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  • Delphi Unicode String Type Stored Directly at its Address (or "Unicode ShortString")

    - by Andreas Rejbrand
    I want a string type that is Unicode and that stores the string directly at the adress of the variable, as is the case of the (Ansi-only) ShortString type. I mean, if I declare a S: ShortString and let S := 'My String', then, at @S, I will find the length of the string (as one byte, so the string cannot contain more than 255 characters) followed by the ANSI-encoded string itself. What I would like is a Unicode variant of this. That is, I want a string type such that, at @S, I will find a unsigned 32-bit integer (or a single byte would be enough, actually) containing the length of the string in bytes (or in characters, which is half the number of bytes) followed by the Unicode representation of the string. I have tried WideString, UnicodeString, and RawByteString, but they all appear only to store an adress at @S, and the actual string somewhere else (I guess this has do do with reference counting and such). Update: The most important reason for this is probably that it would be very problematic if sizeof(string) were variable. I suspect that there is no built-in type to use, and that I have to come up with my own way of storing text the way I want (which actually is fun). Am I right? Update I will, among other things, need to use these strings in packed records. I also need manually to read/write these strings to files/the heap. I could live with fixed-size strings, such as <= 128 characters, and I could redesign the problem so it will work with null-terminated strings. But PChar will not work, for sizeof(PChar) = 1 - it's merely an address. The approach I eventually settled for was to use a static array of bytes. I will post my implementation as a solution later today.

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  • Problem with load testing Web Service - VSTS 2008

    - by Carlos
    Hello, I have a webtest with makes a simple call to a WebService which looks like that: MyWebService webService = new MyWebService(); webService.Timeout = 180000; webService.myMethod(); I am not using ThinkTimes, also the Run Duration is set to 5 minutes. When I ran this test simulating only 1 user, I check the counters and I found something like that: Tests Total: 4500 Network Interface\Bytes sent (agent machine): 35,500 Then I ran the same tests, but this time simulating 2 users and I got something like that: Tests Total: 2225 Network Interface\Bytes sent (agent machine): 30,500 So when I increased the numbers of users the tests/sec was half than when I use only 1 user and the bytes sent by the agent was also lower. I think it is strange, because it doesn't seems I have a bottleneck in my agent machine since CPU is never higher than 30% and I have over 1.5GB of RAM free, also my network utilization is like 0.5% of its capacity. In order to troubleshot this I ran a test using Step Pattern, the simulated users went from 20 to 800 users. When I check the requests/sec it is practically constant through the whole test, so it is clear there is something in my test or my environment which is preventing the number of requests from gets higher. It would be a expected behavior if the "response time" was getting higher because it would tell me the requests wasn't been processed properly, but the strange thing is the response time is practically constant all the time and it is pretty low actually. I have no idea why my agent can't send more requests when I increase the numbers of users, any help/tip/guess would be really appreciate.

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  • error detection/correction/recovery in serial protocols

    - by Jason S
    I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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  • Sending jpegs by tcp socket...sometimes incomplete.

    - by Guy
    Vb.net Hi I've been working on a project for months now (vb 2008 express). There is one final problem which I can't solve. I need to send images to a client from a 'server'(listener). The code below works most of the time but sometimes the image is incomplete. I believe this might be something to do with the tcp packet sizes varying, maybe limited by how busy it is out there on the net. I have seen examples of code that splits the image into chunks and sends them out, but I can't get them to work maybe because I'm using a different vb version. The pictures to be sent are small 20k max. Any working code examples would be wonderful. I have been experimenting and failing with this final hurdle for weeks. Thanks in anticipation. Client----- Sub GetPic() '------- Connect to Server ClientSocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, _ ProtocolType.Tcp) ClientSocket.Connect(Epoint) '------- Send Picture Request Dim Bytes() As Byte = System.Text.ASCIIEncoding.ASCII.GetBytes("Send Picture") ClientSocket.Send(Bytes, Bytes.Length, SocketFlags.None) '------- Receive Response Dim RecvBuffer(20000) As Byte Dim Numbytes As Integer Numbytes = ClientSocket.Receive(RecvBuffer) Dim Darray(Numbytes) As Byte Buffer.BlockCopy(RecvBuffer, 0, Darray, 0, Numbytes) '------- Close Connection ClientSocket.Shutdown(SocketShutdown.Both) ClientSocket.Close() '------- Dim MStrm = New MemoryStream(Darray) Picture = Image.FromStream(MStrm) End Sub Listener----- 'Threaded from a listener Sub ClientThread(ByVal Client As TcpClient) Dim MStrm As New MemoryStream Dim Rbuffer(1024) As Byte Dim Tbyte As Byte() Dim NStrm As NetworkStream = Client.GetStream() Dim I As Integer = NStrm.Read(Rbuffer, 0, Rbuffer.Length) Dim Incoming As String = System.Text.Encoding.ASCII.GetString(Rbuffer, 0, I) If Incoming = "Send Picture" then Picture Save(MStrm, Picture.RawFormat) Tbyte = MStrm.ToArray NStrm.Write(Tbyte, 0, Tbyte.Length) End if Client.Close() End Sub

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  • How can I speed up Subversion checkins? (Using ANKH, latest, Visual Studio 2010)

    - by Timothy Khouri
    I've started working on a new web project with some friends... we are using the latest Subversion server (installed last week), the latest version of ANKH. My web project is a whapping 1.5 megabytes (that's with all images, css files, dll's after compiling, pdb files... etc). Checking in even super small changes (literally adding the letter "x" to a few files for testing)... takes FOREVER! (about 10 seconds - I almost killed myself). The ANKH client is measuring in BYTES PER SECOND ... BYTES? per second... I must be doing something wrong. Does anyone what config file has a joke totallyMessWithPeople=true so that I can turn that off or something? Oh, also, changing one "big" file of a super 10k gains speed up to nearly the speed of light (which is apparently 857 bytes per second). Help me obi wan kenobi, your my only hope! EDIT: As a note... my real work project that uses Visual Source Safe 2005 (I know, ouch) uploads files at about 200-500kbps from this very same computer/internet connection.

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  • C# TCP socket with session

    - by Zé Carlos
    Is there any way of dealing with sessions with sockets in C#? Example of my problem: I have a server with a socket listening on port 5672. TcpListener socket = new TcpListener(localAddr, 5672); socket.Start(); Console.Write("Waiting for a connection... "); // Perform a blocking call to accept requests. TcpClient client = socket.AcceptTcpClient(); Console.WriteLine("Connected to client!"); And i have two clients that will send one byte. Client A send 0x1 and client B send 0x2. From the server side, i read this data like this: Byte[] bytes = new Byte[256]; String data = null; NetworkStream stream = client.GetStream(); while ((stream.Read(bytes, 0, bytes.Length)) != 0) { byte[] answer = new ... stream.Write(answer , 0, answer.Length); } Then client A sends 0x11. I need a way to know that this client is the same that sent "0x1" before.

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  • parse content away from structure in a binary file

    - by Jeff Godfrey
    Using C#, I need to read a packed binary file created using FORTRAN. The file is stored in an "Unformatted Sequential" format as described here (about half-way down the page in the "Unformatted Sequential Files" section): http://www.tacc.utexas.edu/services/userguides/intel8/fc/f_ug1/pggfmsp.htm As you can see from the URL, the file is organized into "chunks" of 130 bytes or less and includes 2 length bytes (inserted by the FORTRAN compiler) surrounding each chunk. So, I need to find an efficient way to parse the actual file payload away from the compiler-inserted formatting. Once I've extracted the actual payload from the file, I'll then need to parse it up into its varying data types. That'll be the next exercise. My first thoughts are to slurp up the entire file into a byte array using File.ReadAllBytes. Then, just iterate through the bytes, skipping the formatting and transferring the actual data to a second byte array. In the end, that second byte array should contain the actual file contents minus all the formatting, which I'd then need to go back through to get what I need. As I'm fairly new to C#, I thought there might be a better, more accepted way of tackling this. Also, in case it's helpful, these files could be fairly large (say 30MB), though most will be much smaller...

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  • Porting - Shared Memory x32 & x64 processes

    - by dpb
    A 32 bit host Windows application setups shared memory (using memory mapped file / CreateFileMapping() API), and then other 32 bit client processes use this shared memory to communicate with each other. I am planning to port the host application to 64 bit platform and once it is ready, I intend that both 32 bit and 64 bit client processes should be able to use the shared memory setup by the main 64 bit host application. The original code written for host x32 application uses "size_t" almost everywhere, since this differs from 4 bytes to 8 bytes as we move from x32 to x64, I am looking for replacing it. I intend to replace "size_t" by "unsigned long long", so that its size will be same on 32 bit & 64 bit. Can you please suggest me better alternative? Also, will the use of "unsigned long long" have performance impact on x32 app .. i guess yes? Research Done - Found very useful articles - a) 20 issue in porting from 32 bit to 64 bit (www.viva64.com) b) No way to restrict/change "size_t" on x64 platform to 4 bytes using compiler flags or any hooks/crooks since it is typedef

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  • How to open the download window when a dynamically created link is clicked in asp.net

    - by Ranjana
    i have stored the txtfile in the database.i need to show the txtfile when i clik the link. and this link has to be created dynamically. my code below: aspx code: aspx.cs protected void Page_Load(object sender, EventArgs e) { if(!Page.IsPostBack) { DataTable dtassignment = new DataTable(); dtassignment = serviceobj.DisplayAssignment(Session["staffname"].ToString()); if (dtassignment != null) { Byte[] bytes = (Byte[])dtassignment.Rows[0]["Data"]; //download(dtassignment); } divlink.InnerHtml = ""; divlink.Visible = true; foreach (DataRow r in dtassignment.Rows) { divlink.InnerHtml += "<a href='" + "'onclick='download(dtassignment)'>" + r["Filename"].ToString() + "</a>" + "<br/>"; } } } - public void download(DataTable dtassignment) { System.Diagnostics.Debugger.Break(); Byte[] bytes = (Byte[])dtassignment.Rows[0]["Data"]; Response.Buffer = true; Response.Charset = ""; Response.Cache.SetCacheability(HttpCacheability.NoCache); Response.ContentType = dtassignment.Rows[0]["ContentType"].ToString(); Response.AddHeader("content-disposition", "attachment;filename=" + dtassignment.Rows[0]["FileName"].ToString()); Response.BinaryWrite(bytes); Response.Flush(); Response.End(); } i have got the link dynamically, but i did not able to download the txtfile when i clik the link. how to carry out this. pls help me out...

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  • GZipStream in an WebHttpResponse producing no data

    - by Pierre 303
    I want to compress my HTTP Responses for client that supports it. Here is the code used to send a standard response: IHttpClientContext context = (IHttpClientContext)sender; IHttpRequest request = e.Request; string responseBody = "This is some random text"; IHttpResponse response = request.CreateResponse(context); using (StreamWriter writer = new StreamWriter(response.Body)) { writer.WriteLine(responseBody); writer.Flush(); response.Send(); } The code above works fine. Now I added gzip support below. When I test it with a browser that supports gzip or a custom method, it returns an empty string. I'm sure I'm missing something simple, but I just can't find it... IHttpClientContext context = (IHttpClientContext)sender; IHttpRequest request = e.Request; string acceptEncoding = request.Headers["Accept-Encoding"]; string responseBody = "This is some random text"; IHttpResponse response = request.CreateResponse(context); if (acceptEncoding != null && acceptEncoding.Contains("gzip")) { byte[] bytes = ASCIIEncoding.ASCII.GetBytes(responseBody); response.AddHeader("Content-Encoding", "gzip"); using (GZipStream writer = new GZipStream(response.Body, CompressionMode.Compress)) { writer.Write(bytes, 0, bytes.Length); writer.Flush(); response.Send(); } } else { using (StreamWriter writer = new StreamWriter(response.Body)) { writer.WriteLine(responseBody); writer.Flush(); response.Send(); } }

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  • Get Image from Byte Aarray.

    - by Arun Thakkar
    Hello Everyone!! Hope You all are fine and also in one of your best of moods!! Hope You all are Enjoying iPhone development. I herewith one issue that i am not able to solve, may be i don't know the depth concept of iPhone. So Its my humble requet to you to guide me or suggest or share your ideas. I do find an issue with getting an image from Bytes array. I am calling a webservice which returns an image in form of Bytes Array as response. I have Converted this bytes array in to form of NSData, Now i have NSData, But When i Try to get an image from this NSData, It shows nil. I Did lots of R&D and Find one suggestion to use base64 encoder, But unfortunately because of not proper guidance I was not able to Implement that. I was also suggested to use OPenSSL Library for base64 from url http://www.cocoadev.com/index.pl?BaseSixtyFour But again i was not able to include #include #include these two files. as in Newer Version of SDK 3.X family Apple has depreciated those (as i guess). So Now i need help from you guys. kindly help me if you have solution or if you know the steps to solve these. Looking Forwards. Regards, Arun Thakkar

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  • How memset initializes an array of integers by -1?

    - by haccks
    The manpage says about memset: #include <string.h> void *memset(void *s, int c, size_t n) The memset() function fills the first n bytes of the memory area pointed to by s with the constant byte c. It is clear that memset can't be used to initialize int array as shown below: int a[10]; memset(a, 1, sizeof(a)); it is because int is represented by 4 bytes (say) and one can not get the desired value for the integers in array a. But I often see the programmers use memset to set the int array elements to either 0 or -1. int a[10]; int b[10]; memset(a, 0, sizeof(a)); memset(b, -1, sizeof(b)); As per my understanding, initializing with integer 0 is OK because 0 can be represented in 1 byte (may be I am wrong in this context). But how it is possible to initialize b with -1 (a 4 bytes value)?

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  • How to decrypt a string encrypted with HMACSHA1?

    - by Bob
    I'm an encryption novice trying to pass some values back and forth between systems. I can encrypt the value, but can't seem to figure out how to decrypt on the other end. I've created a simple Windows Forms application using VB.NET. Trying to input a value and a key, encrypt and then decrypt to get the original value. Here's my code so far. Any help greatly appreciated. Thanks. Imports System Imports System.IO Imports System.Security.Cryptography Imports System.Text Public Class Form1 Private Sub btnEncode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncode.Click Dim hmacsha1 As New HMACSHA1(Encoding.ASCII.GetBytes(txtKey.Text)) Dim hashValue As Byte() = hmacsha1.ComputeHash(Encoding.ASCII.GetBytes(txtValue.Text)) txtResult.Text = BytesToHexString(hashValue) hmacsha1.Clear() End Sub Private Sub btnDecode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDecode.Click '??? End Sub Private Function BytesToHexString(ByVal bytes As Byte()) As String Dim output As String = String.Empty Dim i As Integer = 0 Do While i < bytes.Length output += bytes(i).ToString("X2") i += 1 Loop Return output End Function End Class

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  • What do the 'size' numbers mean in the windbg !heap output?

    - by pj4533
    I see output like this in my DMP file: Heap entries for Segment00 in Heap 00150000 00150640: 00640 . 00040 [01] - busy (40) 00150680: 00040 . 01808 [01] - busy (1800) 00151e88: 01808 . 00210 [01] - busy (208) 00152098: 00210 . 00228 [00] 001522c0: 00228 . 00030 [01] - busy (22) 001522f0: 00030 . 00018 [01] - busy (10) 00152308: 00018 . 00048 [01] - busy (3c) The WinDbg docs say this: Heap entries for Segment00 in Heap 250000 0x01 - HEAP_ENTRY_BUSY 0x02 - HEAP_ENTRY_EXTRA_PRESENT 0x04 - HEAP_ENTRY_FILL_PATTERN 0x08 - HEAP_ENTRY_VIRTUAL_ALLOC 0x10 - HEAP_ENTRY_LAST_ENTRY 0x20 - HEAP_ENTRY_SETTABLE_FLAG1 0x40 - HEAP_ENTRY_SETTABLE_FLAG2 Entry Prev Cur 0x80 - HEAP_ENTRY_SETTABLE_FLAG3 Address Size Size flags (Bytes used) (Tag name) 00250000: 00000 . 00b90 [01] - busy (b90) 00250b90: 00b90 . 00038 [01] - busy (38) 00250bc8: 00038 . 00040 [07] - busy (24), tail fill (NTDLL!LDR Database) The spacing is weird in the docs though. Does that mean 'entry address' and 'prev size' and 'cur size', or are the 'entry' 'prev' and 'cur' not for the line below? What does 'prev size' and 'cur size' mean? Especially with regard to 'bytes used'. What is the difference between 'bytes used' and 'cur size'?

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  • Potential problem with C standard malloc'ing chars.

    - by paxdiablo
    When answering a comment to another answer of mine here, I found what I think may be a hole in the C standard (c1x, I haven't checked the earlier ones and yes, I know it's incredibly unlikely that I alone among all the planet's inhabitants have found a bug in the standard). Information follows: Section 6.5.3.4 ("The sizeof operator") para 2 states "The sizeof operator yields the size (in bytes) of its operand". Para 3 of that section states: "When applied to an operand that has type char, unsigned char, or signed char, (or a qualified version thereof) the result is 1". Section 7.20.3.3 describes void *malloc(size_t sz) but all it says is "The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate". It makes no mention at all what units are used for the argument. Annex E startes the 8 is the minimum value for CHAR_BIT so chars can be more than one byte in length. My question is simply this: In an environment where a char is 16 bits wide, will malloc(10 * sizeof(char)) allocate 10 chars (20 bytes) or 10 bytes? Point 1 above seems to indicate the former, point 2 indicates the latter. Anyone with more C-standard-fu than me have an answer for this?

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  • Reading a binary file in perl: Bad File Descriptor

    - by Magicked
    I'm trying to read a binary file 40 bytes at a time, then check to see if all those bytes are 0x00, and if so ignore them. If not, it will write them back out to another file (basically just cutting out large blocks of null bytes). This may not be the most efficient way to do this, but I'm not worried about that. However, right now I'm getting a "Bad File Descriptor" error and I cannot figure out why. my $comp = "\x00" * 40; my $byte_count = 0; my $infile = "/home/magicked/image1"; my $outfile = "/home/magicked/image1_short"; open IN, "<$infile"; open OUT, ">$outfile"; binmode IN; binmode OUT; my ($buf, $data, $n); while (read (IN, $buf, 40)) { ### Problem is here ### $boo = 1; for ($i = 0; $i < 40; $i++) { if ($comp[$i] != $buf[$i]) { $i = 40; print OUT $buf; $byte_count += 40; } } } die "Problems! $!\n" if $!; close OUT; close IN; I marked with a comment where it is breaking. Thanks for any help!

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  • Why do I get "Bad File Descriptor" when I try to read a file with Perl?

    - by Magicked
    I'm trying to read a binary file 40 bytes at a time, then check to see if all those bytes are 0x00, and if so ignore them. If not, it will write them back out to another file (basically just cutting out large blocks of null bytes). This may not be the most efficient way to do this, but I'm not worried about that. However, right now I'm getting a "Bad File Descriptor" error and I cannot figure out why. my $comp = "\x00" * 40; my $byte_count = 0; my $infile = "/home/magicked/image1"; my $outfile = "/home/magicked/image1_short"; open IN, "<$infile"; open OUT, ">$outfile"; binmode IN; binmode OUT; my ($buf, $data, $n); while (read (IN, $buf, 40)) { ### Problem is here ### $boo = 1; for ($i = 0; $i < 40; $i++) { if ($comp[$i] != $buf[$i]) { $i = 40; print OUT $buf; $byte_count += 40; } } } die "Problems! $!\n" if $!; close OUT; close IN; I marked with a comment where it is breaking. Thanks for any help!

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  • PHP sessions dying in a few seconds

    - by beauchette
    I have a problem with my server : my sessions are dying on their own after a few seconds. here are two page examples : page1.php : <? session_start(); $_SESSION['x'] = 'moo'; ?> page2.php : <? session_start(); echo $_SESSION['x']; ?> php's settings are debian's untouched : no auto start, 1440 seconds maxlifetime, etc so, if I visit page1.php et then page2.php I'm supposed to see 'moo' for 24 minutes, in my case, you have 'moo' for about 5 seconds. Then I observed that the actual session file, was 44 bytes long, and then 0 a few seconds later, without any other intervention than a few 'ls' to observe the phenomenon, I really have no clue as to what happens and any help would be appreciated. EDIT: after some fiddling (mainly not doing much besides restarting my server 3 or 4 times) I was able to have my quick example working. and then I noticed that sessions in my session.save_path directory are all 44 bytes except for some that are 0 bytes, so it's like it's working but not always. which is even more frustrating.

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  • Calculating and saving space in Postgresql

    - by punkish
    I have a table in Pg like so CREATE TABLE t ( a BIGSERIAL NOT NULL, -- 8 b b SMALLINT, -- 2 b c SMALLINT, -- 2 b d REAL, -- 4 b e REAL, -- 4 b f REAL, -- 4 b g INTEGER, -- 4 b h REAL, -- 4 b i REAL, -- 4 b j SMALLINT, -- 2 b k INTEGER, -- 4 b l INTEGER, -- 4 b m REAL, -- 4 b CONSTRAINT a_pkey PRIMARY KEY (a) ) The above adds up to 50 bytes per row. My experience is that I need another 40% to 50% for system overhead, without even any user-created indexes to the above. So, about 75 bytes per row. I will have many, many rows in the table, potentially upward of 145 billion rows, so the table is going to be pushing 13-14 Terabytes. What tricks, if any, could I use to compact this table? My possible ideas below -- Convert the REAL values to INTEGERs. If they can stored as SMALLINT, that is a saving of 2 bytes per field. Convert the columns b .. m into an array. I don't need to search on those columns, but I do need to be able to return one column's value at a time. So, if I need column g, I could do something like SELECT a, arr[5] FROM t; Would I save space with the array option? Would there be a speed penalty? Any other ideas?

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  • problem with kCFSocketReadCallBack

    - by zp26
    Hello. I have a problem with my program. I created a socket with "kCFSocketReadCallBack. My intention was to call the "acceptCallback" only when it receives a string to the socket. Instead my program does not just accept the connection always goes into "startReceive" stop doing so and sometimes crash the program. Can anybody help? Thanks readSocket = CFSocketCreateWithNative( NULL, fd, kCFSocketReadCallBack, AcceptCallback, &context ); static void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) // Called by CFSocket when someone connects to our listening socket. // This implementation just bounces the request up to Objective-C. { ServerVistaController * obj; #pragma unused(address) // assert(address == NULL); assert(data != NULL); obj = (ServerVistaController *) info; assert(obj != nil); #pragma unused(s) assert(s == obj->listeningSocket); if (type & kCFSocketAcceptCallBack){ [obj acceptConnection:*(int *)data]; } if (type & kCFSocketAcceptCallBack){ [obj startReceive:*(int *)data]; } } -(void)startReceive:(int)fd { CFReadStreamRef readStream = NULL; CFIndex bytes; UInt8 buffer[MAXLENGTH]; CFStreamCreatePairWithSocket( kCFAllocatorDefault, fd, &readStream, NULL); if(!readStream){ close(fd); [self updateLabel:@"No readStream"]; } CFReadStreamOpen(readStream); [self updateLabel:@"OpenStream"]; bytes = CFReadStreamRead( readStream, buffer, sizeof(buffer)); if (bytes < 0) { [self updateLabel:(NSString*)buffer]; close(fd); } CFReadStreamClose(readStream); }

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  • IndexOutOfRangeException when a stream is a multiple of the buffer size

    - by dnord
    I don't have a lot of experience with streams and buffers, but I'm having to do it for a project, and I'm stuck on an exception being thrown when the stream I'm reading is a multiple of the buffer size I've chosen. Let me show you: My code starts by reading bufferSize (100, let's say) bytes from the stream: numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); Then, I loop through a while loop: while (numberOfBytesRead == bufferSize) { BufferWriter.Write(output); BufferWriter.Flush(); index += bufferSize; numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); } ... and, once we get to a non-bufferSize read, we know we've hit the end of the stream and can move on. But if the bufferSize is 100, and the stream is 200, we'll read positions 0-99, 100-199, and then the attempt to read 200-299 errors out. I'd like it if it returned 0, but it throws an error. What I'm doing to handle that is, well, a try-catch: catch (System.IndexOutOfRangeException) numberOfBytesRead = 0; ...which ends the loop, and successfully finishes the thing, but we all know I don't want to control code flow with error handling. Is there a better (more standard?) way to handle stream reading when the stream length is unknown? This seems like a small wrinkle in a fairly reasonable strategy for reading streams, but I just don't know if I've got it wrong or what. The specifics of this (which I've cleaned up a little bit for posting) are a MySqlDataReader hitting a LARGEBLOB column. It's working whenever the buffer is larger than the number of returned bytes, or when the number of returned bytes is not a multiple of bufferSize. Because we don't, in that case, throw an IndexOutOfRangeException.

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  • Why is short project lifetime and other situation-specific reasons used to excuse crappy code? [clos

    - by sharptooth
    Every now and then (including on SO) people say things implying that "if the project is short lived you can leave obvious defects there" or "that memory leak only accounts for 100 bytes per whole program lifetime and could be left". Now in my practice I always reuse company-owned code to the greatest extent I can. Like if I need something and I can find it in the company codebase I take it from there and reuse or adapt. This means that any crappy code will be reused as well and I might notice or not notice defects therein. So the defect in some "test we only need for a month" can slip into a proram we ship to customers. And a leak that "only accounted for 100 bytes per lifetime" now could account for 100 bytes 10 times per second in a server application intended to run for months. That's why I don't understand why excuses like that are offered. Is our compamy the only one having a source control? Or are we the only company that requires writing human-readable code? Could anyone shed a light on why people seriously offer such excuses?

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  • g-wan - reproducing the performance claims

    - by user2603628
    Using gwan_linux64-bit.tar.bz2 under Ubuntu 12.04 LTS unpacking and running gwan then pointing wrk at it (using a null file null.html) wrk --timeout 10 -t 2 -c 100 -d20s http://127.0.0.1:8080/null.html Running 20s test @ http://127.0.0.1:8080/null.html 2 threads and 100 connections Thread Stats Avg Stdev Max +/- Stdev Latency 11.65s 5.10s 13.89s 83.91% Req/Sec 3.33k 3.65k 12.33k 75.19% 125067 requests in 20.01s, 32.08MB read Socket errors: connect 0, read 37, write 0, timeout 49 Requests/sec: 6251.46 Transfer/sec: 1.60MB .. very poor performance, in fact there seems to be some kind of huge latency issue. During the test gwan is 200% busy and wrk is 67% busy. Pointing at nginx, wrk is 200% busy and nginx is 45% busy: wrk --timeout 10 -t 2 -c 100 -d20s http://127.0.0.1/null.html Thread Stats Avg Stdev Max +/- Stdev Latency 371.81us 134.05us 24.04ms 91.26% Req/Sec 72.75k 7.38k 109.22k 68.21% 2740883 requests in 20.00s, 540.95MB read Requests/sec: 137046.70 Transfer/sec: 27.05MB Pointing weighttpd at nginx gives even faster results: /usr/local/bin/weighttp -k -n 2000000 -c 500 -t 3 http://127.0.0.1/null.html weighttp - a lightweight and simple webserver benchmarking tool starting benchmark... spawning thread #1: 167 concurrent requests, 666667 total requests spawning thread #2: 167 concurrent requests, 666667 total requests spawning thread #3: 166 concurrent requests, 666666 total requests progress: 9% done progress: 19% done progress: 29% done progress: 39% done progress: 49% done progress: 59% done progress: 69% done progress: 79% done progress: 89% done progress: 99% done finished in 7 sec, 13 millisec and 293 microsec, 285172 req/s, 57633 kbyte/s requests: 2000000 total, 2000000 started, 2000000 done, 2000000 succeeded, 0 failed, 0 errored status codes: 2000000 2xx, 0 3xx, 0 4xx, 0 5xx traffic: 413901205 bytes total, 413901205 bytes http, 0 bytes data The server is a virtual 8 core dedicated server (bare metal), under KVM Where do I start looking to identify the problem gwan is having on this platform ? I have tested lighttpd, nginx and node.js on this same OS, and the results are all as one would expect. The server has been tuned in the usual way with expanded ephemeral ports, increased ulimits, adjusted time wait recycling etc.

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  • Convert a image to a monochrome byte array

    - by Scott Chamberlain
    I am writing a library to interface C# with the EPL2 printer language. One feature I would like to try to implement is printing images, the specification doc says p1 = Width of graphic Width of graphic in bytes. Eight (8) dots = one (1) byte of data. p2 = Length of graphic Length of graphic in dots (or print lines) Data = Raw binary data without graphic file formatting. Data must be in bytes. Multiply the width in bytes (p1) by the number of print lines (p2) for the total amount of graphic data. The printer automatically calculates the exact size of the data block based upon this formula. I plan on my source image being a 1 bit per pixel bmp file, already scaled to size. I just don't know how to get it from that format in to a byte[] for me to send off to the printer. I tried ImageConverter.ConvertTo(Object, Type) it succeeds but the array it outputs is not the correct size and the documentation is very lacking on how the output is formatted. My current test code. Bitmap i = (Bitmap)Bitmap.FromFile("test.bmp"); ImageConverter ic = new ImageConverter(); byte[] b = (byte[])ic.ConvertTo(i, typeof(byte[])); Any help is greatly appreciated even if it is in a totally different direction.

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  • Benefits of "Don't Fragment" on TCP Packets?

    - by taspeotis
    One of our customers is having trouble submitting data from our application (on their PC) to a server (different geographical location). When sending packets under 1100 bytes everything works fine, but above this we see TCP retransmitting the packet every few seconds and getting no response. The packets we are using for testing are about 1400 bytes (but less than 1472). I can send an ICMP ping to www.google.com that is 1472 bytes and get a response (so it's not their router/first few hops). I found that our application sets the DF flag for these packets, and I believe a router along the way to the server has an MTU less than/equal to 1100 and dropping the packet. This affects 1 client in 5000, but since everybody's routes will be different this is expected. The data is a SOAP envelope and we expect a SOAP response back. I can't justify WHY we do it, the code to do this was written by a previous developer. So... Are there are benefits OR justification to setting the DF flag on TCP packets for application data? I can think of reasons it is needed for network diagnostics applications but not in our situation (we want the data to get to the endpoint, fragmented or not). One of our sysadmins said that it might have something to do with us using SSL, but as far as I know SSL is like a stream and regardless of fragmentation, as long as the stream is rebuilt at the end, there's no problem. If there's no good justification I will be changing the behaviour of our application. Thanks in advance.

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