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• Secure hash and salt for PHP passwords

  - by luiscubal

  It is currently said that MD5 is partially unsafe. Taking this into consideration, I'd like to know which mechanism to use for password protection. Is “double hashing” a password less secure than just hashing it once? Suggests that hashing multiple times may be a good idea. How to implement password protection for individual files? Suggests using salt. I'm using PHP. I want a safe and fast password encryption system. Hashing a password a million times may be safer, but also slower. How to achieve a good balance between speed and safety? Also, I'd prefer the result to have a constant number of characters. The hashing mechanism must be available in PHP It must be safe It can use salt (in this case, are all salts equally good? Is there any way to generate good salts?) Also, should I store two fields in the database(one using MD5 and another one using SHA, for example)? Would it make it safer or unsafer? In case I wasn't clear enough, I want to know which hashing function(s) to use and how to pick a good salt in order to have a safe and fast password protection mechanism. EDIT: The website shouldn't contain anything too sensitive, but still I want it to be secure. EDIT2: Thank you all for your replies, I'm using hash("sha256",$salt.":".$password.":".$id) Questions that didn't help: What's the difference between SHA and MD5 in PHP Simple Password Encryption Secure methods of storing keys, passwords for asp.net How would you implement salted passwords in Tomcat 5.5

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• Stack and Hash joint

  - by Alexandru

  I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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• Debugging SQL Server Slowness: Same Database, Different Servers

  - by Craig Walker

  For a while now we've been having anecdotal slowness on our newly-minted (VMWare-based) SQL Server 2005 database servers. Recently the problem has come to a head and I've started looking for the root cause of the issue. Here's the weird part: on the stored procedure that I'm using as a performance test case, I get a 30x difference in the execution speed depending on which DB server I run it on. This is using the same database (mdf) and log (ldf) files, detached, copied, and reattached from the slow server to the fast one. This doesn't appear to be a (virtualized) hardware issue: he slow server has 4x the CPU capacity and 2x the memory as the fast one. As best as I can tell, the problem lies in the environment/configuration of the servers (either operating system or SQL Server installation). However, I've checked a bunch of variables (SQL Server config options, running services, disk fragmentation) and found nothing that has made a difference in testing. What things should I be looking at? What tools can I use to investigate why this is happening?

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• Uploadify and rails 3 authenticity tokens

  - by Ceilingfish

  Hi chaps, I'm trying to get a file upload progress bar working in a rails 3 app using uploadify (http://www.uploadify.com) and I'm stuck at authenticity tokens. My current uploadify config looks like <script type="text/javascript" charset="utf-8"> $(document).ready(function() { $("#zip_input").uploadify({ 'uploader': '/flash/uploadify.swf', 'script': $("#upload").attr('action'), 'scriptData': { 'format': 'json', 'authenticity_token': encodeURIComponent('<%= form_authenticity_token if protect_against_forgery? %>') }, 'fileDataName': "world[zip]", //'scriptAccess': 'always', // Incomment this, if for some reason it doesn't work 'auto': true, 'fileDesc': 'Zip files only', 'fileExt': '*.zip', 'width': 120, 'height': 24, 'cancelImg': '/images/cancel.png', 'onComplete': function(event, data) { $.getScript(location.href) }, // We assume that we can refresh the list by doing a js get on the current page 'displayData': 'speed' }); }); </script> But I am getting this response from rails: Started POST "/worlds" for 127.0.0.1 at 2010-04-22 12:39:44 ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken): Rendered /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta3/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms) Rendered /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (6.6ms) Rendered /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta3/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (12.2ms) This appears to be because I'm not sending the authentication cookie along with the request. Does anyone know how I can get the values I should be sending there, and how I can make rails read it from HTTP POST rather than trying to find it as a cookie?

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• Looking for ideas how to refactor my (complex) algorithm

  - by _simon_

  I am trying to write my own Game of Life, with my own set of rules. First 'concept', which I would like to apply, is socialization (which basicaly means if the cell wants to be alone or in a group with other cells). Data structure is 2-dimensional array (for now). In order to be able to move a cell to/away from a group of another cells, I need to determine where to move it. The idea is, that I evaluate all the cells in the area (neighbours) and get a vector, which tells me where to move the cell. Size of the vector is 0 or 1 (don't move or move) and the angle is array of directions (up, down, right, left). This is a image with representation of forces to a cell, like I imagined it (but reach could be more than 5): Let's for example take this picture: Forces from lower left neighbour: down (0), up (2), right (2), left (0) Forces from right neighbour : down (0), up (0), right (0), left (2) sum : down (0), up (2), right (0), left (0) So the cell should go up. I could write an algorithm with a lot of if statements and check all cells in the neighbourhood. Of course this algorithm would be easiest if the 'reach' parameter is set to 1 (first column on picture 1). But what if I change reach parameter to 10 for example? I would need to write an algorithm for each 'reach' parameter in advance... How can I avoid this (notice, that the force is growing potentialy (1, 2, 4, 8, 16, 32,...))? Can I use specific design pattern for this problem? Also: the most important thing is not speed, but to be able to extend initial logic. Things to take into consideration: reach should be passed as a parameter i would like to change function, which calculates force (potential, fibonacci) a cell can go to a new place only if this new place is not populated watch for corners (you can't evaluate right and top neighbours in top-right corner for example)

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• Setting up a "cookieless domain" to improve site performance

  - by Django Reinhardt

  I was reading in Google's documentation about improving site speed. One of their recommendations is serving static content (images, css, js, etc.) from a "cookieless domain": Static content, such as images, JS and CSS files, don't need to be accompanied by cookies, as there is no user interaction with these resources. You can decrease request latency by serving static resources from a domain that doesn't serve cookies. Google then says that the best way to do this is to buy a new domain and set it to point to your current one: To reserve a cookieless domain for serving static content, register a new domain name and configure your DNS database with a CNAME record that points the new domain to your existing domain A record. Configure your web server to serve static resources from the new domain, and do not allow any cookies to be set anywhere on this domain. In your web pages, reference the domain name in the URLs for the static resources. This is pretty straight forward stuff, except for the bit where it says to "configure your web server to serve static resources from the new domain, and do not allow any cookies to be set anywhere on this domain". From what I've read, there's no setting in IIS that allows you to say "serve static resources", so how do I prevent ASP.NET from setting cookies on this new domain? At present, even if I'm just requesting a .jpg from the new domain, it sets a cookie on my browser, even though our application's cookies are set to our old domain. For example, ASP.NET sets an ".ASPXANONYMOUS" cookie that (as far as I'm aware) we're not telling it to do. Apologies if this is a real newb question, I'm new at this! Thanks.

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• iPhone - dequeueReusableCellWithIdentifier usage

  - by Jukurrpa

  Hi, I'm working on a iPhone app which has a pretty large UITableView with data taken from the web, so I'm trying to optimize its creation and usage. I found out that dequeueReusableCellWithIdentifier is pretty useful, but after seeing many source codes using this, I'm wondering if the usage I make of this function is the good one. Here is what people usually do: UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"Cell"]; // Add elements to the cell return cell; And here is the way I did it: NSString identifier = [NSString stringWithFormat:@"Cell @d", indexPath.row]: // The cell row UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier]; if (cell != nil) return cell; cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:identifier]; // Add elements to the cell return cell; The difference is that people use the same identifier for every cell, so dequeuing one only avoids to alloc a new one. For me, the point of queuing was to give each cell a unique identifier, so when the app asks for a cell it already displayed, neither allocation nor element adding have to be done. In fine I don't know which is best, the "common" method ceils the table's memory usage to the exact number of cells it display, whislt the method I use seems to favor speed as it keeps all calculated cells, but can cause large memory consumption (unless there's an inner limit to the queue). Am I wrong to use it this way? Or is it just up to the developper, depending on his needs?

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• Find unique vertices from a 'triangle-soup'

  - by sum1stolemyname

  I am building a CAD-file converter on top of two libraries (Opencascade and DWF Toolkit). However, my question is plattform agnostic: Given: I have generated a mesh as a list of triangular faces form a model constructed through my application. Each Triangle is defined through three vertexes, which consist of three floats (x, y & z coordinate). Since the triangles form a mesh, most of the vertices are shared by more then one triangle. Goal: I need to find the list of unique vertices, and to generate an array of faces consisting of tuples of three indices in this list. What i want to do is this: //step 1: build a list of unique vertices for each triangle for each vertex in triangle if not vertex in listOfVertices Add vertex to listOfVertices //step 2: build a list of faces for each triangle for each vertex in triangle Get Vertex Index From listOfvertices AddToMap(vertex Index, triangle) While I do have an implementation which does this, step1 (the generation of the list of unique vertices) is really slow in the order of O(n!), since each vertex is compared to all vertices already in the list. I thought "Hey, lets build a hashmap of my vertices' components using std::map, that ought to speed things up!", only to find that generating a unique key from three floating point values is not a trivial task. Here, the experts of stackoverflow come into play: I need some kind of hash-function which works on 3 floats, or any other function generating a unique value from a 3d-vertex position.

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• Does replace into have a where clause?

  - by Lajos Arpad

  I'm writing an application and I'm using MySQL as DBMS, we are downloading property offers and there were some performance issues. The old architecture looked like this: A property is updated. If the number of affected rows is not 1, then the update is not considered successful, elseway the update query solves our problem. If the update was not successful, and the number of affected rows is more than 1, we have duplicates and we delete all of them. After we deleted duplicates if needed if the update was not successful, an insert happens. This architecture was working well, but there were some speed issues, because properties are deleted if they were not updated for 15 days. Theoretically the main problem is deleting properties, because some properties are alive for months and the indexes are very far from each other (we are talking about 500, 000+ properties). Our host told me to use replace into instead of deleting properties and all deprecated properties should be considered as DEAD. I've done this, but problems started to occur because of syntax error and I couldn't find anywhere an example of replace into with a where clause (I'd like to replace a DEAD property with the new property instead of deleting the old property and insert a new to assure optimization). My query looked like this: replace into table_name(column1, ..., columnn) values(value1, ..., valuen) where ID = idValue Of course, I've calculated idValue and handled everything but I had a syntax error. I would like to know if I'm wrong and there is a where clause for replace into. I've found an alternative solution, which is even better than replace into (using simply an update query) because deletes are happening behind the curtains if I use replace into, but I would like to know if I'm wrong when I say that replace into doesn't have a where clause. For more reference, see this link: http://dev.mysql.com/doc/refman/5.0/en/replace.html Thank you for your answers in advance, Lajos Árpád

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• Is there any special tool for interactive GUI development

  - by niko

  Hi, Currently I am preparing exercises about networks and mobile communications for students. I was thinking about creating an interactive user-interface which enables the user to drag&drop predefined elements and then implement a logic based upon element distances etc. An example would be to place two base stations (a predefined element with several properties), set the scale in the interface and then check the signal interferrence in the environment (user-interface). The first part might be too abstract whereas the example might be too specific, but I was wondering whether there already exists any friendly framework or language which enables developers to create interactive interfaces (for teaching/learning purpouses) in short ammount of time. Usually I write applications for PC environment in .NET but in this case it would take too much time to create a specific interface for every exercise. I would appreciate if anyone could suggest any way to create interactive user-interface in short ammount of time. Are there any special programming languages or development tools for this kind of applications or are there any useful frameworks for .NET, Java or any other language to speed up the development of user-interfaces? Thank you!

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• Delphi threads deadlock

  - by Lobuno

  Hello! I am having a problem sometimes with a deadlock when destroying some threads. I've tried to debug the problem but the deadlock never seems to exist when debugging in the IDE, perhaps because of the low speed of the events in the ide. The problem: The main thread creates several threads when the application starts. The threads are always alive and synchronizing with the main thread. No problems at all. The threads are destroyed when the applcation ends (mainform.onclose) like this: thread1.terminate; thread1.waitfor; thread1.free; and so on. but some times one of the threads (which logs some string to a memo, using synchronize) will lock the whole application when closing. I suspect that the thread is synchronizing when I call waitform and the harmaggeddon happens, but that's is just a guess because the deadlock never happens when debbuging (or I've never been able to reproduce it anyway). Any advice?

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• GAE Task Queue oddness

  - by b3nw

  I have been testing the taskqueue with mixed success. Currently I am using the default queue, in default settings ect ect.... I have a test url setup which inserts about 8 tasks into the queue. With short order, all 8 are completed properly. So far so good. The problem comes up when I re-load that url twice under say a minute. Now watching the task queue, all the tasks are added properly, but only the first batch execute it seems. But the "Run in Last Minute" # shows the right number of tasks being run.... The request logs tell a different story. They show only the first set of 8 running, but all task creation urls working successfully. The oddness of this is that if I wait say a minute between the task creation url requests, it will work fine. Oddly enough changing the bucket_size or execution speed does not seem to help. Only the first batch are executed. I have also reduced the number of requests all the way down to 2, and still found only the first 2 execute. Any others added display the same issues as above. Any suggestions? Thanks

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• How to modernize an enormous legacy database?

  - by smayers81

  I have a question, just looking for suggestions here. So, my application is 'modernizing' a desktop application by converting it to the web, with an ICEFaces UI and server side written in Java. However, they are keeping around the same Oracle database, which at current count has about 700-900 tables and probably a billion total records in the tables. Some individual tables have 250 million rows, many have over 25 million. Needless to say, the database is not scaling well. As a result, the performance of the application is looking to be abysmal. The architects / decision makers-that-be have all either refused or are unwilling to restructure the persistence. So, basically we are putting a fresh coat of paint on a functional desktop application that currently serves most user needs and does so with relative ease and quick performance. I am having trouble sleeping at night thinking of how poorly this application is going to perform and how difficult it is going to be for everyday users to do their job. So, my question is, what options do I have to mitigate this impending disaster? Is there some type of intermediate layer I can put in between the database and the Java code to speed up performance while at the same time keeping the database structure intact? Caching is obviously an option, but I don't see that as being a cure-all. Is it possible to layer a NoSQL DB in between or something?

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• How to implement a counter when using golang's goroutine?

  - by MrROY

  I'm trying to make a queue struct that have push and pop functions. I need to use 10 threads push and another 10 threads pop data, just like i did in the code below. Questions : 1. I need to print out how much i have pushed/popped, but i don't know how to do that. 2. Is there anyway to speed up my code ? the code is too slow for me. package main import ( "runtime" "time" ) const ( DATA_SIZE_PER_THREAD = 10000000 ) type Queue struct { records string } func (self Queue) push(record chan interface{}) { // need push counter record <- time.Now() } func (self Queue) pop(record chan interface{}) { // need pop counter <- record } func main() { runtime.GOMAXPROCS(runtime.NumCPU()) //record chan record := make(chan interface{},1000000) //finish flag chan finish := make(chan bool) queue := new(Queue) for i:=0; i<10; i++ { go func() { for j:=0; j<DATA_SIZE_PER_THREAD; j++ { queue.push(record) } finish<-true }() } for i:=0; i<10; i++ { go func() { for j:=0; j<DATA_SIZE_PER_THREAD; j++ { queue.pop(record) } finish<-true }() } for i:=0; i<20; i++ { <-finish } }

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• Vote on Pros and Cons of Java HTML to XML cleaners

  - by George Bailey

  I am looking to allow HTML emails (and other HTML uploads) without letting in scripts and stuff. I plan to have a white list of safe tags and attributes as well as a whitelist of CSS tags and value regexes (to prevent automatic return receipt). I asked a question: Parse a badly formatted XML document (like an HTML file) I found there are many many ways to do this. Some systems have built in sanitizers (which I don't care so much about). This page is a very nice listing page but I get kinda lost http://java-source.net/open-source/html-parsers It is very important that the parsers never throw an exception. There should always be best guess results to the parse/clean. It is also very important that the result is valid XML that can be traversed in Java. I posted some product information and said Community Wiki. Please post any other product suggestions you like and say Community Wiki so they can be voted on. Also any comments or wiki edits on what part of a certain product is better and what is not would be greatly appreciated. (for example,, speed vs accuracy..) It seems that we will go with either jsoup (seems more active and up to date) or TagSoup (compatible with JDK4 and been around awhile). A +1 for any of these products would be if they could convert all style sheets into inline style on the elements.

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• LINQ compiled query DataBind issue

  - by Brian

  Hello All, I have a pretty extensive reporting page that uses LINQ. There is one main function that returns an IQueryable object. I then further filter / aggregate the returned query depending on the report the user needs. I changed this function to a compiled query, it worked great, and the speed increase was astonishing. The only problem comes when i want to databind the results. I am databinding to a standard asp.net GridView and it works fine, no problems. I am also databinding to an asp.net chart control, this is where my page is throwing an error. this works well: GridView gv = new GridView(); gv.DataSource = gridSource; But this does not: Series s1 = new Series("Series One"); s1.Points.DataBindXY(gridSource, "Month", gridSource, "Success"); The error i receive is this: System.NotSupportedException Specified method is not supported When i look into my gridSource var at run time i see this using a typical linq query: SELECT [t33].[value2] AS [Year], [t33].[value22] AS [Month], [t33].[value3] AS [Calls]...... I see this after i change the query to compiled: {System.Linq.OrderedEnumerable<<>f__AnonymousType15<string,int,int,int,int,int,int,int>,string>} This is obviously the reason why the databindxy is no longer working, but i am not sure how to get around it. Any help would be appreciated! Thanks

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• java distributed cache for low latency, high availability

  - by Shahbaz

  I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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• YUI: ensuring DOM elements and scripts are ready

  - by dound

  If I put my inline script after the DOM elements it interacts with, should I still use YUI 3's domready event? I haven't noticed any problems, and it seems like I can count on the browser loading the page sequentially. (I already use YUI().use('node', ... to make sure the YUI functions I need have been loaded since the YUI script is a separate file.) Is there a way to speed up the loading of widgets like YUI 2's calendar? I load the appropriate script in <head> element of my page. I use YUI().use('yui2-calendar', ... to make sure the Calendar widget is available. Unfortunately, this causes a short but noticeable delay when I load my page with the calendar. If I omit the YUI().use('yui2-calendar', ... code then it shows up without a noticeable delay - but I guess this could cause the Calendar to not show up at all if the YUI script doesn't load in time? With regards to #2, is it possible to reduce the visual artifact of the calendar not being present and then showing up? I've made it slightly better by specifying a height and width for the parent div so that at least the space is already allocated = minimal shifting around when it does load.

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• What is the fastest way to pull a few element values out of XML files in Perl?

  - by Anon Guy

  I have a bunch of XML files that are about 1-2 megabytes in size. Actually, more than a bunch, there are millions. They're all well-formed and many are even validated against their schema (confirmed with libxml2). All were created by the same app, so they're in a consistent format (though this could theoretically change in the future). I want to check the values of one element in each file from within a Perl script. Speed is important (I'd like to take less than a second per file) and as noted I already know the files are well-formed. I am sorely tempted to simply 'open' the files in Perl and scan through until I see the element I am looking for, grab the value (which is near the start of the file), and close the file. On the other hand, I could use an XML parser (which might protect me from future changes to the XML formatting) but I suspect it will be slower than I'd like. Can anyone recommend an appropriate approach and/or parser? Thanks in advance.

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• WCF Double Hop questions about Security and Binding.

  - by Ken Maglio

  Background information: .Net Website which calls a service (aka external service) facade on an app server in the DMZ. This external service then calls the internal service which is on our internal app server. From there that internal service calls a stored procedure (Linq to SQL Classes), and passes the serialized data back though to the external service, and from there back to the website. We've done this so any communication goes through an external layer (our external app server) and allows interoperability; we access our data just like our clients consuming our services. We've gotten to the point in our development where we have completed the system and it all works, the double hop acts as it should. However now we are working on securing the entire process. We are looking at using TransportWithMessageCredentials. We want to have WS2007HttpBinding for the external for interoperability, but then netTCPBinding for the bridge through the firewall for security and speed. Questions: If we choose WS2007HttpBinding as the external services binding, and netTCPBinding for the internal service is this possible? I know WS-* supports this as does netTCP, however do they play nice when passing credential information like user/pass? If we go to Kerberos, will this impact anything? We may want to do impersonation in the future. If you can when you answer post any reference links about why you're answering the way you are, that would be very helpful to us. Thanks!

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• JSON: Jackson stream parser - is it really worth it?

  - by synic

  I'm making pretty heavy use of JSON parsing in an app I'm writing. Most of what I have done is already implemented using Android's built in JSONObject library (is it json-lib?). JSONObject appears to create instances of absolutely everything in the JSON string... even if I don't end up using all of them. My app currently runs pretty well, even on a G1. My question is this: are the speed and memory benefits from using a stream parser like Jackson worth all the trouble? By trouble, I mean this: As far as I can tell, there are three downsides to using Jackson instead of the built in library: Dependency on an external library. This makes your .apk bigger in the end. Not a huge deal. Your app is more fragile. Since the parsing is not done automatically, it is more vulnerable to changes in the JSON text that it's parsing. I'm extremely worried that malformed JSON will result in infinite loops (as pull parsing requires a lot of while loops). Writing code to parse JSON via a stream parser is ugly and tedious.

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• Unhandled Exception with c++ app on Visual Studio 2008 release build - occurs when returning from fu

  - by Rich

  Hi, I have a (rather large) application that I have written in C++ and until recently it has been running fine outside of visual studio from the release build. However, now, whenever I run it it says "Unhandled exception at 0x77cf205b in myprog.exe: 0xC0000005: Access violation writing location 0x45000200.", and leads me to "crtexe.c" at line 582 ("mainret = main(argc, argv, envp);") if I attempt to debug it. Note that this problem never shows if I run my debug executable outside of visual studio, or if I run my debug or release build within visual studio. It only happens when running the release build outside of visual studio. I have been through and put plenty of printfs and a couple of while(1)s in it to see when it actually crashed, and found that the access violation occurs at exactly the point that the value is returned from the function (I'm returning a pointer to an object). I don't fully understand why I would get an access violation at the point it returns, and it doesn't seem to matter what I'm returning as it still occurs when I return 0. The point it started crashing was when I added a function which does a lot of reading from a file using ifstream. I am opening the stream every time I attempt to read a new file and close it when I finish reading it. If I keep attempting to run it, it will run once in about 20 tries. It seems a lot more reliable if I run it off my pen drive (it seems to crash the first 3 or 4 times then run fine after that - maybe it's due to its slower read speed). Thanks for your help, and if I've missed anything let me know.

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• Is SQLDataReader slower than using the command line utility sqlcmd?

  - by Andrew

  I was recently advocating to a colleague that we replace some C# code that uses the sqlcmd command line utility with a SqlDataReader. The old code uses: System.Diagnostics.ProcessStartInfo procStartInfo = new System.Diagnostics.ProcessStartInfo("cmd", "/c " + sqlCmd); wher sqlCmd is something like "sqlcmd -S " + serverName + " -y 0 -h-1 -Q " + "\"" + "USE [" + database + "]" + ";+ txtQuery.Text +"\"";\ The results are then parsed using regular expressions. I argued that using a SQLDataReader woud be more in line with industry practices, easier to debug and maintain and probably faster. However, the SQLDataReader approach is at least the same speed and quite possibly slower. I believe I'm doing everything correctly with SQLDataReader. The code is: using (SqlConnection connection = new SqlConnection()) { try { SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder(connectionString); connection.ConnectionString = builder.ToString(); ; SqlCommand command = new SqlCommand(queryString, connection); connection.Open(); SqlDataReader reader = command.ExecuteReader(); // do stuff w/ reader reader.Close(); } catch (Exception ex) { outputMessage += (ex.Message); } } I've used System.Diagnostics.Stopwatch to time both approaches and the command line utility (called from C# code) does seem faster (20-40%?). The SqlDataReader has the neat feature that when the same code is called again, it's lightening fast, but for this application we don't anticipate that. I have already done some research on this problem. I note that the command line utility sqlcmd uses OLE DB technology to hit the database. Is that faster than ADO.NET? I'm really suprised, especially since the command line utility approach involves starting up a process. I really thought it would be slower. Any thoughts? Thanks, Dave

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• What strategy do you use to sync your code when working from home

  - by Ben Daniel

  At my work I currently have my development environment inside a Virtual Machine. When I need to do work from home I copy my VM and any databases I need onto a laptop drive sized external USB drive. After about 10 minutes of copying I put the drive in my pocket and head home, copy back the VM and databases onto my personal computer and I'm ready to work. I follow the same steps to take the work back with me. So if I count the total amount of time I spend waiting around for files to finish copying in order for me to take work home and bring it back again, it comes to around 40 minutes! I do have a VPN connection to my work from home (providing the internet is up at both sites) and a decent internet speed (8mbits down/?up) but I find Remote Desktoping into my work machine laggy enough for me to want to work on my VM directly. So in looking at what other options I have or how I could improve my existing option I'm interested in what strategy you use or recommend to do work at home and keeping your code/environment in sync. EDIT: I'd prefer an option where I don't have to commit my changes into version control before I leave work - as I like to make meaningful descriptive comments in my commits, committing would take longer than just copying my VM onto a portable drive! lol Also I'd prefer a solution where my dev environment stays in sync too. Having said that I'm still very interested in your own solutions even if they don't exactly solve my problem as best as I'd like. :)

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• How to temporarily replace one primitive type with another when compiling to different targets in c#

  - by Keith

  How to easily/quickly replace float's for doubles (for example) for compiling to two different targets using these two particular choices of primitive types? Discussion: I have a large amount of c# code under development that I need to compile to alternatively use float, double or decimals depending on the use case of the target assembly. Using something like “class MYNumber : Double” so that it is only necessary to change one line of code does not work as Double is sealed, and obviously there is no #define in C#. Peppering the code with #if #else statements is also not an option, there is just too much supporting Math operators/related code using these particular primitive types. I am at a loss on how to do this apparently simple task, thanks! Edit: Just a quick comment in relation to boxing mentioned in Kyles reply: Unfortunately I need to avoid boxing, mainly since float's are being chosen when maximum speed is required, and decimals when maximum accuracy is the priority (and taking the 20x+ performance hit is acceptable). Boxing would probably rules out decimals as a valid choice and defeat the purpose somewhat. Edit2: For reference, those suggesting generics as a possible answer to this question note that there are many issues which count generics out (at least for our needs). For an overview and further references see Using generics for calculations

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