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• fastest (low latency) method for Inter Process Communication between Java and C/C++

  - by Bastien

  Hello, I have a Java app, connecting through TCP socket to a "server" developed in C/C++. both app & server are running on the same machine, a Solaris box (but we're considering migrating to Linux eventually). type of data exchanged is simple messages (login, login ACK, then client asks for something, server replies). each message is around 300 bytes long. Currently we're using Sockets, and all is OK, however I'm looking for a faster way to exchange data (lower latency), using IPC methods. I've been researching the net and came up with references to the following technologies: - shared memory - pipes - queues but I couldn't find proper analysis of their respective performances, neither how to implement them in both JAVA and C/C++ (so that they can talk to each other), except maybe pipes that I could imagine how to do. can anyone comment about performances & feasibility of each method in this context ? any pointer / link to useful implementation information ? thanks for your help

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• OSX: Why is GetProcessInformation() causing a segfault?

  - by anthony

  Here's my C method to get the pid of the Finder process. GetProcessInformation() is causing a segfault. Why? Here's the function: static OSStatus GetFinderPID(pid_t *pid) { ProcessSerialNumber psn = {kNoProcess, kNoProcess}; ProcessInfoRec info; OSStatus status = noErr; info.processInfoLength = sizeof(ProcessInfoRec); info.processName = nil; while (!status) { status = GetNextProcess(&psn); if (!status) { status = GetProcessInformation(&psn, &info); } if (!status && info.processType == 'FNDR' && info.processSignature == 'MACS') { return GetProcessPID(&psn, pid); } } return status; } Here's the backtrace: Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x0000000032aaaba7 0x00007fffffe00623 in __bzero () (gdb) bt #0 0x00007fffffe00623 in __bzero () #1 0x00007fff833adaed in CreateFSRef () #2 0x00007fff833ab53b in FSPathMakeRefInternal () #3 0x00007fff852fc32d in _CFGetFSRefFromURL () #4 0x00007fff852fbfe0 in CFURLGetFSRef () #5 0x00007fff85dd273f in GetProcessInformation () #6 0x0000000100000bef in GetFinderPID [inlined] () at /path/to/main.c:21

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• uzing libgz to inflate a gz input

  - by Pierre

  Hi all, I'm currently trying to use the zlib to inflate a source of gzipped data. It seems that the inflate API in zlib cannot inflate a gzipped data ( The example http://www.zlib.net/zpipe.c fails to read a gzipped file: "zpipe: invalid or incomplete deflate data" ). I noticed that there is a gzopen function in this API, but , as far as I understand, it only works with a filename or a file descriptor. Can I use this API if my source of gzipped data is stored in memory, in a sql blob, etc... ? Many Thanks Pierre

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• lowest latency, least overhead app server?

  - by Mark Harrison

  I'm designing an application which will have a network interface for feeding out large numbers of very small metadata requests. The application code itself is very fast, basically looking up data cached in memory and sending it to the client. What's the absolute lowest latency I can get for a network application server running on a linux box? This will be an internal app running on gigE with no authentication. Any language/framework considered, with a preference for C, C++, or Python. Likewise for protocol, although HTTP would be nice.

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• Using C Structs which contains ObjC Objects?

  - by GuidoMB

  I'm using C structs in objc and I've created a function that assembles the structure like the one from the Cocoa API. The things is that this structure is not like NSRect o NSPoint this structure packs objc objects soo I'm seeing a potential memory leak here. Do I need to provide a function to 'release' the structure? I'am not creating a ISKNewsCategory class because there will be no behavior but Do you think this is a good approach or I should define the class even doe there will be no behavior? typedef struct ISK_NewsCategory { NSString *name; NSString *code } ISKNewsCategory; NS_INLINE ISKNewsCategory ISKMakeNewsCategory(NSString *name, NSString *code) { ISKNewsCategory category; category.name = [name retain]; category.code = [code retain]; return category; }

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• C# - Removing items from lists and all references to them.

  - by LiamV

  Hi there, I'm facing a situation where I have dependent objects and I would like to be able to remove an object and all references to it. Say I have an object structure like the code below, with a Branch type which references two Nodes. public class Node { // Has Some Data! } public class Branch { // Contains references to Nodes public Node NodeA public Node NodeB } public class Graph { public List<Node> Nodes; public List<Branch> Branches; } If I remove a Node from the Nodes list in the Graph class, it is still possible that one or more Branch objects still contains a reference to the removed Node, thus retaining it in memory, whereas really what I would quite like would be to set any references to the removed Node to null and let the garbage collection kick in. Other than enumerating through each Branch and checking each Node reference sequentially, are there any smart ideas on how I remove references to the Node in each Branch instance AND indeed any other class which reference the removed Node? Much appreciated, Liam

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• Using transactions with ADO.NET Data Adapters.

  - by Ergwun

  Scenario: I want to let multiple (2 to 20, probably) server applications use a single database using ADO.NET. I want individual applications to be able to take ownership of sets of records in the database, hold them in memory (for speed) in DataSets, respond to client requests on the data, perform updates, and prevent other applications from updating those records until ownership has been relinquished. I'm new to ADO.NET, but it seems like this should be possible using transactions with Data Adapters (ADO.NET disconnected layer). Question part 1: Is that the right way to try and do this? Question part 2: If that is the right way, can anyone point me at any tutorials or examples of this kind of approach (in C#)? Question part 3: If I want to be able to take ownership of individual records and release them independently, am I going to need a separate transaction for each record, and by extension a separate DataAdapter and DataSet to hold each record, or is there a better way to do that? Each application will likely hold ownership of thousands of records simultaneously.

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• Boiler plate code replacement - is there anything bad about this code?

  - by Benjol

  I've recently created these two (unrelated) methods to replace lots of boiler-plate code in my winforms application. As far as I can tell, they work ok, but I need some reassurance/advice on whether there are some problems I might be missing. (from memory) static class SafeInvoker { //Utility to avoid boiler-plate InvokeRequired code //Usage: SafeInvoker.Invoke(myCtrl, () => myCtrl.Enabled = false); public static void Invoke(Control ctrl, Action cmd) { if (ctrl.InvokeRequired) ctrl.BeginInvoke(new MethodInvoker(cmd)); else cmd(); } //Replaces OnMyEventRaised boiler-plate code //Usage: SafeInvoker.RaiseEvent(this, MyEventRaised) public static void RaiseEvent(object sender, EventHandler evnt) { var handler = evnt; if (handler != null) handler(sender, EventArgs.Empty); } } EDIT: See related question here UPDATE Following on from deadlock problems (related in this question), I have switched from Invoke to BeginInvoke (see an explanation here). Another Update Regarding the second snippet, I am increasingly inclined to use the 'empty delegate' pattern, which fixes this problem 'at source' by declaring the event directly with an empty handler, like so: event EventHandler MyEventRaised = delegate {};

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• SQLiteException Unknown error

  - by -providergeoff.bruckner

  Does anyone know what this means? I'm trying to start a transaction in onActivityResult() to insert a row based on the received result. 03-05 15:39:51.937: ERROR/Database(2387): Failure 21 (out of memory) on 0x0 when preparing 'BEGIN EXCLUSIVE;'. 03-05 15:39:51.967: DEBUG/AndroidRuntime(2387): Shutting down VM 03-05 15:39:51.967: WARN/dalvikvm(2387): threadid=3: thread exiting with uncaught exception (group=0x40013140) 03-05 15:39:51.967: ERROR/AndroidRuntime(2387): Uncaught handler: thread main exiting due to uncaught exception 03-05 15:39:52.137: ERROR/AndroidRuntime(2387): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {com.ozdroid/com.ozdroid.load.LoadView}: android.database.sqlite.SQLiteException: unknown error: BEGIN EXCLUSIVE; ... 03-05 15:39:52.137: ERROR/AndroidRuntime(2387): Caused by: android.database.sqlite.SQLiteException: unknown error: BEGIN EXCLUSIVE; ... 03-05 15:39:52.137: ERROR/AndroidRuntime(2387): at android.database.sqlite.SQLiteDatabase.beginTransaction(SQLiteDatabase.java:434)

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• A JTAG emulator for use with a Hawkboard and OpenOCD?

  - by David Brown

  I'd like to try bare metal ARM programming with the Hawkboard, but the deployment process looks awful. I'm totally new to this, so I could be misunderstanding the instructions, but it appears that I have to use a program called AISgen to convert the binary file, then boot with u-Boot over UART and copy the AIS binary into memory. Not only is that a lot of stuff to do every time I make a change, it also doesn't give me the ability to debug with GDB. The best solution for this that I can find is JTAG. But the prices for these JTAG emulators look ridiculous. I'm not even sure which ones will work with the Hawkboard and which ones won't. So far, my best bet appears to be the Flyswatter, but the pin layout is different. Basically, I need something that's relatively cheap and works with the Hawkboard and OpenOCD. Any suggestions? Or is there another way I could do this, perhaps?

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• How to handle a C# console application terminating?

  - by Nick R

  If I have a console application, is there any way I can handle the following: Ctrl-C (I know the answer to this. Using Console.TreatControlCAsInput and Console.CancelKeyPress) Session termination, such as when someone logs off Process exit, such as when someone uses the task manager to close the application. I know that if I was writing a unix application, I would handle various signals to catch the request to close (SIGTERM from memory), but I also know I need to handle these messages pretty quickly and exit before the system does a kill -9 (SIGKILL). But for a C# console application, I'm not sure how to do this.

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• Optimizing a large iteration of PHP objects (EAV-based)

  - by Aron Rotteveel

  I am currently working on a project that utilizes the EAV model. This turns out to work quite well, but like many others I am now stumbling upon some performance issues. The data set in this particular case consists of aproximately 2500 entities, each with aprox. 150 attributes. Each entity and each attribute is represented by a PHP-object. Since most parts of the application only iterate through a filtered set of entities, we have not had very large issues yet. Now, however, I am working on an algorithm that requires iteration over the entire dataset, which causes a major impact on performance. This information is perhaps not very much to work with, but since this is an architectural problem, I am hoping for a architectural pattern to help me on the way as well. Each entity, including it's attributes takes up aprox. 500KB of memory.

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• Someone is using the struct name as a variable name too. What does the code really say? (c++)

  - by EvilTeach

  This morning we found an old chunk of code that was causing a library call to crash. struct fred { int a; int b; int c; }; fred fred[MAX_SIZE+1]; memset( fred, 0, sizeof(fred) * MAX_SIZE+1 ); It appears that the sizeof(fred) may have been the full array size, rather than the structure size, as it was overwriting a great deal of memory. The fact that it compiled without warning on several different systems seemed odd. Is there a correct semantic for this case where the type and variable name are colliding? or is this some sort of undefined behavior? or just a defect? I haven't been been clever enough to find anything on Google or our language help. Thanks Evil

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• Advanced Java book in the lines of CLR via c# or C# in Depth?

  - by devoured elysium

  I want to learn about how things work in depth in Java. Coming from a c# background, there were a couple of very good books that go really deep in c# (C# in depth, CLR via c#, just to name the most popular). Is there anything like that in Java? I searched it up on amazon but nothing seemed to go that deep in Java as the two above go in c#. I don't want to know more about specific classes, or how to use this library or that other library, I want to learn how the objects are created on memory, how they get created on the stack, heap, etc. A more fundamental knowledge, let's say. I've read some chapters of Effective Java and The Java Programming Language but they don't seem to go so deep as I'd want them to go. Maybe there are other people that know both c# and Java that have read any of the referred books and know any that might be useful? Thanks

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• Custom ASP.NET MVC cache controllers in a shared hosting environment?

  - by Daniel Crenna

  I'm using custom controllers that cache static resources (CSS, JS, etc.) and images. I'm currently working with a hosting provider that has set me up under a full trust profile. Despite being in full trust, my controllers fail because the caching strategy relies on the File class to directly open a resource file prior to treatment and storage in memory. Is this something that would likely occur in all full trust shared hosting environments or is this specific to my host? The static files live within my application's structure and not in an arbitrary server path. It seems to me that custom caching would require code to access the file directly, and am hoping someone else has dealt with this issue.

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• loading mp3 from file using random access to flash.media.Sound

  - by Irfan Mulic

  We are migrating application from Delphi to Flex (Air) that plays mp3 files from random access big file. it has positions and sizes to extract mp3 data to FileStream-MemoryStream and then we use bass.dll to play it from memory stream. Now I have to play those same mp3's in flex but I am not sure how... I was reading something similar for reading/writing data using ByteArray from here but how to apply it to flash.media.Sound ? http://livedocs.adobe.com/flex/3/html/help.html?content=ByteArrays_2.html Any help?

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• C++ Static array vs. Dynamic array?

  - by user69514

  What is the difference between a static array and a dynamic array in C++? I have to do an assignment for my class and it says not to use static arrays, only dynamic arrays. I've looked in the book and online, but I don't seem to understand. I thought static was created at compile time and dynamic at runtime, but I might be mistaken this with memory allocation. Can you explain to me the difference between static array and dynamic array in C++? Thnaks.

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• Java OutOfMemoryError strange behaviour

  - by Evgeniy Dorofeev

  Assuming we have a max memory of 256M, why does this code work: public static void main(String... args) { for (int i = 0; i < 2; i++) { byte[] a1 = new byte[150000000]; } byte[] a2 = new byte[150000000]; } but this one throw an OOME? public static void main(String... args) { //for (int i = 0; i < 2; i++) { byte[] a1 = new byte[150000000]; } byte[] a2 = new byte[150000000]; }

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• How can I get this code involving unique_ptr to compile?!

  - by Neil G

  #include <vector> #include <memory> using namespace std; class A { public: A(): i(new int) {} A(A const& a) = delete; A(A &&a): i(move(a.i)) {} unique_ptr<int> i; }; class AGroup { public: void AddA(A &&a) { a_.emplace_back(move(a)); } vector<A> a_; }; int main() { AGroup ag; ag.AddA(A()); return 0; } does not compile... (says that unique_ptr's copy constructor is deleted) I tried replacing move with forward. Not sure if I did it right, but it didn't work for me.

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• Application crash when using an NSTimer and pushViewController

  - by Cesar

  I'm using an NSTimer to implement a 3 seconds splash screen. If a don't use a timer the view it's correctly pushed but if I use the timer for adding a little delay the application crash with a EXC_BAD_ACCESS. I'm pretty sure the answer contains "memory management" but I can't get the point... @interface RootViewController : UIViewController { NSTimer *timer; } -(void)changeView:(NSTimer*)theTimer; @property(nonatomic,retain) NSTimer *timer; ... @implementation RootViewController @synthesize timer; - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; [[self navigationController] setNavigationBarHidden:YES]; timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(changeView:) userInfo:nil repeats:NO]; } -(void)changeView:(NSTimer*)theTimer { NSLog(@"timer fired"); //Crash here, but only if called using a timer [[self navigationController] pushViewController:list animated:YES]; }

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• How to prevent a globally overridden "new" operator from being linked in from external library

  - by mprudhom

  In our iPhone XCode 3.2.1 project, we're linking in 2 external static C++ libraries, libBlue.a and libGreen.a. libBlue.a globally overrides the "new" operator for it's own memory management. However, when we build our project, libGreen.a winds up using libBlue's new operator, which results in a crash (presumably because libBlue.a is making assumptions about the kinds of structures being allocated). Both libBlue.a and libGreen.a are provided by 3rd parties, so we can't change any of their source code or build options. When we remove libBlue.a from the project, libGreen.a doesn't have any issues. However, no amount of shuffling the linking order of the libraries seems to fix the problem, nor does any experimentation with the various linking flags. Is there some way to tell XCode to tell the linker to "have libGreen's use of the new operator use the standard C++ new operator rather than the one redefined by libBlue"?

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• How do laziness and I/O work together in Haskell?

  - by Bill

  I'm trying to get a deeper understanding of laziness in Haskell. I was imagining the following snippet today: data Image = Image { name :: String, pixels :: String } image :: String -> IO Image image path = Image path <$> readFile path The appeal here is that I could simply create an Image instance and pass it around; if I need the image data it would be read lazily - if not, the time and memory cost of reading the file would be avoided: main = do image <- image "file" putStrLn $ length $ pixels image But is that how it actually works? How is laziness compatible with IO? Will readFile be called regardless of whether I access pixels image or will the runtime leave that thunk unevaluated if I never refer to it? If the image is indeed read lazily, then isn't it possible I/O actions could occur out of order? For example, what if immediately after calling image I delete the file? Now the putStrLn call will find nothing when it tries to read.

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• Problem with SqlServer 2005 when opening connections

  - by Jose Obregon

  I have a Winforms application and I use EntLib to connect to a SQL Server 2005 DB. The application is working ok, but sometimes, and lately more often, we have started receiving this error from the db when opening the connection: A connection was successfully established with the server, but then an error occurred during the login process. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.) (Microsoft SQL Server, Error: 233) The problem is intermittent. The user works well for a couple of hours and then suddenly the exception is thrown. Sometimes it happens when we run a small process that loads a file and then inserts the data to the db.

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• HTTP status code for "success with errors"?

  - by Richard Levasseur

  I've poked around a bit, but I don't see an HTTP status code for when a request's succeeds, but there is an error after the "point of no return". e.g., Say you process a request, its committed to the database, but while returning the result you run of memory, or encounter a NPE, or what have you. It would have been a 200 response, but now, internally, you aren't able to return the proper, well-formed response. 202 Accepted doesn't seem to fit since we've already processed the request. What status code means "Success, but errors"? Does one even exist?

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• LNK1106 with big binary resource

  - by E Dominique

  I have a rather huge .dat-file (896MB) included as a BIN resource in my project. Now I get a LNK1106 link error ("fatal error LNK1106: invalid file or disk full: cannot seek to 0x382A3920".) I use Visual Studio 2005 under Windows XP, and have tried on a 4GB RAM machine with high Virtual Memory settings and lots of disk space. I have tried a number of different optimization flags, but to no avail. Does anyone have a clue? EDIT: I have narrowed it down to a specific size of the compiled resource. If the .res file is 544078588 bytes (about 518.9MB) or larger, the error occurs. If it is smaller it works just fine. Still no solution, though...

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