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• At what point asynchronous reading of disk I/O is more efficient than synchronous?

  - by blesh

  Assuming there is some bit of code that reads files for multiple consumers, and the files are of any arbitrary size: At what size does it become more efficient to read the file asynchronously? Or to put it another way, how small must a file be for it to be faster just to read it synchronously? I've noticed (and perhaps I'm incorrect) that when reading very small files, it takes longer to read them asynchronously than synchronously (in particular with .NET). I'm assuming this has to do with set up time for things like I/O Completion Ports, threads, etc. Is there any rule of thumb to help out here? Or is it dependent on the system and the environment?

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• What is wrong with this code for reading binary files? [on hold]

  - by qed

  What is wrong with this code for reading binary files? It compiles OK, but will not print out the file as planned, in fact, it prints nothing at all. #include <iostream> #include <fstream> int main(int argc, const char *argv[]) { if (argc < 2) { ::std::cerr << "usage: " << argv[0] << " <filename>\n"; return 1; } ::std::basic_ifstream<unsigned char> in(argv[1], ::std::ios::binary); unsigned char uc; while (in.get(uc)) { printf("%02X ", uc); } // TODO: error handling, in case the file could not be opened or read return 0; }

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• Java - HtmlUnit - Unable to save HTML to file (in some cases)

  - by Walter White

  Hi all, I am having intermittent issues saving the response HTML in HtmlUnit. Caused by: java.io.IOException: Unable to save file:C:\ccview\PP50773_4.0_walter\TSC_hca\Applications\HCA_J2EE\HCA\target\HtmlUnitTests\single\1\com\pnc\tsc\hca\ui\test\SiteCrawler\crawlSiteAsProvider\10.SiteCrawler.crawl.html at com.pnc.tsc.hca.ui.util.GetUtil.save(GetUtil.java:128) at com.pnc.tsc.hca.ui.util.GetUtil.add(GetUtil.java:75) at com.pnc.tsc.hca.ui.util.GetUtil.click(GetUtil.java:49) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:87) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:61) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:63) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:63) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:63) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawl(SiteCrawler.java:54) at com.pnc.tsc.hca.ui.test.SiteCrawler.crawlSiteAsProvider(SiteCrawler.java:50) ... 15 more Caused by: java.lang.RuntimeException: java.io.IOException: The system cannot find the path specified at com.gargoylesoftware.htmlunit.html.XmlSerializer.getAttributesFor(XmlSerializer.java:165) at com.gargoylesoftware.htmlunit.html.XmlSerializer.printOpeningTag(XmlSerializer.java:126) at com.gargoylesoftware.htmlunit.html.XmlSerializer.printXml(XmlSerializer.java:83) at com.gargoylesoftware.htmlunit.html.XmlSerializer.printXml(XmlSerializer.java:93) at com.gargoylesoftware.htmlunit.html.XmlSerializer.printXml(XmlSerializer.java:93) at com.gargoylesoftware.htmlunit.html.XmlSerializer.asXml(XmlSerializer.java:73) at com.gargoylesoftware.htmlunit.html.XmlSerializer.save(XmlSerializer.java:55) at com.gargoylesoftware.htmlunit.html.HtmlPage.save(HtmlPage.java:2259) at com.pnc.tsc.hca.ui.util.GetUtil.save(GetUtil.java:126) ... 24 more Caused by: java.io.IOException: The system cannot find the path specified at java.io.WinNTFileSystem.createFileExclusively(Native Method) at java.io.File.createNewFile(File.java:883) at com.gargoylesoftware.htmlunit.html.XmlSerializer.createFile(XmlSerializer.java:216) at com.gargoylesoftware.htmlunit.html.XmlSerializer.getAttributesFor(XmlSerializer.java:160) ... 32 more Now, the parent directory exists and some other files have already been written to the directory. Looking at the filename, I don't see anything that would stand out as a red flag indicating the filename is bad. What can I do to correct this error? Thanks, Walter

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• On MacOSX, in a C++ program, what guarantees can I have on file IO

  - by anon

  I am on MacOSX. I am writing a multi threaded program. One thread does logging. The non-logging threads may crash at any time. What conventions should I adopt in the logger / what guarantees can I have? I would prefer a solution where even if I crash during part of a write, previous writes still go to disk, and when reading back the log, I can figure out "ah, I wrote 100 complete enties, then I crashed on the 101th". Thanks!

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• Problems related to showing MessageBox from non-GUI threads

  - by Hans Løken

  I'm working on a heavily data-bound Win.Forms application where I've found some strange behavior. The app has separate I/O threads receiving updates through asynchronous web-requests which it then sends to the main/GUI thread for processing and updating of application-wide data-stores (which in turn may be data-bound to various GUI-elements, etc.). The server at the other end of the web-requests requires periodic requests or the session times out. I've gone through several attempted solutions of dealing with thread-issues etc. and I've observed the following behavior: If I use Control.Invoke for sending updates from I/O-thread(s) to main-thread and this update causes a MessageBox to be shown the main form's message pump stops until the user clicks the ok-button. This also blocks the I/O-thread from continuing eventually leading to timeouts on the server. If I use Control.BeginInvoke for sending updates from I/O-thread(s) to main-thread the main form's message pump does not stop, but if the processing of an update leads to a messagebox being shown, the processing of the rest of that update is halted until the user clicks ok. Since the I/O-threads keep running and the message pump keeps processing messages several BeginInvoke's for updates may be called before the one with the message box is finished. This leads to out-of-sequence updates which is unacceptable. I/O-threads add updates to a blocking queue (very similar to http://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net/530228#530228). GUI-thread uses a Forms.Timer that periodically applies all updates in the blocking queue. This solution solves both the problem of blocking I/O threads and sequentiality of updates i.e. next update will be never be started until previous is finished. However, there is a small performance cost as well as introducing a latency in showing updates that is unacceptable in the long run. I would like update-processing in the main-thread to be event-driven rather than polling. So to my question. How should I do this to: avoid blocking the I/O-threads guarantee that updates are finished in-sequence keep the main message pump running while showing a message box as a result of an update.

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• Of Datagridviews, databinding, and non validating cell values.

  - by Yanko Hernández Alvarez

  Lets simplify. Lets say I have this class: class T { public string Name { get; set; } public int Age { get; set; } public int height{ get; set; } ... } and I have a DataGridView's DataSource bound to a BindingList <T>, with N columns, each one bound to each property. I need to: Allow the user to enter non validating ages, heights, etc (for instance "aaa") Color the cells with non validating values (red background) Retain the non validating values displayed until the form is closed (I don't want to lose the values entered until the form is closed, so the user has the option to correct the bad cells anytime he wants BEFORE closing the form) Keep the last correct values entered for each cell with non validating values entered. When the form is closed, ditch the non validating values and keep the last correct values entered. Is there any easy way to do this?

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• Blocking problem, C#, .net, Deserializing XML to object problem

  - by fernando

  Hi I have a blocking problem I have XML file under some url http://myserver/mywebApp/myXML.xml In the below code which I run in Console Application, bookcollection has null Books field :( <books> <book id="5352"> <date>1986-05-05</date> <title> Alice in chains </title> </book> <book id="4334"> <date>1986-05-05</date> <title> 1000 ways to heaven </title> </book> <book id="1111"> <date>1986-05-05</date> <title> Kitchen and me </title> </book> </books> XmlDocument doc = new XmlDocument(); doc.Load("http://myserver/mywebapp/myXML.xml"); BookCollection books = new BookCollection(); XmlNodeReader reader2 = new XmlNodeReader(doc.DocumentElement); XmlSerializer ser2 = new XmlSerializer(books.GetType()); object obj = ser2.Deserialize(reader2); BookCollection books2= (BookCollection)obj; using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { [Serializable()] public class Book { [System.Xml.Serialization.XmlAttribute("id")] public string id { get; set; } [System.Xml.Serialization.XmlElement("date")] public string date { get; set; } [System.Xml.Serialization.XmlElement("title")] public string title { get; set; } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Xml.Serialization; namespace ConsoleApplication1 { [Serializable()] [System.Xml.Serialization.XmlRootAttribute("books", Namespace = "", IsNullable = false)] public class BookCollection { [XmlArray("books")] [XmlArrayItem("book", typeof(Book))] public Book[] Books { get; set; } } }

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• Blocking problem Deserializing XML to object problem

  - by fernando

  I have a blocking problem I have XML file under some url http://myserver/mywebApp/myXML.xml In the below code which I run in Console Application, bookcollection has null Books field :( <books> <book id="5352"> <date>1986-05-05</date> <title> Alice in chains </title> </book> <book id="4334"> <date>1986-05-05</date> <title> 1000 ways to heaven </title> </book> <book id="1111"> <date>1986-05-05</date> <title> Kitchen and me </title> </book> </books> XmlDocument doc = new XmlDocument(); doc.Load("http://myserver/mywebapp/myXML.xml"); BookCollection books = new BookCollection(); XmlNodeReader reader2 = new XmlNodeReader(doc.DocumentElement); XmlSerializer ser2 = new XmlSerializer(books.GetType()); object obj = ser2.Deserialize(reader2); BookCollection books2= (BookCollection)obj; using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { [Serializable()] public class Book { [System.Xml.Serialization.XmlAttribute("id")] public string id { get; set; } [System.Xml.Serialization.XmlElement("date")] public string date { get; set; } [System.Xml.Serialization.XmlElement("title")] public string title { get; set; } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Xml.Serialization; namespace ConsoleApplication1 { [Serializable()] [System.Xml.Serialization.XmlRootAttribute("books", Namespace = "", IsNullable = false)] public class BookCollection { [XmlArray("books")] [XmlArrayItem("book", typeof(Book))] public Book[] Books { get; set; } } }

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• FileInfo.MoveTo() vs File.Move()

  - by Eric

  Is there any difference between these two methods of moving a file? System.IO.FileInfo f = new System.IO.FileInfo(@"c:\foo.txt"); f.MoveTo(@"c:\bar.txt"); //vs System.IO.File.Move(@"c:\foo.txt", @"c:\bar.txt");

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• please give me a solution

  - by user327832

  here is the code i have written so far but ended up giving me error import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; public class Main { public static void main(String[] args) throws Exception { File file = new File("c:\\filea.txt"); InputStream is = new FileInputStream(file); long length = file.length(); System.out.println (length); bytes[] bytes = new bytes[(int) length]; try { int offset = 0; int numRead = 0; while (numRead >= 0) { numRead = is.read(bytes); } } catch (IOException e) { System.out.println ("Could not completely read file " + file.getName()); } is.close(); Object[] see = new Object[(int) length]; see[1] = bytes; System.out.println ((String[])see[1]); } }

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• non blocking TCP-acceptor not reading from socket

  - by Abruzzo Forte e Gentile

  I have the code below implementing a NON-Blocking TCP acceptor. Clients are able to connect without any problem and the writing seems occurring as well, but the acceptor doesn't read anything from the socket and the call to read() blocks indefinitely. Am I using some wrong setting for the acceptor? Kind Regards AFG int main(){ create_programming_socket(); poll_programming_connect(); while(1){ poll_programming_read(); } } int create_programming_socket(){ int cnt = 0; p_listen_socket = socket( AF_INET, SOCK_STREAM, 0 ); if( p_listen_socket < 0 ){ return 1; } int flags = fcntl( p_listen_socket, F_GETFL, 0 ); if( fcntl( p_listen_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ return 1; } bzero( (char*)&p_serv_addr, sizeof(p_serv_addr) ); p_serv_addr.sin_family = AF_INET; p_serv_addr.sin_addr.s_addr = INADDR_ANY; p_serv_addr.sin_port = htons( p_port ); if( bind( p_listen_socket, (struct sockaddr*)&p_serv_addr , sizeof(p_serv_addr) ) < 0 ) { return 1; } listen( p_listen_socket, 5 ); return 0; } int poll_programming_connect(){ int retval = 0; static socklen_t p_clilen = sizeof(p_cli_addr); int res = accept( p_listen_socket, (struct sockaddr*)&p_cli_addr, &p_clilen ); if( res > 0 ){ p_conn_socket = res; int flags = fcntl( p_conn_socket, F_GETFL, 0 ); if( fcntl( p_conn_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ retval = 1; }else{ p_connected = true; } }else if( res == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): accept(c_listen_socket) would block\n"); }else{ retval = 1; } return retval; } int poll_programming_read(){ int retval = 0; bzero( p_buffer, 256 ); int numbytes = read( p_conn_socket, p_buffer, 255 ); if( numbytes > 0 ) { fprintf( stderr, "poll_sock(): read() read %d bytes\n", numbytes ); pkt_struct2_t tx_buf; int fred; int i; } else if( numbytes == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): read() would block\n"); } else { close( p_conn_socket ); p_connected = false; retval = 1; } return retval; }

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• dealing with IO vs pure code in haskell

  - by Drakosha

  I'm writing a shell script (my 1st non-example in haskell) which is supposed to list a directory, get every file size, do some string manipulation (pure code) and then rename some files. I'm not sure what i'm doing wrong, so 2 questions: How should i arrange the code in such program? I have a specific issue, i get the following error, what am i doing wrong? error: Couldn't match expected type [FilePath]' against inferred typeIO [FilePath]' In the second argument of mapM', namelyfileNames' In a stmt of a 'do' expression: files <- (mapM getFileNameAndSize fileNames) In the expression: do { fileNames <- getDirectoryContents; files <- (mapM getFileNameAndSize fileNames); sortBy cmpFilesBySize files } code: getFileNameAndSize fname = do (fname, (withFile fname ReadMode hFileSize)) getFilesWithSizes = do fileNames <- getDirectoryContents files <- (mapM getFileNameAndSize fileNames) sortBy cmpFilesBySize files

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• Web-based (intranet / non-hosted) timesheet / project tracking tools

  - by warren

  I realize some similar questions have been asked along these lines before, but from reading-through them today, it appears they don't match my use case. I am looking for a web-based, non-hosted time and project tracking tool. I've downloaded Collabtive so far, but am looking for other suggestions, too. My list of requirements: runs on standard LAMP stack non-hosted (ie, there is an option to download and run it on a local server) not a desktop/single-user application easy-to-use - my audience is a mix of technical and non-technical folks easy to maintain - when time for upgrading comes, I'd really like to not have to rebuild the app (a la ./configure ; make ; make install) needs to support multiple users free-form project additions: we don't have a central project management authority (users should be able to add whatever they're working on, not merely from a drop-down) Does anyone here have experience with such tools? It doesn't have to be free.. but free is always nice :)

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• Web-based (intranet / non-hosted) timesheet / project tracking tools

  - by warren

  I realize some similar questions have been asked along these lines before, but from reading-through them today, it appears they don't match my use case. I am looking for a web-based, non-hosted time and project tracking tool. I've downloaded Collabtive and Achievo so far, but am looking for other suggestions, too. My list of requirements: runs on standard LAMP stack non-hosted (ie, there is an option to download and run it on a local server) not a desktop/single-user application easy-to-use - my audience is a mix of technical and non-technical folks easy to maintain - when time for upgrading comes, I'd really like to not have to rebuild the app (a la ./configure ; make ; make install) needs to support multiple users free-form project additions: we don't have a central project management authority (users should be able to add whatever they're working on, not merely from a drop-down) Does anyone here have experience with such tools? It doesn't have to be free.. but free is always nice :)

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• ESXi with non-headless VM

  - by Mike

  I'm going to receive a Xeon Server/Workstation soon and I was thinking about installing ESXi to host some server applications that I want (ex: SVN server, Web server, media server, etc). Most of these will be headless VM's. My question is: on top of all these headless VM's, is it possible for ESXi to have another VM that would be non-headless (so that it will output video through the VGA/DVI port)? Or are all VM's within ESXi only accessible through remote connections? I'll be using this non-headless VM like a regular workstation: browsing, development, media, gaming maybe. The other alternative I was thinking about is to install a very lightweight operating system and have the headless VM's running in Virtualbox. If it is possible to have have a non-headless VM, what would be the performance compared to a regular workstation? Noticeable or not when gaming?

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• non-mapped virtual memory & total number of connections

  - by tszming

  We have two MongoDB data nodes (replica set) - Primary & Secondary. I noticed that the non-mapped virtual memory is relatively high and wondering if they are hurting our MongoDB performance (The server usually peaked at around 6-7K queries per sec). In MMS, it was stated: "The most common case of usage of a high amount of memory for non-mapped is that there are very many connections to the database." So we checked the memory usage with db.serverStatus().mem in our Secondary: { "bits" : 64, "resident" : 6846, "virtual" : 416797, "supported" : true, "mapped" : 205549, "mappedWithJournal" : 411098, "note" : "virtual minus mapped is large. could indicate a memory leak" } Note: We are using 2.0.4 and now the default stack size should be 1MB per connection. The current number of connections is around 1.1K, but the non-mapped virtual memory (virtual-mappedWithJournal) is around 5699 MB. The trend is quite stable so I can't say there is a leak here, but where is the memory gone? Any idea?

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

  - by AJ

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

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• java.io.IOException: Premature EOF

  - by jouzef19

  Hi: I am trying to download an xml file using Stream and things was fine , until the xml size became bigger than 9 MB , so i've got this error java.io.IOException: Premature EOF this is the code BufferedInputStream bfi = null; try { bfi = new BufferedInputStream(new URL("The URL").openStream()); String name = "name.xml"; FileOutputStream fb = new FileOutputStream(name); BufferedOutputStream bout = new BufferedOutputStream(fb, 1024); byte[] data = new byte[1024]; int x = 0; while ((x = bfi.read(data, 0, 1024)) >= 0) { bout.write(data, 0, x); } this.deletePhishTankDatabase(this.recreateFileName()); ptda.insertDownloadTime(hour, day, month, year); bout.close(); bfi.close(); } catch (IOException ex) { Logger.getLogger(PhishTankDataBase.class.getName()).log(Level.SEVERE, null, ex); } finally { try { bfi.close(); } catch (IOException ex) { Logger.getLogger(PhishTankDataBase.class.getName()).log(Level.SEVERE, null, ex); } } } else { System.out.println("You can't do anything"); return; } thanks in advanced

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• Hibernate JDBCConnectionException: Communications link failure and java.io.EOFException: Can not read response from server

  - by Marc

  I get a quite well-known using MySql jdbc driver : JDBCConnectionException: Communications link failure, java.io.EOFException: Can not read response from server. This is caused by the wait_timeout parameter in my.cnf. So I decided to use c3p0 pool connection along with Hibernate. Here is what I added to hibernate.cfg.xml : <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="c3p0.min_size">10</property> <property name="c3p0.max_size">100</property> <property name="c3p0.timeout">1000</property> <property name="c3p0.preferredTestQuery">SELECT 1</property> <property name="c3p0.acquire_increment">1</property> <property name="c3p0.idle_test_period">2</property> <property name="c3p0.max_statements">50</property> idle_test_period is volontarily low for test purposes. Looking at the mysql logs I can see the "SELECT 1" request which is regularly sent to the mysql server so it works. Unfortunately I still get this EOF exception within my app if I wait longer than 'wait_timout' seconds (set to 10 for test purposes). I'm using Hibernate 4.1.1 and mysql-jdbc-connector 5.1.18. So what am I doing wrong? Thanks, Marc.

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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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• Rapid Opening and Closing System.IO.StreamWriter in C#

  - by ccomet

  Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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• Problem with a blocking network task

  - by user326967

  Hello everyone. I'm new in Java so please forgive any obscene errors that I may make :) I'm developing a program in Java that among other things it should also handle clients that will connect to a server. The server has 3 threads running, and I have created them in the following way : DaemonForUI du; DaemonForPort da; DaemonForCheck dc; da = new DaemonForPort(3); dc = new DaemonForCheck(5); du = new DaemonForUI(7); Thread t_port = new Thread(da); Thread t_check = new Thread(dc); Thread t_ui = new Thread(du); t_port.setName("v1.9--PORTd"); t_check.setName("v1.9-CHECKd"); t_ui.setName("v1.9----UId"); t_port.start(); t_check.start(); t_ui.start(); Each thread handles a different aspect of the complete program. The thread t_ui is responsible to accept asynchronous incoming connections from clients, process the sent data and send other data back to the client. When I remove all the commands from the previous piece of code that has to with the t_ui thread, everything runs ok which in my case means that the other threads are printing their debug messages. If I set the t_ui thread to run too, then the whole program blocks at the "accept" of the t_ui thread. After reading at online manuals I saw that the accepted connections should be non-blocking, therefore use something like that : public ServerSocketChannel ssc = null; ssc = ServerSocketChannel.open(); ssc.socket().bind(new InetSocketAddress(port)); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); if (sc == null) { ; } else { System.out.println("The server and client are connected!"); System.out.println("Incoming connection from: " + sc.socket().getRemoteSocketAddress()); in = new DataInputStream(new BufferedInputStream(sc.socket().getInputStream())); out = new DataOutputStream(new BufferedOutputStream(sc.socket().getOutputStream())); //other magic things take place after that point... The thread for t_ui is created as follows : class DaemonForUI implements Runnable{ private int cnt; private int rr; public ListenerForUI serverListener; public DaemonForUI(int rr){ cnt = 0; this.rr = rr; serverListener = new ListenerForUI(); } public static String getCurrentTime() { final String DATE_FORMAT_NOW = "yyyy-MM-dd HH:mm:ss"; Calendar cal = Calendar.getInstance(); SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT_NOW); return (sdf.format(cal.getTime())); } public void run() { while(true) { System.out.println(Thread.currentThread().getName() + "\t (" + cnt + ")\t (every " + rr + " sec) @ " + getCurrentTime()); try{ Thread.sleep(rr * 1000); cnt++; } catch (InterruptedException e){ e.printStackTrace(); } } } } Obviously, I'm doing something wrong at the creation of the socket or at the use of the thread. Do you know what is causing the problem? Every help would be greatly appreciated.

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• Testing a Non-blocking Queue

  - by jsw

  I've ported the non-blocking queue psuedocode here to C#. The code below is meant as a near verbatim copy of the paper. What approach would you take to test the implementation? Note: I'm running in VS2010 so I don't have CHESS support yet. using System.Threading; #pragma warning disable 0420 namespace ConcurrentCollections { class QueueNodePointer<T> { internal QueueNode<T> ptr; internal QueueNodePointer() : this(null) { } internal QueueNodePointer(QueueNode<T> ptr) { this.ptr = ptr; } } class QueueNode<T> { internal T value; internal QueueNodePointer<T> next; internal QueueNode() : this(default(T)) { } internal QueueNode(T value) { this.value = value; this.next = new QueueNodePointer<T>(); } } public class ConcurrentQueue<T> { private volatile int count = 0; private QueueNodePointer<T> qhead = new QueueNodePointer<T>(); private QueueNodePointer<T> qtail = new QueueNodePointer<T>(); public ConcurrentQueue() { var node = new QueueNode<T>(); node.next.ptr = null; this.qhead.ptr = this.qtail.ptr = node; } public int Count { get { return this.count; } } public void Enqueue(T value) { var node = new QueueNode<T>(value); node.next.ptr = null; QueueNodePointer<T> tail; QueueNodePointer<T> next; while (true) { tail = this.qtail; next = tail.ptr.next; if (tail == this.qtail) { if (next.ptr == null) { var newtail = new QueueNodePointer<T>(node); if (Interlocked.CompareExchange(ref tail.ptr.next, newtail, next) == next) { Interlocked.Increment(ref this.count); break; } else { Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } } } } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(node), tail); } public T Dequeue() { T value; while (true) { var head = this.qhead; var tail = this.qtail; var next = head.ptr.next; if (head == this.qhead) { if (head.ptr == tail.ptr) { if (next.ptr == null) { return default(T); } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } else { value = next.ptr.value; var newhead = new QueueNodePointer<T>(next.ptr); if (Interlocked.CompareExchange(ref this.qhead, newhead, head) == head) { Interlocked.Decrement(ref this.count); break; } } } } return value; } } } #pragma warning restore 0420

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• Problems with blocking reads using libudev on Linux

  - by Steve Hawkins

  We are using the following routine (on Linux, with libudev) to read data from a PIC microcontroller configured as a USB HID device. The data is sent only when a button connected to the PIC microcontroller is pressed or released. The routine is missing messages from the PIC controller, and I suspect that this is because the call to poll below is not behaving as it should. The call to poll will reliably block for 1 second util the first message is read. As soon as the first message is read, the call to poll returns immediately instead of blocking for 1 second (1000 milliseconds) like it should. I have worked around this problem by closing and re-opening the device after each read. This makes poll behave correctly, but I think that closing and re-opening the device may be the reason for the lost messages. bool PicIo::Receive (unsigned char* picData, const size_t picDataSize) { static hiddev_report_info hidReportInfo; static hiddev_usage_ref_multi hidUsageRef; if (-1 == PicDeviceDescriptor()) { return false; } // Determine whether or not there is data available to be read pollfd pollFd; pollFd.fd = PicDeviceDescriptor(); pollFd.events = POLLIN; int dataPending = poll (&pollFd, 1, 1000); if (dataPending <= 0) { return false; } // Initialize the HID Report structure for an input report hidReportInfo.report_type = HID_REPORT_TYPE_INPUT; hidReportInfo.report_id = 0; hidReportInfo.num_fields = 64; if (-1 == ioctl(PicDeviceDescriptor(), HIDIOCGREPORT, &hidReportInfo)) { return false; } // Initizlize the HID Usage Reference for an Input report hidUsageRef.uref.report_type = HID_REPORT_TYPE_INPUT; hidUsageRef.uref.report_id = 0; hidUsageRef.uref.field_index = 0; hidUsageRef.uref.usage_index = 0; hidUsageRef.num_values = 64; if (-1 == ioctl(PicDeviceDescriptor(), HIDIOCGUSAGES, &hidUsageRef)) { return false; } // Transfer bytes from the usage report into the return value. for (size_t idx=0; (idx < 64) && (idx < picDataSize); ++idx) { picData[idx] = hidUsageRef.values[idx]; } return true; } The function PicDeviceDescriptor() does checking on the device to make sure that it is present. Here are the pertinent details of the PicDeviceDescriptor function, showing how the device is begin opened. int PicIo::PicDeviceDescriptor(int command) { struct stat statInfo; static int picDeviceDescriptor = -1; string picDevicePath = "/dev/usb/hiddev0"; if ((-1 != picDeviceDescriptor) && (CLOSE == command)) { close (picDeviceDescriptor); picDeviceDescriptor = -1; } else if ((-1 != picDeviceDescriptor) && (-1 == fstat(picDeviceDescriptor, &statInfo))) { // Handle the case where the PIC device had previously been detected, and // is now disconnected. close (picDeviceDescriptor); picDeviceDescriptor = -1; } else if ((-1 == picDeviceDescriptor) && (m_picDevice.IsConnected())) { // Create the PIC device descriptor if the PIC device is present (i.e. its // device node is present) and if the descriptor does not already exist picDeviceDescriptor = open (picDevicePath.c_str(), O_RDONLY); } return picDeviceDescriptor; } I'm sure that I'm doing something wrong, but I've Googled the issue and cannot seem to find any relevant answers. Any help would be very much appreciated -- Thx.

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• IOException during blocking network NIO in JDK 1.7

  - by Bass

  I'm just learning NIO, and here's the short example I've written to test how a blocking NIO can be interrupted: class TestBlockingNio { private static final boolean INTERRUPT_VIA_THREAD_INTERRUPT = true; /** * Prevent the socket from being GC'ed */ static Socket socket; private static SocketChannel connect(final int port) { while (true) { try { final SocketChannel channel = SocketChannel.open(new InetSocketAddress(port)); channel.configureBlocking(true); return channel; } catch (final IOException ioe) { try { Thread.sleep(1000); } catch (final InterruptedException ie) { } continue; } } } private static byte[] newBuffer(final int length) { final byte buffer[] = new byte[length]; for (int i = 0; i < length; i++) { buffer[i] = (byte) 'A'; } return buffer; } public static void main(final String args[]) throws IOException, InterruptedException { final int portNumber = 10000; new Thread("Reader") { public void run() { try { final ServerSocket serverSocket = new ServerSocket(portNumber); socket = serverSocket.accept(); /* * Fully ignore any input from the socket */ } catch (final IOException ioe) { ioe.printStackTrace(); } } }.start(); final SocketChannel channel = connect(portNumber); final Thread main = Thread.currentThread(); final Thread interruptor = new Thread("Inerruptor") { public void run() { System.out.println("Press Enter to interrupt I/O "); while (true) { try { System.in.read(); } catch (final IOException ioe) { ioe.printStackTrace(); } System.out.println("Interrupting..."); if (INTERRUPT_VIA_THREAD_INTERRUPT) { main.interrupt(); } else { try { channel.close(); } catch (final IOException ioe) { System.out.println(ioe.getMessage()); } } } } }; interruptor.setDaemon(true); interruptor.start(); final ByteBuffer buffer = ByteBuffer.allocate(32768); int i = 0; try { while (true) { buffer.clear(); buffer.put(newBuffer(buffer.capacity())); buffer.flip(); channel.write(buffer); System.out.print('X'); if (++i % 80 == 0) { System.out.println(); Thread.sleep(100); } } } catch (final ClosedByInterruptException cbie) { System.out.println("Closed via Thread.interrupt()"); } catch (final AsynchronousCloseException ace) { System.out.println("Closed via Channel.close()"); } } } In the above example, I'm writing to a SocketChannel, but noone is reading from the other side, so eventually the write operation hangs. This example works great when run by JDK-1.6, with the following output: Press Enter to interrupt I/O XXXX Interrupting... Closed via Thread.interrupt() — meaning that only 128k of data was written to the TCP socket's buffer. When run by JDK-1.7 (1.7.0_25-b15 and 1.7.0-u40-b37), however, the very same code bails out with an IOException: Press Enter to interrupt I/O XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXX Exception in thread "main" java.io.IOException: Broken pipe at sun.nio.ch.FileDispatcherImpl.write0(Native Method) at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:47) at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93) at sun.nio.ch.IOUtil.write(IOUtil.java:65) at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:487) at com.example.TestBlockingNio.main(TestBlockingNio.java:109) Can anyone explain this different behaviour?

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