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• Sync Vs. Async Sockets Performance in C#

  - by Michael Covelli

  Everything that I read about sockets in .NET says that the asynchronous pattern gives better performance (especially with the new SocketAsyncEventArgs which saves on the allocation). I think this makes sense if we're talking about a server with many client connections where its not possible to allocate one thread per connection. Then I can see the advantage of using the ThreadPool threads and getting async callbacks on them. But in my app, I'm the client and I just need to listen to one server sending market tick data over one tcp connection. Right now, I create a single thread, set the priority to Highest, and call Socket.Receive() with it. My thread blocks on this call and wakes up once new data arrives. If I were to switch this to an async pattern so that I get a callback when there's new data, I see two issues The threadpool threads will have default priority so it seems they will be strictly worse than my own thread which has Highest priority. I'll still have to send everything through a single thread at some point. Say that I get N callbacks at almost the same time on N different threadpool threads notifying me that there's new data. The N byte arrays that they deliver can't be processed on the threadpool threads because there's no guarantee that they represent N unique market data messages because TCP is stream based. I'll have to lock and put the bytes into an array anyway and signal some other thread that can process what's in the array. So I'm not sure what having N threadpool threads is buying me. Am I thinking about this wrong? Is there a reason to use the Async patter in my specific case of one client connected to one server?

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• Display a Photo Gallery using Asp.Net and SQL

  - by sweetcoder

  I have recently added photos to my SQL database and have displayed them on an *.aspx page using Asp:Image. The ImageUrl for this control stored in a separate *.aspx page. It works great for profile pictures. I have a new issue at hand. I need each user to be able to have their own photo gallery page. I want the photos to be stored in the sql database. Storing the photos is not difficult. The issue is displaying the photos. I want the photos to be stored in a thumbnail grid fashion, when the user clicks on the photo, it should bring up the photo on a separate page. What is the best way to do this. Obviously it is not to use Asp:Image. I am curious if I should use a Gridview. If so, how do I do that and should their be a thumbnail size stored in the database for this? Once the picture is click on how does the other page look so that it displays the correct image. I would think it is not correct to send the photoId through the url. Below is code from the page I use to display profile pictures. protected void Page_Load(object sender, EventArgs e) { string sql = "SELECT [ProfileImage] FROM [UserProfile] WHERE [UserId] = '" + User.Identity.Name.ToString() + "'"; string strCon = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["SocialSiteConnectionString"].ConnectionString; SqlConnection conn = new SqlConnection(strCon); SqlCommand comm = new SqlCommand(sql, conn); conn.Open(); Response.ContentType = "image/jpeg"; Response.BinaryWrite((byte[])comm.ExecuteScalar()); conn.Close(); }

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• JQuery BlockUI - How to unblock UI after file download?

  - by Dan

  Using ASP.Net, JQuery and BlockUI, I'm trying to unblock the UI after a download file dialog is shown. I block the UI when export button is clicked: <script type="text/javascript"> $(document).ready(function(){ $('#<%= BtnExport.ClientID%>').click(function(){ $.blockUI(); }); }); </script> After this, I generate the file server side using: private void SendFileToUser(byte[] file, string contentType, string filename) { Response.Clear(); Response.ContentType = contentType; Response.AppendHeader("Content-Disposition", "attachment; filename="+filename); Response.OutputStream.Write(file,0,file.Length); Response.OutputStream.Flush(); Response.End(); } After this code has executed, I would like to unblock the UI. I have considered different options: Poll using Ajax calls to see if the file has been generated. Store the file in Session and redirect to same page and generate download then. But both options seem ackward, and I think there must be a clever JavaScript way to get a handle on or wait for a file dialog. Any suggestions?

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• OpenSSL.NET can't export private key with null Cipher

  - by Nick

  I've recently discovered OpenSSL.NET and it's a pretty sweet little wrapper. I'm trying to execute the following code: public static void DoSomething(byte[] buf) { OpenSSL.Core.BIO input = new OpenSSL.Core.BIO(buf); OpenSSL.X509.X509Certificate b = OpenSSL.X509.X509Certificate.FromPKCS12(input, "passphrase"); OpenSSL.Core.BIO outs = OpenSSL.Core.BIO.MemoryBuffer(false); b.PrivateKey.WritePrivateKey(outs, OpenSSL.Crypto.Cipher.Null, "passphrase"); outs.SetClose(OpenSSL.Core.BIO.CloseOption.Close); Console.WriteLine(outs.ReadString()); } Problem comes at the "b.PrivateKey.WritePrivateKey(.." line. I want to write the private key out without any encryption. According to spec, if I use a Null cipher type this should do the trick, but it never works, regardless of the cert I use in buf. Here's the exception: error:0D0A706C:asn1 encoding routines:PKCS5_pbe2_set:cipher has no object identifier error:2307D00D:PKCS12 routines:PKCS8_encrypt:ASN1 lib I know this part works fine because if I specify any other cipher type, it exports the private key without fail. Anyone have any suggestions?

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• Hibernate: OutOfMemoryError persisting Blob when printing log message

  - by paul

  I have a Hibernate Entity: @Entity class Foo { //... @Lob public byte[] getBytes() { return bytes; } //.... } My VM is configured with a maximum heap size of 512 MB. When I try to persist an object which has a 75 MB large object, I get an OutOfMemoryError. The names of the methods in the stack trace (StringBuilder, ByteArrayBlobType.toLoggableString, pretty.Printer.toString) suggest that hibernate is trying to write a very large log message that contains my object. Am I correct about why hibernate is using so much memory? What is the simplest way to work around this problem? java.lang.OutOfMemoryError: Java heap space at java.lang.AbstractStringBuilder.<init>(AbstractStringBuilder.java:44) at java.lang.StringBuilder.<init>(StringBuilder.java:81) at org.hibernate.type.ByteArrayBlobType.toString(ByteArrayBlobType.java:117) at org.hibernate.type.ByteArrayBlobType.toLoggableString(ByteArrayBlobType.java:127) at org.hibernate.pretty.Printer.toString(Printer.java:53) at org.hibernate.pretty.Printer.toString(Printer.java:90) at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:97) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000) at org.jboss.seam.persistence.HibernateSessionProxy.flush(HibernateSessionProxy.java:181)

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• How to reproduce System.Security.Cryptography.SHA1Managed result in Python

  - by joetyson

  Here's the deal: I'm moving a .NET website to Python. I have a database with passwords hashed using the System.Security.Cryptography.SHA1Managed utility. I'm creating the hash in .NET with the following code: string hashedPassword = Cryptographer.CreateHash("MYHasher", userInfo.Password); The MYHasher block looks like this: <add algorithmType="System.Security.Cryptography.SHA1Managed, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=blahblahblah" saltEnabled="true" type="Microsoft.Practices.EnterpriseLibrary.Security.Cryptography.HashAlgorithmProvider, Microsoft.Practices.EnterpriseLibrary.Security.Cryptography, Version=3.0.0.0, Culture=neutral, PublicKeyToken=daahblahdahdah" name="MYHasher" /> So for a given password, I get back and store in the database a 48 byte salted sha1. I assume the last 8 bytes are the salt. I have tried to reproduce the hashing process in python by doing a sha1(salt + password) and sha1(password + salt) but I'm having no luck. My question to you: How are the public keys being used? How is the password rehashed using the salt. How is the salt created? (e.g., When I say saltEnabled="true", what extra magic happens?) I need specific details that don't just reference other .NET libraries, I'm looking for the actual operational logic that happens in the blackbox. Thanks!

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• ReportViewer add Parameters ...

  - by user95542

  Hi, I need help.Well, i need add image logo in reportviewer dynamically.I get this image from db, convert toBase64 and i need add in reportviewer.... this code next.. rpViewer.LocalReport.EnableExternalImages = true; Company _company = db.Companys.Where(c => c.codCompany == c.codCompany).Single(); //first step byte[] img = _company.imagem.ToArray(); // i get image from db MemoryStream _ms = new MemoryStream(img); string logo = Convert.ToBase64String(img); //convert to base64 // 2 step List<ReportParameter> lstReportParams = new List<ReportParameter>();//Create params lstReportParams.Add(new ReportParameter("Logo", logo)); lstReportParams.Add(new ReportParameter("LogoMimeType", "image/png")); this.rpViewer.LocalReport.SetParameters(lstReportParams); // Here don´t work´s {"An error occurred during local report processing."} {"An attempt was made to set a report parameter 'Logo' that is not defined in this report."} this.rpViewer.RefreshReport(); In Rldc.... MIMEType =Parameters!LogoMimeType.value Value ="System.Convert.FromBase64String(Parameters!Logo.Value)" Why not work? Why is not recognizing the parameter? need help urgente.I can load that image in reportviewer...Thank´s..

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• Why this strange behavior of sqlbulkcopy in a asp.net website running under iis?

  - by Pandiya Chendur

  I'm using SqlClient.SqlBulkCopy to try and bulk copy a csv file into a database. I am getting the following error after calling the ..WriteToServer method. "The given value of type String from the data source cannot be converted to type bit of the specified target column." Here is my code, dt.Columns.Add("IsDeleted", typeof(byte)); dt.Columns.Add(new DataColumn("CreatedDate", typeof(DateTime))); foreach (DataRow dr in dt.Rows) { if (dr["MobileNo2"] == "" && dr["DriverName2"] == "") { dr["MobileNo2"] = null; dr["DriverName2"] = ""; } dr["IsDeleted"] = Convert.ToByte(0); dr["CreatedDate"] = Convert.ToDateTime(System.DateTime.Now.ToString()); } string connectionString = System.Configuration.ConfigurationManager. ConnectionStrings["connectionString"].ConnectionString; SqlBulkCopy sbc = new SqlBulkCopy(connectionString); sbc.DestinationTableName = "DailySchedule"; sbc.ColumnMappings.Add("WirelessId", "WirelessId"); sbc.ColumnMappings.Add("RegNo", "RegNo"); sbc.ColumnMappings.Add("DriverName1", "DriverName1"); sbc.ColumnMappings.Add("MobileNo1", "MobileNo1"); sbc.ColumnMappings.Add("DriverName2", "DriverName2"); sbc.ColumnMappings.Add("MobileNo2", "MobileNo2"); sbc.ColumnMappings.Add("IsDeleted", "IsDeleted"); sbc.ColumnMappings.Add("CreatedDate", "CreatedDate"); sbc.WriteToServer(dt); sbc.Close(); There is no error when running under visual studio developement server but it gives me an error when running under iis..... Here is my sql server table details, [Id] [int] IDENTITY(1,1) NOT NULL, [WirelessId] [int] NULL, [RegNo] [nvarchar](50) NULL, [DriverName1] [nvarchar](50) NULL, [MobileNo1] [numeric](18, 0) NULL, [DriverName2] [nvarchar](50) NULL, [MobileNo2] [numeric](18, 0) NULL, [IsDeleted] [tinyint] NULL, [CreatedDate] [datetime] NULL,

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• Linux Device Driver - what's wrong with my device_read()?

  - by Rob

  My device /dev/my_inc is meant to take a positive integer N represented as an ascii string, and store it. Any read from /dev/my_inc will produce the ascii string representation of N + 1. The problem is that when I cat /dev/my_inc, I only get the first byte of myinc_value output to my shell, even though I have bytes_read == 2 at the end of my loop. /* Read from the device *********************/ static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t *offset) { char c; int bytes_read = 0; int value = myinc_value + 1; printk(KERN_INFO "my_inc device_read() called with value %d and msg %s.\n", value, msg); /* No bytes read if pointer to 0 */ if (*msg_ptr == 0) return 0; /* Put the incremented value in msg */ snprintf(msg, MAX_LENGTH, "%d", value); /* Put bytes from msg into user space buffer */ while (length && *msg_ptr) { c = *(msg_ptr++); printk(KERN_INFO "%s device_read() read %c.", DEV_NAME, c); if(put_user(c, buffer++)) return -EFAULT; length--; bytes_read++; } printk("my_inc device_read() returning %d.\n", bytes_read); /* Return bytes copied */ return bytes_read; }

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• HttpRequest.BeginWebRequest not executing asynchronously

  - by Shawn Simon

  I have the following code: Private Function CreateRequest() As HttpWebRequest Dim request As HttpWebRequest = HttpWebRequest.Create(_url) request.Method = "POST" request.ContentType = "application/x-www-form-urlencoded" Dim postData As String = String.Join("&", GetPostData().Select(Function(s) String.Format("{0}={1}", s.Key, HttpUtility.UrlEncode(s.Value))).ToArray) Dim data As Byte() = (New ASCIIEncoding).GetBytes(postData) request.Timeout = _maxTimeoutSeconds * 1000 Dim stream = request.GetRequestStream stream.Write(data, 0, data.Length) stream.Close() Return request End Function Public Sub SendAsync(ByVal callback As Action(Of ResponseBase)) Dim request = CreateRequest() _attemptCount += 1 Dim reqID As Integer If _loggingContext IsNot Nothing Then Try reqID = Log.NotesRequest(_url.ToString, GetPostData, _loggingContext) Catch ex As Exception ErrorTracker.LogError(ex) End Try End If Dim responseState As New ResponseState responseState.LoggedNotesRequestID = reqID responseState.Request = request responseState.Callback = callback Dim response = request.BeginGetResponse(New AsyncCallback(AddressOf RespCallback), responseState) End Sub Private Sub RespCallback(ByVal ar As IAsyncResult) Dim responseState As ResponseState = CType(ar.AsyncState, ResponseState) ' Process response... I set up the request to go to a mock server which sleeps for 30 seconds. When I call BeginGetResponse, the application just waits at that line of code for the response. I want it to carry on with the app, and then just run the callback whenever it finishes. This code is run from a web page, and my callback just logs the response and sends an email. I don't want to use to have to wait for the response.

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• Reading bmp file for steganography

  - by Shantanu Gupta

  I am trying to read a bmp file in C++(Turbo). But i m not able to print binary stream. I want to encode txt file into it and decrypt it. How can i do this. I read that bmp file header is of 54 byte. But how and where should i append txt file in bmp file. ? I know only Turbo C++, so it would be helpfull for me if u provide solution or suggestion related to topic for the same. int main() { ifstream fr; //reads ofstream fw; // wrrites to file char c; int random; clrscr(); char file[2][100]={"s.bmp","s.txt"}; fr.open(file[0],ios::binary);//file name, mode of open, here input mode i.e. read only if(!fr) cout<<"File can not be opened."; fw.open(file[1],ios::app);//file will be appended if(!fw) cout<<"File can not be opened"; while(!fr) cout<<fr.get(); // error should be here. but not able to find out what error is it fr.close(); fw.close(); getch(); } This code is running fine when i pass txt file in binary mode

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• Complex ModelBinders and being in charge of creating part of the model

  - by Kieron

  Hi, I've a scenario where I need to bind to an interface - in order to create the correct type, I've got a custom model binder that knows how to create the correct concrete type (which can differ). However, the type created never has the fields correctly filled in. I know I'm missing something blindingly simple here, but can anyone tell me why or at least what I need to do for the model binder to carry on it's work and bind the properties? public class ProductModelBinder : DefaultModelBinder { override public object BindModel (ControllerContext controllerContext, ModelBindingContext bindingContext) { if (bindingContext.ModelType == typeof (IProduct)) { var content = GetProduct (bindingContext); return content; } var result = base.BindModel (controllerContext, bindingContext); return result; } IProduct GetProduct (ModelBindingContext bindingContext) { var idProvider = bindingContext.ValueProvider.GetValue ("Id"); var id = (Guid)idProvider.ConvertTo (typeof (Guid)); var repository = RepositoryFactory.GetRepository<IProductRepository> (); var product = repository.Get (id); return product; } } The Model in my case is a complex type that has an IProduct property, and it's those values I need filled in. Model: [ProductBinder] public class Edit : IProductModel { public Guid Id { get; set; } public byte[] Version { get; set; } public IProduct Product { get; set; } }

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• Using Unicode in fancyvrb’s VerbatimOut

  - by Konrad Rudolph

  Problem VerbatimOut from the “fancyvrb” package doesn’t play nicely with UTF-8 characters. Minimal working example: \documentclass{minimal} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{fancyvrb} \begin{document} \begin{VerbatimOut}{\jobname.test} é \end{VerbatimOut} \input{\jobname.test} \end{document} Error message When compiled using pdflatex mini, this gives the error File ended while scanning use of \UTFviii@three@octets. A different error occurs when the sole occurrence of é above is replaced by something else, e.g. é */: Package inputenc Error: Unicode char \u8:### not set up for use with LaTeX. – indicating that in this case, LaTeX succeeds in reading a multi-byte UTF-8 character, but not knowing what to do with it (i.e. it’s the wrong character). In fact, when I open the produced .test file manually, it contains the character é, but in Latin-1 encoding! Proof: when I open the files in a hex editor, I get the following: Original file: C3 A9 (corresponds to LATIN SMALL LETTER E WITH ACUTE in UTF-8) Written file: E9 (corresponds to é in Latin-1) Question How to set VerbatimOut up correctly? filecontents* (from “filecontents”) shows that it can work. Unfortunately, I don’t understand either code so I cannot fix fancyvrb’s code by replicating the logic from filecontents manually. I also cannot use filecontents* instead of VerbatimOut because the former doesn’t work within a \newenvironment, while the latter does. (Oh, by the way: vanilla Verbatim instead of VerbatimOut also works as expected. The error seems to occur when writing the file, not when reading the verbatim input)

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• Still about SSD potentials...write and read speed

  - by Macroideal

  HI Gurus, I have been working on SSD(solid state disk) for several months..Problems and Questions hit my head unexpectedly..Coz i am a virgin in ssd... Esp these days i was testing the write-read speed of ssd, which I was always caring.... however result turned out not good as I expected, or even worse Three kinds of read-write were implemented in my test 1. read and write directly from and into ssd, with openning ssd as a whole device. in windows: _open("\\:g", ***).. It can be very tricky and hairy that you'd write a data with size of folds of 512, at the disk position of folds of 512bytes... So, If you wanto write just a byte or 4 bytes, you'v to write at least a whole sector one time. 2. Read and write data from and into files located in SSD... 3. Read and Write data from and into files in mechanical Disk I compared the pratices below...I found ssd sucks...the ssd performs worse than mechanical disk... so i am wondering where i can get the potential performance of ssd, since ssd is said to a substitute for mechanical disk in the future.. Nevertheless, I test ssd with a pro-hard-disk tools..ssd is like twice speedier than mechanical disk. So, why? Thanx very much...If you know tips of ssd...follow me

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• Determine whether .NET assemblies were built from the same source

  - by Clayton

  Does anyone know of a way to compare two .NET assemblies to determine whether they were built from the "same" source files? I am aware that there are some differencing utilities available, such as the plugin for Reflector, but I am not interested in viewing differences in a GUI, I just want an automated way to compare a collection of binaries to see whether they were built from the same (or equivalent) source files. I understand that multiple different source files could produce the same IL, and realise that the process would only be sensitive to differences in the IL, not the original source. The main obstacle to just comparing the byte streams for the two assemblies is that .NET includes a field called "MVID" (Module Version Identifier) the assembly. This appears to have a different value for every compilation, so if you build the same code twice the assembly will be different. A related question is, does anyone know how to force the MVID to be the same for each compilation? This would avoid us needing to have a comparison process that is insensitive to differences in the value of the MVID. A consistent MVID would be preferable, as this means that standard checksums could be used. The background behind this is that a third-party company is responsible for independently reviewing and signing off our releases, prior to us being permitted to release to Production. This includes reviewing the source code. They want to independently confirm that the source code we give them matches the binaries that we earlier built, tested and currently plan to deploy. We are looking for a process that allows them to independently build the system from the source we supply them with, and the compare the checksums against the checksums for the binaries we have tested. thanks

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• Reading binary data from serial port using Dejan TComport Delphi component

  - by johnma

  Apologies for this question but I am a bit of a noob with Delphi. I am using Dejan TComport component to get data from a serial port. A box of equipment connected to the port sends about 100 bytes of binary data to the serial port. What I want to do is extract the bytes as numerical values into an array so that I can perform calculations on them. TComport has a method Read(buffer,Count) which reads DATA from input buffer. function Read(var Buffer; Count: Integer): Integer; The help says the Buffer variable must be large enough to hold Count bytes but does not provide any example of how to use this function. I can see that the Count variable holds the number of bytes received but I can't find a way to access the bytes in Buffer. TComport also has a methord Readstr which reads data from input buffer into a STRING variable. function ReadStr(var Str: String; Count: Integer): Integer; Again the Count variable shows the number of bytes received and I can use Memo1.Text:=str to display some information but obviously Memo1 has problems displaying the control characters. I have tried various ways to try and extract the byte data from Str but so far without success. I am sure it must be easy. Here's hoping.

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• ListField with image In Blackberry JDE

  - by Karthick

  I use the following code to retrieve image from the phone or SDCard and I use that image in to my ListField. It gives the output but it takes very Long time to produce the screen. How to solve this problem ?? Can any one help me?? Thanks in advance!!! String text = fileholder.getFileName(); try{ String path="file:///"+fileholder.getPath()+text; //path=”file:///SDCard/BlackBerry/pictures/image.bmp” InputStream inputStream = null; //Get File Connection FileConnection fileConnection = (FileConnection) Connector.open(path); inputStream = fileConnection.openInputStream(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); int j = 0; while((j=inputStream.read()) != -1) { baos.write(j); } byte data[] = baos.toByteArray(); inputStream.close(); fileConnection.close(); //Encode and Resize image EncodedImage eImage = EncodedImage.createEncodedImage(data,0,data.length); int scaleFactorX = Fixed32.div(Fixed32.toFP(eImage.getWidth()), Fixed32.toFP(180)); int scaleFactorY = Fixed32.div(Fixed32.toFP(eImage.getHeight()), Fixed32.toFP(180)); eImage=eImage.scaleImage32(scaleFactorX, scaleFactorY); Bitmap bitmapImage = eImage.getBitmap(); graphics.drawBitmap(0, y+1, 40, 40,bitmapImage, 0, 0); graphics.drawText(text, 25, y,0,width); } catch(Exception e){}

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• BN_hex2bn magicaly segfaults in openSSL

  - by xunil154

  Greetings, this is my first post on stackoverflow, and i'm sorry if its a bit long. I'm trying to build a handshake protocol for my own project and am having issues with the server converting the clients RSA's public key to a Bignum. It works in my clent code, but the server segfaults when attempting to convert the hex value of the clients public RSA to a bignum. I have already checked that there is no garbidge before or after the RSA data, and have looked online, but i'm stuck. header segment: typedef struct KEYS { RSA *serv; char* serv_pub; int pub_size; RSA *clnt; } KEYS; KEYS keys; Initializing function: // Generates and validates the servers key /* code for generating server RSA left out, it's working */ //Set client exponent keys.clnt = 0; keys.clnt = RSA_new(); BN_dec2bn(&keys.clnt->e, RSA_E_S); // RSA_E_S contains the public exponent Problem code (in Network::server_handshake): // *Recieved an encrypted message from the network and decrypt into 'buffer' (1024 byte long)* cout << "Assigning clients RSA" << endl; // I have verified that 'buffer' contains the proper key if (BN_hex2bn(&keys.clnt->n, buffer) < 0) { Error("ERROR reading server RSA"); } cout << "clients RSA has been assigned" << endl; The program segfaults at BN_hex2bn(&keys.clnt->n, buffer) with the error (valgrind output) Invalid read of size 8 at 0x50DBF9F: BN_hex2bn (in /usr/lib/libcrypto.so.0.9.8) by 0x40F23E: Network::server_handshake() (Network.cpp:177) by 0x40EF42: Network::startNet() (Network.cpp:126) by 0x403C38: main (server.cpp:51) Address 0x20 is not stack'd, malloc'd or (recently) free'd Process terminating with default action of signal 11 (SIGSEGV) Access not within mapped region at address 0x20 at 0x50DBF9F: BN_hex2bn (in /usr/lib/libcrypto.so.0.9.8) And I don't know why it is, Im using the exact same code in the client program, and it works just fine. Any input is greatly appriciated!

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• what type of bug causes a program to slowly use more processor power and all of a sudden go to 100%?

  - by reinier

  Hi, I was hoping to get some good ideas as to what might be causing a really nasty bug. This is a program which is transmitting data over a socket, and also receives messages back. I could explain lots more, but I don't think this will help here. I'm just searching for hypothetical problems which can cause the following behaviour: program runs processor time slowly accumulates (till around 60%) all of a sudden (could be after 30 but also after 60 seconds) the processor time shoots to 100%. the program halts completely In my syslog it always ends on one line with a memory allocation (something similar to: myArray = new byte[16384]) in the same thread. now here is the weird part: if I set the debugger anywhere...it immediately stops on that line. So just the act of setting a breakpoint, made the thread continue (it wasn't running since I saw no log output anymore) I was thinking 'deadlock' but that would not cause 100% processor power. If anything, the opposite. Also, setting a breakpoint would not cause a deadlock to end. anyone else a theoretical suggestion as to what kind of 'construct' might cause this effect? (apart from 'bad programming') ;^) thanks EDIT: I just noticed.... by setting the sendspeed slower, the problem shows itself much later than expected. I would think around the same amount of packets send...but no the amount of packets send is much higher this way before it has the same problem.

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• C# File IO with Streams - Best Memory Buffer Size

  - by AJ

  Hi, I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance). Thanks in advance for any ideas, Adam

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• How to draw an overlay on a SurfaceView used by Camera on Android?

  - by Cristian Castiblanco

  I have a simple program that draws the preview of the Camera into a SurfaceView. What I'm trying to do is using the onPreviewFrame method, which is invoked each time a new frame is drawn into the SurfaceView, in order to execute the invalidate method which is supposed to invoke the onDraw method. In fact, the onDraw method is being invoked, but nothing there is being printed (I guess the camera preview is overwriting the text I'm trying to draw). This is a simplify version of the SurfaceView subclass I have: public class Superficie extends SurfaceView implements SurfaceHolder.Callback { SurfaceHolder mHolder; public Camera camera; Superficie(Context context) { super(context); mHolder = getHolder(); mHolder.addCallback(this); mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } public void surfaceCreated(final SurfaceHolder holder) { camera = Camera.open(); try { camera.setPreviewDisplay(holder); camera.setPreviewCallback(new PreviewCallback() { public void onPreviewFrame(byte[] data, Camera arg1) { invalidar(); } }); } catch (IOException e) {} } public void invalidar(){ invalidate(); } public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { Camera.Parameters parameters = camera.getParameters(); parameters.setPreviewSize(w, h); camera.setParameters(parameters); camera.startPreview(); } @Override public void draw(Canvas canvas) { super.draw(canvas); // nothing gets drawn :( Paint p = new Paint(Color.RED); canvas.drawText("PREVIEW", canvas.getWidth() / 2, canvas.getHeight() / 2, p); } }

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• x86 opcode alignment references and guidelines

  - by mrjoltcola

  I'm generating some opcodes dynamically in a JIT compiler and I'm looking for guidelines for opcode alignment. 1) I've read comments that briefly "recommend" alignment by adding nops after calls 2) I've also read about using nop for optimizing sequences for parallelism. 3) I've read that alignment of ops is good for "cache" performance Usually these comments don't give any supporting references. Its one thing to read a blog or a comment that says, "its a good idea to do such and such", but its another to actually write a compiler that implements specific op sequences and realize most material online, especially blogs, are not useful for practical application. So I'm a believer in finding things out myself (disassembly, etc. to see what real world apps do). This is one case where I need some outside info. I notice compilers will usually start an odd byte instruction immediately after whatever previous instruction sequence there was. So the compiler is not taking any special care in most cases. I see "nop" here or there, but usually it seems nop is used sparingly, if at all. How critical is opcode alignment? Can you provide references for cases that I can actually use for implementation? Thanks.

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• Ascii Bytes Array To Int32 or Double

  - by Michael Covelli

  I'm re-writing alibrary with a mandate to make it totally allocation free. The goal is to have 0 collections after the app's startup phase is done. Previously, there were a lot of calls like this: Int32 foo = Int32.Parse(ASCIIEncoding.ASCII.GetString(bytes, start, length)); Which I believe is allocating a string. I couldn't find a C# library function that would do the same thing automatically. I looked at the BitConverter class, but it looks like that is only if your Int32 is encoded with the actual bytes that represent it. Here, I have an array of bytes representing Ascii characters that represent an Int32. Here's what I did public static Int32 AsciiBytesToInt32(byte[] bytes, int start, int length) { Int32 Temp = 0; Int32 Result = 0; Int32 j = 1; for (int i = start + length - 1; i >= start; i--) { Temp = ((Int32)bytes[i]) - 48; if (Temp < 0 || Temp > 9) { throw new Exception("Bytes In AsciiBytesToInt32 Are Not An Int32"); } Result += Temp * j; j *= 10; } return Result; } Does anyone know of a C# library function that already does this in a more optimal way? Or an improvement to make the above run faster (its going to be called millions of times during the day probably). Thanks!

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• Character encoding issues when generating MD5 hash cross-platform

  - by rogueprocess

  This is a general question about character encoding when using MD5 libraries in various languages. My concern is: suppose I generate an MD5 hash using a native Python string object, like this: message = "hello world" m = md5() m.update(message) Then I take a hex version of that MD5 hash using: m.hexdigest() and send the message & MD5 hash via a network, let's say, a JMS message or a HTTP request. Now I get this message in a Java program in the form of a native Java string, along with the checksum. Then I generate an MD5 hash using Java, like this (using the Commons Codec library): String md5 = org.apache.commons.codec.digest.DigestUtils.DigestUtils.md5Hex(s) My feeling is that this is wrong because I have not specified character encodng at either end. So the original hash will be based on the bytes of the Python version of the string; the Java one will be based on the bytes of the Java version of the string , these two byte sequences will often not be the same - is that right? So really I need to specify "UTF-8" or whatever at both ends right? (I am actually getting an intermittent error in my code where the MD5 checksum fails, and I suspect this is the reason - but because it's intermittent, it's difficult to say if changing this fixes it or not. ) Thank you!

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• Use UdpClient with IPv4 and IPv6?

  - by mazzzzz

  A little while ago I created a class to deal with my LAN networking programs. I recently upgraded one of my laptops to windows 7 and relized that windows 7 (or at least the way I have it set up) only supports IPv6, but my desktop is still back in the Windows xp days, and only uses IPv4. The class I created uses the UdpClient class, and is currently setup to only work with IPv4.. Is there a way to modify my code to allow sending and receiving of IPv6 and IPv4 packets?? It would be hard to scrap the classes code, a lot of my programs rely on this class. I would like to keep the class as close to its original state, so I don't need to modify my older programs, only switch out the old class for the updated one. Thanks for any and all help, Max Send: using System.Net.Sockets;UdpClient tub = new UdpClient (); tub.Connect ( new IPEndPoint ( ToIP, ToPort ) ); UdpState s = new UdpState (); s.client = tub; s.endpoint = new IPEndPoint ( ToIP, ToPort ); tub.BeginSend ( data, data.Length, new AsyncCallback ( SendCallBack ),s); private void SendCallBack ( IAsyncResult result ) { UdpClient client = (UdpClient)( (UdpState)( result.AsyncState ) ).client; IPEndPoint endpoint = (IPEndPoint)( (UdpState)( result.AsyncState ) ).endpoint; client.EndSend ( result ); } Receive: UdpClient tub = new UdpClient (ReceivePort); UdpState s = new UdpState (); s.client = tub; s.endpoint = new IPEndPoint ( ReceiveIP, ReceivePort ); s.callback = cb; tub.BeginReceive ( new AsyncCallback ( receivedPacket ), s ); public void receivedPacket (IAsyncResult result) { UdpClient client = (UdpClient)( (UdpState)( result.AsyncState ) ).client; IPEndPoint endpoint = (IPEndPoint)( (UdpState)( result.AsyncState ) ).endpoint; Byte[] receiveBytes = client.EndReceive ( result, ref endpoint ); ReceivedPacket = new Packet ( receiveBytes ); client.Close(); //Do what ever with the packets now }

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