros over some of the other patterns and that is the ability to extend your code without touching source code and what I mean by that is let’s say you’re writing a library that you know either other teammates or other people just out there on the Internet in general are going to be using. With the prototype pattern, you can actually write your code in such a way that we’re leveraging the JavaScript property and by doing that now you can extend my code that I wrote without touching my source code script or you can even override my code and perform some new functionality. Again, without touching my code.  And so you get kind of the benefit of the almost like inheritance or overriding in object oriented languages with this prototype pattern and it makes it kind of attractive that way definitely from a maintenance standpoint because, you know, you don’t want to modify a script I wrote because I might roll out version 2 and now you’d have to track where you change things and it gets a little tricky. So with this you just override those pieces or extend them and get that functionality and that’s kind of some of the benefits that that pattern offers out of the box. [Fritz]  And then the revealing module pattern, how does that differ from the prototype pattern and what problem does that solve differently? [Dan]  Yeah, so the prototype pattern and there’s another one that’s kind of really closely lined with revealing module pattern called the revealing prototype pattern and it also uses the prototype key word but it’s very similar to the one you just asked about the revealing module pattern. [Fritz]  Okay. [Dan]  This is a really popular one out there. In fact, we did a project for Microsoft that was very, very heavy JavaScript. It was an HMTL5 jQuery type app and we use this pattern for most of the structure if you will for the JavaScript code and what it does in a nutshell is allows you to get that encapsulation so you have really a single function wrapper that wraps all your other child functions but it gives you the ability to do public versus private members and this is kind of a sort of debate out there on the web. Some people feel that all JavaScript code should just be directly accessible and others kind of like to be able to hide their, truly their private stuff and a lot of people do that. You just put an underscore in front of your field or your variable name or your function name and that kind of is the defacto way to say hey, this is private. With the revealing module pattern you can do the equivalent of what objective oriented languages do and actually have private members that you literally can’t get to as an external consumer of the JavaScript code and then you can expose only those members that you want to be public. Now, you don’t get the benefit though of the prototype feature, which is I can’t easily extend the revealing module pattern type code if you don’t like something I’m doing, chances are you’re probably going to have to tweak my code to fix that because we’re not leveraging prototyping but in situations where you’re writing apps that are very specific to a given target app, you know, it’s not a library, it’s not going to be used in other apps all over the place, it’s a pattern I actually like a lot, it’s very simple to get going and then if you do like that public/private feature, it’s available to you. [Fritz]  Yeah, that’s interesting. So it’s almost, you can either go private by convention just by using a standard naming convention or you can actually enforce it by using the prototype pattern. [Dan]  Yeah, that’s exactly right. [Fritz]  So one of the things that I know I run across in JavaScript and I’m curious to get your take on is we do have all these different techniques of encapsulation and each one is really quite different when you’re using closures versus simply, you know, referencing member variables and adding them to your objects that the syntax changes with each pattern and the usage changes. So what would you recommend for people starting out in a brand new JavaScript project? Should they all sort of decide beforehand on what patterns they’re going to stick to or do you change it based on what part of the library you’re working on? I know that’s one of the points of confusion in this space. [Dan]  Yeah, it’s a great question. In fact, I just had a company ask me about that. So which one do I pick and, of course, there’s not one answer fits all. [Fritz]  Right. [Dan]  So it really depends what you just said is absolutely in my opinion correct, which is I think as a, especially if you’re on a team or even if you’re just an individual a team of one, you should go through and pick out which pattern for this particular project you think is best. Now if it were me, here’s kind of the way I think of it. If I were writing a let’s say base library that several web apps are going to use or even one, but I know that there’s going to be some pieces that I’m not really sure on right now as I’m writing I and I know people might want to hook in that and have some better extension points, then I would look at either the prototype pattern or the revealing prototype. Now, really just a real quick summation between the two the revealing prototype also gives you that public/private stuff like the revealing module pattern does whereas the prototype pattern does not but both of the prototype patterns do give you the benefit of that extension or that hook capability. So, if I were writing a library that I need people to override things or I’m not even sure what I need them to override, I want them to have that option, I’d probably pick a prototype, one of the prototype patterns. If I’m writing some code that is very unique to the app and it’s kind of a one off for this app which is what I think a lot of people are kind of in that mode as writing custom apps for customers, then my personal preference is the revealing module pattern you could always go with the module pattern as well which is very close but I think the revealing module patterns a little bit cleaner and we go through that in the course and explain kind of the syntax there and the differences. [Fritz]  Great, that makes a lot of sense. [Fritz]  I appreciate you taking the time, Dan, and I hope everyone takes a chance to look at your course and sort of make these decisions for themselves in their next JavaScript project. Dan’s course is, Structuring JavaScript Code and it’s available now in the Pluralsight Library. So, thank you very much, Dan. [Dan]  Thanks for having me again.

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  • Connecting Linux to WatchGuard Firebox SSL (OpenVPN client)

    Recently, I got a new project assignment that requires to connect permanently to the customer's network through VPN. They are using a so-called SSL VPN. As I am using OpenVPN since more than 5 years within my company's network I was quite curious about their solution and how it would actually be different from OpenVPN. Well, short version: It is a disguised version of OpenVPN. Unfortunately, the company only offers a client for Windows and Mac OS which shouldn't bother any Linux user after all. OpenVPN is part of every recent distribution and can be activated in a couple of minutes - both client as well as server (if necessary). WatchGuard Firebox SSL - About dialog Borrowing some files from a Windows client installation Initially, I didn't know about the product, so therefore I went through the installation on Windows 8. No obstacles (and no restart despite installation of TAP device drivers!) here and the secured VPN channel was up and running in less than 2 minutes or so. Much appreciated from both parties - customer and me. Of course, this whole client package and my long year approved and stable installation ignited my interest to have a closer look at the WatchGuard client. Compared to the original OpenVPN client (okay, I have to admit this is years ago) this commercial product is smarter in terms of file locations during installation. You'll be able to access the configuration and key files below your roaming application data folder. To get there, simply enter '%AppData%\WatchGuard\Mobile VPN' in your Windows/File Explorer and confirm with Enter/Return. This will display the following files: Application folder below user profile with configuration and certificate files From there we are going to borrow four files, namely: ca.crt client.crt client.ovpn client.pem and transfer them to the Linux system. You might also be able to isolate those four files from a Mac OS client. Frankly, I'm just too lazy to run the WatchGuard client installation on a Mac mini only to find the folder location, and I'm going to describe why a little bit further down this article. I know that you can do that! Feedback in the comment section is appreciated. Configuration of OpenVPN (console) Depending on your distribution the following steps might be a little different but in general you should be able to get the important information from it. I'm going to describe the steps in Ubuntu 13.04 (Raring Ringtail). As usual, there are two possibilities to achieve your goal: console and UI. Let's what it is necessary to be done. First of all, you should ensure that you have OpenVPN installed on your system. Open your favourite terminal application and run the following statement: $ sudo apt-get install openvpn network-manager-openvpn network-manager-openvpn-gnome Just to be on the safe side. The four above mentioned files from your Windows machine could be copied anywhere but either you place them below your own user directory or you put them (as root) below the default directory: /etc/openvpn At this stage you would be able to do a test run already. Just in case, run the following command and check the output (it's the similar information you would get from the 'View Logs...' context menu entry in Windows: $ sudo openvpn --config client.ovpn Pay attention to the correct path to your configuration and certificate files. OpenVPN will ask you to enter your Auth Username and Auth Password in order to establish the VPN connection, same as the Windows client. Remote server and user authentication to establish the VPN Please complete the test run and see whether all went well. You can disconnect pressing Ctrl+C. Simplifying your life - authentication file In my case, I actually set up the OpenVPN client on my gateway/router. This establishes a VPN channel between my network and my client's network and allows me to switch machines easily without having the necessity to install the WatchGuard client on each and every machine. That's also very handy for my various virtualised Windows machines. Anyway, as the client configuration, key and certificate files are located on a headless system somewhere under the roof, it is mandatory to have an automatic connection to the remote site. For that you should first change the file extension '.ovpn' to '.conf' which is the default extension on Linux systems for OpenVPN, and then open the client configuration file in order to extend an existing line. $ sudo mv client.ovpn client.conf $ sudo nano client.conf You should have a similar content to this one here: dev tunclientproto tcp-clientca ca.crtcert client.crtkey client.pemtls-remote "/O=WatchGuard_Technologies/OU=Fireware/CN=Fireware_SSLVPN_Server"remote-cert-eku "TLS Web Server Authentication"remote 1.2.3.4 443persist-keypersist-tunverb 3mute 20keepalive 10 60cipher AES-256-CBCauth SHA1float 1reneg-sec 3660nobindmute-replay-warningsauth-user-pass auth.txt Note: I changed the IP address of the remote directive above (which should be obvious, right?). Anyway, the required change is marked in red and we have to create a new authentication file 'auth.txt'. You can give the directive 'auth-user-pass' any file name you'd like to. Due to my existing OpenVPN infrastructure my setup differs completely from the above written content but for sake of simplicity I just keep it 'as-is'. Okay, let's create this file 'auth.txt' $ sudo nano auth.txt and just put two lines of information in it - username on the first, and password on the second line, like so: myvpnusernameverysecretpassword Store the file, change permissions, and call openvpn with your configuration file again: $ sudo chmod 0600 auth.txt $ sudo openvpn --config client.conf This should now work without being prompted to enter username and password. In case that you placed your files below the system-wide location /etc/openvpn you can operate your VPNs also via service command like so: $ sudo service openvpn start client $ sudo service openvpn stop client Using Network Manager For newer Linux users or the ones with 'console-phobia' I'm going to describe now how to use Network Manager to setup the OpenVPN client. For this move your mouse to the systray area and click on Network Connections => VPN Connections => Configure VPNs... which opens your Network Connections dialog. Alternatively, use the HUD and enter 'Network Connections'. Network connections overview in Ubuntu Click on 'Add' button. On the next dialog select 'Import a saved VPN configuration...' from the dropdown list and click on 'Create...' Choose connection type to import VPN configuration Now you navigate to your folder where you put the client files from the Windows system and you open the 'client.ovpn' file. Next, on the tab 'VPN' proceed with the following steps (directives from the configuration file are referred): General Check the IP address of Gateway ('remote' - we used 1.2.3.4 in this setup) Authentication Change Type to 'Password with Certificates (TLS)' ('auth-pass-user') Enter User name to access your client keys (Auth Name: myvpnusername) Enter Password (Auth Password: verysecretpassword) and choose your password handling Browse for your User Certificate ('cert' - should be pre-selected with client.crt) Browse for your CA Certificate ('ca' - should be filled as ca.crt) Specify your Private Key ('key' - here: client.pem) Then click on the 'Advanced...' button and check the following values: Use custom gateway port: 443 (second value of 'remote' directive) Check the selected value of Cipher ('cipher') Check HMAC Authentication ('auth') Enter the Subject Match: /O=WatchGuard_Technologies/OU=Fireware/CN=Fireware_SSLVPN_Server ('tls-remote') Finally, you have to confirm and close all dialogs. You should be able to establish your OpenVPN-WatchGuard connection via Network Manager. For that, click on the 'VPN Connections => client' entry on your Network Manager in the systray. It is advised that you keep an eye on the syslog to see whether there are any problematic issues that would require some additional attention. Advanced topic: routing As stated above, I'm running the 'WatchGuard client for Linux' on my head-less server, and since then I'm actually establishing a secure communication channel between two networks. In order to enable your network clients to get access to machines on the remote side there are two possibilities to enable that: Proper routing on both sides of the connection which enables both-direction access, or Network masquerading on the 'client side' of the connection Following, I'm going to describe the second option a little bit more in detail. The Linux system that I'm using is already configured as a gateway to the internet. I won't explain the necessary steps to do that, and will only focus on the additional tweaks I had to do. You can find tons of very good instructions and tutorials on 'How to setup a Linux gateway/router' - just use Google. OK, back to the actual modifications. First, we need to have some information about the network topology and IP address range used on the 'other' side. We can get this very easily from /var/log/syslog after we established the OpenVPN channel, like so: $ sudo tail -n20 /var/log/syslog Or if your system is quite busy with logging, like so: $ sudo less /var/log/syslog | grep ovpn The output should contain PUSH received message similar to the following one: Jul 23 23:13:28 ios1 ovpn-client[789]: PUSH: Received control message: 'PUSH_REPLY,topology subnet,route 192.168.1.0 255.255.255.0,dhcp-option DOMAIN ,route-gateway 192.168.6.1,topology subnet,ping 10,ping-restart 60,ifconfig 192.168.6.2 255.255.255.0' The interesting part for us is the route command which I highlighted already in the sample PUSH_REPLY. Depending on your remote server there might be multiple networks defined (172.16.x.x and/or 10.x.x.x). Important: The IP address range on both sides of the connection has to be different, otherwise you will have to shuffle IPs or increase your the netmask. {loadposition content_adsense} After the VPN connection is established, we have to extend the rules for iptables in order to route and masquerade IP packets properly. I created a shell script to take care of those steps: #!/bin/sh -eIPTABLES=/sbin/iptablesDEV_LAN=eth0DEV_VPNS=tun+VPN=192.168.1.0/24 $IPTABLES -A FORWARD -i $DEV_LAN -o $DEV_VPNS -d $VPN -j ACCEPT$IPTABLES -A FORWARD -i $DEV_VPNS -o $DEV_LAN -s $VPN -j ACCEPT$IPTABLES -t nat -A POSTROUTING -o $DEV_VPNS -d $VPN -j MASQUERADE I'm using the wildcard interface 'tun+' because I have multiple client configurations for OpenVPN on my server. In your case, it might be sufficient to specify device 'tun0' only. Simplifying your life - automatic connect on boot Now, that the client connection works flawless, configuration of routing and iptables is okay, we might consider to add another 'laziness' factor into our setup. Due to kernel updates or other circumstances it might be necessary to reboot your system. Wouldn't it be nice that the VPN connections are established during the boot procedure? Yes, of course it would be. To achieve this, we have to configure OpenVPN to automatically start our VPNs via init script. Let's have a look at the responsible 'default' file and adjust the settings accordingly. $ sudo nano /etc/default/openvpn Which should have a similar content to this: # This is the configuration file for /etc/init.d/openvpn## Start only these VPNs automatically via init script.# Allowed values are "all", "none" or space separated list of# names of the VPNs. If empty, "all" is assumed.# The VPN name refers to the VPN configutation file name.# i.e. "home" would be /etc/openvpn/home.conf#AUTOSTART="all"#AUTOSTART="none"#AUTOSTART="home office"## ... more information which remains unmodified ... With the OpenVPN client configuration as described above you would either set AUTOSTART to "all" or to "client" to enable automatic start of your VPN(s) during boot. You should also take care that your iptables commands are executed after the link has been established, too. You can easily test this configuration without reboot, like so: $ sudo service openvpn restart Enjoy stable VPN connections between your Linux system(s) and a WatchGuard Firebox SSL remote server. Cheers, JoKi

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  • T-SQL Tuesday #33: Trick Shots: Undocumented, Underdocumented, and Unknown Conspiracies!

    - by Most Valuable Yak (Rob Volk)
    Mike Fal (b | t) is hosting this month's T-SQL Tuesday on Trick Shots.  I love this choice because I've been preoccupied with sneaky/tricky/evil SQL Server stuff for a long time and have been presenting on it for the past year.  Mike's directives were "Show us a cool trick or process you developed…It doesn’t have to be useful", which most of my blogging definitely fits, and "Tell us what you learned from this trick…tell us how it gave you insight in to how SQL Server works", which is definitely a new concept.  I've done a lot of reading and watching on SQL Server Internals and even attended training, but sometimes I need to go explore on my own, using my own tools and techniques.  It's an itch I get every few months, and, well, it sure beats workin'. I've found some people to be intimidated by SQL Server's internals, and I'll admit there are A LOT of internals to keep track of, but there are tons of excellent resources that clearly document most of them, and show how knowing even the basics of internals can dramatically improve your database's performance.  It may seem like rocket science, or even brain surgery, but you don't have to be a genius to understand it. Although being an "evil genius" can help you learn some things they haven't told you about. ;) This blog post isn't a traditional "deep dive" into internals, it's more of an approach to find out how a program works.  It utilizes an extremely handy tool from an even more extremely handy suite of tools, Sysinternals.  I'm not the only one who finds Sysinternals useful for SQL Server: Argenis Fernandez (b | t), Microsoft employee and former T-SQL Tuesday host, has an excellent presentation on how to troubleshoot SQL Server using Sysinternals, and I highly recommend it.  Argenis didn't cover the Strings.exe utility, but I'll be using it to "hack" the SQL Server executable (DLL and EXE) files. Please note that I'm not promoting software piracy or applying these techniques to attack SQL Server via internal knowledge. This is strictly educational and doesn't reveal any proprietary Microsoft information.  And since Argenis works for Microsoft and demonstrated Sysinternals with SQL Server, I'll just let him take the blame for it. :P (The truth is I've used Strings.exe on SQL Server before I ever met Argenis.) Once you download and install Strings.exe you can run it from the command line.  For our purposes we'll want to run this in the Binn folder of your SQL Server instance (I'm referencing SQL Server 2012 RTM): cd "C:\Program Files\Microsoft SQL Server\MSSQL11\MSSQL\Binn" C:\Program Files\Microsoft SQL Server\MSSQL11\MSSQL\Binn> strings *sql*.dll > sqldll.txt C:\Program Files\Microsoft SQL Server\MSSQL11\MSSQL\Binn> strings *sql*.exe > sqlexe.txt   I've limited myself to DLLs and EXEs that have "sql" in their names.  There are quite a few more but I haven't examined them in any detail. (Homework assignment for you!) If you run this yourself you'll get 2 text files, one with all the extracted strings from every SQL DLL file, and the other with the SQL EXE strings.  You can open these in Notepad, but you're better off using Notepad++, EditPad, Emacs, Vim or another more powerful text editor, as these will be several megabytes in size. And when you do open it…you'll find…a TON of gibberish.  (If you think that's bad, just try opening the raw DLL or EXE file in Notepad.  And by the way, don't do this in production, or even on a running instance of SQL Server.)  Even if you don't clean up the file, you can still use your editor's search function to find a keyword like "SELECT" or some other item you expect to be there.  As dumb as this sounds, I sometimes spend my lunch break just scanning the raw text for anything interesting.  I'm boring like that. Sometimes though, having these files available can lead to some incredible learning experiences.  For me the most recent time was after reading Joe Sack's post on non-parallel plan reasons.  He mentions a new SQL Server 2012 execution plan element called NonParallelPlanReason, and demonstrates a query that generates "MaxDOPSetToOne".  Joe (formerly on the Microsoft SQL Server product team, so he knows this stuff) mentioned that this new element was not currently documented and tried a few more examples to see what other reasons could be generated. Since I'd already run Strings.exe on the SQL Server DLLs and EXE files, it was easy to run grep/find/findstr for MaxDOPSetToOne on those extracts.  Once I found which files it belonged to (sqlmin.dll) I opened the text to see if the other reasons were listed.  As you can see in my comment on Joe's blog, there were about 20 additional non-parallel reasons.  And while it's not "documentation" of this underdocumented feature, the names are pretty self-explanatory about what can prevent parallel processing. I especially like the ones about cursors – more ammo! - and am curious about the PDW compilation and Cloud DB replication reasons. One reason completely stumped me: NoParallelHekatonPlan.  What the heck is a hekaton?  Google and Wikipedia were vague, and the top results were not in English.  I found one reference to Greek, stating "hekaton" can be translated as "hundredfold"; with a little more Wikipedia-ing this leads to hecto, the prefix for "one hundred" as a unit of measure.  I'm not sure why Microsoft chose hekaton for such a plan name, but having already learned some Greek I figured I might as well dig some more in the DLL text for hekaton.  Here's what I found: hekaton_slow_param_passing Occurs when a Hekaton procedure call dispatch goes to slow parameter passing code path The reason why Hekaton parameter passing code took the slow code path hekaton_slow_param_pass_reason sp_deploy_hekaton_database sp_undeploy_hekaton_database sp_drop_hekaton_database sp_checkpoint_hekaton_database sp_restore_hekaton_database e:\sql11_main_t\sql\ntdbms\hekaton\sqlhost\sqllang\hkproc.cpp e:\sql11_main_t\sql\ntdbms\hekaton\sqlhost\sqllang\matgen.cpp e:\sql11_main_t\sql\ntdbms\hekaton\sqlhost\sqllang\matquery.cpp e:\sql11_main_t\sql\ntdbms\hekaton\sqlhost\sqllang\sqlmeta.cpp e:\sql11_main_t\sql\ntdbms\hekaton\sqlhost\sqllang\resultset.cpp Interesting!  The first 4 entries (in red) mention parameters and "slow code".  Could this be the foundation of the mythical DBCC RUNFASTER command?  Have I been passing my parameters the slow way all this time? And what about those sp_xxxx_hekaton_database procedures (in blue)? Could THEY be the secret to a faster SQL Server? Could they promise a "hundredfold" improvement in performance?  Are these special, super-undocumented DIB (databases in black)? I decided to look in the SQL Server system views for any objects with hekaton in the name, or references to them, in hopes of discovering some new code that would answer all my questions: SELECT name FROM sys.all_objects WHERE name LIKE '%hekaton%' SELECT name FROM sys.all_objects WHERE object_definition(OBJECT_ID) LIKE '%hekaton%' Which revealed: name ------------------------ (0 row(s) affected) name ------------------------ sp_createstats sp_recompile sp_updatestats (3 row(s) affected)   Hmm.  Well that didn't find much.  Looks like these procedures are seriously undocumented, unknown, perhaps forbidden knowledge. Maybe a part of some unspeakable evil? (No, I'm not paranoid, I just like mysteries and thought that punching this up with that kind of thing might keep you reading.  I know I'd fall asleep without it.) OK, so let's check out those 3 procedures and see what they reveal when I search for "Hekaton": sp_createstats: -- filter out local temp tables, Hekaton tables, and tables for which current user has no permissions -- Note that OBJECTPROPERTY returns NULL on type="IT" tables, thus we only call it on type='U' tables   OK, that's interesting, let's go looking down a little further: ((@table_type<>'U') or (0 = OBJECTPROPERTY(@table_id, 'TableIsInMemory'))) and -- Hekaton table   Wellllll, that tells us a few new things: There's such a thing as Hekaton tables (UPDATE: I'm not the only one to have found them!) They are not standard user tables and probably not in memory UPDATE: I misinterpreted this because I didn't read all the code when I wrote this blog post. The OBJECTPROPERTY function has an undocumented TableIsInMemory option Let's check out sp_recompile: -- (3) Must not be a Hekaton procedure.   And once again go a little further: if (ObjectProperty(@objid, 'IsExecuted') <> 0 AND ObjectProperty(@objid, 'IsInlineFunction') = 0 AND ObjectProperty(@objid, 'IsView') = 0 AND -- Hekaton procedure cannot be recompiled -- Make them go through schema version bumping branch, which will fail ObjectProperty(@objid, 'ExecIsCompiledProc') = 0)   And now we learn that hekaton procedures also exist, they can't be recompiled, there's a "schema version bumping branch" somewhere, and OBJECTPROPERTY has another undocumented option, ExecIsCompiledProc.  (If you experiment with this you'll find this option returns null, I think it only works when called from a system object.) This is neat! Sadly sp_updatestats doesn't reveal anything new, the comments about hekaton are the same as sp_createstats.  But we've ALSO discovered undocumented features for the OBJECTPROPERTY function, which we can now search for: SELECT name, object_definition(OBJECT_ID) FROM sys.all_objects WHERE object_definition(OBJECT_ID) LIKE '%OBJECTPROPERTY(%'   I'll leave that to you as more homework.  I should add that searching the system procedures was recommended long ago by the late, great Ken Henderson, in his Guru's Guide books, as a great way to find undocumented features.  That seems to be really good advice! Now if you're a programmer/hacker, you've probably been drooling over the last 5 entries for hekaton (in green), because these are the names of source code files for SQL Server!  Does this mean we can access the source code for SQL Server?  As The Oracle suggested to Neo, can we return to The Source??? Actually, no. Well, maybe a little bit.  While you won't get the actual source code from the compiled DLL and EXE files, you'll get references to source files, debugging symbols, variables and module names, error messages, and even the startup flags for SQL Server.  And if you search for "DBCC" or "CHECKDB" you'll find a really nice section listing all the DBCC commands, including the undocumented ones.  Granted those are pretty easy to find online, but you may be surprised what those web sites DIDN'T tell you! (And neither will I, go look for yourself!)  And as we saw earlier, you'll also find execution plan elements, query processing rules, and who knows what else.  It's also instructive to see how Microsoft organizes their source directories, how various components (storage engine, query processor, Full Text, AlwaysOn/HADR) are split into smaller modules. There are over 2000 source file references, go do some exploring! So what did we learn?  We can pull strings out of executable files, search them for known items, browse them for unknown items, and use the results to examine internal code to learn even more things about SQL Server.  We've even learned how to use command-line utilities!  We are now 1337 h4X0rz!  (Not really.  I hate that leetspeak crap.) Although, I must confess I might've gone too far with the "conspiracy" part of this post.  I apologize for that, it's just my overactive imagination.  There's really no hidden agenda or conspiracy regarding SQL Server internals.  It's not The Matrix.  It's not like you'd find anything like that in there: Attach Matrix Database DM_MATRIX_COMM_PIPELINES MATRIXXACTPARTICIPANTS dm_matrix_agents   Alright, enough of this paranoid ranting!  Microsoft are not really evil!  It's not like they're The Borg from Star Trek: ALTER FEDERATION DROP ALTER FEDERATION SPLIT DROP FEDERATION   #tsql2sday

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  • How To Make Hundreds of Complex Photo Edits in Seconds With Photoshop Actions

    - by Eric Z Goodnight
    Have a huge folder of images needing tweaks? A few hundred adjustments may seem like a big, time consuming job—but read one to see how Photoshop can do repetitive tasks automatically, even if you don’t know how to program! Photoshop Actions are a simple way to program simple routines in Photoshop, and are a great time saver, allowing you to re-perform tasks over and over, saving you minutes or hours, depending on the job you have to work on. See how any bunch of images and even some fairly complicated photo tweaking can be done automatically to even hundreds of images at once. When Can I use Photoshop Actions? Photoshop actions are a way of recording the tools, menus, and keys pressed while using the program. Each time you use a tool, adjust a color, or use the brush, it can be recorded and played back over any file Photoshop can open. While it isn’t perfect and can get very confused if not set up correctly, it can automate editing hundreds of images, saving you hours and hours if you have big jobs with complex edits. The image illustrated above is a template for a polaroid-style picture frame. If you had several hundred images, it would actually be a simple matter to use Photoshop Actions to create hundreds of new images inside the frame in almost no time at all. Let’s take a look at how a simple folder of images and some Image editing automation can turn lots of work into a simple and easy job. Creating a New Action Actions is a default part of the “Essentials” panel set Photoshop begins with as a default. If you can’t see the panel button under the “History” button, you can find Actions by going to Window > Actions or pressing Alt + F9. Click the in the Actions Panel, pictured in the previous illustration on the left. Choose to create a “New Set” in order to begin creating your own custom Actions. Name your action set whatever you want. Names are not relevant, you’ll simply want to make it obvious that you have created it. Click OK. Look back in the layers panel. You’ll see your new Set of actions has been added to the list. Click it to highlight it before going on. Click the again to create a “New Action” in your new set. If you care to name your action, go ahead. Name it after whatever it is you’re hoping to do—change the canvas size, tint all your pictures blue, send your image to the printer in high quality, or run multiple filters on images. The name is for your own usage, so do what suits you best. Note that you can simplify your process by creating shortcut keys for your actions. If you plan to do hundreds of edits with your actions, this might be a good idea. If you plan to record an action to use every time you use Photoshop, this might even be an invaluable step. When you create a new Action, Photoshop automatically begins recording everything you do. It does not record the time in between steps, but rather only the data from each step. So take your time when recording and make sure you create your actions the way you want them. The square button stops recording, and the circle button starts recording again. With these basics ready, we can take a look at a sample Action. Recording a Sample Action Photoshop will remember everything you input into it when it is recording, even specific photographs you open. So begin recording your action when your first photo is already open. Once your first image is open, click the record button. If you’re already recording, continue on. Using the File > Place command to insert the polaroid image can be easier for Actions to deal with. Photoshop can record with multiple open files, but it often gets confused when you try it. Keep your recordings as simple as possible to ensure your success. When the image is placed in, simply press enter to render it. Select your background layer in your layers panel. Your recording should be following along with no trouble. Double click this layer. Double clicking your background layer will create a new layer from it. Allow it to be renamed “Layer 0” and press OK. Move the “polaroid” layer to the bottom by selecting it and dragging it down below “Layer 0” in the layers panel. Right click “Layer 0” and select “Create Clipping Mask.” The JPG image is cropped to the layer below it. Coincidentally, all actions described here are being recorded perfectly, and are reproducible. Cursor actions, like the eraser, brush, or bucket fill don’t record well, because the computer uses your mouse movements and coordinates, which may need to change from photo to photo. Click the to set your Photograph layer to a “Screen” blending mode. This will make the image disappear when it runs over the white parts of the polaroid image. With your image layer (Layer 0) still selected, navigate to Edit > Transform > Scale. You can use the mouse to resize your Layer 0, but Actions work better with absolute numbers. Visit the Width and Height adjustments in the top options panel. Click the chain icon to link them together, and adjust them numerically. Depending on your needs, you may need to use more or less than 30%. Your image will resize to your specifications. Press enter to render, or click the check box in the top right of your application. + Click on your bottom layer, or “polaroid” in this case. This creates a selection of the bottom layer. Navigate to Image > Crop in order to crop down to your bottom layer selection Your image is now resized to your bottommost layer, and Photoshop is still recording to that effect. For additional effect, we can navigate to Image > Image Rotation > Arbitrary to rotate our image by a small tilt. Choosing 3 degrees clockwise , we click OK to render our choice. Our image is rotated, and this step is recorded. Photoshop will even record when you save your files. With your recording still going, find File > Save As. You can easily tell Photoshop to save in a new folder, other than the one you have been working in, so that your files aren’t overwritten. Navigate to any folder you wish, but do not change the filename. If you change the filename, Photoshop will record that name, and save all your images under whatever you type. However, you can change your filetype without recording an absolute filename. Use the pulldown tab and select a different filetype—in this instance, PNG. Simply click “Save” to create a new PNG based on your actions. Photoshop will record the destination and the change in filetype. If you didn’t edit the name of your file, it will always use the variable filename of any image you open. (This is very important if you want to edit hundreds of images at once!) Click File > Close or the red “X” in the corner to close your filetype. Photoshop can record that as well. Since we have already saved our image as a JPG, click “NO” to not overwrite your original image. Photoshop will also record your choice of “NO” for subsequent images. In your Actions panel, click the stop button to complete your action. You can always click the record button to add more steps later, if you want. This is how your new action looks with its steps expanded. Curious how to put it into effect? Read on to see how simple it is to use that recording you just made. Editing Lots of Images with Your New Action Open a large number of images—as many as you care to work with. Your action should work immediately with every image on screen, although you may have to test and re-record, depending on how you did. Actions don’t require any programming knowledge, but often can get confused or work in a counter-intuitive way. Record your action until it is perfect. If it works once without errors, it’s likely to work again and again! Find the “Play” button in your Actions Panel. With your custom action selected, click “Play” and your routine will edit, save, and close each file for you. Keep bashing “Play” for each open file, and it will keep saving and creating new files until you run out of work you need to do. And in mere moments, a complicated stack of work is done. Photoshop actions can be very complicated, far beyond what is illustrated here, and can even be combined with scripts and other actions, creating automated creation of potentially very complex files, or applying filters to an entire portfolio of digital photos. Have questions or comments concerning Graphics, Photos, Filetypes, or Photoshop? Send your questions to [email protected], and they may be featured in a future How-To Geek Graphics article. Image Credits: All images copyright Stephanie Pragnell and author Eric Z Goodnight, protected under Creative Commons. Latest Features How-To Geek ETC How To Make Hundreds of Complex Photo Edits in Seconds With Photoshop Actions How to Enable User-Specific Wireless Networks in Windows 7 How to Use Google Chrome as Your Default PDF Reader (the Easy Way) How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Smart Taskbar Is a Thumb Friendly Android Task Launcher Comix is an Awesome Comics Archive Viewer for Linux Get the MakeUseOf eBook Guide to Speeding Up Windows for Free Need Tech Support? Call the Star Wars Help Desk! [Video Classic] Reclaim Vertical UI Space by Adding a Toolbar to the Left or Right Side of Firefox Androidify Turns You into an Android-style Avatar

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  • Clean Code Developer & Certification in IT - MSCC 21.09.2013

    It was a very busy weekend this time, and quite some hectic to organise the second meetup on a Saturday for the Mauritius Software Craftsmanship Community (MSCC) but it was absolutely fun. Following, I'm writing a brief summary about the topics we spoke about and the new impulses I got. "What a meetup... I was positively impressed. At the beginning I thought that noone would actually show up but then by the time the room got filled. Lots of conversation, great dialogues and fantastic networking between fresh students, experienced students, experienced employees, and self-employed attendees. That's what community is all about!" Above quote was my first reaction shortly after the gathering. And despite being busy during the weekend and yesterday, I took my time to reflect a little bit on things happened and statements made before writing it here on my blog. Additionally, I was also very curious about possible reactions and blogs from other attendees. Reactions from other craftsmen Let me quickly give you some links and quotes from others first... "Like Jochen posted on facebook, that was indeed a 5+ hours marathon (maybe 4 hours for me but still) … Wohoo! We’re indeed a bunch of crazy geeks who did not realise how time flew as we dived into the myriad discussions that sprouted. Yet in the end everyone was happy (:" -- Ish on MSCC meetup - The marathon (: "And the 4hours spent @ Talking drums bore its fruit..I was doing something I never did before....reading the borrowed book while walking....and though I was not that familiar with things mentionned in the book...I was skimming,scanning & flipping...reading titles...short paragraphs...and I skipped pages till I reached home." -- Yannick on Mauritius Software Craftsmanship 1st Meet-up "Hi Developers, Just wanted to share with you the meetups i attended last Saturday - [...] - The second meetup is the one hosted by Jochen Kirstätter, the MSCC, where the attendees were Craftsman, no woman, this time - all sharing the same passion of being a developer - even though it is on different platforms(Windows - Windows Phone - Linux - Adobe(yes a designer) - .Net) - but we manage to sit at the same table - sharing developer views and experience in the corporate world - also talking about good practice when coding( where Jochen initiated a discussion on Clean Coding ) i could not stay till the end - but from what i have heard - the longer you stay the more fun you have till 1600. Developers in the Facebook grouping i invite you to stay tuned about the various developer communities popping up - where you can come to share and learn good practices, develop the entrepreneurial spirit, and learn and share your passion about technologies" -- Arnaud on Facebook More feedback has been posted on the event directly. So, should I really write more? Wouldn't that spoil the impressions? Starting the day with a surprise Indeed, I was very pleased to stumble over the existence of Mobile Monday Mauritius on LinkedIn, an association about any kind of mobile app development, mobile gadgets and latest smartphones on the market. Despite the Monday in their name they had scheduled their recent meeting on Saturday between 10:00 and 12:00hrs. Wow, what a coincidence! Let's grap the bull by its horns and pay them an introductory visit. As they chose the Ebene Accelerator at the Orange Tower in Ebene it was a no-brainer to leave home a bit earlier and stop by. It was quite an experience and fun to talk to the geeks over there. Really looking forward to organise something together.... Arriving at the venue As the children got a bit uneasy at the MoMo gathering and I didn't want to disturb them too much, we arrived early at Bagatelle. Well, no problems as we went for a decent breakfast at Food Lover's Market. Shortly afterwards we went to our venue location, Talking Drums, and prepared the room for the meeting. We only had to take off a repro-painting of the wall in order to have a decent area for the projector. All went very smooth and my two little ones were of great help. Just in time, our first craftsman Avinash arrived on the spot. And then the waiting started... Luckily, not too long. Bit by bit more and more IT people came to join our meeting. Meanwhile, I used the time to give a brief introduction about the MSCC in general, what we are (hm, maybe I am) trying to achieve and that the recent phase is completely focused on creating more awareness that a community like the MSCC is active here in Mauritius. As soon as we reached some 'critical mass' of about ten people I asked everyone for a short introduction and bio, just in case... Conversation between participants started to kick in and we were actually more networking than having a focus on our topics of the day. Quick updates on latest news and development around the MSCC Finally, Clean Code Developer No matter how the position is actually called, whether it is Software Engineer, Software Developer, Programmer, Architect, or Craftsman, anyone working in IT is facing almost the same obstacles. As for the process of writing software applications there are re-occurring patterns and principles combined with some common exercise and best practices on how to resolve them. Initiated by the must-read book 'Clean Code' by Robert C. Martin (aka Uncle Bob) the concept of the Clean Code Developer (CCD) was born already some years ago. CCD is much likely to traditional martial arts where you create awareness of certain principles and learn how to apply practices to improve your style. The CCD initiative recommends to indicate your level of knowledge and experience with coloured wrist bands - equivalent to the belt colours - for various reasons. Frankly speaking, I think that the biggest advantage here is provided by the obvious recognition of conceptual understanding. For example, take the situation of a team meeting... A member with a higher grade in CCD, say Green grade, sees that there are mainly Red grades to talk to, and adjusts her way of communication to their level of understanding. The choice of words might change as certain elements of CCD are not yet familiar to all team members. So instead of talking in an abstract way which only Green grades could follow the whole scenario comes down to Red grade level. Different story, better results... Similar to learning martial arts, we only covered two grades during this occasion - black and red. Most interestingly, there was quite some positive feedback and lots of questions about the principles and practices of the red grade. And we gathered real-world examples from various craftsman and discussed them. Following the Clean Code Developer Red Grade and some annotations from our meetup: CCD Red Grade - Principles Don't Repeat Yourself - DRY Keep It Simple, Stupid (and Short) - KISS Beware of Optimisations! Favour Composition over Inheritance - FCoI Interestingly most of the attendees already heard about those key words but couldn't really classify or categorize them. It's very similar to a situation in which you do not the particular for a thing and have to describe it to others... until someone tells you the actual name and suddenly all is very simple. CCD Red Grade - Practices Follow the Boy Scouts Rule Root Cause Analysis - RCA Use a Version Control System Apply Simple Refactoring Pattern Reflect Daily Introduction to the principles and practices of Clean Code Developer - here: Red Grade As for the various ToDo's we commonly agreed that the Boy Scout Rule clearly is not limited to software development or IT administration but applies to daily life in general. Same for the root cause analysis, btw. We really had good stories with surprisingly endings and conclusions. A quick check about who is using a version control system brought more drive into the conversation. Not only that we had people that aren't using any VCS at all, we also had the 'classic' approach of backup folders and naming conventions as well as the VCS 'junkie' that has to use multiple systems at a time. Just for the records: Git and GitHub seem to be in favour of some of the attendees. Regarding the daily reflection at the end of the day we came up with an easy solution: Wrap it up as a blog entry! Certifications in IT This is kind of a controversy in IT in general. Is it interesting to go for certifications or are they completely obsolete? What are the possibilities to get certified? What are the options we have in Mauritius? How would certificates stand compared to other educational tracks like Computer Science or Web Design. The ratio between craftsmen with certifications like MCP, MSTS, CCNA or LPI versus the ones without wasn't in favour for the first group but there was a high interest in the topic itself and some were really surprised to hear that exam preparations are completely free available online including temporarily voucher codes for either discounts or completely free exams. Furthermore, we discussed possible options on forming so-called study groups on a specific certificates and organising more frequent meetups in order to learn together. Taking into consideration that we have sponsored access to the video course material of Pluralsight (and now PeepCode as well as TrainSignal), we might give it a try by the end of the year. Current favourites are LPIC Level 1 and one of the Microsoft exams 40-78x. Feedback and ideas for the MSCC The closing conversations and discussions about how the MSCC is recently doing, what are the possibilities and what's (hopefully) going to happen in the future were really fertile and I made a couple of mental bullet points which I'm looking forward to tackle down together with orher craftsmen. Eventually, it might be a good option to elaborate on some issues during our weekly Code & Coffee sessions one Wednesday morning. Active discussion on various IT topics like certifications (LPI, MCP, CCNA, etc) and sharing experience Finally, we made it till the end of the planned time. Well, actually the talk was still on and we continued even after 16:00hrs. Unfortunately, we (the children and I) had to leave for evening activities. My resume of the day... It was great to have 15 craftsmen in one room. There are hundreds of IT geeks out there in Mauritius, and as Mauritius Software Craftsmanship Community we still have a lot of work to do to pass on the message to some more key players and companies. Currently, it seems that we are able to attract a good number of students in Computer Science... but we have a lot more to offer, even or especially for IT people on the job. I'm already looking forward to our next Saturday meetup in the near future. PS: Meetup pictures are courtesy of Nirvan Pagooah. Thanks for sharing...

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  • C#: Handling Notifications: inheritance, events, or delegates?

    - by James Michael Hare
    Often times as developers we have to design a class where we get notification when certain things happen. In older object-oriented code this would often be implemented by overriding methods -- with events, delegates, and interfaces, however, we have far more elegant options. So, when should you use each of these methods and what are their strengths and weaknesses? Now, for the purposes of this article when I say notification, I'm just talking about ways for a class to let a user know that something has occurred. This can be through any programmatic means such as inheritance, events, delegates, etc. So let's build some context. I'm sitting here thinking about a provider neutral messaging layer for the place I work, and I got to the point where I needed to design the message subscriber which will receive messages from the message bus. Basically, what we want is to be able to create a message listener and have it be called whenever a new message arrives. Now, back before the flood we would have done this via inheritance and an abstract class: 1:  2: // using inheritance - omitting argument null checks and halt logic 3: public abstract class MessageListener 4: { 5: private ISubscriber _subscriber; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber) 11: { 12: _subscriber = subscriber; 13: _messageThread = new Thread(MessageLoop); 14: _messageThread.Start(); 15: } 16:  17: // user will override this to process their messages 18: protected abstract void OnMessageReceived(Message msg); 19:  20: // handle the looping in the thread 21: private void MessageLoop() 22: { 23: while(!_isHalted) 24: { 25: // as long as processing, wait 1 second for message 26: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 27: if(msg != null) 28: { 29: OnMessageReceived(msg); 30: } 31: } 32: } 33: ... 34: } It seems so odd to write this kind of code now. Does it feel odd to you? Maybe it's just because I've gotten so used to delegation that I really don't like the feel of this. To me it is akin to saying that if I want to drive my car I need to derive a new instance of it just to put myself in the driver's seat. And yet, unquestionably, five years ago I would have probably written the code as you see above. To me, inheritance is a flawed approach for notifications due to several reasons: Inheritance is one of the HIGHEST forms of coupling. You can't seal the listener class because it depends on sub-classing to work. Because C# does not allow multiple-inheritance, I've spent my one inheritance implementing this class. Every time you need to listen to a bus, you have to derive a class which leads to lots of trivial sub-classes. The act of consuming a message should be a separate responsibility than the act of listening for a message (SRP). Inheritance is such a strong statement (this IS-A that) that it should only be used in building type hierarchies and not for overriding use-specific behaviors and notifications. Chances are, if a class needs to be inherited to be used, it most likely is not designed as well as it could be in today's modern programming languages. So lets look at the other tools available to us for getting notified instead. Here's a few other choices to consider. Have the listener expose a MessageReceived event. Have the listener accept a new IMessageHandler interface instance. Have the listener accept an Action<Message> delegate. Really, all of these are different forms of delegation. Now, .NET events are a bit heavier than the other types of delegates in terms of run-time execution, but they are a great way to allow others using your class to subscribe to your events: 1: // using event - ommiting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private bool _isHalted = false; 6: private Thread _messageThread; 7:  8: // assign the subscriber and start the messaging loop 9: public MessageListener(ISubscriber subscriber) 10: { 11: _subscriber = subscriber; 12: _messageThread = new Thread(MessageLoop); 13: _messageThread.Start(); 14: } 15:  16: // user will override this to process their messages 17: public event Action<Message> MessageReceived; 18:  19: // handle the looping in the thread 20: private void MessageLoop() 21: { 22: while(!_isHalted) 23: { 24: // as long as processing, wait 1 second for message 25: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 26: if(msg != null && MessageReceived != null) 27: { 28: MessageReceived(msg); 29: } 30: } 31: } 32: } Note, now we can seal the class to avoid changes and the user just needs to provide a message handling method: 1: theListener.MessageReceived += CustomReceiveMethod; However, personally I don't think events hold up as well in this case because events are largely optional. To me, what is the point of a listener if you create one with no event listeners? So in my mind, use events when handling the notification is optional. So how about the delegation via interface? I personally like this method quite a bit. Basically what it does is similar to inheritance method mentioned first, but better because it makes it easy to split the part of the class that doesn't change (the base listener behavior) from the part that does change (the user-specified action after receiving a message). So assuming we had an interface like: 1: public interface IMessageHandler 2: { 3: void OnMessageReceived(Message receivedMessage); 4: } Our listener would look like this: 1: // using delegation via interface - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private IMessageHandler _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler.OnMessageReceived(msg); 28: } 29: } 30: } 31: } And they would call it by creating a class that implements IMessageHandler and pass that instance into the constructor of the listener. I like that this alleviates the issues of inheritance and essentially forces you to provide a handler (as opposed to events) on construction. Well, this is good, but personally I think we could go one step further. While I like this better than events or inheritance, it still forces you to implement a specific method name. What if that name collides? Furthermore if you have lots of these you end up either with large classes inheriting multiple interfaces to implement one method, or lots of small classes. Also, if you had one class that wanted to manage messages from two different subscribers differently, it wouldn't be able to because the interface can't be overloaded. This brings me to using delegates directly. In general, every time I think about creating an interface for something, and if that interface contains only one method, I start thinking a delegate is a better approach. Now, that said delegates don't accomplish everything an interface can. Obviously having the interface allows you to refer to the classes that implement the interface which can be very handy. In this case, though, really all you want is a method to handle the messages. So let's look at a method delegate: 1: // using delegation via delegate - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler(msg); 28: } 29: } 30: } 31: } Here the MessageListener now takes an Action<Message>.  For those of you unfamiliar with the pre-defined delegate types in .NET, that is a method with the signature: void SomeMethodName(Message). The great thing about delegates is it gives you a lot of power. You could create an anonymous delegate, a lambda, or specify any other method as long as it satisfies the Action<Message> signature. This way, you don't need to define an arbitrary helper class or name the method a specific thing. Incidentally, we could combine both the interface and delegate approach to allow maximum flexibility. Doing this, the user could either pass in a delegate, or specify a delegate interface: 1: // using delegation - give users choice of interface or delegate 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // passes the interface method as a delegate using method group 19: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 20: : this(subscriber, handler.OnMessageReceived) 21: { 22: } 23:  24: // handle the looping in the thread 25: private void MessageLoop() 26: { 27: while(!_isHalted) 28: { 29: // as long as processing, wait 1 second for message 30: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 31: if(msg != null) 32: { 33: _handler(msg); 34: } 35: } 36: } 37: } } This is the method I tend to prefer because it allows the user of the class to choose which method works best for them. You may be curious about the actual performance of these different methods. 1: Enter iterations: 2: 1000000 3:  4: Inheritance took 4 ms. 5: Events took 7 ms. 6: Interface delegation took 4 ms. 7: Lambda delegate took 5 ms. Before you get too caught up in the numbers, however, keep in mind that this is performance over over 1,000,000 iterations. Since they are all < 10 ms which boils down to fractions of a micro-second per iteration so really any of them are a fine choice performance wise. As such, I think the choice of what to do really boils down to what you're trying to do. Here's my guidelines: Inheritance should be used only when defining a collection of related types with implementation specific behaviors, it should not be used as a hook for users to add their own functionality. Events should be used when subscription is optional or multi-cast is desired. Interface delegation should be used when you wish to refer to implementing classes by the interface type or if the type requires several methods to be implemented. Delegate method delegation should be used when you only need to provide one method and do not need to refer to implementers by the interface name.

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