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• Most secure way to access my home Linux server while I am on the road? Specialized solution wanted

  - by Ace Paus

  I think many people may be in my situation. I travel on business with a laptop. And I need secure access to files from the office (which in my case is my home). The short version of my question: How can I make SSH/SFTP really secure when only one person needs to connect to the server from one laptop? In this situation, what special steps would make it almost impossible for anyone else to get online access to the server? A lot more details: I use Ubuntu Linux on both my laptop (KDE) and my home/office server. Connectivity is not a problem. I can tether to my phone's connection if needed. I need access to a large number of files (around 300 GB). I don't need all of them at once, but I don't know in advance which files I might need. These files contain confidential client info and personal info such as credit card numbers, so they must be secure. Given this, I don't want store all these files on Dropbox or Amazon AWS, or similar. I couldn't justify that cost anyway (Dropbox don't even publish prices for plans above 100 GB, and security is a concern). However, I am willing to spend some money on a proper solution. A VPN service, for example, might be part of the solution? Or other commercial services? I've heard about PogoPlug, but I don't know if there is a similar service that might address my security concerns? I could copy all my files to my laptop because it has the space. But then I have to sync between my home computer and my laptop and I found in the past that I'm not very good about doing this. And if my laptop is lost or stolen, my data would be on it. The laptop drive is an SSD and encryption solutions for SSD drives are not good. Therefore, it seems best to keep all my data on my Linux file server (which is safe at home). Is that a reasonable conclusion, or is anything connected to the Internet such a risk that I should just copy the data to the laptop (and maybe replace the SSD with an HDD, which reduces battery life and performance)? I view the risks of losing a laptop to be higher. I am not an obvious hacking target online. My home broadband is cable Internet, and it seems very reliable. So I want to know the best (reasonable) way to securely access my data (from my laptop) while on the road. I only need to access it from this one computer, although I may connect from either my phone's 3G/4G or via WiFi or some client's broadband, etc. So I won't know in advance which IP address I'll have. I am leaning toward a solution based on SSH and SFTP (or similar). SSH/SFTP would provided about all the functionality I anticipate needing. I would like to use SFTP and Dolphin to browse and download files. I'll use SSH and the terminal for anything else. My Linux file server is set up with OpenSSH. I think I have SSH relatively secured. I'm using Denyhosts too. But I want to go several steps further. I want to get the chances that anyone can get into my server as close to zero as possible while still allowing me to get access from the road. I'm not a sysadmin or programmer or real "superuser". I have to spend most of my time doing other things. I've heard about "port knocking" but I have never used it and I don't know how to implement it (although I'm willing to learn). I have already read a number of articles with titles such as: Top 20 OpenSSH Server Best Security Practices 20 Linux Server Hardening Security Tips Debian Linux Stop SSH User Hacking / Cracking Attacks with DenyHosts Software more... I have not implemented every single thing I've read about. I probably can't do that. But maybe there is something even better I can do in my situation because I only need access from a single laptop. I'm just one user. My server does not need to be accessible to the general public. Given all these facts, I'm hoping I can get some suggestions here that are within my capability to implement and that leverage these facts to create a great deal better security than general purpose suggestions in the articles above.

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• WCF security via message headers

  - by exalted

  I'm trying to implement "some sort of" server-client & zero-config security for some WCF service. The best (as well as easiest to me) solution that I found on www is the one described at http://www.dotnetjack.com/post/Automate-passing-valuable-information-in-WCF-headers.aspx (client-side) and http://www.dotnetjack.com/post/Processing-custom-WCF-header-values-at-server-side.aspx (corrisponding server-side). Below is my implementation for RequestAuth (descibed in the first link above): using System; using System.Diagnostics; using System.ServiceModel; using System.ServiceModel.Configuration; using System.ServiceModel.Dispatcher; using System.ServiceModel.Description; using System.ServiceModel.Channels; namespace AuthLibrary { /// <summary> /// Ref: http://www.dotnetjack.com/post/Automate-passing-valuable-information-in-WCF-headers.aspx /// </summary> public class RequestAuth : BehaviorExtensionElement, IClientMessageInspector, IEndpointBehavior { [DebuggerBrowsable(DebuggerBrowsableState.Never)] private string headerName = "AuthKey"; [DebuggerBrowsable(DebuggerBrowsableState.Never)] private string headerNamespace = "http://some.url"; public override Type BehaviorType { get { return typeof(RequestAuth); } } protected override object CreateBehavior() { return new RequestAuth(); } #region IClientMessageInspector Members // Keeping in mind that I am SENDING something to the server, // I only need to implement the BeforeSendRequest method public void AfterReceiveReply(ref System.ServiceModel.Channels.Message reply, object correlationState) { throw new NotImplementedException(); } public object BeforeSendRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel) { MessageHeader<string> header = new MessageHeader<string>(); header.Actor = "Anyone"; header.Content = "TopSecretKey"; //Creating an untyped header to add to the WCF context MessageHeader unTypedHeader = header.GetUntypedHeader(headerName, headerNamespace); //Add the header to the current request request.Headers.Add(unTypedHeader); return null; } #endregion #region IEndpointBehavior Members public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters) { throw new NotImplementedException(); } public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { clientRuntime.MessageInspectors.Add(this); } public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher) { throw new NotImplementedException(); } public void Validate(ServiceEndpoint endpoint) { throw new NotImplementedException(); } #endregion } } So first I put this code in my client WinForms application, but then I had problems signing it, because I had to sign also all third-party references eventhough http://msdn.microsoft.com/en-us/library/h4fa028b(v=VS.80).aspx at section "What Should Not Be Strong-Named" states: In general, you should avoid strong-naming application EXE assemblies. A strongly named application or component cannot reference a weak-named component, so strong-naming an EXE prevents the EXE from referencing weak-named DLLs that are deployed with the application. For this reason, the Visual Studio project system does not strong-name application EXEs. Instead, it strong-names the Application manifest, which internally points to the weak-named application EXE. I expected VS to avoid this problem, but I had no luck there, it complained about all the unsigned references, so I created a separate "WCF Service Library" project inside my solution containing only code above and signed that one. At this point entire solution compiled just okay. And here's my problem: When I fired up "WCF Service Configuration Editor" I was able to add new behavior element extension (say "AuthExtension"), but then when I tried to add that extension to my end point behavior it gives me: Exception has been thrown by the target of an invocation. So I'm stuck here. Any ideas?

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• Call Webservice without adding a WebReference - with Complex Types

  - by ck

  I'm using the code at This Site to call a webservice dynamically. [SecurityPermissionAttribute(SecurityAction.Demand, Unrestricted = true)] public static object CallWebService(string webServiceAsmxUrl, string serviceName, string methodName, object[] args) { System.Net.WebClient client = new System.Net.WebClient(); //-Connect To the web service using (System.IO.Stream stream = client.OpenRead(webServiceAsmxUrl + "?wsdl")) { //--Now read the WSDL file describing a service. ServiceDescription description = ServiceDescription.Read(stream); ///// LOAD THE DOM ///////// //--Initialize a service description importer. ServiceDescriptionImporter importer = new ServiceDescriptionImporter(); importer.ProtocolName = "Soap12"; // Use SOAP 1.2. importer.AddServiceDescription(description, null, null); //--Generate a proxy client. importer.Style = ServiceDescriptionImportStyle.Client; //--Generate properties to represent primitive values. importer.CodeGenerationOptions = System.Xml.Serialization.CodeGenerationOptions.GenerateProperties; //--Initialize a Code-DOM tree into which we will import the service. CodeNamespace nmspace = new CodeNamespace(); CodeCompileUnit unit1 = new CodeCompileUnit(); unit1.Namespaces.Add(nmspace); //--Import the service into the Code-DOM tree. This creates proxy code //--that uses the service. ServiceDescriptionImportWarnings warning = importer.Import(nmspace, unit1); if (warning == 0) //--If zero then we are good to go { //--Generate the proxy code CodeDomProvider provider1 = CodeDomProvider.CreateProvider("CSharp"); //--Compile the assembly proxy with the appropriate references string[] assemblyReferences = new string[5] { "System.dll", "System.Web.Services.dll", "System.Web.dll", "System.Xml.dll", "System.Data.dll" }; CompilerParameters parms = new CompilerParameters(assemblyReferences); CompilerResults results = provider1.CompileAssemblyFromDom(parms, unit1); //-Check For Errors if (results.Errors.Count > 0) { StringBuilder sb = new StringBuilder(); foreach (CompilerError oops in results.Errors) { sb.AppendLine("========Compiler error============"); sb.AppendLine(oops.ErrorText); } throw new System.ApplicationException("Compile Error Occured calling webservice. " + sb.ToString()); } //--Finally, Invoke the web service method Type foundType = null; Type[] types = results.CompiledAssembly.GetTypes(); foreach (Type type in types) { if (type.BaseType == typeof(System.Web.Services.Protocols.SoapHttpClientProtocol)) { Console.WriteLine(type.ToString()); foundType = type; } } object wsvcClass = results.CompiledAssembly.CreateInstance(foundType.ToString()); MethodInfo mi = wsvcClass.GetType().GetMethod(methodName); return mi.Invoke(wsvcClass, args); } else { return null; } } } This works fine when I use built in types, but for my own classes, I get this: Event Type: Error Event Source: TDX Queue Service Event Category: None Event ID: 0 Date: 12/04/2010 Time: 12:12:38 User: N/A Computer: TDXRMISDEV01 Description: System.ArgumentException: Object of type 'TDXDataTypes.AgencyOutput' cannot be converted to type 'AgencyOutput'. Server stack trace: at System.RuntimeType.CheckValue(Object value, Binder binder, CultureInfo culture, BindingFlags invokeAttr) at System.Reflection.MethodBase.CheckArguments(Object[] parameters, Binder binder, BindingFlags invokeAttr, CultureInfo culture, Signature sig) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) at TDXQueueEngine.GenericWebserviceProxy.CallWebService(String webServiceAsmxUrl, String serviceName, String methodName, Object[] args) in C:\CkAdmDev\TDXQueueEngine\TDXQueueEngine\TDXQueueEngine\GenericWebserviceProxy.cs:line 76 at TDXQueueEngine.TDXQueueWebserviceItem.Run() in C:\CkAdmDev\TDXQueueEngine\TDXQueueEngine\TDXQueueEngine\TDXQueueWebserviceItem.cs:line 99 at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs) at System.Runtime.Remoting.Messaging.StackBuilderSink.PrivateProcessMessage(RuntimeMethodHandle md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs) at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink) Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.EndInvokeHelper(Message reqMsg, Boolean bProxyCase) at System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(Object NotUsed, MessageData& msgData) at TDXQueueEngine.TDXQueue.RunProcess.EndInvoke(IAsyncResult result) at TDXQueueEngine.TDXQueue.processComplete(IAsyncResult ar) in C:\CkAdmDev\TDXQueueEngine\TDXQueueEngine\TDXQueueEngine\TDXQueue.cs:line 130 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. The classes reference the same assembly and the same version. Do I need to include my assembly as a reference when building the temporary assembly? If so, how? Thanks.

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• Optimizing Jaro-Winkler algorithm

  - by Pentium10

  I have this code for Jaro-Winkler algorithm taken from this website. I need to run 150,000 times to get distance between differences. It takes a long time, as I run on an Android mobile device. Can it be optimized more? public class Jaro { /** * gets the similarity of the two strings using Jaro distance. * * @param string1 the first input string * @param string2 the second input string * @return a value between 0-1 of the similarity */ public float getSimilarity(final String string1, final String string2) { //get half the length of the string rounded up - (this is the distance used for acceptable transpositions) final int halflen = ((Math.min(string1.length(), string2.length())) / 2) + ((Math.min(string1.length(), string2.length())) % 2); //get common characters final StringBuffer common1 = getCommonCharacters(string1, string2, halflen); final StringBuffer common2 = getCommonCharacters(string2, string1, halflen); //check for zero in common if (common1.length() == 0 || common2.length() == 0) { return 0.0f; } //check for same length common strings returning 0.0f is not the same if (common1.length() != common2.length()) { return 0.0f; } //get the number of transpositions int transpositions = 0; int n=common1.length(); for (int i = 0; i < n; i++) { if (common1.charAt(i) != common2.charAt(i)) transpositions++; } transpositions /= 2.0f; //calculate jaro metric return (common1.length() / ((float) string1.length()) + common2.length() / ((float) string2.length()) + (common1.length() - transpositions) / ((float) common1.length())) / 3.0f; } /** * returns a string buffer of characters from string1 within string2 if they are of a given * distance seperation from the position in string1. * * @param string1 * @param string2 * @param distanceSep * @return a string buffer of characters from string1 within string2 if they are of a given * distance seperation from the position in string1 */ private static StringBuffer getCommonCharacters(final String string1, final String string2, final int distanceSep) { //create a return buffer of characters final StringBuffer returnCommons = new StringBuffer(); //create a copy of string2 for processing final StringBuffer copy = new StringBuffer(string2); //iterate over string1 int n=string1.length(); int m=string2.length(); for (int i = 0; i < n; i++) { final char ch = string1.charAt(i); //set boolean for quick loop exit if found boolean foundIt = false; //compare char with range of characters to either side for (int j = Math.max(0, i - distanceSep); !foundIt && j < Math.min(i + distanceSep, m - 1); j++) { //check if found if (copy.charAt(j) == ch) { foundIt = true; //append character found returnCommons.append(ch); //alter copied string2 for processing copy.setCharAt(j, (char)0); } } } return returnCommons; } } I mention that in the whole process I make just instance of the script, so only once jaro= new Jaro(); If you are going to test and need examples so not break the script, you will find it here, in another thread for python optimization.

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• Problem receving in RXTX

  - by drhorrible

  I've been using RXTX for about a year now, without too many problems. I just started a new program to interact with a new piece of hardware, so I reused the connect() method I've used on my other projects, but I have a weird problem I've never seen before. The Problem The device works fine, because when I connect with hyperterminal, I send things and receive what I expect, and Serial Port Monitor(SPM) reflects this. However, when I run the simple hyperterminal-clone I wrote to diagnose the problem I'm having with my main app, bytes are sent, according to SPM, but nothing is received, and my SerialPortEventListener never fires. Even when I check for available data in the main loop, reader.ready() returns false. If I ignore this check, then I get an exception, details below. Relevant section of connect() method // Configure and open port port = (SerialPort) CommPortIdentifier.getPortIdentifier(name) .open(owner,1000) port.setSerialPortParams(baud, databits, stopbits, parity); port.setFlowControlMode(fc_mode); final BufferedReader br = new BufferedReader( new InputStreamReader( port.getInputStream(), "US-ASCII")); // Add listener to print received characters to screen port.addEventListener(new SerialPortEventListener(){ public void serialEvent(SerialPortEvent ev) { try { System.out.println("Received: "+br.readLine()); } catch (IOException e) { e.printStackTrace(); } } }); port.notifyOnDataAvailable(); Exception java.io.IOException: Underlying input stream returned zero bytes at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:268) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158) at java.io.InputStreamReader.read(InputStreamReader.java:167) at java.io.BufferedReader.fill(BufferedReader.java:136) at java.io.BufferedReader.read(BufferedReader.java:157) at <my code> The big question (again) I think I've eliminated all possible hardware problems, so what could be wrong with my code, or the RXTX library? Edit: something interesting When I open hyperterminal after sending a bunch of commands from java that should have gotten responses, all of the responses appear immediately, as if they had been put in the buffer somewhere, but unavailable. Edit 2: Tried something new, same results I ran the code example found here, with the same results. No data came in, but when I switched to a new program, it came all at once. Edit 3 The hardware is fine, and even a different computer has the same problem. I am not using any sort of USB adapter. I've started using PortMon, too, and it's giving me some interesting results. Hyperterminal and RXTX are not using the same settings, and RXTX always polls the port, unlike HyperTerminal, but I still can't see what settings would affect this. As soon as I can isolate the configuration from the constant polling, I'll post my PortMon logs. Edit 4 Is it possible that some sort of Windows update in the last 3 months could have caused this? It has screwed up one of my MATLAB mex-based programs once. Edit 5 I've also noticed some things that are different between HyperTerminal, RXTX, and a separate program I found that communicates with the device (but doesn't do what I want, which is why I'm rolling my own program) HyperTerminal - set to no flow control, but Serial Port Monitor's RTS and DTR indicators are green Other program - not sure what settings it thinks it's using, but only SPM's RTS indicator is green RXTX - no matter what flow control I set, only SPM's CTS and DTR indicators are on. From Serial Port Monitor's help files (paraphrased): the indicators display the state of the serial control lines RTS - Request To Send CTS - Clear To Send DTR - Data Terminal Ready

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• Object of type 'customObject' cannot be converted to type 'customObject'.

  - by Phani Kumar PV

  i am receiving the follwing error when i am invoking a custom object "Object of type 'customObject' cannot be converted to type 'customObject'." Following is the scenario when i am getting the error i am invoking a method in a dll dynamically. Load an assembly CreateInstance.... calling MethodInfo.Invoke() passing int, string as a parameter for my method is working fine = No exceptions are thrown. But if I try and pass a one of my own custom class objects as a parameter, then I get an ArgumentException exception, and it is not either an ArgumentOutOfRangeException or ArgumentNullException. "Object of type 'customObject' cannot be converted to type 'customObject'." I am doing this in a web application. The class file containing the method is in a different proj . also the custom object is a sepearte class in the same file. there is no such thing called a static aseembly in my code. I am trying to invoke a webmethod dynamically. this webmethod is having the customObject type as an input parameter. So when i invoke the webmethod i am dynamically creating the proxy assembly and all. From the same assembly i am trying to create an instance of the cusotm object assinging the values to its properties and then passing this object as a parameter and invoking the method. everything is dynamic and nothing is created static.. :( add reference is not used. Following is a sample code i tried to create it public static object CallWebService(string webServiceAsmxUrl, string serviceName, string methodName, object[] args) { System.Net.WebClient client = new System.Net.WebClient(); //-Connect To the web service using (System.IO.Stream stream = client.OpenRead(webServiceAsmxUrl + "?wsdl")) { //--Now read the WSDL file describing a service. ServiceDescription description = ServiceDescription.Read(stream); ///// LOAD THE DOM ///////// //--Initialize a service description importer. ServiceDescriptionImporter importer = new ServiceDescriptionImporter(); importer.ProtocolName = "Soap12"; // Use SOAP 1.2. importer.AddServiceDescription(description, null, null); //--Generate a proxy client. importer.Style = ServiceDescriptionImportStyle.Client; //--Generate properties to represent primitive values. importer.CodeGenerationOptions = System.Xml.Serialization.CodeGenerationOptions.GenerateProperties; //--Initialize a Code-DOM tree into which we will import the service. CodeNamespace nmspace = new CodeNamespace(); CodeCompileUnit unit1 = new CodeCompileUnit(); unit1.Namespaces.Add(nmspace); //--Import the service into the Code-DOM tree. This creates proxy code //--that uses the service. ServiceDescriptionImportWarnings warning = importer.Import(nmspace, unit1); if (warning == 0) //--If zero then we are good to go { //--Generate the proxy code CodeDomProvider provider1 = CodeDomProvider.CreateProvider("CSharp"); //--Compile the assembly proxy with the appropriate references string[] assemblyReferences = new string[5] { "System.dll", "System.Web.Services.dll", "System.Web.dll", "System.Xml.dll", "System.Data.dll" }; CompilerParameters parms = new CompilerParameters(assemblyReferences); CompilerResults results = provider1.CompileAssemblyFromDom(parms, unit1); //-Check For Errors if (results.Errors.Count > 0) { StringBuilder sb = new StringBuilder(); foreach (CompilerError oops in results.Errors) { sb.AppendLine("========Compiler error============"); sb.AppendLine(oops.ErrorText); } throw new System.ApplicationException("Compile Error Occured calling webservice. " + sb.ToString()); } //--Finally, Invoke the web service method Type foundType = null; Type[] types = results.CompiledAssembly.GetTypes(); foreach (Type type in types) { if (type.BaseType == typeof(System.Web.Services.Protocols.SoapHttpClientProtocol)) { Console.WriteLine(type.ToString()); foundType = type; } } object wsvcClass = results.CompiledAssembly.CreateInstance(foundType.ToString()); MethodInfo mi = wsvcClass.GetType().GetMethod(methodName); return mi.Invoke(wsvcClass, args); } else { return null; } } } I cant find anything static being done by me. any help is greatly appreciated. Regards, Phani Kumar PV

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• Understanding the memory consumption on iPhone

  - by zoul

  Hello! I am working on a 2D iPhone game using OpenGL ES and I keep hitting the 24 MB memory limit – my application keeps crashing with the error code 101. I tried real hard to find where the memory goes, but the numbers in Instruments are still much bigger than what I would expect. I ran the application with the Memory Monitor, Object Alloc, Leaks and OpenGL ES instruments. When the application gets loaded, free physical memory drops from 37 MB to 23 MB, the Object Alloc settles around 7 MB, Leaks show two or three leaks a few bytes in size, the Gart Object Size is about 5 MB and Memory Monitor says the application takes up about 14 MB of real memory. I am perplexed as where did the memory go – when I dig into the Object Allocations, most of the memory is in the textures, exactly as I would expect. But both my own texture allocation counter and the Gart Object Size agree that the textures should take up somewhere around 5 MB. I am not aware of allocating anything else that would be worth mentioning, and the Object Alloc agrees. Where does the memory go? (I would be glad to supply more details if this is not enough.) Update: I really tried to find where I could allocate so much memory, but with no results. What drives me wild is the difference between the Object Allocations (~7 MB) and real memory usage as shown by Memory Monitor (~14 MB). Even if there were huge leaks or huge chunks of memory I forget about, the should still show up in the Object Allocations, shouldn’t they? I’ve already tried the usual suspects, ie. the UIImage with its caching, but that did not help. Is there a way to track memory usage “debugger-style”, line by line, watching each statement’s impact on memory usage? What I have found so far: I really am using that much memory. It is not easy to measure the real memory consumption, but after a lot of counting I think the memory consumption is really that high. My fault. I found no easy way to measure the memory used. The Memory Monitor numbers are accurate (these are the numbers that really matter), but the Memory Monitor can’t tell you where exactly the memory goes. The Object Alloc tool is almost useless for tracking the real memory usage. When I create a texture, the allocated memory counter goes up for a while (reading the texture into the memory), then drops (passing the texture data to OpenGL, freeing). This is OK, but does not always happen – sometimes the memory usage stays high even after the texture has been passed on to OpenGL and freed from “my” memory. This means that the total amount of memory allocated as shown by the Object Alloc tool is smaller than the real total memory consumption, but bigger than the real consumption minus textures (real – textures < object alloc < real). Go figure. I misread the Programming Guide. The memory limit of 24 MB applies to textures and surfaces, not the whole application. The actual red line lies a bit further, but I could not find any hard numbers. The consensus is that 25–30 MB is the ceiling. When the system gets short on memory, it starts sending the memory warning. I have almost nothing to free, but other applications do release some memory back to the system, especially Safari (which seems to be caching the websites). When the free memory as shown in the Memory Monitor goes zero, the system starts killing. I had to bite the bullet and rewrite some parts of the code to be more efficient on memory, but I am probably still pushing it. I

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• How do you automap List<float> or float[] with Fluent NHibernate?

  - by Tom Bushell

  Having successfully gotten a sample program working, I'm now starting to do Real Work with Fluent NHibernate - trying to use Automapping on my project's class heirarchy. It's a scientific instrumentation application, and the classes I'm mapping have several properties that are arrays of floats e.g. private float[] _rawY; public virtual float[] RawY { get { return _rawY; } set { _rawY = value; } } These arrays can contain a maximum of 500 values. I didn't expect Automapping to work on arrays, but tried it anyway, with some success at first. Each array was auto mapped to a BLOB (using SQLite), which seemed like a viable solution. The first problem came when I tried to call SaveOrUpdate on the objects containing the arrays - I got "No persister for float[]" exceptions. So my next thought was to convert all my arrays into ILists e.g. public virtual IList<float> RawY { get; set; } But now I get: NHibernate.MappingException: Association references unmapped class: System.Single Since Automapping can deal with lists of complex objects, it never occured to me it would not be able to map lists of basic types. But after doing some Googling for a solution, this seems to be the case. Some people seem to have solved the problem, but the sample code I saw requires more knowledge of NHibernate than I have right now - I didn't understand it. Questions: 1. How can I make this work with Automapping? 2. Also, is it better to use arrays or lists for this application? I can modify my app to use either if necessary (though I prefer lists). Edit: I've studied the code in Mapping Collection of Strings, and I see there is test code in the source that sets up an IList of strings, e.g. public virtual IList<string> ListOfSimpleChildren { get; set; } [Test] public void CanSetAsElement() { new MappingTester<OneToManyTarget>() .ForMapping(m => m.HasMany(x => x.ListOfSimpleChildren).Element("columnName")) .Element("class/bag/element").Exists(); } so this must be possible using pure Automapping, but I've had zero luck getting anything to work, probably because I don't have the requisite knowlege of manually mapping with NHibernate. Starting to think I'm going to have to hack this (by encoding the array of floats as a single string, or creating a class that contains a single float which I then aggregate into my lists), unless someone can tell me how to do it properly. End Edit Here's my CreateSessionFactory method, if that helps formulate a reply... private static ISessionFactory CreateSessionFactory() { ISessionFactory sessionFactory = null; const string autoMapExportDir = "AutoMapExport"; if( !Directory.Exists(autoMapExportDir) ) Directory.CreateDirectory(autoMapExportDir); try { var autoPersistenceModel = AutoMap.AssemblyOf<DlsAppOverlordExportRunData>() .Where(t => t.Namespace == "DlsAppAutomapped") .Conventions.Add( DefaultCascade.All() ) ; sessionFactory = Fluently.Configure() .Database(SQLiteConfiguration.Standard .UsingFile(DbFile) .ShowSql() ) .Mappings(m => m.AutoMappings.Add(autoPersistenceModel) .ExportTo(autoMapExportDir) ) .ExposeConfiguration(BuildSchema) .BuildSessionFactory() ; } catch (Exception e) { Debug.WriteLine(e); } return sessionFactory; }

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• Odd tcp deadlock under windows

  - by John Robertson

  We are moving large amounts of data on a LAN and it has to happen very rapidly and reliably. Currently we use windows TCP as implemented in C++. Using large (synchronous) sends moves the data much faster than a bunch of smaller (synchronous) sends but will frequently deadlock for large gaps of time (.15 seconds) causing the overall transfer rate to plummet. This deadlock happens in very particular circumstances which makes me believe it should be preventable altogether. More importantly if we don't really know the cause we don't really know it won't happen some time with smaller sends anyway. Can anyone explain this deadlock? Deadlock description (OK, zombie-locked, it isn't dead, but for .15 or so seconds it stops, then starts again) The receiving side sends an ACK. The sending side sends a packet containing the end of a message (push flag is set) The call to socket.recv takes about .15 seconds(!) to return About the time the call returns an ACK is sent by the receiving side The the next packet from the sender is finally sent (why is it waiting? the tcp window is plenty big) The odd thing about (3) is that typically that call doesn't take much time at all and receives exactly the same amount of data. On a 2Ghz machine that's 300 million instructions worth of time. I am assuming the call doesn't (heaven forbid) wait for the received data to be acked before it returns, so the ack must be waiting for the call to return, or both must be delayed by something else. The problem NEVER happens when there is a second packet of data (part of the same message) arriving between 1 and 2. That part very clearly makes it sound like it has to do with the fact that windows TCP will not send back a no-data ACK until either a second packet arrives or a 200ms timer expires. However the delay is less than 200 ms (its more like 150 ms). The third unseemly character (and to my mind the real culprit) is (5). Send is definitely being called well before that .15 seconds is up, but the data NEVER hits the wire before that ack returns. That is the most bizarre part of this deadlock to me. Its not a tcp blockage because the TCP window is plenty big since we set SO_RCVBUF to something like 500*1460 (which is still under a meg). The data is coming in very fast (basically there is a loop spinning out data via send) so the buffer should fill almost immediately. According to msdn the buffer being full and at least one pending send should cause the data to be sent (though in another place it mentions that there various "heuristics" used in deciding when a send hits the wire). Anway, why the sender doesn't actually send more data during that .15 second pause is the most bizarre part to me. The information above was captured on the receiving side via wireshark (except of course the socket.recv return times which were logged in a text file). We tried changing the send buffer to zero and turning off Nagle on the sender (yes, I know Nagle is about not sending small packets - but we tried turning Nagle off in case that was part of the unstated "heuristics" affecting whether the message would be posted to the wire. Technically microsoft's Nagle is that a small packet isn't sent if the buffer is full and there is an outstanding ACK, so it seemed like a possibility).

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• Taking screenshots in Windows Vista, Windows 7, with transparent areas outside the app region

  - by Steve Sheldon

  Hey Folks, I am trying to take a screenshot of an application and I would like to make the parts of the rectangle that are not part of the applications region be transparent. So for instance on a standard windows application I would like to make the rounded corners transparent. I wrote a quick test application which works on on XP (or vista/windows 7 with aero turned off): protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); Graphics g = e.Graphics; // Just find a window to test with IntPtr hwnd = FindWindowByCaption(IntPtr.Zero, "Calculator"); WINDOWINFO info = new WINDOWINFO(); info.cbSize = (uint)Marshal.SizeOf(info); GetWindowInfo(hwnd, ref info); Rectangle r = Rectangle.FromLTRB(info.rcWindow.Left, info.rcWindow.Top, info.rcWindow.Right, info.rcWindow.Bottom); IntPtr hrgn = CreateRectRgn(info.rcWindow.Left, info.rcWindow.Top, info.rcWindow.Right, info.rcWindow.Bottom); GetWindowRgn(hwnd, hrgn); // fill a rectangle which would be where I would probably // write some mask color g.FillRectangle(Brushes.Red, r); // fill the region over the top, all I am trying to do here // is show the contrast between the applications region and // the rectangle that the region would be placed in Region region = Region.FromHrgn(hrgn); region.Translate(info.rcWindow.Left, info.rcWindow.Top); g.FillRegion(Brushes.Blue, region); } Quick side note: before commenting that this code is doing stuff it shouldn't (or should do, like dispose) in a paint function, I know, it's not going anywhere but this post and is designed purely as a way to quickly show the problem, and that it does... OK, back to the problem ;) When I run this test app on XP (or Vista/Windows 7 with Aero off), I get something like this, which is great because I can eek an xor mask out of this that can be used later with BitBlt. Here is the problem, on Vista or Windows 7 with Aero enabled, there isn't necessarily a region on the window, in fact in most cases there isn't. Can anybody help me figure out how to get the region of the application like this on these platforms. Here are some of the approaches I have already tried... 1. Using the PrintWindow function: This doesn't work because it gives back a screenshot taken of the window with Aero off and this window is a different shape from the window returned with Aero on 2 Using the Desktop Window Manager API to get a full size thumbnail: This didn't work because it draws directly to the screen and from what I can tell you can't get a screenshot directly out of this api. Yeah, I could open a window with a pink background, show the thumbnail, take a screenshot then hide this temporary window but thats a horrible user experience and a complete hack I would rather not have my name on. 3. Using Graphics.CopyFromScreen or some other pinvoke variant of this: This doesn't work because I can't assume that the window I need information from is at the top of the z-order on the screen. Right now, the best solution I can think of is to special case Aero on Windows 7 and Vista to manually rub out the corners by hard coding some graphics paths I paint out but this solution would suck since any application that performs custom skinning will break this. Can you think of another or better solution? If you are here, thanks for taking time to read this post, I appreciate any help or direction that you can offer!

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• WCF endpoint exception

  - by Lijo

  Hi Team, I am just trying with various WCF(in .Net 3.0) scenarios. I am using self hosting. I am getting an exception as "Service 'MyServiceLibrary.NameDecorator' has zero application (non-infrastructure) endpoints. This might be because no configuration file was found for your application, or because no service element matching the service name could be found in the configuration file, or because no endpoints were defined in the service element." I have a config file as follows (which has an endpoint) <?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <services> <service name="Lijo.Samples.NameDecorator" behaviorConfiguration="WeatherServiceBehavior"> <host> <baseAddresses> <add baseAddress="http://localhost:8010/ServiceModelSamples/FreeServiceWorld"/> </baseAddresses> </host> <endpoint address="" binding="wsHttpBinding" contract="Lijo.Samples.IElementaryService" /> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="WeatherServiceBehavior"> <serviceMetadata httpGetEnabled="true"/> <serviceDebug includeExceptionDetailInFaults="False"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> </configuration> And a Host as using System.ServiceModel; using System.ServiceModel.Dispatcher; using System.ServiceModel.Channels; using System.ServiceModel.Description; using System.Runtime.Serialization; namespace MySelfHostConsoleApp { class Program { static void Main(string[] args) { System.ServiceModel.ServiceHost myHost = new ServiceHost(typeof(MyServiceLibrary.NameDecorator)); myHost.Open(); Console.ReadLine(); } } } My Service is as follows using System.ServiceModel; using System.Runtime.Serialization; namespace MyServiceLibrary { [ServiceContract(Namespace = "http://Lijo.Samples")] public interface IElementaryService { [OperationContract] CompanyLogo GetLogo(); } public class NameDecorator : IElementaryService { public CompanyLogo GetLogo() { CircleType cirlce = new CircleType(); CompanyLogo logo = new CompanyLogo(cirlce); return logo; } } [DataContract] public abstract class IShape { public abstract string SelfExplain(); } [DataContract(Name = "Circle")] public class CircleType : IShape { public override string SelfExplain() { return "I am a Circle"; } } [DataContract(Name = "Triangle")] public class TriangleType : IShape { public override string SelfExplain() { return "I am a Triangle"; } } [DataContract] [KnownType(typeof(CircleType))] [KnownType(typeof(TriangleType))] public class CompanyLogo { private IShape m_shapeOfLogo; [DataMember] public IShape ShapeOfLogo { get { return m_shapeOfLogo; } set { m_shapeOfLogo = value; } } public CompanyLogo(IShape shape) { m_shapeOfLogo = shape; } } } Could you please help me to understand what I am missing here? Thanks Lijo

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• c# SendMessage and Skype woes

  - by Xcelled194

  I'm trying to create an add-on to Skype with C#. I don't want to use Skype4COM, as I'd like the experience with messages and such. Unfortunately, the messages are tripping me up. I've got the pumps and such set up. They all work, and my app successfully sends the "APIDiscover" message to Skype, gets a "PendingAuth" response and then the "AttachSuccess" message. However, when I try to send "ping" to Skype (to which it should reply "pong") nothing happens. The return code from SendMessage is 0 but Marshall.GetLastWin32Error is 1400 (Invalid handle). The handle was returned with the AttachSuccess method. The equivalent C++ code does work, so I'm at a loss. First is the C++ code I'm using as a guide: Here's the (cut down) message pump. You can ignore everything but where I put the //<---- static LRESULT APIENTRY SkypeAPITest_Windows_WindowProc( HWND hWindow, UINT uiMessage, WPARAM uiParam, LPARAM ulParam) { LRESULT lReturnCode; bool fIssueDefProc; lReturnCode=0; fIssueDefProc=false; switch(uiMessage) { case WM_COPYDATA: if( hGlobal_SkypeAPIWindowHandle==(HWND)uiParam ) { PCOPYDATASTRUCT poCopyData=(PCOPYDATASTRUCT)ulParam; printf( "Message from Skype(%u): %.*s\n", poCopyData->dwData, poCopyData->cbData, poCopyData->lpData); lReturnCode=1; } break; default: if( uiMessage==uiGlobal_MsgID_SkypeControlAPIAttach ) { switch(ulParam) { case SKYPECONTROLAPI_ATTACH_SUCCESS: printf("!!! Connected; to terminate issue #disconnect\n"); hGlobal_SkypeAPIWindowHandle=(HWND)uiParam;//<---- Right here is where we receive the handle from Skype. break; } if( fIssueDefProc ) lReturnCode=DefWindowProc( hWindow, uiMessage, uiParam, ulParam); return(lReturnCode); } and this is the (again dumbed down) "sending message" code void __cdecl Global_InputProcessingThread(void *) { static char acInputRow[1024]; bool fProcessed; if( SendMessageTimeout( HWND_BROADCAST, uiGlobal_MsgID_SkypeControlAPIDiscover, (WPARAM)hInit_MainWindowHandle, 0, SMTO_ABORTIFHUNG, 1000, NULL)!=0 ) { while(Global_Console_ReadRow( acInputRow, sizeof(acInputRow)-1)) { if( fProcessed==false && hGlobal_SkypeAPIWindowHandle!=NULL ) { COPYDATASTRUCT oCopyData; // send command to skype oCopyData.dwData=0; oCopyData.lpData=acInputRow; oCopyData.cbData=strlen(acInputRow)+1; if( oCopyData.cbData!=1 ) { if( SendMessage( hGlobal_SkypeAPIWindowHandle, WM_COPYDATA, (WPARAM)hInit_MainWindowHandle, (LPARAM)&oCopyData)==FALSE ) { hGlobal_SkypeAPIWindowHandle=NULL; printf("!!! Disconnected\n"); } } } } } SendMessage( hInit_MainWindowHandle, WM_CLOSE, 0, 0); SetEvent(hGlobal_ThreadShutdownEvent); fGlobal_ThreadRunning=false; } And now here's my C# public bool PreFilterMessage(ref Message m) { Console.WriteLine(m.ToString()); if (m.Msg == WM_COPYDATA && SkypeAPIWindowHandle == m.WParam) { SkypeMessage(m); return true; } if (m.Msg == MsgApiAttach) { switch (m.LParam.ToInt32()) { case (int)SkypeControlAPIAttach.SUCCESS: SkypeAPIWindowHandle = m.WParam; //Here's where we set the Skype Handle AttachSuccess(m); return true; } } return false; //Defer all other messages } And here is my DLL import and Sending code [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] static extern IntPtr SendMessageA(IntPtr hWnd, UInt32 Msg, IntPtr wParam, ref MsgHelper.COPYDATASTRUCT lParam); public static void Command(string c) { if (c.Last() != '\0') c += "\0"; //Make string null terminated Console.WriteLine(); MsgHelper.COPYDATASTRUCT cda = new MsgHelper.COPYDATASTRUCT(); cda.dwData = new IntPtr(0); cda.lpData = c; cda.cbData = c.Length + 1; Marshal.GetLastWin32Error(); //Clear last error Console.WriteLine(SendMessageA(mHelper.SkypeAPIWindowHandle, MsgHelper.WM_COPYDATA, IntPtr.Zero, ref cda)); Console.WriteLine(Marshal.GetLastWin32Error()); } COPYDATASTRUCT is: public struct COPYDATASTRUCT { public IntPtr dwData; public int cbData; [MarshalAs(UnmanagedType.LPStr)] public string lpData; } I think that's everything. Let me know if I forgot something. Any ideas why I'm getting the 1400?

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• Deserializing Metafile

  - by Kildareflare

  I have an application that works with Enhanced Metafiles. I am able to create them, save them to disk as .emf and load them again no problem. I do this by using the gdi32.dll methods and the DLLImport attribute. However, to enable Version Tolerant Serialization I want to save the metafile in an object along with other data. This essentially means that I need to serialize the metafile data as a byte array and then deserialize it again in order to reconstruct the metafile. The problem I have is that the deserialized data would appear to be corrupted in some way, since the method that I use to reconstruct the Metafile raises a "Parameter not valid exception". At the very least the pixel format and resolutions have changed. Code use is below. [DllImport("gdi32.dll")] public static extern uint GetEnhMetaFileBits(IntPtr hemf, uint cbBuffer, byte[] lpbBuffer); [DllImport("gdi32.dll")] public static extern IntPtr SetEnhMetaFileBits(uint cbBuffer, byte[] lpBuffer); [DllImport("gdi32.dll")] public static extern bool DeleteEnhMetaFile(IntPtr hemf); The application creates a metafile image and passes it to the method below. private byte[] ConvertMetaFileToByteArray(Image image) { byte[] dataArray = null; Metafile mf = (Metafile)image; IntPtr enhMetafileHandle = mf.GetHenhmetafile(); uint bufferSize = GetEnhMetaFileBits(enhMetafileHandle, 0, null); if (enhMetafileHandle != IntPtr.Zero) { dataArray = new byte[bufferSize]; GetEnhMetaFileBits(enhMetafileHandle, bufferSize, dataArray); } DeleteEnhMetaFile(enhMetafileHandle); return dataArray; } At this point the dataArray is inserted into an object and serialized using a BinaryFormatter. The saved file is then deserialized again using a BinaryFormatter and the dataArray retrieved from the object. The dataArray is then used to reconstruct the original Metafile using the following method. public static Image ConvertByteArrayToMetafile(byte[] data) { Metafile mf = null; try { IntPtr hemf = SetEnhMetaFileBits((uint)data.Length, data); mf = new Metafile(hemf, true); } catch (Exception ex) { System.Windows.Forms.MessageBox.Show(ex.Message); } return (Image)mf; } The reconstructed metafile is then saved saved to disk as a .emf (Model) at which point it can be accessed by the Presenter for display. private static void SaveFile(Image image, String filepath) { try { byte[] buffer = ConvertMetafileToByteArray(image); File.WriteAllBytes(filepath, buffer); //will overwrite file if it exists } catch (Exception ex) { System.Windows.Forms.MessageBox.Show(ex.Message); } } The problem is that the save to disk fails. If this same method is used to save the original Metafile before it is serialized everything is OK. So something is happening to the data during serialization/deserializtion. Indeed if I check the Metafile properties in the debugger I can see that the ImageFlags, PropertyID, resolution and pixelformats change. Original Format32bppRgb changes to Format32bppArgb Original Resolution 81 changes to 96 I've trawled though google and SO and this has helped me get this far but Im now stuck. Does any one have enough experience with Metafiles / serialization to help..? EDIT: If I serialize/deserialize the byte array directly (without embedding in another object) I get the same problem.

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• Apple push Notification Feedback service Not working

  - by Yassmeen

  Hi, I am developing an iPhone App that uses Apple Push Notifications. On the iPhone side everything is fine, on the server side I have a problem. Notifications are sent correctly however when I try to query the feedback service to obtain a list of devices from which the App has been uninstalled, I always get zero results. I know that I should obtain one result as the App has been uninstalled from one of my test devices. After 24 hours and more I still have no results from the feedback service.. Any ideas? Does anybody know how long it takes for the feedback service to recognize that my App has been uninstalled from my test device? Note: I have another push notification applications on the device so I know that my app is not the only app. The code - C#: public static string CheckFeedbackService(string certaName, string hostName) { SYLogger.Log("Check Feedback Service Started"); ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(ValidateServerCertificate); // Create a TCP socket connection to the Apple server on port 2196 TcpClient tcpClientF = null; SslStream sslStreamF = null; string result = string.Empty; //Contect to APNS& Add the Apple cert to our collection X509Certificate2Collection certs = new X509Certificate2Collection { GetServerCert(certaName) }; //Set up byte[] buffer = new byte[38]; int recd = 0; DateTime minTimestamp = DateTime.Now.AddYears(-1); // Create a TCP socket connection to the Apple server on port 2196 try { using (tcpClientF = new TcpClient(hostName, 2196)) { SYLogger.Log("Client Connected ::" + tcpClientF.Connected); // Create a new SSL stream over the connection sslStreamF = new SslStream(tcpClientF.GetStream(), true,ValidateServerCertificate); // Authenticate using the Apple cert sslStreamF.AuthenticateAsClient(hostName, certs, SslProtocols.Default, false); SYLogger.Log("Stream Readable ::" + sslStreamF.CanRead); SYLogger.Log("Host Name ::"+hostName); SYLogger.Log("Cert Name ::" + certs[0].FriendlyName); if (sslStreamF != null) { SYLogger.Log("Connection Started"); //Get the first feedback recd = sslStreamF.Read(buffer, 0, buffer.Length); SYLogger.Log("Buffer length ::" + recd); //Continue while we have results and are not disposing while (recd > 0) { SYLogger.Log("Reading Started"); //Get our seconds since 1970 ? byte[] bSeconds = new byte[4]; byte[] bDeviceToken = new byte[32]; Array.Copy(buffer, 0, bSeconds, 0, 4); //Check endianness if (BitConverter.IsLittleEndian) Array.Reverse(bSeconds); int tSeconds = BitConverter.ToInt32(bSeconds, 0); //Add seconds since 1970 to that date, in UTC and then get it locally var Timestamp = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(tSeconds).ToLocalTime(); //Now copy out the device token Array.Copy(buffer, 6, bDeviceToken, 0, 32); string deviceToken = BitConverter.ToString(bDeviceToken).Replace("-", "").ToLower().Trim(); //Make sure we have a good feedback tuple if (deviceToken.Length == 64 && Timestamp > minTimestamp) { SYLogger.Log("Feedback " + deviceToken); result = deviceToken; } //Clear array to reuse it Array.Clear(buffer, 0, buffer.Length); //Read the next feedback recd = sslStreamF.Read(buffer, 0, buffer.Length); } SYLogger.Log("Reading Ended"); } } } catch (Exception e) { SYLogger.Log("Authentication failed - closing the connection::" + e); return "NOAUTH"; } finally { // The client stream will be closed with the sslStream // because we specified this behavior when creating the sslStream. if (sslStreamF != null) sslStreamF.Close(); if (tcpClientF != null) tcpClientF.Close(); //Clear array on error Array.Clear(buffer, 0, buffer.Length); } SYLogger.Log("Feedback ended "); return result; }

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• Search engine solution for Django that actually works?

  - by prometheus

  The story so far: Decided to go with Xapian as search backend because it has all search-engine features I was looking for, knows about Unicode, stemming, has few dependencies and requires no bloated app-server installation on top of it. Tried Django and Haystack (plus xapian-haystack, the backend glue code to tie Haystack to Xapian) because it was advertised on quite some blogs as "working". Did not work. Neither django-haystack nor the xapian-haystack project provide a version combination that actually works together. MASTER from both projects yields an error from Xapian, so it's not stable at all. Haystack 1.0.1 and xapian-haystack 1.0.x/1.1.0 are not API-compatible. Plus, in a minimally working installation of Haystack 1.0.1 and xapian-haystack MASTER, any complex query yields zero results due to errors in either django-haystack or xapian-haystack (I double-verified this), maybe because the unit-tests actually test very simple cases, and no edge-cases at all. Tried Djapian. The source-code is riddled with spelling errors (mind you, in variable names, not comments), documentation is also riddled with ambiguities and outdated information that will never lead to a working installation. Not surprisingly, users rarely ask for features but how to get it working in the first place. Next on the plate: exploring Solr (installing a Java environment plus Tomcat gives me headaches, the machine is RAM- and CPU-constrained), or Lucene (slightly less headaches, but still). Before I proceed spending more time with a solution that might or might not work as advertised, I'd like to know: Did anyone ever get an actual, real-world search solution working in Django? I'm serious. I find it really frustrating reading about "large problems mostly solved", and then realizing that you will never get a working installation from the source-code because, actually, all bloggers dealing with those "mostly solved problems" never went past basic installation and copy-pasting the official tutorials. So here are the requirements: must be able to search for 10-100 terms in one query must handle + (term must be present) and - (term must not be present), AND/OR must handle arbitrary grouping (i.e. parentheses around AND/OR) must allow for Django-ORM filtering before or after fulltext-search (i.e. pre-/post-processing of results with the full set of filters that Django knows about) alternatively, there must be a facility to bulk-fetch the result set and transform it into a QuerySet should be light on the machine, so preferably no humongous JVM and Java-based app-server installation Is there anything out there that does this? I'm not interested in anecdotal evidence, or references to some blog posts that claim it should be working. I'd like to hear from someone who actually has a fully-functional setup working in the real world, under real conditions, with real queries. EDIT: Let me repeat again that I'm not so much interested in anecdotal evidence that someone, somewhere has a somewhat running installation working with unspecified properties. I already went there, I read all the blog posts, mailing lists, I contacted the authors, but when it came to actual implementation of real-world scenarios, nothing ever worked as advertised. Also, and a user below brought that point up as well, considering the TCO of any project, I'm definitely not interested in hearing that someone, somewhere was able to pull it off once a vendor parachuted in an unknown number of specialists to monkey-patch the whole installation with specific domain-knowledge that's documented nowhere. So, please, if you claim you have a working installation that actually satisfies minimum requirements for a full-fledged search (see requirements above), please provide the following so that we can all benefit from a search solution for Django that actually solves the problem: exact Linux distribution, release version, exact release version of Haystack (or equivalent) and release version of search backend, exact release version of the search engine publicly (!) available documentation how to set up all components exactly in the way that your installation was set up such that the minimal requirements above are met. Thank you.

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• Search engine solution for Django that actually works?

  - by prometheus

  The story so far: Decided to go with Xapian as search backend because it has all search-engine features I was looking for, knows about Unicode, stemming, has few dependencies and requires no bloated app-server installation on top of it. Tried Django and Haystack (plus xapian-haystack, the backend glue code to tie Haystack to Xapian) because it was advertised on quite some blogs as "working". Did not work. Neither django-haystack nor the xapian-haystack project provide a version combination that actually works together. MASTER from both projects yields an error from Xapian, so it's not stable at all. Haystack 1.0.1 and xapian-haystack 1.0.x/1.1.0 are not API-compatible. Plus, in a minimally working installation of Haystack 1.0.1 and xapian-haystack MASTER, any complex query yields zero results due to errors in either django-haystack or xapian-haystack (I double-verified this), maybe because the unit-tests actually test very simple cases, and no edge-cases at all. Tried Djapian. The source-code is riddled with spelling errors (mind you, in variable names, not comments), documentation is also riddled with ambiguities and outdated information that will never lead to a working installation. Not surprisingly, users rarely ask for features but how to get it working in the first place. Next on the plate: exploring Solr (installing a Java environment plus Tomcat gives me headaches, the machine is RAM- and CPU-constrained), or Lucene (slightly less headaches, but still). Before I proceed spending more time with a solution that might or might not work as advertised, I'd like to know: Did anyone ever get an actual, real-world search solution working in Django? I'm serious. I find it really frustrating reading about "large problems mostly solved", and then realizing that you will never get a working installation from the source-code because, actually, all bloggers dealing with those "mostly solved problems" never went past basic installation and copy-pasting the official tutorials. So here are the requirements: must be able to search for 10-100 terms in one query must handle + (term must be present) and - (term must not be present), AND/OR must handle arbitrary grouping (i.e. parentheses around AND/OR) must allow for Django-ORM filtering before or after fulltext-search (i.e. pre-/post-processing of results with the full set of filters that Django knows about) alternatively, there must be a facility to bulk-fetch the result set and transform it into a QuerySet should be light on the machine, so preferably no humongous JVM and Java-based app-server installation Is there anything out there that does this? I'm not interested in anecdotal evidence, or references to some blog posts that claim it should be working. I'd like to hear from someone who actually has a fully-functional setup working in the real world, under real conditions, with real queries. EDIT: Let me repeat again that I'm not so much interested in anecdotal evidence that someone, somewhere has a somewhat running installation working with unspecified properties. I already went there, I read all the blog posts, mailing lists, I contacted the authors, but when it came to actual implementation of real-world scenarios, nothing ever worked as advertised. Also, and a user below brought that point up as well, considering the TCO of any project, I'm definitely not interested in hearing that someone, somewhere was able to pull it off once a vendor parachuted in an unknown number of specialists to monkey-patch the whole installation with specific domain-knowledge that's documented nowhere. So, please, if you claim you have a working installation that actually satisfies minimum requirements for a full-fledged search (see requirements above), please provide the following so that we can all benefit from a search solution for Django that actually solves the problem: exact Linux distribution, release version, exact release version of Haystack (or equivalent) and release version of search backend, exact release version of the search engine publicly (!) available documentation how to set up all components exactly in the way that your installation was set up such that the minimal requirements above are met. Thank you.

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• DataGridView CheckBox events

  - by Kevin

  I'm making a DataGridView with a series of Checkboxes in it with the same labels horizontally and vertically. Any labels that are the same, the checkboxes will be inactive, and I only want one of the two "checks" for each combination to be valid. The following screenshot shows what I have: Anything that's checked on the lower half, I want UN-checked on the upper. So if [quux, spam] (or [7, 8] for zero-based co-ordinates) is checked, I want [spam, quux] ([8, 7]) un-checked. What I have so far is the following: dgvSysGrid.RowHeadersWidthSizeMode = DataGridViewRowHeadersWidthSizeMode.AutoSizeToAllHeaders; dgvSysGrid.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.AllCells; string[] allsysNames = { "heya", "there", "lots", "of", "names", "foo", "bar", "quux", "spam", "eggs", "bacon" }; // Add a column for each entry, and a row for each entry, and mark the "diagonals" as readonly for (int i = 0; i < allsysNames.Length; i++) { dgvSysGrid.Columns.Add(new DataGridViewCheckBoxColumn(false)); dgvSysGrid.Columns[i].HeaderText = allsysNames[i]; dgvSysGrid.Rows.Add(); dgvSysGrid.Rows[i].HeaderCell.Value = allsysNames[i]; // Mark all of the "diagonals" as unable to change DataGridViewCell curDiagonal = dgvSysGrid[i, i]; curDiagonal.ReadOnly = true; curDiagonal.Style.BackColor = Color.Black; curDiagonal.Style.ForeColor = Color.Black; } // Hook up the event handler so that we can change the "corresponding" checkboxes as needed //dgvSysGrid.CurrentCellDirtyStateChanged += new EventHandler(dgvSysGrid_CurrentCellDirtyStateChanged); dgvSysGrid.CellValueChanged += new DataGridViewCellEventHandler(dgvSysGrid_CellValueChanged); } void dgvSysGrid_CellValueChanged(object sender, DataGridViewCellEventArgs e) { Point cur = new Point(e.ColumnIndex, e.RowIndex); // Change the diagonal checkbox to the opposite state DataGridViewCheckBoxCell curCell = (DataGridViewCheckBoxCell)dgvSysGrid[cur.X, cur.Y]; DataGridViewCheckBoxCell diagCell = (DataGridViewCheckBoxCell)dgvSysGrid[cur.Y, cur.X]; if ((bool)(curCell.Value) == true) { diagCell.Value = false; } else { diagCell.Value = true; } } /// <summary> /// Change the corresponding checkbox to the opposite state of the current one /// </summary> /// <param name="sender"></param> /// <param name="e"></param> void dgvSysGrid_CurrentCellDirtyStateChanged(object sender, EventArgs e) { Point cur = dgvSysGrid.CurrentCellAddress; // Change the diagonal checkbox to the opposite state DataGridViewCheckBoxCell curCell = (DataGridViewCheckBoxCell)dgvSysGrid[cur.X, cur.Y]; DataGridViewCheckBoxCell diagCell = (DataGridViewCheckBoxCell)dgvSysGrid[cur.Y, cur.X]; if ((bool)(curCell.Value) == true) { diagCell.Value = false; } else { diagCell.Value = true; } } The problem comes is that the cell value changed always seems to be "one behind" where you actually click if I use the CellValueChanged event, and I'm not sure how to get the current cell if I'm in the "dirty" state as curCell comes in as a null (suggesting the current cell address is wrong somehow, but I didn't try and get that value out) meaning that path isn't working at all. Basically, how do I get the "right" address with the right boolean value so that my flipping algorithm will work?

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• Opening an SQL CE file at runtime with Entity Framework 4

  - by David Veeneman

  I am getting started with Entity Framework 4, and I an creating a demo app as a learning exercise. The app is a simple documentation builder, and it uses a SQL CE store. Each documentation project has its own SQL CE data file, and the user opens one of these files to work on a project. The EDM is very simple. A documentation project is comprised of a list of subjects, each of which has a title, a description, and zero or more notes. So, my entities are Subject, which contains Title and Text properties, and Note, which has Title and Text properties. There is a one-to-many association from Subject to Note. I am trying to figure out how to open an SQL CE data file. A data file must match the schema of the SQL CE database created by EF4's Create Database Wizard, and I will implement a New File use case elsewhere in the app to implement that requirement. Right now, I am just trying to get an existing data file open in the app. I have reproduced my existing 'Open File' code below. I have set it up as a static service class called File Services. The code isn't working quite yet, but there is enough to show what I am trying to do. I am trying to hold the ObjectContext open for entity object updates, disposing it when the file is closed. So, here is my question: Am I on the right track? What do I need to change to make this code work with EF4? Is there an example of how to do this properly? Thanks for your help. My existing code: public static class FileServices { #region Private Fields // Member variables private static EntityConnection m_EntityConnection; private static ObjectContext m_ObjectContext; #endregion #region Service Methods /// <summary> /// Opens an SQL CE database file. /// </summary> /// <param name="filePath">The path to the SQL CE file to open.</param> /// <param name="viewModel">The main window view model.</param> public static void OpenSqlCeFile(string filePath, MainWindowViewModel viewModel) { // Configure an SQL CE connection string var sqlCeConnectionString = string.Format("Data Source={0}", filePath); // Configure an EDM connection string var builder = new EntityConnectionStringBuilder(); builder.Metadata = "res://*/EF4Model.csdl|res://*/EF4Model.ssdl|res://*/EF4Model.msl"; builder.Provider = "System.Data.SqlServerCe"; builder.ProviderConnectionString = sqlCeConnectionString; var entityConnectionString = builder.ToString(); // Connect to the model m_EntityConnection = new EntityConnection(entityConnectionString); m_EntityConnection.Open(); // Create an object context m_ObjectContext = new Model1Container(); // Get all Subject data IQueryable<Subject> subjects = from s in Subjects orderby s.Title select s; // Set view model data property viewModel.Subjects = new ObservableCollection<Subject>(subjects); } /// <summary> /// Closes an SQL CE database file. /// </summary> public static void CloseSqlCeFile() { m_EntityConnection.Close(); m_ObjectContext.Dispose(); } #endregion }

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• Code Golf: Finite-state machine!

  - by Adam Matan

  Finite state machine A deterministic finite state machine is a simple computation model, widely used as an introduction to automata theory in basic CS courses. It is a simple model, equivalent to regular expression, which determines of a certain input string is Accepted or Rejected. Leaving some formalities aside, A run of a finite state machine is composed of: alphabet, a set of characters. states, usually visualized as circles. One of the states must be the start state. Some of the states might be accepting, usually visualized as double circles. transitions, usually visualized as directed arches between states, are directed links between states associated with an alphabet letter. input string, a list of alphabet characters. A run on the machine begins at the starting state. Each letter of the input string is read; If there is a transition between the current state and another state which corresponds to the letter, the current state is changed to the new state. After the last letter was read, if the current state is an accepting state, the input string is accepted. If the last state was not an accepting state, or a letter had no corresponding arch from a state during the run, the input string is rejected. Note: This short descruption is far from being a full, formal definition of a FSM; Wikipedia's fine article is a great introduction to the subject. Example For example, the following machine tells if a binary number, read from left to right, has an even number of 0s: The alphabet is the set {0,1}. The states are S1 and S2. The transitions are (S1, 0) -> S2, (S1, 1) -> S1, (S2, 0) -> S1 and (S2, 1) -> S2. The input string is any binary number, including an empty string. The rules: Implement a FSM in a language of your choice. Input The FSM should accept the following input: <States> List of state, separated by space mark. The first state in the list is the start state. Accepting states begin with a capital letter. <transitions> One or more lines. Each line is a three-tuple: origin state, letter, destination state) <input word> Zero or more characters, followed by a newline. For example, the aforementioned machine with 1001010 as an input string, would be written as: S1 s2 S1 0 s2 S1 1 S1 s2 0 S1 s2 1 s2 1001010 Output The FSM's run, written as <State> <letter> -> <state>, followed by the final state. The output for the example input would be: S1 1 -> S1 S1 0 -> s2 s2 0 -> S1 S1 1 -> S1 S1 0 -> s2 s2 1 -> s2 s2 0 -> S1 ACCEPT For the empty input '': S1 ACCEPT For 101: S1 1 -> S1 S1 0 -> s2 s2 1 -> s2 REJECT For '10X': S1 1 -> S1 S1 0 -> s2 s2 X REJECT Prize A nice bounty will be given to the most elegant and short solution. Reference implementation A reference Python implementation will be published soon.

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• skips nines in counter object, AS3

  - by VideoDnd

  It's not that noticeable at first, but my counter skips over to zero and ignores the nines. How can I get my counter to not skip over the nines? my FLA import flash.display.Sprite; import flash.events.Event; import flash.utils.Timer; import flash.events.TimerEvent; var timer:Timer; var count:int = 0; var fcount:int = 0; var numbers:NumbersView; trace("-----new NumberDocument created"); timer = new Timer(10); timer.addEventListener(TimerEvent.TIMER, incrementCounter); timer.start(); numbers = new NumbersView(); addChild(numbers); addEventListener(Event.ENTER_FRAME, enterFrameHandler); //addEventListener(Event.ADDED_TO_STAGE, traceMeOut); function incrementCounter(event:TimerEvent) { count++; fcount=int(count*count/1000); } function formatCount(i:int):String { return ("000000000" + i).substr(-9, 9); } function enterFrameHandler(e:Event):void { numbers.setTime(formatCount(fcount)); } function traceMeOut() { trace("-----Im here on stage!"); } NumbersView.as //NumbersView.as - Your Document Class package { import flash.display.MovieClip; public class NumbersView extends MovieClip { private var _listItems:Array; private const numHeight:int = 120; public function NumbersView() { _listItems = new Array(); var item:NumberImage; for (var i:Number = 0; i < 9; i++) { item = new NumberImage(); addChild(item); item.x = i * item.width; _listItems.push(item); } setTime('123456789'); } public function setTime($number:String):void { var nums:Array = $number.split(""); trace(nums); for (var i:Number = 0; i < nums.length; i++) { _listItems[i].start( int(nums[i]) ); } } } } Variation of NumbersView.as with Tweener //...SNIPPET public function setTime($number:String):void { var nums:Array = $number.split(""); for (var i:Number = 0; i < nums.length; i++) { if (nums[i] == previousNums[i]) continue; Tweener.removeTweens(_listItems[i]); var nuNum:int = int(nums[i]); var nuY:int = nuNum == 0 ? 0 : (nuNum - 1) * -numHeight; trace("nuY = " + nuY); trace("cY = " + _listItems[i].y); Tweener.addTween(_listItems[i], { y:nuY, time:0 } ); } previousNums = nums; } Variation of NumbersView.as that doesn't skip 9, but resets from bottom every count //...SNIPPET public function setTime($number:String):void { var nums:Array = $number.split(""); for (var i:Number = 0; i < nums.length; i++) { if (nums[i] == previousNums[i]) continue; Tweener.removeTweens(_listItems[i]); var newY:int = int(nums[i]) * -numHeight; if (_listItems[i].y < 0) _listItems[i].y = numHeight; Tweener.addTween(_listItems[i], { y:newY, time:3 } ); } previousNums = nums; } PUBLIC CLASS extends MovieClip place 'NumbersView.as' in same directory CLASS Library/'right-click' Properties/Class:NumberImage SYMBOL number column 70x1080 numbers 70x120 TWEENER caurina folder in local directory

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• Implement OAuth in Java

  - by phineas

  I made an an attempt to implement OAuth for my programming idea in Java, but I failed miserably. I don't know why, but my code doesn't work. Every time I run my program, an IOException is thrown with the reason "java.io.IOException: Server returned HTTP response code: 401" (401 means Unauthorized). I had a close look at the docs, but I really don't understand why it doesn't work. My OAuth provider I wanted to use is twitter, where I've registered my app, too. Thanks in advance phineas OAuth docs Twitter API wiki Class Base64Coder import java.io.InputStreamReader; import java.io.BufferedReader; import java.io.OutputStream; import java.io.IOException; import java.io.UnsupportedEncodingException; import java.net.URL; import java.net.URLEncoder; import java.net.URLConnection; import java.net.MalformedURLException; import javax.crypto.Mac; import javax.crypto.spec.SecretKeySpec; import java.security.NoSuchAlgorithmException; import java.security.InvalidKeyException; public class Request { public static String read(String url) { StringBuffer buffer = new StringBuffer(); try { /** * get the time - note: value below zero * the millisecond value is used for oauth_nonce later on */ int millis = (int) System.currentTimeMillis() * -1; int time = (int) millis / 1000; /** * Listing of all parameters necessary to retrieve a token * (sorted lexicographically as demanded) */ String[][] data = { {"oauth_callback", "SOME_URL"}, {"oauth_consumer_key", "MY_CONSUMER_KEY"}, {"oauth_nonce", String.valueOf(millis)}, {"oauth_signature", ""}, {"oauth_signature_method", "HMAC-SHA1"}, {"oauth_timestamp", String.valueOf(time)}, {"oauth_version", "1.0"} }; /** * Generation of the signature base string */ String signature_base_string = "POST&"+URLEncoder.encode(url, "UTF-8")+"&"; for(int i = 0; i < data.length; i++) { // ignore the empty oauth_signature field if(i != 3) { signature_base_string += URLEncoder.encode(data[i][0], "UTF-8") + "%3D" + URLEncoder.encode(data[i][1], "UTF-8") + "%26"; } } // cut the last appended %26 signature_base_string = signature_base_string.substring(0, signature_base_string.length()-3); /** * Sign the request */ Mac m = Mac.getInstance("HmacSHA1"); m.init(new SecretKeySpec("CONSUMER_SECRET".getBytes(), "HmacSHA1")); m.update(signature_base_string.getBytes()); byte[] res = m.doFinal(); String sig = String.valueOf(Base64Coder.encode(res)); data[3][1] = sig; /** * Create the header for the request */ String header = "OAuth "; for(String[] item : data) { header += item[0]+"=\""+item[1]+"\", "; } // cut off last appended comma header = header.substring(0, header.length()-2); System.out.println("Signature Base String: "+signature_base_string); System.out.println("Authorization Header: "+header); System.out.println("Signature: "+sig); String charset = "UTF-8"; URLConnection connection = new URL(url).openConnection(); connection.setDoInput(true); connection.setDoOutput(true); connection.setRequestProperty("Accept-Charset", charset); connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + charset); connection.setRequestProperty("Authorization", header); connection.setRequestProperty("User-Agent", "XXXX"); OutputStream output = connection.getOutputStream(); output.write(header.getBytes(charset)); BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream())); String read; while((read = reader.readLine()) != null) { buffer.append(read); } } catch(Exception e) { e.printStackTrace(); } return buffer.toString(); } public static void main(String[] args) { System.out.println(Request.read("http://api.twitter.com/oauth/request_token")); } }

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• Vista/7: How to get glass color?

  - by Ian Boyd

  How do you use DwmGetColorizationColor? The documentation says it returns two values: a 32-bit 0xAARRGGBB containing the color used for glass composition a boolean parameter that is true "if the color is an opaque blend" (whatever that means) Here's a color that i like, a nice puke green: You can notice the color is greeny, and the translucent title bar (against a white background) shows the snot color very clearly: i try to get the color from Windows: DwmGetColorizationColor(dwCcolorization, bIsOpaqueBlend); And i get dwColorization: 0x0D0A0F04 bIsOpaqueBlend: false According to the documentation this value is of the format AARRGGBB, and so contains: AA: 0x0D (13) RR: 0x0A (10) GG: 0x0F (15) BB: 0x04 (4) This supposedly means that the color is (10, 15, 4), with an opacity of ~5.1%. But if you actually look at this RGB value, it's nowhere near my desired snot green. Here is (10, 15, 4) with zero opacity (the original color), and (10,15,4) with 5% opacity against a white/checkerboard background: So the question is: How to get glass color in Windows Vista/7? i tried using DwmGetColorizationColor, but that doesn't work very well. A person with same problem, but a nicer shiny picture to attract you squirrels: So, it boils down to – DwmGetColorizationColor is completely unusable for applications attempting to apply the current color onto an opaque surface. i love this guy's screenshots much better than mine. Using his screenshots as a template, i made up a few more sparklies: For the last two screenshots, the alpha blended chip is a true partially transparent PNG, blending to your browser's background. Cool! (i'm such a geek) Edit 2: Had to arrange them in rainbow color. (i'm such a geek) Edit 3: Well now i of course have to add Yellow. Undocumented/Unsupported/Fragile Workarounds There is an undocumented export from DwmApi.dll at entry point 137, which we'll call DwmGetColorizationParameters: HRESULT GetColorizationParameters_Undocumented(out DWMCOLORIZATIONPARAMS params); struct DWMCOLORIZATIONPARAMS { public UInt32 ColorizationColor; public UInt32 ColorizationAfterglow; public UInt32 ColorizationColorBalance; public UInt32 ColorizationAfterglowBalance; public UInt32 ColorizationBlurBalance; public UInt32 ColorizationGlassReflectionIntensity; public UInt32 ColorizationOpaqueBlend; } We're interested in the first parameter: ColorizationColor. We can also read the value out of the registry: HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM ColorizationColor: REG_DWORD = 0x6614A600 So you pick your poison of creating appcompat issues. You can rely on an undocumented API (which is bad, bad, bad, and can go away at any time) use an undocumented registry key (which is also bad, and can go away at any time) See also Is there a list of valid parameter combinations for GetThemeColor / Visual Styles API How does Windows change Aero Glass color? DWM - Colorization Color Handling Using DWMGetColorizationColor Retrieving Aero Glass base color for opaque surface rendering i've been wanting to ask this question for over a year now. i always knew that it's impossible to answer, and that the only way to get anyone to actually pay attention is to have colorful screenshots; developers are attracted to shiny things. But on the downside it means i had to put all kinds of work into making the lures.

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• SQL query mixing aggregated results and single values

  - by Paul Flowerdew

  I have a table with transactions. Each transaction has a transaction ID, and accounting period (AP), and a posting value (PV), as well as other fields. Some of the IDs are duplicated, usually because the transaction was done in error. To give an example, part of the table might look like: ID PV AP 123 100 2 123 -100 5 In this case the transaction was added in AP2 then removed in AP5. Another example would be: ID PV AP 456 100 2 456 -100 5 456 100 8 In the first example, the problem is that if I am analyzing what was spent in AP2, there is a transaction in there which actually shouldn't be taken into account because it was taken out again in AP5. In the second example, the second two transactions shouldn't be taken into account because they cancel each other out. I want to label as many transactions as possible which shouldn't be taken into account as erroneous. To identify these transactions, I want to find the ones with duplicate IDs whose PVs sum to zero (like ID 123 above) or transactions where the PV of the earliest one is equal to sum(PV), as in the second example. This second condition is what is causing me grief. So far I have SELECT * FROM table WHERE table.ID IN (SELECT table.ID FROM table GROUP BY table.ID HAVING COUNT(*) > 1 AND (SUM(table.PV) = 0 OR SUM(table.PV) = <PV of first transaction in each group>)) ORDER BY table.ID; The bit in chevrons is what I'm trying to do and I'm stuck. Can I do it like this or is there some other method I can use in SQL to do this? Edit 1: Btw I forgot to say that I'm using SQL Compact 3.5, in case it matters. Edit 2: I think the code snippet above is a bit misleading. I still want to mark out transactions with duplicate IDs where sum(PV) = 0, as in the first example. But where the PV of the earliest transaction = sum(PV), as in the second example, what I actually want is to keep the earliest transaction and mark out all the others with the same ID. Sorry if that caused confusion. Edit 3: I've been playing with Clodoaldo's solution and have made some progress, but still can't get quite what I want. I'm trying to get the transactions I know for certain to be erroneous. Suppose the following transactions are also in the table: ID PV AP 789 100 2 789 200 5 789 -100 8 In this example sum(PV) < 0 and the earliest PV < sum(PV) so I don't want to mark any of these out. If I modify Clodoaldo's query as follows: select t.* from t left join ( select id, min(ap) as ap, sum(pv) as sum_pv from t group by id having sum(pv) <> 0 ) s on t.id = s.id and t.ap = s.ap and t.pv = s.sum_pv where s.id is null This gives the result ID PV AP 123 100 2 123 -100 5 456 -100 5 456 100 8 789 100 3 789 200 5 789 -100 8 Whilst the first 4 transactions are ok (they would be marked out), the 789 transactions are also there, and I don't want them. But I can't figure out how to modify the query so that they're not included. Any ideas?

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• Pure JSP without mixing HTML, by writing html as Java-like code

  - by ADTC

  Please read before answering. This is a fantasy programming technique I'm dreaming up. I want to know if there's anything close in real life. The following JSP page: <% html { head { title {"Pure fantasy";} } body { h1 {"A heading with double quote (\") character";} p {"a paragraph";} String s = "a paragraph in string. the date is "; p { s; new Date().toString(); } table (Border.ZERO, new Padding(27)) { tr { for (int i = 0; i < 10; i++) { td {i;} } } } } } %> could generate the following HTML page: <html> <head> <title>Pure fantasy</title> </head> <body> <h1>A heading with double quote (") character</h1> <p>a paragraph</p> <p>a paragraph in string. the date is 11 December 2012</p> <table border="0" padding="27"> <tr> <td>0</td> <td>1</td> <td>2</td> <td>3</td> <td>4</td> <td>5</td> <td>6</td> <td>7</td> <td>8</td> <td>9</td> </tr> </table> </body> </html> The thing about this fantasy is it reuses the same old Java programming language technique that enable customized keywords used in a way similar to if-else-then, while, try-catch etc to represent html tags in a non-html way that can easily be checked for syntactic correctness, and most importantly can easily be mixed up with regular Java code without being lost in a sea of <%, %>, <%=, out.write(), etc. An added feature is that strings can directly be placed as commands to print out into generated HTML, something Java doesn't support (where pure strings have to be assigned to variables before use). Is there anything in real life that comes close? If not, is it possible to define customized keywords in Java or JSP? Or do I have to create an entirely new programming language for that? What problems do you see with this kind of setup? PS: I know you can use HTML libraries to construct HTML using Java code, but the problem with such libraries is, the source code itself doesn't have a readable HTML representation like the code above does - if you get what I mean.

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• Looking for a better design: A readonly in-memory cache mechanism

  - by Dylan Lin

  Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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