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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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  • Load Balance WCF and Share a Remote MSMQ for High Throughput

    - by BarDev
    After a ton of reading in books and on the web, I have noticed hints of information that WCF and MSMQ can be used in achieving high throughput. The information I have seen mentions using multiple WCF services in a farm that reads from a single MSMQ queue. The problem is that I have found paragraphs here and there that mentions that high throughput can be done, but I cannot seem to find a document of how to implement it. The following is an excerpt from a MSDN article. The following paragraph is from Best Practices for Queued Communication http://msdn.microsoft.com/en-us/library/ms731093.aspx To achieve higher throughput and availability, use a farm of WCF services that read from the queue. This requires that all of these services expose the same contract on the same endpoint. The farm approach works best for applications that have high production rates of messages because it enables a number of services to all read from the same queue. This is what I'm trying to solve. I have an intranet application where a client sends a request to a WCF service. But I want the ability to load balance the WCF services on multiple servers in a farm. I also want these WCF services in the farm to do transactional reads from a remote MSMQ when an item is available in the Queue. If this is possible, an issue I have is that I do not understand the activation process of WCF to retrieve messages from a remote queue. If this is possible, does anyone know of any articles or Webcasts that would explain it in detail? BarDev

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  • Do the ‘up to date’ guarantees for values of Java's final fields extend to indirect references?

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed? I'm looking for clarification of the semantics of the Java Memory Model and language spec, rather than alternative solutions like synchronization. My dream answer would be a yes or no, with a reference to the relevant text.

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  • Looking for a lock-free RT-safe single-reader single-writer structure

    - by moala
    Hi, I'm looking for a lock-free design conforming to these requisites: a single writer writes into a structure and a single reader reads from this structure (this structure exists already and is safe for simultaneous read/write) but at some time, the structure needs to be changed by the writer, which then initialises, switches and writes into a new structure (of the same type but with new content) and at the next time the reader reads, it switches to this new structure (if the writer multiply switches to a new lock-free structure, the reader discards these structures, ignoring their data). The structures must be reused, i.e. no heap memory allocation/free is allowed during write/read/switch operation, for RT purposes. I have currently implemented a ringbuffer containing multiple instances of these structures; but this implementation suffers from the fact that when the writer has used all the structures present in the ringbuffer, there is no more place to change from structure... But the rest of the ringbuffer contains some data which don't have to be read by the reader but can't be re-used by the writer. As a consequence, the ringbuffer does not fit this purpose. Any idea (name or pseudo-implementation) of a lock-free design? Thanks for having considered this problem.

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  • problem with revalidating a jframe.

    - by John Quesie
    I have this code which should take the radio button input do a little math and display a popup. which it does fine. but then it is supposed to re validate and ask the next question. when i get to the second question, the answer always comes out as the isSelected(true) value no matter which radio button you click on. SO to be clear the first time through it works fin but when the second question comes up, it just takes the default radio button every time. public class EventHandler implements ActionListener { private Main gui; public EventHandler(Main gui){ this.gui = gui; } public void actionPerformed(ActionEvent e){ String answer = ""; double val = 1; //get current answer set String [] anArr = gui.getAnswers(gui.currentStage, gui.currentQuestion); if(e.getSource() == gui.exit){ System.exit(0); } if(e.getSource() == gui.submit){ if(gui.a1.isSelected()){ answer = anArr[0]; val = gui.getScore(1); } if(gui.a2.isSelected()){ answer = anArr[1]; val = gui.getScore(2); } if(gui.a3.isSelected()){ answer = anArr[2]; val = gui.getScore(3); } if(gui.a4.isSelected()){ answer = anArr[3];; val = gui.getScore(4); } JOptionPane.showMessageDialog(null, popupMessage(answer, val), "Your Answer", 1); //compute answer here //figure out what next question is to send gui.moveOn(); gui.setQA(gui.currentStage, gui.currentQuestion); //resets gui gui.goWest(); gui.q.revalidate(); } } public String popupMessage(String ans, double val){ //displays popup after an answer has been choosen gui.computeScore(val); String text = " You Answered " + ans + " Your score is now " + gui.yourScore ; return text; } } public class Main extends JFrame { public JLabel question; public JButton exit; public JButton submit; public JRadioButton a1; public JRadioButton a2; public JRadioButton a3; public JRadioButton a4; public ButtonGroup bg; public double yourScore = 1; public int currentQuestion = 1; public String currentStage = "startup"; JPanel q; public Main(){ setTitle("Ehtics Builder"); setLocation(400,400); setLayout(new BorderLayout(5,5)); setQA("startup", 1); goNorth(); goEast(); goWest(); goSouth(); goCenter(); pack(); setVisible(true); setDefaultCloseOperation(EXIT_ON_CLOSE); } public void goNorth(){ } public void goWest(){ q = new JPanel(); q.setLayout(new GridLayout(0,1)); q.add(question); bg.add(a1); bg.add(a2); bg.add(a3); bg.add(a4); a1.setSelected(true); q.add(a1); q.add(a2); q.add(a3); q.add(a4); add(q, BorderLayout.WEST); System.out.println(); } public void goEast(){ } public void goSouth(){ JPanel p = new JPanel(); p.setLayout(new FlowLayout(FlowLayout.CENTER)); exit = new JButton("Exit"); submit = new JButton("Submit"); p.add(exit); p.add(submit); add(p, BorderLayout.SOUTH); EventHandler myEventHandler = new EventHandler(this); exit.addActionListener(myEventHandler); submit.addActionListener(myEventHandler); } public void goCenter(){ } public static void main(String[] args) { Main open = new Main(); } public String getQuestion(String type, int num){ //reads the questions from a file String question = ""; String filename = ""; String [] ques; num = num - 1; if(type.equals("startup")){ filename = "startup.txt"; }else if(type.equals("small")){ filename = "small.txt"; }else if(type.equals("mid")){ filename = "mid.txt"; }else if(type.equals("large")){ filename = "large.txt"; }else{ question = "error"; return question; } ques = readFile(filename); for(int i = 0;i < ques.length;i++){ if(i == num){ question = ques[i]; } } return question; } public String [] getAnswers(String type, int num){ //reads the answers from a file String filename = ""; String temp = ""; String [] group; String [] ans; num = num - 1; if(type.equals("startup")){ filename = "startupA.txt"; }else if(type.equals("small")){ filename = "smallA.txt"; }else if(type.equals("mid")){ filename = "midA.txt"; }else if(type.equals("large")){ filename = "largeA.txt"; }else{ System.out.println("Error"); } group = readFile(filename); for(int i = 0;i < group.length;i++){ if(i == num){ temp = group[i]; } } ans = temp.split("-"); return ans; } public String [] getValues(String type, int num){ //reads the answers from a file String filename = ""; String temp = ""; String [] group; String [] vals; num = num - 1; if(type.equals("startup")){ filename = "startupV.txt"; }else if(type.equals("small")){ filename = "smallV.txt"; }else if(type.equals("mid")){ filename = "midV.txt"; }else if(type.equals("large")){ filename = "largeV.txt"; }else{ System.out.println("Error"); } group = readFile(filename); for(int i = 0;i < group.length;i++){ if(i == num){ temp = group[i]; } } vals = temp.split("-"); return vals; } public String [] readFile(String filename){ //reads the contentes of a file, for getQuestions and getAnswers String text = ""; int i = -1; FileReader in = null; File f = new File(filename); try{ in = new FileReader(f); }catch(FileNotFoundException e){ System.out.println("file does not exist"); } try{ while((i = in.read()) != -1) text += ((char)i); }catch(IOException e){ System.out.println("Error reading file"); } try{ in.close(); }catch(IOException e){ System.out.println("Error reading file"); } String [] questions = text.split(":"); return questions; } public void computeScore(double val){ //calculates you score times the value of your answer yourScore = val * yourScore; } public double getScore(int aNum){ //gets the score of an answer, stage and q number is already set in the class aNum = aNum - 1; double val = 0; double [] valArr = new double[4]; for(int i = 0;i < getValues(currentStage, currentQuestion).length;i++){ val = Double.parseDouble(getValues(currentStage, currentQuestion)[i]); valArr[i] = val; } if(aNum == 0){ val = valArr[0]; } if(aNum == 1){ val = valArr[1]; } if(aNum == 2){ val = valArr[2]; } if(aNum == 3){ val = valArr[3]; } // use current stage and questiion and trhe aNum to get the value for that answer return val; } public void nextQuestion(int num){ //sets next question to use currentQuestion = num; } public void nextStage(String sta){ // sets next stage to use currentStage = sta; } public void moveOn(){ // uses the score and current question and stage to determine wher to go next and what stage to use next nextQuestion(2); nextStage("startup"); } public void setQA(String level, int num){ String [] arr = getAnswers(level, num); question = new JLabel(getQuestion(level, num)); bg = new ButtonGroup(); a1 = new JRadioButton(arr[0]); a2 = new JRadioButton(arr[1]); a3 = new JRadioButton(arr[2]); a4 = new JRadioButton(arr[3]); } }

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  • C# PInvoke VerQueryValue returns back OutOfMemoryException?

    - by Bopha
    Hi, Below is the code sample which I got from online resource but it's suppose to work with fullframework, but when I try to build it using C# smart device, it throws exception saying it's out of memory. Does anybody know how can I fix it to use on compact? the out of memory exception when I make the second call to VerQueryValue which is the last one. thanks, [DllImport("coredll.dll")] public static extern bool VerQueryValue(byte[] buffer, string subblock, out IntPtr blockbuffer, out uint len); [DllImport("coredll.dll")] public static extern bool VerQueryValue(byte[] pBlock, string pSubBlock, out string pValue, out uint len); // private static void GetAssemblyVersion() { string filename = @"\Windows\MyLibrary.dll"; if (File.Exists(filename)) { try { int handle = 0; Int32 size = 0; size = GetFileVersionInfoSize(filename, out handle); if (size > 0) { bool retValue; byte[] buffer = new byte[size]; retValue = GetFileVersionInfo(filename, handle, size, buffer); if (retValue == true) { bool success = false; IntPtr blockbuffer = IntPtr.Zero; uint len = 0; //success = VerQueryValue(buffer, "\\", out blockbuffer, out len); success = VerQueryValue(buffer, @"\VarFileInfo\Translation", out blockbuffer, out len); if(success) { int p = (int)blockbuffer; //Reads a 16-bit signed integer from unmanaged memory int j = Marshal.ReadInt16((IntPtr)p); p += 2; //Reads a 16-bit signed integer from unmanaged memory int k = Marshal.ReadInt16((IntPtr)p); string sb = string.Format("{0:X4}{1:X4}", j, k); string spv = @"\StringFileInfo\" + sb + @"\ProductVersion"; string versionInfo; VerQueryValue(buffer, spv, out versionInfo, out len); } } } } catch (Exception err) { string error = err.Message; } } }

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  • fatal error C1075: end of file found before the left brace and read and write files not working

    - by user320950
    could someone also tell me if the actions i am attempting to do which are stated in the comments are correct or not. i am new at c++ and i think its correct but i have doubts #include<iostream> #include<fstream> #include<cstdlib> #include<iomanip> using namespace std; int main() { ifstream in_stream; // reads itemlist.txt ofstream out_stream1; // writes in items.txt ifstream in_stream2; // reads pricelist.txt ofstream out_stream3;// writes in plist.txt ifstream in_stream4;// read recipt.txt ofstream out_stream5;// write display.txt float price=' ',curr_total=0.0; int wrong=0; int itemnum=' '; char next; in_stream.open("ITEMLIST.txt", ios::in); // list of avaliable items if( in_stream.fail() )// check to see if itemlist.txt is open { wrong++; cout << " the error occured here0, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n" << endl; exit(1); } else{ cout << " System ran correctly " << endl; out_stream1.open("listWititems.txt", ios::out); // list of avaliable items if(out_stream1.fail() )// check to see if itemlist.txt is open { wrong++; cout << " the error occured here1, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n"; exit(1); } else{ cout << " System ran correctly " << endl; } in_stream2.open("PRICELIST.txt", ios::in); if( in_stream2.fail() ) { wrong++; cout << " the error occured here2, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n"; exit (1); } else{ cout << " System ran correctly " << endl; } out_stream3.open("listWitdollars.txt", ios::out); if(out_stream3.fail() ) { wrong++; cout << " the error occured here3, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n"; exit (1); } else{ cout << " System ran correctly " << endl; } in_stream4.open("display.txt", ios::in); if( in_stream4.fail() ) { wrong++; cout << " the error occured here4, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n"; exit (1); } else{ cout << " System ran correctly " << endl; } out_stream5.open("showitems.txt", ios::out); if( out_stream5.fail() ) { wrong++; cout << " the error occured here5, you have " << wrong++ << " errors" << endl; cout << "Error opening the file\n"; exit (1); } else{ cout << " System ran correctly " << endl; } in_stream.close(); // closing files. out_stream1.close(); in_stream2.close(); out_stream3.close(); in_stream4.close(); out_stream5.close(); system("pause"); in_stream.setf(ios::fixed); while(in_stream.eof()) { in_stream >> itemnum; cin.clear(); cin >> next; } out_stream1.setf(ios::fixed); while (out_stream1.eof()) { out_stream1 << itemnum; cin.clear(); cin >> next; } in_stream2.setf(ios::fixed); in_stream2.setf(ios::showpoint); in_stream2.precision(2); while((price== (price*1.00)) && (itemnum == (itemnum*1))) { while (in_stream2 >> itemnum >> price) // gets itemnum and price { while (in_stream2.eof()) // reads file to end of file { in_stream2 >> itemnum; in_stream2 >> price; price++; curr_total= price++; in_stream2 >> curr_total; cin.clear(); // allows more reading cin >> next; } } } out_stream3.setf(ios::fixed); out_stream3.setf(ios::showpoint); out_stream3.precision(2); while((price== (price*1.00)) && (itemnum == (itemnum*1))) { while (out_stream3 << itemnum << price) { while (out_stream3.eof()) // reads file to end of file { out_stream3 << itemnum; out_stream3 << price; price++; curr_total= price++; out_stream3 << curr_total; cin.clear(); // allows more reading cin >> next; } return itemnum, price; } } in_stream4.setf(ios::fixed); in_stream4.setf(ios::showpoint); in_stream4.precision(2); while ( in_stream4.eof()) { in_stream4 >> itemnum >> price >> curr_total; cin.clear(); cin >> next; } out_stream5.setf(ios::fixed); out_stream5.setf(ios::showpoint); out_stream5.precision(2); out_stream5 <<setw(5)<< " itemnum " <<setw(5)<<" price "<<setw(5)<<" curr_total " <<endl; // sends items and prices to receipt.txt out_stream5 << setw(5) << itemnum << setw(5) <<price << setw(5)<< curr_total; // sends items and prices to receipt.txt out_stream5 << " You have a total of " << wrong++ << " errors " << endl; }

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  • What file format can represent an uncompressed raster image at 48 or 64 bits per pixel?

    - by finnw
    I am creating screenshots under Windows and using the LockBits function from GDI+ to extract the pixel data, which will then be written to a file. To maximise performance I am also: Using the same PixelFormat as the source bitmap, to avoid format conversion Using the ImageLockModeUserInputBuf flag to extract the pixel data into a pre-allocated buffer This pre-allocated buffer (pointed to by BitmapData::Scan0) is part of a memory-mapped file (to avoid copying the pixel data again.) I will also be writing the code that reads the file, so I can use (or invent) any format I wish. However I would prefer to use a well-known format that existing programs (ideally web browsers) are able to read, because that means I can visually confirm that the images are correct before writing the code for the other program (that reads the image.) I have implemented this successfully for the PixelFormat32bppRGB format, which matches the format of a 32bpp BMP file, so if I extract the pixel data directly into the memory-mapped BMP file and prefix it with a BMP header I get a valid BMP image file that can be opened in Paint and most browsers. Unfortunately one of the machines I am testing on returns pixels in PixelFormat64bppPARGB format (presumably this is influenced by the video adapter driver) and there is no corresponding BMP pixel format for this. Converting to a 16, 24 or 32bpp BMP format slows the program down considerably (as well as being lossy) so I am looking for a file format that can use this pixel format without conversion, so I can extract directly into the memory-mapped file as I have done with the 32bpp format. What raster image file formats support 48bpp and/or 64bpp?

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  • How to Verify Signature, Loading PUBLIC KEY From PEM file?

    - by bbirtle
    I'm posting this in the hope it saves somebody else the hours I lost on this really stupid problem involving converting formats of public keys. If anybody sees a simpler solution or a problem, please let me know! The eCommerce system I'm using sends me some data along with a signature. They also give me their public key in .pem format. The .pem file looks like this: -----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDe+hkicNP7ROHUssGNtHwiT2Ew HFrSk/qwrcq8v5metRtTTFPE/nmzSkRnTs3GMpi57rBdxBBJW5W9cpNyGUh0jNXc VrOSClpD5Ri2hER/GcNrxVRP7RlWOqB1C03q4QYmwjHZ+zlM4OUhCCAtSWflB4wC Ka1g88CjFwRw/PB9kwIDAQAB -----END PUBLIC KEY----- Here's the magic code to turn the above into an "RSACryptoServiceProvider" which is capable of verifying the signature. Uses the BouncyCastle library, since .NET apparently (and appallingly cannot do it without some major headaches involving certificate files): RSACryptoServiceProvider thingee; using (var reader = File.OpenText(@"c:\pemfile.pem")) { var x = new PemReader(reader); var y = (RsaKeyParameters)x.ReadObject(); thingee = (RSACryptoServiceProvider)RSACryptoServiceProvider.Create(); var pa = new RSAParameters(); pa.Modulus = y.Modulus.ToByteArray(); pa.Exponent = y.Exponent.ToByteArray(); thingee.ImportParameters(pa); } And then the code to actually verify the signature: var signature = ... //reads from the packet sent by the eCommerce system var data = ... //reads from the packet sent by the eCommerce system var sha = new SHA1CryptoServiceProvider(); byte[] hash = sha.ComputeHash(Encoding.ASCII.GetBytes(data)); byte[] bSignature = Convert.FromBase64String(signature); ///Verify signature, FINALLY: var hasValidSig = thingee.VerifyHash(hash, CryptoConfig.MapNameToOID("SHA1"), bSignature);

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  • Determining failing sectors on portable flash memory

    - by Faxwell Mingleton
    I'm trying to write a program that will detect signs of failure for portable flash memory devices (thumb drives, etc). I have seen tools in the past that are able to detect failing sectors and other kinds of trouble on conventional mechanical hard drives, but I fear that flash memory does not have the same kind of predictable low-level access to the hardware due to the internal workings of the storage. Things like wear-leveling and other block-remapping techniques (to skip over 'dead' sectors?) lead me to believe that determining if a flash drive is failing will be difficult at best, if not impossible (short of having constant read failures and device unmounts). Flash drives at their end-of-life should be easy to detect (constant CRC discrepancies during reads and all-out failure). But what about drives that might be failing early? Are there any tell-tale signs like slower throughput speeds that might indicate a flash drive is going to fail much sooner than normal? Along the lines of detecting potentially bad blocks, I had considered attempting random reads/writes to a file close to or exactly the size of the entire volume, but even then is it possible that the drive might report sizes under its maximum capacity to account for 'dead' blocks? In short, is there any way to circumvent or at least detect (algorithmically or otherwise) the use of block-remapping or other life extension techniques for flash memory? Let me end this question by expressing my uncertainty as to whether or not this belongs on serverfault.com . This is definitely a hardware-related question, but I also desire a software solution - preferably one that I can program myself. If this question is misplaced, I will be happy to migrate it to serverfault - but I do need a programming solution. Please let me know if you need clarification :) Thanks!

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  • Sql serve Full Text Search with Containstable is very slow when Used in JOIN!

    - by Bob
    Hello, I am using sql 2008 full text search and I am having serious issues with performance depending on how I use Contains or ContainsTable. Here are sample: (table one has about 5000 records and there is a covered index on table1 which has all the fields in the where clause. I tried to simplify the statements so forgive me if there is syntax issues.) Scenario 1: select * from table1 as t1 where t1.field1=90 and t1.field2='something' and Exists(select top 1 * from containstable(table1,*, 'something') as t2 where t2.[key]=t1.id) results: 10 second (very slow) Scenario 2: select * from table1 as t1 join containstable(table1,*, 'something') as t2 on t2.[key] = t1.id where t1.field1=90 and t1.field2='something' results: 10 second (very slow) Scenario 3: Declare @tbl Table(id uniqueidentifier primary key) insert into @tbl select {key] from containstable(table1,*, 'something') select * from table1 as t1 where t1.field1=90 and t1.field2='something' and Exists(select id from @tbl as tbl where id=req1.id) results: fraction of a second (super fast) Bottom line, it seems if I use Containstable in any kind of join or where clause condition of a select statement that also has other conditions, the performance is really bad. In addition if you look at profiler, the number of reads from the database goes to the roof. But if I first do the full text search and put results in a table variable and use that variable everything goes super fast. The number of reads are also much lower. It seems in "bad" scenarios, somehow it gets stuck in a loop which causes it to read many times from teh database but of course I don't understant why. Now the question is first of all whyis that happening? and question two is that how scalable table variables are? what if it results to 10s of thousands of records? is it still going to be fast. Any ideas? Thanks

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  • Java split xml file

    - by CC
    Hi all, I'm working on a piece of code to split files. I want to split flat file (that's ok, it is working fine) and xml file. The idea is to split based of a number of files to split: I have a file, and I want to split it in x files (x is a parameters). I'm doing the split by taking the size of the file and spliting the size by the number of files to split. Then, mysolution was to use a BufferedReader and to use it like while ((n = reader.read(buffer, 0, buffer.length)) != -1) { { The main problem is that for the xml file I cannot just split it, but I have to split it based on a block delimited by a start xml tag and end xml tag: <start tag> bla bla xml stuff </end tag> So I cannot cut a block at the middle. So if when I'm at the half of a block, is the size of my new file is greater than my max, I will have to read until the end of the tag, and then, to start a next file. The problem is that I have all sort of cases, and is a bit difficult to search the end tag. - the block reads a text until the middle of the end tag - the block reads a text until the end of the end tag, and no more other caracter after - etc and in the same time to have a loop and read the next block. Some times the end of a block concatenated with the start of the next one, I have the end xml tag. I hope you get the idea. My question is, does anyone have some algorithm that does that more accurate and who i treating all special cases ? The idea is to split the file as quickly as possible. Thanks alot.

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  • Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

    - by James D
    Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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  • Read alphanumeric characters from csv file in C#

    - by Prasad
    I am using the following code to read my csv file: public DataTable ParseCSV(string path) { if (!File.Exists(path)) return null; string full = Path.GetFullPath(path); string file = Path.GetFileName(full); string dir = Path.GetDirectoryName(full); //create the "database" connection string string connString = "Provider=Microsoft.ACE.OLEDB.12.0;" + "Data Source=\"" + dir + "\\\";" + "Extended Properties=\"text;HDR=Yes;FMT=Delimited;IMEX=1\""; //create the database query string query = "SELECT * FROM " + file; //create a DataTable to hold the query results DataTable dTable = new DataTable(); //create an OleDbDataAdapter to execute the query OleDbDataAdapter dAdapter = new OleDbDataAdapter(query, connString); //fill the DataTable dAdapter.Fill(dTable); dAdapter.Dispose(); return dTable; } But the above doesn't reads the alphanumeric value from the csv file. it reads only i either numeric or alpha. Whats the fix i need to make to read the alphanumeric values? Please suggest.

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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • changing default my.cnf path in mysql

    - by user377941
    I am having two mysql instances on same machine. The installations are on /usr/loca/mysql1 and /usr/local/mysql2. I m having separate my.cnf files located in /etc/mysql1 and /etc/mysql2. I installed the first instance of my sql using source distribution and with the --prefix=/usr/local/mysql1 option. The second one i got from copying and pastinf the same directory to /usr/local/mysql2. When i start the mysql daemon on /usr.local/mysql/libexec it reads the my.cnf file in /etc/mysql1. And if i start the mysql daemon in /usr/local/mysql2 it reads the same my.cnf file. I have separate port numbers and .sock files defined in the .cnf file in those 2 locations. I can read the my.cnf file in the second location by using --defaults-file=/etc/mysql2/my.cnf option on mysqld startup. I dnt need to enter this each and every time i start the daemon. If i am going to have more instances how can i point the correct my.cnf file to read to each and every mysql daemon. What is the retionale behind mysqld links with the my.cnf file. how can i predefine the location of my.cnf file for each instance.

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  • Java OutOfMemoryError message changes when trying to create Arrays of different sizes

    - by Gordon
    In the question by DKSRathore How to simulate the Out Of memory : Requested array size exceeds VM limit some odd behavior was noted when creating an arrays. When creating an array of size Integer.MAX_VALUE an exception with the error java.lang.OutOfMemoryError Requested array size exceeds VM limit was thrown. However when an array was created with a size less than the max but still above the virtual machine memory limit the error message read java.lang.OutOfMemoryError: Java heap space. Testing further I managed to narrow down where the error messages changes. long[] l = new long[2147483645]; exceptions message reads - Requested array size exceeds VM limit long[] l = new long[2147483644]; exceptions message reads - Java heap space errors I increased my virtual machine memory and still produced the same result. Has anyone any idea why this happens? Some extra info: Integer.MAX_VALUE = 2147483647. Edit: Here's the code I used to find the value, might be helpful. int max = Integer.MAX_VALUE; boolean done = false; while (!done) { try { max--; // Throws an error long[] l = new long[max]; // Exit if an error is no longer thrown done = true; } catch (OutOfMemoryError e) { if (!e.getMessage().contains("Requested array size exceeds VM limit")) { System.out.println("Message changes at " + max); done = true; } } }

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  • Bioperl, equivalent of IO::ScalarArray for array of Seq objects?

    - by Ryan Thompson
    In perl, we have IO::ScalarArray for treating the elements of an array like the lines of a file. In BioPerl, we have Bio::SeqIO, which can produce a filehandle that reads and writes Bio::Seq objects instead of strings representing lines of text. I would like to do a combination of the two: I would like to obtain a handle that reads successive Bio::Seq objects from an array of such objects. Is there any way to do this? Would it be trivial for me to implement a module that does this? My reason for wanting this is that I would like to be able to write a subroutine that accepts either a Bio::SeqIO handle or an array of Bio::Seq objects, and I'd like to avoid writing separate loops based on what kind of input I get. Perhaps the following would be better than writing my own IO module? sub process_sequences { my $input = $_[0]; # read either from array of Bio::Seq or from Bio::SeqIO my $nextseq; if (ref $input eq 'ARRAY') { my $pos = 0 $nextseq = sub { return $input->[$pos++] if $pos < @$input}; } } else { $nextseq = sub { $input->getline(); } } while (my $seq = $nextseq->()) { do_cool_stuff_with($seq) } }

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  • How to automatically read in calculated values with PHPExcel?

    - by Edward Tanguay
    I have the following Excel file: I read it in by looping over every cell and getting the value with getCell(...)->getValue(): $highestColumnAsLetters = $this->objPHPExcel->setActiveSheetIndex(0)->getHighestColumn(); //e.g. 'AK' $highestRowNumber = $this->objPHPExcel->setActiveSheetIndex(0)->getHighestRow(); $highestColumnAsLetters++; for ($row = 1; $row < $highestRowNumber + 1; $row++) { $dataset = array(); for ($columnAsLetters = 'A'; $columnAsLetters != $highestColumnAsLetters; $columnAsLetters++) { $dataset[] = $this->objPHPExcel->setActiveSheetIndex(0)->getCell($columnAsLetters.$row)->getValue(); if ($row == 1) { $this->column_names[] = $columnAsLetters; } } $this->datasets[] = $dataset; } However, although it reads in the data fine, it reads in the calculations literally: I understand from discussions like this one that I can use getCalculatedValue() for calculated cells. The problem is that in the Excel sheets I am importing, I do not know beforehand which cells are calculated and which are not. Is there a way for me to read in the value of a cell in a way that automatically gets the value if it has a simple value and gets the result of the calculation if it is a calculation? Answer: It turns out that getCalculatedValue() works for all cells, makes me wonder why this isn't the default for getValue() since I would think one would usually want the value of the calculations instead of the equations themselves, in any case this works: ...->getCell($columnAsLetters.$row)->getCalculatedValue();

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  • Python: slow read & write for millions of small files

    - by Jami
    I am building directory tree which has tons of subdirectories and files. The total directory count is somewhere along 256^32 subdirectories with 256 files in each end which are only a few bytes long. I did this so I would have fast access to these files (since i'm not searching and i'm just directly accessing then via a known file path) I have a python script that builds this filesystem and reads & writes those files. The problem is that when I reach more than 1Gb of total filesize, the read and write methods become extremely slow. Here's the function I have that reads the contents of a file (the file contains an integer string), adds a certain number to it, then writes it back to the original file. def addInFile(path, scoreToAdd): num = scoreToAdd try: shutil.copyfile(path, '/tmp/tmp.txt') fp = open('/tmp/tmp.txt', 'r') num += int(fp.readlines()[0]) fp.close() except: pass fp = open('/tmp/tmp.txt', 'w') fp.write(str(num)) fp.close() shutil.copyfile('/tmp/tmp.txt', path) I previously tried performing linux console commands but it was slower. I copy the file to a temporary file first then access/modify it then copy it back because i found this was faster than directly accessing the file. I think the cause of the slowdown is because there're tons of files. performing this function 1000 times sometimes reach 1 minute now, but before (when there were only a few files, 1000 calls was performed for only less than 1 second) How do you suggest I fix this?

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  • sorting a timer in matlab

    - by AP
    ok it seems like a simple problem, but i am having problem I have a timer for each data set which resets improperly and as a result my timing gets mixed. Any ideas to correct it? without losing any data. Example timer col ideally should be timer , mine reads 1 3 2 4 3 5 4 6 5 1 6 2 how do i change the colum 2 or make a new colum which reads like colum 1 without changing the order of ther rows which have data this is just a example as my file lengths are 86000 long , also i have missing timers which i do not want to miss , this imples no data for that period of time. thanks EDIT: I do not want to change the other columns. The coulm 1 is the gps counter and so it does not sync with the comp timer due to some other issues. I just want to change the row one such that it goes from high to low without effecting other rows. also take care of missing pts ( if i did not care for missing pts simple n=1: max would work.

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  • .net real time stream processing - needed huge and fast RAM buffer

    - by mack369
    The application I'm developing communicates with an digital audio device, which is capable of sending 24 different voice streams at the same time. The device is connected via USB, using FTDI device (serial port emulator) and D2XX Drivers (basic COM driver is to slow to handle transfer of 4.5Mbit). Basically the application consist of 3 threads: Main thread - GUI, control, ect. Bus reader - in this thread data is continuously read from the device and saved to a file buffer (there is no logic in this thread) Data interpreter - this thread reads the data from file buffer, converts to samples, does simple sample processing and saves the samples to separate wav files. The reason why I used file buffer is that I wanted to be sure that I won't loose any samples. The application doesn't use recording all the time, so I've chosen this solution because it was safe. The application works fine, except that buffered wave file generator is pretty slow. For 24 parallel records of 1 minute, it takes about 4 minutes to complete the recording. I'm pretty sure that eliminating the use of hard drive in this process will increase the speed much. The second problem is that the file buffer is really heavy for long records and I can't clean this up until the end of data processing (it would slow down the process even more). For RAM buffer I need at lest 1GB to make it work properly. What is the best way to allocate such a big amount of memory in .NET? I'm going to use this memory in 2 threads so a fast synchronization mechanism needed. I'm thinking about a cycle buffer: one big array, the Bus Reader saves the data, the Data Interpreter reads it. What do you think about it? [edit] Now for buffering I'm using classes BinaryReader and BinaryWriter based on a file.

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  • Is XMLReader a SAX parser, a DOM parser, or neither?

    - by Renesis
    I am testing various methods to read (possibly large, and very often) XML configuration files in PHP. No writing is ever needed. I have two successful implementations, one using SimpleXML (which I know is a DOM parser) and one using XMLReader. I know that a DOM reader must read the whole tree and therefore uses more memory. My tests reflect that. I also know that A SAX parser is an "event-based" parser that uses less memory because it reads each node from the stream without checking what is next. XMLReader also reads from a stream with the cursor providing data about the node it is currently at. So, it definitely sounds like XMLReader (http://us2.php.net/xmlreader) is not a DOM parser, but my question is, is it a SAX parser, or something else? It seems like XMLReader behaves the way a SAX parser does but does not throw the events themselves (in other words, can you construct a SAX parser with XMLReader?) If it is something else, does the classification it's in have a name?

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  • How to automatically read in calculated values with PHPExcel?

    - by Edward Tanguay
    I have the following Excel file: I read it in by looping over every cell and getting the value with getCell(...)->getValue(): $highestColumnAsLetters = $this->objPHPExcel->setActiveSheetIndex(0)->getHighestColumn(); //e.g. 'AK' $highestRowNumber = $this->objPHPExcel->setActiveSheetIndex(0)->getHighestRow(); $highestColumnAsLetters++; for ($row = 1; $row < $highestRowNumber + 1; $row++) { $dataset = array(); for ($columnAsLetters = 'A'; $columnAsLetters != $highestColumnAsLetters; $columnAsLetters++) { $dataset[] = $this->objPHPExcel->setActiveSheetIndex(0)->getCell($columnAsLetters.$row)->getValue(); if ($row == 1) { $this->column_names[] = $columnAsLetters; } } $this->datasets[] = $dataset; } However, although it reads in the data fine, it reads in the calculations literally: I understand from discussions like this one that I can use getCalculatedValue() for calculated cells. The problem is that in the Excel sheets I am importing, I do not know beforehand which cells are calculated and which are not. Is there a way for me to read in the value of a cell in a way that automatically gets the value if it has a simple value and gets the result of the calculation if it is a calculation?

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  • How can I make NSUndoManager's undo/redo action names work properly?

    - by Gabe
    I'm learning Cocoa, and I've gotten undo to work without much trouble. But the setActionName: method is puzzling me. Here's a simple example: a toy app whose windows contain a single text label and two buttons. Press the On button and the label reads 'On'. Press the Off button and the label changes to read 'Off'. Here are the two relevant methods (the only code I wrote for the app): -(IBAction) turnOnLabel:(id)sender { [[self undoManager] registerUndoWithTarget:self selector:@selector(turnOffLabel:) object:self]; [[self undoManager] setActionName:@"Turn On Label"]; [theLabel setStringValue:@"On"]; } -(IBAction) turnOffLabel:(id)sender { [[self undoManager] registerUndoWithTarget:self selector:@selector(turnOnLabel:) object:self]; [[self undoManager] setActionName:@"Turn Off Label"]; [theLabel setStringValue:@"Off"]; } Here's what I expect: I click the On button The label changes to say 'On' In the Edit menu is the item 'Undo Turn On Label' I click that menu item The label changes to say 'Off' In the Edit menu is the item 'Redo Turn On Label' In fact, all these things work as I expect apart from the last one. The item in the Edit menu reads 'Redo Turn Off Label', not 'Redo Turn On Label'. (When I click that menu item, the label does turn to On, as I'd expect, but this makes the menu item's name even more of a mystery. What am i misunderstanding, and how can I get these menu items to display the way I want them to?

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