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  • How can I optimize this loop?

    - by Moshe
    I've got a piece of code that returns a super-long string that represents "search results". Each result is represented by a double HTML break symbol. For example: Result1<br><br>Result 2<br><br>Result3 I've got the following loop that takes each result and puts it into an array, stripping out the break indicator, "kBreakIndicator" (<br><br>). The problem is that this lopp takes way too long to execute. With a few results it's fine, but once you hit a hundred results, it's about 20-30 seconds slower. It's unacceptable performance. What can I do to improve performance? Here's my code: content is the original NSString. NSMutableArray *results = [[NSMutableArray alloc] init]; //Loop through the string of results and take each result and put it into an array while(![content isEqualToString:@""]){ NSRange rangeOfResult = [content rangeOfString:kBreakIndicator]; NSString *temp = (rangeOfResult.location != NSNotFound) ? [content substringToIndex:rangeOfResult.location] : nil; if (temp) { [results addObject:temp]; content = [[[content stringByReplacingOccurrencesOfString:[NSString stringWithFormat:@"%@%@", temp, kBreakIndicator] withString:@""] mutableCopy] autorelease]; }else{ [results addObject:[content description]]; content = [[@"" mutableCopy] autorelease]; } } //Do something with the results array. [results release];

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  • Best suited tool to document message processing done in C written program

    - by user3494614
    I am relatively new to UML and it's seems to be very vast I have a small program which basically receives messages on socket and then depending upon message ID embedded as first byte of message it processes the buffer. There are around 5 different message ID which it processes and communicates on another socket and has around 8 major functions. So program in short is like this. I am not pasting entire .c file or main function but just giving some bits and pieces of it so that to get idea of program flow. int main(int argc, char** argv) { register_shared_mem(); listen(); while(get_next_message(buffer)) { switch((msg)(buffer)->id) { case TYPE1: process1(); answer(); ..... } } } I want to document this is pictorial way like for Message type 1 it calls this function which calls another and which calls another. Please let me know any open source tool which will allow me to quickly draw such kind of UML or sequence diagram and will also allow me to write brief description of what each function does? Thanks In Advance

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  • A better way of getting a data table with various column types into string array

    - by Vlad
    This should be an easy one, looks like I got myself too confused. I get a table from a database, data ranges from varchar to int to Null values. Cheap and dirty way of converting this into a tab-delimited file that I already have is this (shrunken to preserve space, ugliness is kept on par with original): da.Fill(dt) ' da - DataAdapter ' ' dt - DataTable ' Dim lColumns As Long = dt.Columns.Count Dim arrColumns(dt.Columns.Count) As String Dim arrData(dt.Columns.Count) As Object Dim j As Long = 0 Dim arrData(dt.Columns.Count) As Object For i = 0 To dt.Rows.Count - 1 arrData = dt.Rows(i).ItemArray() For j = 0 To arrData.GetUpperBound(0) - 1 arrColumns(j) = arrData(j).ToString Next wrtOutput.WriteLine(String.Join(strFieldDelimiter, arrColumns)) Array.Clear(arrColumns, 0, arrColumns.GetLength(0)) Array.Clear(arrData, 0, arrData.GetLength(0)) Next Not only this is ugly and inefficient, it is also getting on my nerves. Besides, I want, if possible, to avoid the infamous double-loop through the table. I would really appreciate a clean and safe way of rewriting this piece. I like the approach that is used here - especially that is trying to solve the same problem that I have, but it crashes on me when I apply it to my case directly.

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  • mysql_affected_rows() returns 0 for UPDATE statement even when an update actually happens

    - by Alex Moore
    I am trying to get the number of rows affected in a simple mysql update query. However, when I run this code below, PHP's mysql_affected_rows() always equals 0. No matter if foo=1 already (in which case the function should correctly return 0, since no rows were changed), or if foo currently equals some other integer (in which case the function should return 1). $updateQuery = "UPDATE myTable SET foo=1 WHERE bar=2"; mysql_query($updateQuery); if (mysql_affected_rows() > 0) { echo "affected!"; } else { echo "not affected"; // always prints not affected } The UPDATE statement itself works. The INT gets changed in my database. I have also double-checked that the database connection isn't being closed beforehand or anything funky. Keep in mind, mysql_affected_rows doesn't necessarily require you to pass a connection link identifier, though I've tried that too. Details on the function: mysql_affected_rows Any ideas? SOLUTION The part I didn't mention turned out to be the cause of my woes here. This PHP file was being called ten times consecutively in an AJAX call, though I was only looking at the value returned on the last call, ie. a big fat 0. My apologies!

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  • some problem with iOS 4.2.1

    - by bicbac
    Hi, I've been developing an app with MacBook Pro (MBP) so far. Last week one of my friends gave me new macbook air 11"(MBA). so Now I can test my code with more than one machine with the same version of developing tools - Both machine has Xcode (3.2.5) and iOS SDK 4.2.1). After some point my app starts get terminated suddenly(iPhone sumulator), and I was using MBP. I got no error message whatsoever. it just stops. I reckon the crash comes from dealing with memory, like 'release'/ 'double-release'. (I'm not 100% sure though). Anyway I thought there must be some mistake within my code for sure. -Confusion starts from this part.- With my MBA, on the other hand, I don'y see any crash. It just works fine. There is nothing different between MBA & MBP except the h/w specifications. Same code, same versions of XCode and iOS SDK. Is the fact that no crash at MBA suggesting that I have to look somewhere else than the code itself? I red some article and Q&As on iOS4.2.1 and XCode 3.2.5 that the most recent version of XCode doesn't recognize the iOS 4.2.1 since the 4.2.1 came out later the 3.2.5. Is it the reason? I have no idea at this moment what should be the next move. thanks

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  • How do I redirect standard output to a file in Perl? [closed]

    - by rockyurock
    I want to send standard output to the file "my_output.txt" but failed. Here's the output: inside value loop ------------------------------------------------------------ Server listening on UDP port 5001 Receiving 1470 byte datagrams UDP buffer size: 108 KByte (default) ------------------------------------------------------------ [ 3] local 192.168.16.2 port 5001 connected with 192.168.16.1 port 3189 [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams [ 3] 0.0- 5.0 sec 2.14 MBytes 3.61 Mbits/sec 0.369 ms 0/ 1528 (0%) inside value loop3 clue1 clue2 inside value loop4 one iperf completed *************************************** When I enable the local *STDOUT; in below code then I could see the above output on command prompt display (ofcourse server is sending some data): my $file = 'my_output.txt'; use Win32::Process; print"inside value loop\n"; # redirect stdout to a file #local *STDOUT; open STDOUT, '>', $file or die "can't redirect STDOUT to <$file> $!"; Win32::Process::Create(my $ProcessObj, "D:\\IOT_AUTOMATION_UTILITY\\_SATURDAY_09-04-10\\adb_cmd.bat", "adb shell /data/app/iperf -u -s -p 5001", 0, NORMAL_PRIORITY_CLASS, ".") || die ErrorReport(); #$alarm_time = $IPERF_RUN_TIME+10; #20sec #$ProcessObj->Wait(40); #print"inside value loop2\n"; #sleep $alarm_time; sleep 40; $ProcessObj->Kill(0); sub ErrorReport{ print Win32::FormatMessage( Win32::GetLastError() ); }

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  • I just discovered why all ASP.Net websites are slow, and I am trying to work out what to do about it

    - by James
    I just discovered that every request in an ASP.Net web application gets a Session lock at the begging of a request, and then releases it at the end of the request!!! I mean, WTF Microsoft! In case the implication is lost on you, as it was from me at first, this basically means the following: Anytime an ASP.Net webpage is taking a long time to load (maybe due to a slow database call or whatever), and the user decides they want to navigate to a different page because they are tired of waiting, THEY CANT! The ASP.Net session lock forces the new page request to wait until the original request has finished its painfully slow load. Arrrgh. Anytime an UpdatePanel is loading slowly, and the user decides to navigate to a different page before the UpdadePanel has finished updating... THEY CANT! The ASP.Net session lock forces the new page request to wait until the original request has finished its painfully slow load. Double Arrrgh! So what are the options? So far I have come up with: Implement a Custom SessionStateDataStore, which ASP.Net supports. I haven't found too many out there to copy, and it seems kind of high risk and easy to mess up. Keep track of all requests in progress, and if a request comes in from the same user, cancel the original request. Seems kind of extreme, but it would work (I think) Don't user Session! When I need some kind of state for the user, I could just user Cache instead, and key items on the authenticated user's name, or some such thing. Again seems kind of extreme I really can't believe that the ASP.Net Microsoft team would have left such a huge performance bottleneck in the framework at version 4.0! Am I missing something obvious? How hard would it be to use a ThreadSafe collection for the Session? Arrrrghhhhhh. Any advice much appreciated.

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  • Cancelling BackgroundWorker While Running

    - by Nevets
    I have an application in which I launch a window that displays byte data coming in from a 3rd party tool. I have included .CancelAsync() and .CancellationPending into my code (see below) but I have another issue that I am running into. private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) { Thread popupwindow = new Thread(() => test()); popupwindow.Start(); // start test script if(backgroundWorker.CancellationPending == true) { e.Cancel = true; } } private voide window_FormClosing(object sender, FormClosingEventArgs e) { try { this.backgroundWorker.CancelAsync(); } catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); } } Upon cancelling the test I get an `InvalidOperationException occurred" error from my rich text box in my pop-up window. It states that "Invoke or BeginInvoke" cannot be called on a control until the window handle has been created". I am not entirely sure what that means and would appreciate your help. LogWindow code for Rich Text Box: public void LogWindowText(LogMsgType msgtype, string msgIn) { rtbSerialNumberValue.Invoke(new EventHandler(delegate { rtbWindow.SelectedText = string.Empty; rtbWindow.SelectionFont = new Font(rtbWindow.SelectionFont, FontStyle.Bold); rtbWindow.SelectionColor = LogMsgTypeColor[(int)msgtype]; rtbWindow.AppendText(msgIn); rtbWindow.ScrollToCaret(); })); }

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  • Positioning objects in views during re-orientation in iPad

    - by Arni
    iPad Gurus: Apple wants us to support all orientations. I take that to mean that a particular layout should either rotate so that all objects are positioned relatively the same OR, if that doesn't look good, then they ought to be repositioned, OR two views ought to be designed and built. If I rely on the built-in rotation mechanism, the objects either get resized or they straddle the edge of the page in one orientation or the other, or they disappear from view altogether. I can't seem to find the right settings to get the objects to align clearly so they are seen in each orientation. Repositioning leads to a lot of if statements in the View Controller. So I don't think Apple had that in mind. I tried replacing views and even view controllers in "willRotateToInterfaceOrientation" method, but that either causes crashes or the portrait views end up in landscape unexpectedly and vv. Moreover, two view controllers means double the coding for the same view. There must be proper way to handle orientation changes, but I have searched the internet and documentation and sample code in vain for something that works. How is this done properly? Thanks!

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  • help me refactor iteration over a generic collection

    - by Biswanath
    Hi, I am working with a generic data structure, say MyGeneric<Type>. There is a case where I have to iterate over all the values it holds The code I am trying to do. for ( all the keys in myGeneric ) { // do lot of stuff here } Now the generic can hold base type as double and string and it can hold some user-defined type also. There is a particular situation where I have to some specific work depending upon the type of the generic. so the final code block looks something like this for( all the keys in myGeneric ) { if key is type foo then //do foo foo else if key is of type bar //do bar bar } Now, as complexity sensitive as I am I do not like to have an if condition in the for loop. So the next solution I did was if myGeneric is of type foo call fooIterator(myGeneric) if myGenric is of type bar call barItetrator(myGeneric) function FooIterator() { // ..... // foo work //...... } function BarItetrator() { // ..... // bar work //...... } Then again when somebody sees my code then I am quite sure that they will shout where is the "refactoring". What is the ideal thing to do in this situation ? Thanks.

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  • sendto is returning ENOBUF

    - by user338159
    Hi, I am currently running an old system on Tru64 which involves lots of UDP sockets using the sendto() function. The sockets are used in our code to send messages to/from various processes and then eventually on to a thick client app that is connected remotely. Occasionally the socket to the thick client gets stuck, this can cause some of these messages to get built up. My question is how can I determine the current buffer size, and how do I determine the maximum message buffer. The code below gives a snippet of how I set up the port and use the sendto function. /* need to adjust the maximum size we can send on this / / as it needs to be able to cope with the biggest / / messages we send / lenlen = sizeof(len) ; / allow double for when the system is under load */ len = 2 * C_MAX_MESSAGE_DATA_SIZE ; lpos_setsockopt(FATAL, msg_socket,SOL_SOCKET, SO_SNDBUF, &len, lenlen, &error_no) ; result = sendto( msg_socket, (char *)message, (int)message_len, flags, dest_addr, addrlen); Note. We have ported this application to Linux and the problem does not seem to appear there. Any help would be greatly appreciated. Regards

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  • jQuery Hover Fade Button with an Active State

    - by Tim
    I do not want to double post a question; I was trying to post an add-on to my first question that I was looking for additional help. How does one go about this? Here is the original question. jQuery Hover Fade Button with an Active State Was hoping to see if there is a solution to the glitch I found. The problem I am now looking for help with is all other buttons still have the hover effect, but a button that was once active no longer does. <ul class="buttons"> <li><a class="button" href="#">button 1</a></li> <li><a class="button" href="#">button 2</a></li> <li><a class="button" href="#">button 3</a></li> </ul> Best way to explain this. If button 2 is clicked – it is now active. Buttons 1 and 3 will still hover. If you click on button 1 – it is now active and button 2 will no longer hover while button 3 will. Eventually when you go through the series of all buttons the animation hover is no longer.

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  • How to update a string property of an sqlite database item

    - by Thomas Joos
    hi all, I'm trying to write an application that checks if there is an active internet connection. If so it reads an xml and checks every 'lastupdated' item ( php generated string ). It compares it to the database items and if there is a new value, this particular item needs to be updated. My code seems to work ( compiles, no error messages, no failures, .. ) but I notice that the particular property does not change, it becomese (null). When I output the binded string value it returns the correct string value I want to update into the db.. Any idea what I'm doing wrong? const char *sql = "update myTable Set last_updated=? Where node_id =?"; sqlite3_stmt *statement; // Preparing a statement compiles the SQL query into a byte-code program in the SQLite library. // The third parameter is either the length of the SQL string or -1 to read up to the first null terminator. if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL) == SQLITE_OK){ NSLog(@"last updated item: %@", [d lastupdated]); sqlite3_bind_text(statement, 1, [d lastupdated],-1,SQLITE_TRANSIENT); sqlite3_bind_int (statement, 2, [d node_id]); }else { NSLog(@"SQLite statement error!"); } if(SQLITE_DONE != sqlite3_step(statement)){ NSAssert1(0, @"Error while updating. '%s'", sqlite3_errmsg(database)); }else { NSLog(@"SQLite Update done!"); }

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  • Write file need to optimised for heavy traffic part 2

    - by Clayton Leung
    For anyone interest to see where I come from you can refer to part 1, but it is not necessary. write file need to optimised for heavy traffic Below is a snippet of code I have written to capture some financial tick data from the broker API. The code will run without error. I need to optimize the code, because in peak hours the zf_TickEvent method will be call more than 10000 times a second. I use a memorystream to hold the data until it reaches a certain size, then I output it into a text file. The broker API is only single threaded. void zf_TickEvent(object sender, ZenFire.TickEventArgs e) { outputString = string.Format("{0},{1},{2},{3},{4}\r\n", e.TimeStamp.ToString(timeFmt), e.Product.ToString(), Enum.GetName(typeof(ZenFire.TickType), e.Type), e.Price, e.Volume); fillBuffer(outputString); } public class memoryStreamClass { public static MemoryStream ms = new MemoryStream(); } void fillBuffer(string outputString) { byte[] outputByte = Encoding.ASCII.GetBytes(outputString); memoryStreamClass.ms.Write(outputByte, 0, outputByte.Length); if (memoryStreamClass.ms.Length > 8192) { emptyBuffer(memoryStreamClass.ms); memoryStreamClass.ms.SetLength(0); memoryStreamClass.ms.Position = 0; } } void emptyBuffer(MemoryStream ms) { FileStream outStream = new FileStream("c:\\test.txt", FileMode.Append); ms.WriteTo(outStream); outStream.Flush(); outStream.Close(); } Question: Any suggestion to make this even faster? I will try to vary the buffer length but in terms of code structure, is this (almost) the fastest? When memorystream is filled up and I am emptying it to the file, what would happen to the new data coming in? Do I need to implement a second buffer to hold that data while I am emptying my first buffer? Or is c# smart enough to figure it out? Thanks for any advice

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  • C++, Ifstream opens local file but not file on HTTP Server

    - by fammi
    Hi, I am using ifstream to open a file and then read from it. My program works fine when i give location of the local file on my system. for eg /root/Desktop/abc.xxx works fine But once the location is on the http server the file fails to open. for eg http://192.168.0.10/abc.xxx fails to open. Is there any alternate for ifstream when using a URL address? thanks. part of the code where having problem: bool readTillEof = (endIndex == -1) ? true : false; // Open the file in binary mode and seek to the end to determine file size ifstream file ( fileName.c_str ( ), ios::in|ios::ate|ios::binary ); if ( file.is_open ( ) ) { long size = (long) file.tellg ( ); long numBytesRead; if ( readTillEof ) { numBytesRead = size - startIndex; } else { numBytesRead = endIndex - startIndex + 1; } // Allocate a new buffer ptr to read in the file data BufferSptr buf (new Buffer ( numBytesRead ) ); mpStreamingClientEngine->SetResponseBuffer ( nextRequest, buf ); // Seek to the start index of the byte range // and read the data file.seekg ( startIndex, ios::beg ); file.read ( (char *)buf->GetData(), numBytesRead ); // Pass on the data to the SCE // and signal completion of request mpStreamingClientEngine->HandleDataReceived( nextRequest, numBytesRead); mpStreamingClientEngine->MarkRequestCompleted( nextRequest ); // Close the file file.close ( ); } else { // Report error to the Streaming Client Engine // as unable to open file AHS_ERROR ( ConnectionManager, " Error while opening file \"%s\"\n", fileName.c_str ( ) ); mpStreamingClientEngine->HandleRequestFailed( nextRequest, CONNECTION_FAILED ); } }

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  • How to load/save C++ class instance (using STL containers) to disk

    - by supert
    I have a C++ class representing a hierarchically organised data tree which is very large (~Gb, basically as large as I can get away with in memory). It uses an STL list to store information at each node plus iterators to other nodes. Each node has only one parent, but 0-10 children. Abstracted, it looks something like: struct node { public: node_list_iterator parent; // iterator to a single parent node double node_data_array[X]; map<int,node_list_iterator> children; // iterators to child nodes }; class strategy { private: list<node> tree; // hierarchically linked list of nodes struct some_other_data; public: void build(); // build the tree void save(); // save the tree from disk void load(); // load the tree from disk void use(); // use the tree }; I would like to implement the load() and save() to disk, and it should be fairly fast, however the obvious problems are: I don't know the size in advance; The data contains iterators, which are volatile; My ignorance of C++ is prodigious. Could anyone suggest a pure C++ solution please?

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  • transferring binary files between systems

    - by tim
    Hi guys I'm trying to transfer my files between 2 UNIX clusters, the data is pure numeric (vectors of double) in binary form. Unfortunately one of the systems is IBM ppc997 and the other is AMD Opteron, It seems the format of binary numbers in these systems are different. I have tried 3 ways till now: 1- Changed my files to ASCII format (i.e. saved a number at each line in a text file), sent them to the destination and changed them again to binary on the target system (they both are UNIX, no end of line character difference??!) 2- Sent pure binaries to the destination 3- used uuencode sent them to the destination and decoded them Unfortunately any of these methods does not work (my code in the destination system generates garbage, while it works on the first system, I'm 100% sure the code itself is portable). I don't know what else I can do? Do you have any idea? I'm not a professional, please don't use computer scientists terminology! And: my codes are in C, so by binary I mean a one to one mapping between memory and hard disk. Thanks

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  • Audio Streaming Latency

    - by killianmcc
    I'm writing a UDP local area network video chat system and have got the video and audio streams working. However I'm experiencing a little latency (about half a second) in the audio and was wondering what codecs would provide the least latency. I'm using NAudio (http://naudio.codeplex.com/) which provides me access to the following codecs for streaming; Speex Narrow Band (VBR) Speex Wide Band (16kHz)(VBR) Speex Ultra Wide Band (32kHz)(VBR) DSP Group TrueSpeech (8.5kbps) GSM 6.10 (13kbps) Microsoft ADPCM (32.8kbps) G.711 a-law (64kbps) G.722 16kHz (64kbps) G.711 mu-law (64kbps) PCM 8kHz 16 bit uncompressed (128kbps) I've tried them out and I'm not noticing much difference. Is there any others that I should download and try to reduce latency? I'm only going to be sending voice over the connection but I'm not really worried about quality or background noises too much. UPDATE I'm sending the audio in blocks like so; waveIn = new WaveIn(); waveIn.BufferMilliseconds = 50; waveIn.DeviceNumber = inputDeviceNumber; waveIn.WaveFormat = codec.RecordFormat; waveIn.DataAvailable += waveIn_DataAvailable; void waveIn_DataAvailable(object sender, WaveInEventArgs e) { if (connected) { byte[] encoded = codec.Encode(e.Buffer, 0, e.BytesRecorded); udpSender.Send(encoded, encoded.Length); } }

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  • WCF: get generic type object (e.g. MyObject<T>) from remote machine

    - by Aaron
    I have two applications that are communicating through WCF. On the server the following object exists: public class MyObject<T> { ... public Entry<T> GetValue() } Where Entry<T> is another object with T Data as a public property. T could be any number of types (string, double, etc) On the client I have ClientObject<T> that needs to get the value of Data from the server (same type). Since I'm using WCF, I have to define my ServiceContract as an interface, and I can't have ClientObject<T> call Entry<T> GetMyObjectValue (string Name) which calls GetValue on the correct MyObject<T> because my interface isn't aware of the type information. I've tried implementing separate GetValue functions (GetMyObjectValueDouble, GetMyObjectValueString) in the interface and then have ClientObject determine the correct one to call. However, Entry<T> val = (Entry<T>)GetMyObjectValueDouble(...); doesn't work because it's not sure about the type information. How can I go about getting a generic object over WCF with the correct type information? Let me know if there are other details I can provide. Thanks!

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  • C# : Regular Expression

    - by Pramodh
    I'm having a set of row data as follows List<String> l_lstRowData = new List<string> { "Data 1 32:01805043*0FFFFFFF", "Data 3, 20.0e-3", "Data 2, 1.0e-3 172:?:CRC" , "Data 6" }; and two List namely "KeyList" and "ValueList" like List<string> KeyList = new List<string>(); List<string> ValueList = new List<string>(); I need to fill the two List<String> from the data from l_lstRowData using Pattern Matching And here is my Pattern for this String l_strPattern = @"(?<KEY>(Data|data|DATA)\s[0-9]*[,]?[ ][0-9e.-]*)[ \t\r\n]*(?<Value>[0-9A-Za-z:?*!. \t\r\n\-]*)"; Regex CompiledPattern=new Regex(l_strPattern,RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace); So finally the two Lists will contain KeyList { "Data 1" } { "Data 3, 20.0e-3" } { "Data 2, 1.0e-3" } { "Data 6" } ValueList { "32:01805043*0FFFFFFF" } { "" } { "172:?:CRC" } { "" } Scenerio: The Group KEY in the Pattern Should match "The data followed by an integer value , and the if there exist a comma(,) then the next string i.e a double value The Group Value in the Pattern should match string after the whitespace.In the first string it should match 32:01805043*0FFFFFFF but in the 3rd 172:?:CRC. Here is my sample code for (int i = 0; i < l_lstRowData.Count; i++) { MatchCollection M = CompiledPattern.Matches(l_lstRowData[i], 0); KeyList.Add(M[0].Groups["KEY"].Value); ValueList.Add(M[0].Groups["Value"].Value); } But my Pattern is not working in this situation. Please help me to rewrite my Pattern.

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  • How to avoid concurrent execution of a time-consuming task without blocking?

    - by Diego V
    I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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  • Fast serialization/deserialization of structs

    - by user256890
    I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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  • powershell missing member methods in array

    - by Andrew
    Hi Guys I have (yet another) powershell query. I have an array in powershell which i need to use the remove() and split commands on. Normally you set an array (or variable) and the above methods exist. On the below $csv2 array both methods are missing, i have checked using the get-member cmd. How can i go about using remove to get rid of lines with nan. Also how do i split the columns into two different variables. at the moment each element of the array displays one line, for each line i need to convert it into two variables, one for each column. timestamp Utilization --------- ----------- 1276505880 2.0763250000e+00 1276505890 1.7487730000e+00 1276505900 1.6906890000e+00 1276505910 1.7972880000e+00 1276505920 1.8141900000e+00 1276505930 nan 1276505940 nan 1276505950 0.0000000000e+00 $SystemStats = (Get-F5.iControl).SystemStatistics $report = "c:\snmp\data" + $gObj + ".csv" ### Allocate a new Query Object and add the inputs needed $Query = New-Object -TypeName iControl.SystemStatisticsPerformanceStatisticQuery $Query.object_name = $i $Query.start_time = $startTime $Query.end_time = 0 $Query.interval = $interval $Query.maximum_rows = 0 ### Make method call passing in an array of size one with the specified query $ReportData = $SystemStats.get_performance_graph_csv_statistics( (,$Query) ) ### Allocate a new encoder and turn the byte array into a string $ASCII = New-Object -TypeName System.Text.ASCIIEncoding $csvdata = $ASCII.GetString($ReportData[0].statistic_data) $csv2 = convertFrom-CSV $csvdata $csv2

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  • File IO with Streams - Best Memory Buffer Size

    - by AJ
    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).

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  • Why do I get "request for member in something not a struct or union" from this code?

    - by pyroxene
    I'm trying to teach myself C by coding up a linked list. I'm new to pointers and memory management and I'm getting a bit confused. I have this code: /* Remove a node from the list and rejiggle the pointers */ void rm_node(struct node **listP, int index) { struct node *prev; struct node *n = *listP; if (index == 0) { *listP = *listP->next; free(n); return; } for (index; index > 0; index--) { n = n->next; if (index == 2) { prev = n; } } prev->next = n->next; free(n); } to remove an element from the list. If I want to remove the first node, I still need some way of referring to the list, which is why the listP arg is a double pointer, so it can point to the first element of the list and allow me to free the node that used to be the head. However, when I try to dereference listP to access the pointer to the next node, the compiler tells me error: request for member ‘next’ in something not a structure or union . What am I doing wrong here? I think I might be hopelessly mixed up..?

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