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  • Designing a database file format

    - by RoliSoft
    I would like to design my own database engine for educational purposes, for the time being. Designing a binary file format is not hard nor the question, I've done it in the past, but while designing a database file format, I have come across a very important question: How to handle the deletion of an item? So far, I've thought of the following two options: Each item will have a "deleted" bit which is set to 1 upon deletion. Pro: relatively fast. Con: potentially sensitive data will remain in the file. 0x00 out the whole item upon deletion. Pro: potentially sensitive data will be removed from the file. Con: relatively slow. Recreating the whole database. Pro: no empty blocks which makes the follow-up question void. Con: it's a really good idea to overwrite the whole 4 GB database file because a user corrected a typo. I will sell this method to Twitter ASAP! Now let's say you already have a few empty blocks in your database (deleted items). The follow-up question is how to handle the insertion of a new item? Append the item to the end of the file. Pro: fastest possible. Con: file will get huge because of all the empty blocks that remain because deleted items aren't actually deleted. Search for an empty block exactly the size of the one you're inserting. Pro: may get rid of some blocks. Con: you may end up scanning the whole file at each insert only to find out it's very unlikely to come across a perfectly fitting empty block. Find the first empty block which is equal or larger than the item you're inserting. Pro: you probably won't end up scanning the whole file, as you will find an empty block somewhere mid-way; this will keep the file size relatively low. Con: there will still be lots of leftover 0x00 bytes at the end of items which were inserted into bigger empty blocks than they are. Rigth now, I think the first deletion method and the last insertion method are probably the "best" mix, but they would still have their own small issues. Alternatively, the first insertion method and scheduled full database recreation. (Probably not a good idea when working with really large databases. Also, each small update in that method will clone the whole item to the end of the file, thus accelerating file growth at a potentially insane rate.) Unless there is a way of deleting/inserting blocks from/to the middle of the file in a file-system approved way, what's the best way to do this? More importantly, how do databases currently used in production usually handle this?

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  • Turning Floats into Their Closest (UTF-8 Character) Fraction.

    - by Mark Tomlin
    I want to take any real number, and return the closest number, with the closest fraction as available in the UTF-8 character set, appropriate. 0/4 = 0.00 = # < .125 1/4 = 0.25 = ¼ # > .125 & < .375 2/4 = 0.50 = ½ # > .375 & < .625 3/4 = 0.75 = ¾ # > .625 & < .875 4/4 = 1.00 = # > .875 I made this function to do that task: function displayFraction($realNumber) { if (!is_float($realNumber)) { return $realNumber; } list($number, $decimal) = explode('.', $realNumber); $decimal = '.' . $decimal; switch($decimal) { case $decimal < 0.125: return $number; case $decimal > 0.125 && $decimal < 0.375: return $number . '¼'; # 188 ¼ &#188; case $decimal > 0.375 && $decimal < 0.625: return $number . '½'; # 189 ½ &#189; case $decimal > 0.625 && $decimal < 0.875: return $number . '¾'; # 190 ¾ &#190; case $decimal < 0.875: return ++$number; } } What are the better / diffrent way to do this? echo displayFraction(3.1) . PHP_EOL; # Outputs: 3 echo displayFraction(3.141593) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.267432) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.38) . PHP_EOL; # Outputs: 3½ Expand my mind!

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  • USB windows xp final USB access issues

    - by Lex Dean
    I basically understand you C++ people, Please do not get distracted because I'm writing in Delphi. I have a stable USB Listing method that accesses all my USB devices I get the devicepath, and this structure: TSPDevInfoData = packed record Size: DWORD; ClassGuid: TGUID; DevInst: DWORD; // DEVINST handle Reserved: DWord; end; I get my ProductID and VenderID successfully from my DevicePath Lists all USB devices connected to the computer at the time That enables me to access the registry data to each device in a stable way. What I'm lacking is a little direction Is friendly name able to be written inside the connected USB Micro chips by the firmware programmer? (I'm thinking of this to identify the device even further, or is this to help identify Bulk data transfer devices like memory sticks and camera's) Can I use SPDRP_REMOVAL_POLICY_OVERRIDE to some how reset these polices What else can I do with the registry details. Identifying when some one unplugs a device The program is using (in windows XP standard) I used a documented windows event that did not respond. Can I read a registry value to identify if its still connected? using CreateFileA (DevicePath) to send and receive data I have read when some one unplugs in the middle of a data transfer its difficult clearing resources. what can IoCreateDevice do for me and how does one use it for that task This two way point of connection status and system lock up situations is very concerning. Has some one read anything about this subject recently? My objectives are to 1. list connected USB devices identify a in development Micro Controller from everything else send and receive data in a stable and fast way to the limits of the controller No lock up's transferring data Note I'm not using any service packs I understand everything USB is in ANSI when windows xp is not and .Net is all about ANSI (what a waste of memory) I plan to continue this project into a .net at a later date as an addition. MSDN gives me Structures and Functions and what should link to what ok but say little to what they get used for. What is available in my language Delphi is way over priced that it needs a major price drop.

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  • Trying to create an infinite for loop that can stop using function doIt()

    - by JoeOzz
    Hey guys, I'm new to javascript and I'm doing a project for my final in class. I need to make it so this game engine I manipulated causes the generation button to go for an infinite loop. I also need to stop it using (Reset==1). Any help? Here's the code I have so far if that helps: function generation() { for(y2=0; y2<2500; y2++) { tempmapactual[y2]=mapactual[y2]; } for (g=0;g<2500;g++) { neighbours=0; for (h=0;h<8;h++) { if (g+coords[h]>0 && g+coords[h]<2499 && mapactual[g+coords[h]]=="white.gif") {neighbours=neighbours+1;} } if (neighbours>=4 || neighbours==1 || neighbours==0) {tempmapactual[g]="black.gif";} if (neighbours==3) {tempmapactual[g]="white.gif";} } for(y3=0; y3<2500; ++y3) { if (mapactual[y3]!=tempmapactual[y3]) { mapactual[y3]=tempmapactual[y3]; document.images[y3+offset].src=mapactual[y3]; } } } </script> <script> function doIt() { for (i=0; i<X; i++) { // This is where I have trouble. What part of generation() do I call? } if (Reset==1) break; // This will kill the loop instantly. } } </script> <script> window.onload(doIt($(X).value))); </script> <form> <input type="button" value="generate" onClick="generation();"> </form> <form> <input type="text"> </form> <form> <input type="button" value="Infinite Loop!" onclick="doIt();"> </form> <form> <input type="button" value="Reset" onclick="doIt();"> </form>

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  • The best way to separate admin functionality from a public site?

    - by AndrewO
    I'm working on a site that's grown both in terms of user-base and functionality to the point where it's becoming evident that some of the admin tasks should be separate from the public website. I was wondering what the best way to do this would be. For example, the site has a large social component to it, and a public sales interface. But at the same time, there's back office tasks, bulk upload processing, dashboards (with long running queries), and customer relations tools in the admin section that I would like to not be effected by spikes in public traffic (or effect the public-facing response time). The site is running on a fairly standard Rails/MySQL/Linux stack, but I think this is more of an architecture problem than an implementation one: mainly, how does one keep the data and business logic in sync between these different applications? Some strategies that I'm evaluating: 1) Create a slave database of the public facing database on another machine. Extract out all of the model and library code so that it can be shared between the applications. Create new controllers and views for the admin interfaces. I have limited experience with replication and am not even sure that it's supposed to be used this way (most of the time I've seen it, it's been for scaling out the read capabilities of the same application, rather than having multiple different ones). I'm also worried about the potential for latency issues if the slave is not on the same network. 2) Create new more task/department-specific applications and use a message oriented middleware to integrate them. I read Enterprise Integration Patterns awhile back and they seemed to advocate this for distributed systems. (Alternatively, in some cases the basic Rails-style RESTful API functionality might suffice.) But, I have nightmares about data synchronization issues and the massive re-architecting that this would entail. 3) Some mixture of the two. For example, the only public information necessary for some of the back office tasks is a read-only completion time or status. Would it make sense to have that on a completely separate system and send the data to public? Meanwhile, the user/group admin functionality would be run on a separate system sharing the database? The downside is, this seems to keep many of the concerns I have with the first two, especially the re-architecting. I'm sure the answers are going to be highly dependent on a site's specific needs, but I'd love to hear success (or failure) stories.

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  • Generate MetaData with ANT

    - by Neil Foley
    I have a folder structure that contains multiple javascript files, each of these files need a standard piece of text at the top = //@include "includes.js" Each folder needs to contain a file named includes.js that has an include entry for each file in its directory and and entry for the include file in its parent directory. I'm trying to achive this using ant and its not going too well. So far I have the following, which does the job of inserting the header but not without actually moving or copying the file. I have heard people mentioning the <replace> task to do this but am a bit stumped. <?xml version="1.0" encoding="UTF-8"?> <project name="JavaContentAssist" default="start" basedir="."> <taskdef resource="net/sf/antcontrib/antcontrib.properties"> <classpath> <pathelement location="C:/dr_workspaces/Maven Repository/.m2/repository/ant-contrib/ant-contrib/20020829/ant-contrib-20020829.jar"/> </classpath> </taskdef> <target name="start"> <foreach target="strip" param="file"> <fileset dir="${basedir}"> <include name="**/*.js"/> <exclude name="**/includes.js"/> </fileset> </foreach> </target> <target name="strip"> <move file="${file}" tofile="${a_location}" overwrite="true"> <filterchain> <striplinecomments> <comment value="//@" /> </striplinecomments> <concatfilter prepend="${basedir}/header.txt"> </concatfilter> </filterchain> </move> </target> </project> As for the generation of the include files in the dir I'm not sure where to start at all. I'd appreciate if somebody could point me in the right direction.

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  • How can I prevent external MSBuild files from being cached (by Visual Studio) during a project build

    - by Damian Powell
    I have a project in my solution which started life as a C# library project. It's got nothing of any interest in it in terms of code, it is merely used as a dependency in the other projects in my solution in order to ensure that it is built first. One of the side-effects of building this project is that a shared AssemblyInfo.cs is created which contains the version number in use by the other projects. I have done this by adding the following to the .csproj file: <ItemGroup> <None Include="Properties\AssemblyInfo.Shared.cs.in" /> <Compile Include="Properties\AssemblyInfo.Shared.cs" /> <None Include="VersionInfo.targets" /> </ItemGroup> <Import Project="$(ProjectDir)VersionInfo.targets" /> <Target Name="BeforeBuild" DependsOnTargets="UpdateSharedAssemblyInfo" /> The referenced file, VersionInfo.targets, contains the following: <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <PropertyGroup> <!-- Some properties defining tool locations and the name of the AssemblyInfo.Shared.cs.in file etc. --> </PropertyGroup> <Target Name="UpdateSharedAssemblyInfo"> <!-- Uses the Exec task to run one of the tools to generate AssemblyInfo.Shared.cs based on the location of AssemblyInfo.Shared.cs.in and some of the other properties. --> </Target> </Project> The contents of the VersionInfo.targets file could simply be embedded within the .csproj file but it is external because I am trying to turn all of this into a project template. I want the users of the template to be able to add the new project to the solution, edit the VersionInfo.targets file, and run the build. The problem is that modifying and saving the VersionInfo.targets file and rebuilding the solution has no effect - the project file uses the values from the .targets file as they were when the project was opened. Even unloading and reloading the project has no effect. In order to get the new values, I need to close Visual Studio and reopen it (or reload the solution). How can I set this up so that the configuration is external to the .csproj file and not cached between builds?

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  • Save HashMap data into SQLite

    - by Matthew
    I'm Trying to save data from Json into SQLite. For now I keep the data from Json into HashMap. I already search it, and there's said use the ContentValues. But I still don't get it how to use it. I try looking at this question save data to SQLite from json object using Hashmap in Android, but it doesn't help a lot. Is there any option that I can use to save the data from HashMap into SQLite? Here's My code. MainHellobali.java // Hashmap for ListView ArrayList<HashMap<String, String>> all_itemList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main_helloballi); all_itemList = new ArrayList<HashMap<String, String>>(); // Calling async task to get json new getAllItem().execute(); } private class getAllItem extends AsyncTask<Void, Void, Void> { @Override protected Void doInBackground(Void... arg0) { // Creating service handler class instance ServiceHandler sh = new ServiceHandler(); // Making a request to url and getting response String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET); Log.d("Response: ", "> " + jsonStr); if (jsonStr != null) { try { all_item = new JSONArray(jsonStr); // looping through All Contacts for (int i = 0; i < all_item.length(); i++) { JSONObject c = all_item.getJSONObject(i); String item_id = c.getString(TAG_ITEM_ID); String category_name = c.getString(TAG_CATEGORY_NAME); String item_name = c.getString(TAG_ITEM_NAME); // tmp hashmap for single contact HashMap<String, String> allItem = new HashMap<String, String>(); // adding each child node to HashMap key => value allItem.put(TAG_ITEM_ID, item_id); allItem.put(TAG_CATEGORY_NAME, category_name); allItem.put(TAG_ITEM_NAME, item_name); // adding contact to contact list all_itemList.add(allItem); } } catch (JSONException e) { e.printStackTrace(); } } else { Log.e("ServiceHandler", "Couldn't get any data from the url"); } return null; } } I have DatabasehHandler.java and AllItem.java too. I can put it in here if its necessary. Thanks before ** Add Edited Code ** // looping through All Contacts for (int i = 0; i < all_item.length(); i++) { JSONObject c = all_item.getJSONObject(i); String item_id = c.getString(TAG_ITEM_ID); String category_name = c.getString(TAG_CATEGORY_NAME); String item_name = c.getString(TAG_ITEM_NAME); DatabaseHandler databaseHandler = new DatabaseHandler(this); //error here "The Constructor DatabaseHandler(MainHellobali.getAllItem) is undefined }

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  • Java program has errors, 80 lines of code

    - by user2961687
    I have a problem with a program. It contains a lot of errors in Eclipse. Sorry for my english and thank you in advance. Here is the task: I. Declare a class that contains private fields Jam: String taste, double weight Create constructors containing variables as parameters: (String taste, double weight), (double weight), (String taste). Parameters constructors should initialize class fields. In case the constructor does not provide the necessary parameter, it must be assumed that the field taste must have the value "No Name" and weight - 100.0. Introduce the use of all constructors creating objects that represent three kinds of jams. Note: it must be assumed that the only constructor with two parameters can be assigned to fields of the class. Declare a class Jar that contains the field Jam jam, a dedicated constructor initiating all declared fields and methods: open close isItOpen Next, create an object of class Jar and fill it with the selected type of jam, operations repeat for all the kinds of jams. This is my code this far: public class App { public static void main(String[] args) { Jam strawberry = new Jam("strawberry", 20.45); Jam raspberry = new Jam(40.50); Jam peach = new Jam("peach"); Jar jar_1 = new Jar(); Jar jar_2 = new Jar(); Jar jar_3 = new Jar(); jar_1.open(); jar_1.fillIn(strawberry); jar_2.fillIn(peach); jar_3.fillIn(raspberry); } } class Jam { String taste; double weight; public Jam(String taste, double weight) { this.taste = taste; this.weight = weight; } public Jam(double weight) { this.taste = "No name"; this.weight = weight; } public Jam(String taste) { this.taste = taste; this.weight = 100.0; } } class Jar { public Jam Jam = new Jam(); private String state_jar; public Jar() { Jam.weight = 0; Jam.taste = ""; state_jar = "closed"; } public static String open() { state_jar = open; return state_jar; } public static String close() { state_jar = "closed"; return state_jar; } public static boolean isItOpen() { return state_jar; } public void fillIn(Jam jam) { if (isItOpen == false) open(); this.Jam.weight = jam.weight; this.Jam.taste = jam.taste; this.Jam.close(); } }

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  • Best way to run remote VBScript in ASP.net? WMI or PsExec?

    - by envinyater
    I am doing some research to find out the best and most efficient method for this. I will need to execute remote scripts on a number of Window Servers/Computers (while we are building them). I have a web application that is going to automate this task, I currently have my prototype working to use PsExec to execute remote scripts. This requires PsExec to be installed on the system. A colleague suggested I should use WMI for this. I did some research in WMI and I couldn't find what I'm looking for. I want to either upload the script to the server and execute it and read the results, or already have the script on the server and execute it and read the results. I would prefer the first option though! Which is more ideal, PsExec or WMI? For reference, this is my prototype PsExec code. This script is only executing a small script to get the Windows OS and Service Pack Info. Protected Sub windowsScript(ByVal COMPUTERNAME As String) ' Create an array to store VBScript results Dim winVariables(2) As String nameLabel.Text = Name.Text ' Use PsExec to execute remote scripts Dim Proc As New System.Diagnostics.Process ' Run PsExec locally Proc.StartInfo = New ProcessStartInfo("C:\Windows\psexec.exe") ' Pass in following arguments to PsExec Proc.StartInfo.Arguments = COMPUTERNAME & " -s cmd /C c:\systemInfo.vbs" Proc.StartInfo.RedirectStandardInput = True Proc.StartInfo.RedirectStandardOutput = True Proc.StartInfo.UseShellExecute = False Proc.Start() ' Pause for script to run System.Threading.Thread.Sleep(1500) Proc.Close() System.Threading.Thread.Sleep(2500) 'Allows the system a chance to finish with the process. Dim filePath As String = COMPUTERNAME & "\TTO\somefile.txt" 'Download file created by script on Remote system to local system My.Computer.Network.DownloadFile(filePath, "C:\somefile.txt") System.Threading.Thread.Sleep(1000) ' Pause so file gets downloaded ''Import data from text file into variables textRead("C:\somefile.txt", winVariables) WindowsOSLbl.Text = winVariables(0).ToString() SvcPckLbl.Text = winVariables(1).ToString() System.Threading.Thread.Sleep(1000) ' ''Delete the file on server - we don't need it anymore Dim Proc2 As New System.Diagnostics.Process Proc2.StartInfo = New ProcessStartInfo("C:\Windows\psexec.exe") Proc2.StartInfo.Arguments = COMPUTERNAME & " -s cmd /C del c:\somefile.txt" Proc2.StartInfo.RedirectStandardInput = True Proc2.StartInfo.RedirectStandardOutput = True Proc2.StartInfo.UseShellExecute = False Proc2.Start() System.Threading.Thread.Sleep(500) Proc2.Close() ' Delete file locally File.Delete("C:\somefile.txt") End Sub

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  • How to obtain the first cluster of the directory's data in FAT using C# (or at least C++) and Win32A

    - by DarkWalker
    So I have a FAT drive, lets say H: and a directory 'work' (full path 'H:\work'). I need to get the NUMBER of the first cluster of that directory. The number of the first cluster is 2-bytes value, that is stored in the 26th and 27th bytes of the folder enty (wich is 32 bytes). Lets say I am doing it with file, NOT a directory. I can use code like this: static public string GetDirectoryPtr(string dir) { IntPtr ptr = CreateFile(@"H:\Work\dover.docx", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, 0,//FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero); try { const uint bytesToRead = 2; byte[] readbuffer = new byte[bytesToRead]; if (ptr.ToInt32() == -1) return String.Format("Error: cannot open direcotory {0}", dir); if (SetFilePointer(ptr, 26, 0, 0) == -1) return String.Format("Error: unable to set file pointer on file {0}", ptr); uint read = 0; // real count of read bytes if (!ReadFile(ptr, readbuffer, bytesToRead, out read, 0)) return String.Format("cant read from file {0}. Error #{1}", ptr, Marshal.GetLastWin32Error()); int result = readbuffer[0] + 16 * 16 * readbuffer[1]; return result.ToString();//ASCIIEncoding.ASCII.GetString(readbuffer); } finally { CloseHandle(ptr); } } And it will return some number, like 19 (quite real to me, this is the only file on the disk). But I DONT need a file, I need a folder. So I am puttin FILE_FLAG_BACKUP_SEMANTICS param for CreateFile call... and dont know what to do next =) msdn is very clear on this issue http://msdn.microsoft.com/en-us/library/aa365258(v=VS.85).aspx It sounds to me like: "There is no way you can get a number of the folder's first cluster". The most desperate thing is that my tutor said smth like "You are going to obtain this or you wont pass this course". The true reason why he is so sure this is possible is because for 10 years (or may be more) he recieved the folder's first cluster number as a HASH of the folder's addres (and I was stupid enough to point this to him, so now I cant do it the same way) PS: This is the most spupid task I have ever had!!! This value is not really used anythere in program, it is only fcking pointless integer.

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  • Generating custom-form documents from base-form plus XML?

    - by KlaymenDK
    Hi all, this is my first stack overflow, and it's a complex one. Sorry. My task is to generate custom documents from a basic template plus some XML without having a custom form design element for each case. Here's the whole picture: We are building a Lotus Notes (client, not web) application for world-wide application access control; the scope is something like 400.000 users being able to request access to any of 1000+ applications. Each application needs its own request form -- different number of approvers, various info required, that sort of thing. We simply can't have a thousand forms in a database (one per application), and anyway their maintenance really needs to be pushed from the developers to the application owners. So instead of custom forms, we'd like to create a generic "template" form that stores a block of basic fields, but then allows application owners to define another block of fields dynamically -- "I want a mandatory plain-text field named 'Name' here, and then a date field named 'Due' here that must be later than today's date, and then ...". I hope this makes sense (if not, think of it as a generic questionnaire application). I pretty much have the structure in place for designing the dynamic fields (form builder GUI - XML-encoded data - pre-rendered DXL for injecting into a form), including mark-up for field types, value options, and rudimentary field validation instructions. My problem is generating a document with this dynamic content injected at the proper location (without needing a custom form design element for each case). Doing the dynamic content via HTML is out. The Notes client web rendering is simply way too poor, and it would be quite a challenge to implement things like field validation instructions, date selectors, and name look-ups. DXL, on the other hand, would allow us to use native Notes fields and code. As a tech demo, I've managed to implement a custom form generator that injects the pre-rendered DXL for the dynamic content into a base form; but as I said, we don't want a ton of custom form design elements. I've tried to implement a way to create a document with the "store form in document" flag set, but once I've created the document from the base form, I can't get DXL access to the stored form design, and so I can't inject my dynamic content. I know this is not something Notes was ever intended to do. Has anyone ever tried something like it (and gotten away with it)? Thanks for reading this far. With a boatload of thanks in advance, Jan Gundtofte-Bruun

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  • Move options between multiple lists

    - by Martha
    We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. EDIT: Having now actually sat down to try to code the non-javascripty bits, I need to revise my question, because I realized that multiple select lists won't really work from the "how do I inform the server about all this lovely new information" standpoint. So the html code is now a pseudo-listbox, i.e. an unordered list (ul) displayed in a box with a scrollbar, and each list item (<li>) has a set of five radio buttons (unselected/own/read/like/heard). My task is still roughly the same: how to take this one list and make it easy to categorize the items, in such a way that the user can tell at a glance what is in what category. (The pseudo-listbox has some of the same disadvantages as a multi-select listbox, namely it's hard to tell what's selected if the list is long enough to scroll.) The dream solution would be a drag-and-drop type thing, but at this point even buttons would be OK. Another modification (a good one) is that the client has revised the lists, so the longest is now "only" 62 items long (instead of the many hundreds they had before). The categories will still mostly contain zero, one, or two selected items, possibly a couple more if the user was overzealous. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :) [existing code deleted because it's largely irrelevant.]

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  • Efficient list compacting

    - by Patrik
    Suppose you have a list of unsigned ints. Suppose some elements are equal to 0 and you want to push them back. Currently I use this code (list is a pointer to a list of unsigned ints of size n for (i = 0; i < n; ++i) { if (list[i]) continue; int j; for (j = i + 1; j < n && !list[j]; ++j); int z; for (z = j + 1; z < n && list[z]; ++z); if (j == n) break; memmove(&(list[i]), &(list[j]), sizeof(unsigned int) * (z - j))); int s = z - j + i; for(j = s; j < z; ++j) list[j] = 0; i = s - 1; } Can you think of a more efficient way to perform this task? The snippet is purely theoretical, in the production code, each element of list is a 64 bytes struct EDIT: I'll post my solution. Many thanks to Jonathan Leffler. void RemoveDeadParticles(int * list, int * n) { int i, j = *n - 1; for (; j >= 0 && list[j] == 0; --j); for (i = 0; i < j; ++i) { if (list[i]) continue; memcpy(&(list[i]), &(list[j]), sizeof(int)); list[j] = 0; for (; j >= 0 && list[j] == 0; --j); if (i == j) break; } *n = i + 1; }

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  • Multi-Threading Question Concerning WPF

    - by Andrew
    Hello, I'm a newbie to threading, and I don't really know how to code a particular task. I would like to handle a mouse click event on a window that will kick off a while loop in a seperate thread. This thread, which is distinct from the UI thread, should call a function in the while loop which updates a label on the window being serviced by the UI thread. The while loop should stop running when the left mouse button is no longer being pressed. All the loop does is increment a counter, and then repeatedly call the function which displays the updated value in the window. The code for the window and all of the threading is given below (I keep getting some error about STA threading, but don't know where to put the attribute). Also, I'm hoping to use this solution, if it ever works, in another project that makes asynchronous calls elsewhere to a service via wcf, so I was hoping not to make any application-wide special configurations, since I'm really new to multi-threading and am quite worried about breaking other code in a larger program... Here's what I have: <Window x:Class="WpfApplication2.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication2" Name="MyMainWindow" Title="MainWindow" Width="200" Height="150" PreviewMouseLeftButtonDown="MyMainWindow_PreviewMouseLeftButtonDown"> <Label Height="28" Name="CounterLbl" /> </Window> And here's the code-behind: using System.Windows; using System.Windows.Input; using System.Threading; namespace WpfApplication2 { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { private int counter = 0; public MainWindow() { InitializeComponent(); } private delegate void EmptyDelegate(); private void MyMainWindow_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) { Thread counterThread = new Thread(new ThreadStart(MyThread)); counterThread.Start(); } private void MyThread() { while (Mouse.LeftButton == MouseButtonState.Pressed) { counter++; Dispatcher.Invoke(new EmptyDelegate(UpdateLabelContents), null); } } private void UpdateLabelContents() { CounterLbl.Content = counter.ToString(); } } } Anyways, multi-threading is really new to me, and I don't have any experience implementing it, so any thoughts or suggestions are welcome! Thanks, Andrew

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  • Is the recent trend toward widescreen (16:9) computer monitors a plus or minus for programmers?

    - by DanM
    It's almost gotten to the point where you can't buy a conventional (4:3) monitor anymore. Pretty much everything is widescreen. This is fine for watching movies or TV, but is it good or bad for programming? My initial thoughts on the issue are that widescreens are a net negative for programmers. Here are some of the disadvantages I see: Poor space utiliziation One disadvantage of widescreens you can't argue with is that they offer poor space utilization for the amount of total pixels you get. For example, my Thinkpad, which I bought just before the widescreen craze, has a 15" monitor with a native resolution of 1600 x 1200. The newer 15.4" Thinkpads run at most 1680 x 1050. So (if you do the math) you get fewer pixels in a wider (but not shorter) package. With desktop monitors, you pay a price in terms of desk space used. Two 1680 x 1050 monitors will simply take up more of your desk than two 1600 x 1200 monitors (assuming equal dot pitch). More scrolling If you compare a 1680 x 1050 monitor to a 1600 x 1200 monitor, you get 80 extra pixels of width but 150 fewer pixels of height. The height reduction means you lose approximately 11 lines of code. That's less you can see on the screen at one time and more scrolling you have to do. This harms productivity, maybe not dramatically, but insidiously. Less room for wide panels Widescreens also mean you lose space for wide but short panels common in programming environments. If you use Visual Studio, for example, your code window will be that much shorter when viewing the Find Results, Task List, or Error List (all of which I use frequently). This isn't to say the 80 pixels of extra width you get with widescreen would never be useful, but I tend to keep my lines of code short, so seeing more lines would be more valuable to me than seeing fewer, longer lines. What do you think? Do you agree/disagree? Are you now using one or more widescreen monitors for development? What resolution are you running on each? Do you ever miss the height of the traditional 4:3 monitor? Would you complain if your monitors were one inch narrower but two inches taller?

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  • SEO Help with Pages Indexed by Google

    - by Joe Majewski
    I'm working on optimizing my site for Google's search engine, and lately I've noticed that when doing a "site:www.joemajewski.com" query, I get results for pages that shouldn't be indexed at all. Let's take a look at this page, for example: http://www.joemajewski.com/wow/profile.php?id=3 I created my own CMS, and this is simply a breakdown of user id #3's statistics, which I noticed is indexed by Google, although it shouldn't be. I understand that it takes some time before Google's results reflect accurately on my site's content, but this has been improperly indexed for nearly six months now. Here are the precautions that I have taken: My robots.txt file has a line like this: Disallow: /wow/profile.php* When running the url through Google Webmaster Tools, it indicates that I did, indeed, correctly create the disallow command. It did state, however, that a page that doesn't get crawled may still get displayed in the search results if it's being linked to. Thus, I took one more precaution. In the source code I included the following meta data: <meta name="robots" content="noindex,follow" /> I am assuming that follow means to use the page when calculating PageRank, etc, and the noindex tells Google to not display the page in the search results. This page, profile.php, is used to take the $_GET['id'] and find the corresponding registered user. It displays a bit of information about that user, but is in no way relevant enough to warrant a display in the search results, so that is why I am trying to stop Google from indexing it. This is not the only page Google is indexing that I would like removed. I also have a WordPress blog, and there are many category pages, tag pages, and archive pages that I would like removed, and am doing the same procedures to attempt to remove them. Can someone explain how to get pages removed from Google's search results, and possibly some criteria that should help determine what types of pages that I don't want indexed. In terms of my WordPress blog, the only pages that I truly want indexed are my articles. Everything else I have tried to block, with little luck from Google. Can someone also explain why it's bad to have pages indexed that don't provide any new or relevant content, such as pages for WordPress tags or categories, which are clearly never going to receive traffic from Google. Thanks!

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  • In a PHP project, how do you organize and access your helper objects?

    - by Pekka
    How do you organize and manage your helper objects like the database engine, user notification, error handling and so on in a PHP based, object oriented project? Say I have a large PHP CMS. The CMS is organized in various classes. A few examples: the database object user management an API to create/modify/delete items a messaging object to display messages to the end user a context handler that takes you to the right page a navigation bar class that shows buttons a logging object possibly, custom error handling etc. I am dealing with the eternal question, how to best make these objects accessible to each part of the system that needs it. my first apporach, many years ago was to have a $application global that contained initialized instances of these classes. global $application; $application->messageHandler->addMessage("Item successfully inserted"); I then changed over to the Singleton pattern and a factory function: $mh =&factory("messageHandler"); $mh->addMessage("Item successfully inserted"); but I'm not happy with that either. Unit tests and encapsulation become more and more important to me, and in my understanding the logic behind globals/singletons destroys the basic idea of OOP. Then there is of course the possibility of giving each object a number of pointers to the helper objects it needs, probably the very cleanest, resource-saving and testing-friendly way but I have doubts about the maintainability of this in the long run. Most PHP frameworks I have looked into use either the singleton pattern, or functions that access the initialized objects. Both fine approaches, but as I said I'm happy with neither. I would like to broaden my horizon on what is possible here and what others have done. I am looking for examples, additional ideas and pointers towards resources that discuss this from a long-term, real-world perspective. Also, I'm interested to hear about specialized, niche or plain weird approaches to the issue. Bounty I am following the popular vote in awarding the bounty, the answer which is probably also going to give me the most. Thank you for all your answers!

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  • Sitecore E-Commerce Module - Discount/Promotional Codes

    - by Zachary Kniebel
    I am working on a project for which I must use Sitecore's E-Commerce Module (and Sitecore 6.5 rev. 120706 - aka 'Update 5') to create a web-store. One of the features that I am trying to implement is a generic promotional/discount code system - customer enters a code at checkout which grants a discount like 'free shipping', '20% off', etc. At the moment, I am looking for some guidance (a high-level solution, a few pseudo-ideas, some references to review, etc) as to how this can be accomplished. Summary: What I am looking for is a way to detect whether or not the user entered a promo code at a previous stage in the checkout line, and to determine what that promo code is, if they did. Progress Thus Far: I have thoroughly reviewed all of the Sitecore E-Commerce Services (SES) documentation, especially "SES Order Line Extension" documentation (which I believe will have to be modified/extended in order to accomplish this task). Additionally, I have thoroughly reviewed the Sitecore Community article Extending Sitecore E-Commerce - Pricing and believe that it may be a useful guide for applying a discount statically, but does not say much in the way of applying a discount dynamically. After reviewing these documents, I have come up with the following possible high-level solution to start from: I create a template to represent a promotional code, which holds all data relevant to the promotion (percent off, free shipping, code, etc). I then create another template (based on the Product Search Group template) that holds a link to an item within a global "Promotional Code" items folder. Next, I use the Product Search Group features of my new template to choose which products to apply the discount to. In the source code for the checkout I create a class that checks if a code has been entered and, if so, somehow carry it through the rest of the checkout process. This is where I get stuck. More Details: No using cookies No GET requests No changing/creating/deleting items in the Sitecore Database during the checkout process (e.g., no manipulation of fields of a discount item during checkout to signal that the discount has been applied) must stay within the scope of C# Last Notes: I will update this post with any more information that I find/progress that I make. I upgrade all answers that are relevant and detailed, thought-provoking, or otherwise useful to me and potentially useful to others, in addition to any high-level answers that serve as a feasible solution to this problem; even if your idea doesn't help me, if I think it will help someone else I will still upgrade it. Thanks, in advance, for all your help! :)

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  • How can I ignore an http request without clearing the browser?

    - by Timid Developer
    To prevent duplicate requests (i.e. pressing F5 right after clicking a command button), I've setup my page base class to ignore the request if it's detected as a duplicate. When I say 'ignore' I mean Response.End() Now I thought I've seen this work before, where there's an issue, I just Response.End() and the users page just does nothing. I don't know the exact circumstance in which this worked, but I'm unable to repeat it now. Now when I call Response.End(), I just get an empty browser. More specifically, I get this html. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=utf-8"></HEAD> <BODY></BODY></HTML> I setup the following test app to confirm the problem is not elsewhere in my app. Here it is: Add the following to an aspx form <asp:Label ID="lbl" Text="0" runat="server" /><br /> <asp:Button ID="btnAdd1" Text="Add 1" runat="server" /><br /> <asp:Button ID="btnAdd2" Text="Add 2" runat="server" /><br /> <asp:Button ID="btnAdd3" Text="Add 3" runat="server" /><br /> And here's the code behind file using System; namespace TestDupRequestCancellation { public partial class _Default : System.Web.UI.Page { protected void Page_Init(object sender, EventArgs e) { btnAdd1.Click += btnAdd1_Click; btnAdd2.Click += btnAdd2_Click; btnAdd3.Click += btnAdd3_Click; } protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) CurrentValue = 0; else if (Int32.Parse(lbl.Text) != CurrentValue) Response.End(); } protected void Page_PreRender(object sender, EventArgs e) { lbl.Text = CurrentValue.ToString(); } protected int CurrentValue { get { return Int32.Parse(Session["CurrentValue"].ToString()); } set { Session["CurrentValue"] = value.ToString(); } } void btnAdd3_Click(object sender, EventArgs e) { CurrentValue += 3; } void btnAdd2_Click(object sender, EventArgs e) { CurrentValue += 2; } void btnAdd1_Click(object sender, EventArgs e) { CurrentValue += 1; } } } When you load the page, clicking any button does what is expected, but if you press F5 at any time after pressing one of the buttons, it will detect it as a duplicate request and call Response.End() which promptly ends the task. Which leaves the user with an empty browser. Is there anyway to leave the user with the page as it was, so they can just click a button? Also; please note that this code is the simplest code I could come up with to demonstrate my problem. It's not meant to demonstrate how to check for dup requests.

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  • Is this a legitimate implementation of a 'remember me' function for my web app?

    - by user246114
    Hi, I'm trying to add a "remember me" feature to my web app to let a user stay logged in between browser restarts. I think I got the bulk of it. I'm using google app engine for the backend which lets me use java servlets. Here is some pseudo-code to demo: public class MyServlet { public void handleRequest() { if (getThreadLocalRequest().getSession().getAttribute("user") != null) { // User already has session running for them. } else { // No session, but check if they chose 'remember me' during // their initial login, if so we can have them 'auto log in' // now. Cookie[] cookies = getThreadLocalRequest().getCookies(); if (cookies.find("rememberMePlz").exists()) { // The value of this cookie is the cookie id, which is a // unique string that is in no way based upon the user's // name/email/id, and is hard to randomly generate. String cookieid = cookies.find("rememberMePlz").value(); // Get the user object associated with this cookie id from // the data store, would probably be a two-step process like: // // select * from cookies where cookieid = 'cookieid'; // select * from users where userid = 'userid fetched from above select'; User user = DataStore.getUserByCookieId(cookieid); if (user != null) { // Start session for them. getThreadLocalRequest().getSession() .setAttribute("user", user); } else { // Either couldn't find a matching cookie with the // supplied id, or maybe we expired the cookie on // our side or blocked it. } } } } } // On first login, if user wanted us to remember them, we'd generate // an instance of this object for them in the data store. We send the // cookieid value down to the client and they persist it on their side // in the "rememberMePlz" cookie. public class CookieLong { private String mCookieId; private String mUserId; private long mExpirationDate; } Alright, this all makes sense. The only frightening thing is what happens if someone finds out the value of the cookie? A malicious individual could set that cookie in their browser and access my site, and essentially be logged in as the user associated with it! On the same note, I guess this is why the cookie ids must be difficult to randomly generate, because a malicious user doesn't have to steal someone's cookie - they could just randomly assign cookie values and start logging in as whichever user happens to be associated with that cookie, if any, right? Scary stuff, I feel like I should at least include the username in the client cookie such that when it presents itself to the server, I won't auto-login unless the username+cookieid match in the DataStore. Any comments would be great, I'm new to this and trying to figure out a best practice. I'm not writing a site which contains any sensitive personal information, but I'd like to minimize any potential for abuse all the same, Thanks

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  • A better way to delete a list of elements from multiple tables

    - by manyxcxi
    I know this looks like a 'please write the code' request, but some basic pointer/principles for doing this the right way should be enough to get me going. I have the following stored procedure: CREATE PROCEDURE `TAA`.`runClean` (IN idlist varchar(1000)) BEGIN DECLARE EXIT HANDLER FOR NOT FOUND ROLLBACK; DECLARE EXIT HANDLER FOR SQLEXCEPTION ROLLBACK; DECLARE EXIT HANDLER FOR SQLWARNING ROLLBACK; START TRANSACTION; DELETE FROM RunningReports WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_TEST WHERE run_id IN (idlist); DELETE FROM RunHistory WHERE id IN (idlist); COMMIT; END $$ It is called by a PHP script to clean out old run history. It is not particularly efficient as you can see and I would like to speed it up. The PHP script gathers the ids to remove from the tables with the following query: $query = "SELECT id, stop_time FROM RunHistory WHERE config_id = $configId AND save = 0 AND NOT(stop_time IS NULL) ORDER BY stop_time"; It keeps the last five run entries and deletes all the rest. So using this query to bring back all the IDs, it determines which ones to delete and keeps the 'newest' five. After gathering the IDs it sends them to the stored procedure to remove them from the associated tables. I'm not very good with SQL, but I ASSUME that using an IN statement and not joining these tables together is probably the least efficient way I can do this, but I don't know enough to ask anything but "how do I do this better?" If possible, I would like to do this all in my stored procedure using a query to gather all the IDs except for the five 'newest', then delete them. Another twist, run entries can be marked save (save = 1) and should not be deleted. The RunHistory table looks like this: CREATE TABLE `TAA`.`RunHistory` ( `id` int(11) NOT NULL auto_increment, `start_time` datetime default NULL, `stop_time` datetime default NULL, `config_id` int(11) NOT NULL, [...] `save` tinyint(1) NOT NULL default '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;

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  • Dealing with personal failure

    - by codeelegance
    A while ago I was given the task of updating and extending the functionality of a software project. I was given a year to make the needed changes working solo. A month into development I came to the conclusion that it would take longer to change the existing product than to rewrite it from the ground up. I'd never attempted a complete rewrite so I talked with my boss about it and he was thrilled with the idea. I'm a fan of agile development but had never had the opportunity to take advantage of all of the prescribed practices so when I set to work I tried to incorporate as many as I could. I didn't have direct access to the customer and my coworkers (non-programmers) knew the business domain but were already so busy they didn't really have time to participate in design meetings so I resigned to working in the dark and occasionally calling one of them over to my desk to get feedback on my progress. I used TDD and refactored mercilessly and even tried taking a domain driven design approach. Things went well for a while. As the deadline came closer and the complexity of the project grew my productivity start slipping. I found myself cutting corners and ignoring the practices I had established as the pressure increased to meet the deadline. I also started working late nights and weekends to keep up with the load. In the end it made little difference how hard I worked. The project missed its deadline and what was completed wasn't enough to give to the customer. I had failed. Not only had I not finished on time but the previous version had sat untouched for almost a year so it wouldn't be of any help. Luckily we had another product that offered some of the same functionality. My boss decided to cancel the project entirely and moved all our orphaned customers to the other product. I spent weeks (along with everyone else at the company) manning the phones providing technical support for those customers. After it was all over, my boss was gracious enough not to fire me for nearly ruining the company. I was moved to the other product and have been trying to redeem myself ever since. Where did I go wrong? Has anyone else had to deal with this kind of defeat? How did you recover?

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  • Infinite loop when adding a row to a list in a class in python3

    - by Margaret
    I have a script which contains two classes. (I'm obviously deleting a lot of stuff that I don't believe is relevant to the error I'm dealing with.) The eventual task is to create a decision tree, as I mentioned in this question. Unfortunately, I'm getting an infinite loop, and I'm having difficulty identifying why. I've identified the line of code that's going haywire, but I would have thought the iterator and the list I'm adding to would be different objects. Is there some side effect of list's .append functionality that I'm not aware of? Or am I making some other blindingly obvious mistake? class Dataset: individuals = [] #Becomes a list of dictionaries, in which each dictionary is a row from the CSV with the headers as keys def field_set(self): #Returns a list of the fields in individuals[] that can be used to split the data (i.e. have more than one value amongst the individuals def classified(self, predicted_value): #Returns True if all the individuals have the same value for predicted_value def fields_exhausted(self, predicted_value): #Returns True if all the individuals are identical except for predicted_value def lowest_entropy_value(self, predicted_value): #Returns the field that will reduce <a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29">entropy</a> the most def __init__(self, individuals=[]): and class Node: ds = Dataset() #The data that is associated with this Node links = [] #List of Nodes, the offspring Nodes of this node level = 0 #Tree depth of this Node split_value = '' #Field used to split out this Node from the parent node node_value = '' #Value used to split out this Node from the parent Node def split_dataset(self, split_value): fields = [] #List of options for split_value amongst the individuals datasets = {} #Dictionary of Datasets, each one with a value from fields[] as its key for field in self.ds.field_set()[split_value]: #Populates the keys of fields[] fields.append(field) datasets[field] = Dataset() for i in self.ds.individuals: #Adds individuals to the datasets.dataset that matches their result for split_value datasets[i[split_value]].individuals.append(i) #<---Causes an infinite loop on the second hit for field in fields: #Creates subnodes from each of the datasets.Dataset options self.add_subnode(datasets[field],split_value,field) def add_subnode(self, dataset, split_value='', node_value=''): def __init__(self, level, dataset=Dataset()): My initialisation code is currently: if __name__ == '__main__': filename = (sys.argv[1]) #Takes in a CSV file predicted_value = "# class" #Identifies the field from the CSV file that should be predicted base_dataset = parse_csv(filename) #Turns the CSV file into a list of lists parsed_dataset = individual_list(base_dataset) #Turns the list of lists into a list of dictionaries root = Node(0, Dataset(parsed_dataset)) #Creates a root node, passing it the full dataset root.split_dataset(root.ds.lowest_entropy_value(predicted_value)) #Performs the first split, creating multiple subnodes n = root.links[0] n.split_dataset(n.ds.lowest_entropy_value(predicted_value)) #Attempts to split the first subnode.

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  • Approach for authentication and storing user details.

    - by cappuccino
    Hey folks, I am using the Zend Framework but my question is broadly about sessions / databases / auth (PHP MySQL). Currently this is my approach to authentication: 1) User signs in, the details are checked in database. - Standard stuff really. 2) If the details are correct only the user's unique ID is stored in the session and a security token (user unique ID + IP + Browser info + salt). The session in written to the filesystem. I've been reading around and many are saying that storing stuff in sessions is not a good idea, and that you should really only write a unique ID which refers back to the user's details and a security token to prevent session hijacking. So this is the approach i've taken, i use to write the user's details in session, but i've moved that out. Wanted to know your opinions on this. I'm keeping sessions in the filesystem since i don't run on multiple servers, and since i'm only writting a tiny tiny bit of data to sessions, i thought that performance would be greater keeping sessions in the filesystem to reduce load on the database. Once the session is written on authentication, it really is only read-only from then on. 3) The rest of the user's details (like subscription details, permissions, account info etc) are cached in the filesystem (this can always be easily moved to memory if i wanted even more performance). So rather than keeping the user's details in session, the user's details are cached in the file system. I'm using Zend_Cache and the unique cache id is something like md5(/cache/auth/2892), the number is the unique id of the user. I guess the benefit of this method is that once the user is logged in, there is essentially not database queries being run to get the user's details. Just wonder if this approach is better than keeping the whole lot in session... 4) As the user moves throughout the site the only thing that is checked is the ID in the session and the security token. So, overall the first question is 1) is the filesystem more efficient than a database for this purpose 2) have i taken enough security precautions 3) is separating user detail's from the session into a cached file a pointless task? Thanks.

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