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  • Any HTTP proxies with explicit, configurable support for request/response buffering and delayed conn

    - by Carlos Carrasco
    When dealing with mobile clients it is very common to have multisecond delays during the transmission of HTTP requests. If you are serving pages or services out of a prefork Apache the child processes will be tied up for seconds serving a single mobile client, even if your app server logic is done in 5ms. I am looking for a HTTP server, balancer or proxy server that supports the following: A request arrives to the proxy. The proxy starts buffering in RAM or in disk the request, including headers and POST/PUT bodies. The proxy DOES NOT open a connection to the backend server. This is probably the most important part. The proxy server stops buffering the request when: A size limit has been reached (say, 4KB), or The request has been received completely, headers and body Only now, with (part of) the request in memory, a connection is opened to the backend and the request is relayed. The backend sends back the response. Again the proxy server starts buffering it immediately (up to a more generous size, say 64KB.) Since the proxy has a big enough buffer the backend response is stored completely in the proxy server in a matter of miliseconds, and the backend process/thread is free to process more requests. The backend connection is immediately closed. The proxy sends back the response to the mobile client, as fast or as slow as it is capable of, without having a connection to the backend tying up resources. I am fairly sure you can do 4-6 with Squid, and nginx appears to support 1-3 (and looks like fairly unique in this respect). My question is: is there any proxy server that empathizes these buffering and not-opening-connections-until-ready capabilities? Maybe there is just a bit of Apache config-fu that makes this buffering behaviour trivial? Any of them that it is not a dinosaur like Squid and that supports a lean single-process, asynchronous, event-based execution model? (Siderant: I would be using nginx but it doesn't support chunked POST bodies, making it useless for serving stuff to mobile clients. Yes cheap 50$ handsets love chunked POSTs... sigh)

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  • What is the header of an array in .NET

    - by Thomas
    Hi all, I have a little bit seen the representation of an array in memory with Windbg and SOS plugin. Here it is the c# : class myobj{ public int[] arr; } class Program{ static void Main(string[] args){ myobj o = new myobj(); o.arr = new int[7]; o.arr[0] = 0xFFFFFF; o.arr[1] = 0xFFFFFF; o.arr[2] = 0xFFFFFF; o.arr[3] = 0xFFFFFF; o.arr[4] = 0xFFFFFF; } } I break at final of Main, and I observ : 0:000> !clrstack -l OS Thread Id: 0xc3c (0) ESP EIP 0015f0cc 0043d1cf test.Program.Main(System.String[]) LOCALS: 0x0015f0d8 = 0x018a2f58 0:000 !do 0x018a2f58 Name: test.myobj MethodTable: 0026309c EEClass: 00261380 Size: 12(0xc) bytes (C:\Users\admin\Documents\Visual Studio 2008\Projects\test\test\bin\Debug\test.exe) Fields: MT Field Offset Type VT Attr Value Name 01324530 4000001 4 System.Int32[] 0 instance 018a2f64 tab 0:000 dd 018a2f64 018a2f64 01324530 00000007 00ffffff 00ffffff 018a2f74 00ffffff 00ffffff 00ffffff 00000000 018a2f84 00000000 00000000 00000000 00000000 018a2f94 00000000 00000000 00000000 00000000 018a2fa4 00000000 00000000 00000000 00000000 018a2fb4 00000000 00000000 00000000 00000000 018a2fc4 00000000 00000000 00000000 00000000 018a2fd4 00000000 00000000 00000000 00000000 I can see that the header contains the size of the array (00000007) but my question is : what is the value 01324530 ? Thanks !

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  • XMLStreamReader and a real stream

    - by Yuri Ushakov
    Update There is no ready XML parser in Java community which can do NIO and XML parsing. This is the closest I found, and it's incomplete: http://wiki.fasterxml.com/AaltoHome I have the following code: InputStream input = ...; XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance(); XMLStreamReader streamReader = xmlInputFactory.createXMLStreamReader(input, "UTF-8"); Question is, why does the method #createXMLStreamReader() expects to have an entire XML document in the input stream? Why is it called a "stream reader", if it can't seem to process a portion of XML data? For example, if I feed: <root> <child> to it, it would tell me I'm missing the closing tags. Even before I begin iterating the stream reader itself. I suspect that I just don't know how to use a XMLStreamReader properly. I should be able to supply it with data by pieces, right? I need it because I'm processing a XML stream coming in from network socket, and don't want to load the whole source text into memory. Thank you for help, Yuri.

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  • Suitable ESXi Spec

    - by Canacourse
    Finally I have some money to buy a new server and replace the one I have been using for 10 years. Im thinking of running ESXi on the new server. And intend to use it as follows; One W2008 R2 Guest running Exchange, File store, SVN and an accounting application for day to day running of the company. Multiple Guest VMs W2K, XP, Vista & WIN7 that were setup for testing in-house & real customer images also for testing. Probably Two Server Guest Os's W2003 & W2008 running at the same time again for testing. One Guest VM for builds & Continuous integration. Possibly one Guest running W220R2 for a customer website (Portal) This server will have to last another 10 years so I want to get the spec right. Althought I am clear on the memory and disk requirments I am not so clear on the processor(s). Im thinking of 2 Quadcore processors but welcome advice on this. Proposed Spec 10GB Ram 2TB Sata Drives (Hardware Raid 1) 2 Processors (TBC) Normally 3 Server VM's will running concurrently and the other VMs will be started as required. Max expected VMs running about 7. Max users = 4. TIA..

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  • Why does setting this member in C fail?

    - by Lee Crabtree
    I'm writing a Python wrapper for a C++ library, and I'm getting a really weird when trying to set a struct's field in C. If I have a struct like this: struct Thing { PyOBJECT_HEAD unsigned int val; }; And have two functions like this: static PyObject* Thing_GetBit(Thing* self, PyObject* args) { unsigned int mask; if(!PyArg_ParseTuple(args, "I", &mask) Py_RETURN_FALSE; if((self->val & mask) != 0) Py_RETURN_TRUE; Py_RETURN_FALSE; } static PyObject* Thing_SetBit(Thing* self, PyObject* args) { unsigned int mask; bool on; if(!PyArg_ParseTuple(args, "Ii", &mask, &on)) Py_RETURN_FALSE; if(on) thing->val |= mask; else thing->val &= ~mask; Py_RETURN_TRUE; } Python code that calls the first method works just fine, giving back the value of the struct member. Calls to the SetBit method give an error about an object at address foo accessing memory at address bar, which couldn't be "written". I've poked around the code, and it's like I can look at the value all I want, both from C and Python, but the instant I try to set it, it blows up in my face. Am I missing something fundamental here?

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  • rewrite not a member of LiftRules

    - by José Leal
    Hi guys, I was following http://www.assembla.com/wiki/show/liftweb/URL_Rewriting tutorial for url rewritting in liftweb.. but I get this error: error: value rewrite is not a member of object net.liftweb.http.LiftRules .. it is really odd.. and the documentation says that it exists. I'm using idea IDE, and I've done everything from scratch, using the lift maven blank archifact. Some more info: [INFO] ------------------------------------------------------------------------ [INFO] Building Joseph3 [INFO] task-segment: [tomcat:run] [INFO] ------------------------------------------------------------------------ [INFO] Preparing tomcat:run [INFO] [resources:resources {execution: default-resources}] [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 0 resource [INFO] [yuicompressor:compress {execution: default}] [INFO] nb warnings: 0, nb errors: 0 [INFO] artifact org.mortbay.jetty:jetty: checking for updates from scala-tools.org [INFO] artifact org.mortbay.jetty:jetty: checking for updates from central [INFO] [compiler:compile {execution: default-compile}] [INFO] Nothing to compile - all classes are up to date [INFO] [scala:compile {execution: default}] [INFO] Checking for multiple versions of scala [INFO] /home/dpz/Scala/Doit/Joseph3/src/main/scala:-1: info: compiling [INFO] Compiling 2 source files to /home/dpz/Scala/Doit/Joseph3/target/classes at 1274922123910 [ERROR] /home/dpz/Scala/Doit/Joseph3/src/main/scala/bootstrap/liftweb/Boot.scala:16: error: value rewrite is not a member of object net.liftweb.http.LiftRules [INFO] LiftRules.rewrite.prepend(NamedPF("ProductExampleRewrite") { [INFO] ^ [ERROR] one error found [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1(Exit value: 1) [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 19 seconds [INFO] Finished at: Thu May 27 03:02:07 CEST 2010 [INFO] Final Memory: 20M/175M [INFO] ------------------------------------------------------------------------ Process finished with exit code 1 enter code here

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  • What is the most efficient way to display decoded video frames in Qt?

    - by Jason
    What is the fastest way to display images to a Qt widget? I have decoded the video using libavformat and libavcodec, so I already have raw RGB or YCbCr 4:2:0 frames. I am currently using a QGraphicsView with a QGraphicsScene object containing a QGraphicsPixmapItem. I am currently getting the frame data into a QPixmap by using the QImage constructor from a memory buffer and converting it to QPixmap using QPixmap::fromImage(). I like the results of this and it seems relatively fast, but I can't help but think that there must be a more efficient way. I've also heard that the QImage to QPixmap conversion is expensive. I have implemented a solution that uses an SDL overlay on a widget, but I'd like to stay with just Qt since I am able to easily capture clicks and other user interaction with the video display using the QGraphicsView. I am doing any required video scaling or colorspace conversions with libswscale so I would just like to know if anyone has a more efficient way to display the image data after all processing has been performed. Thanks.

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  • Default template parameters with forward declaration

    - by Seth Johnson
    Is it possible to forward declare a class that uses default arguments without specifying or knowing those arguments? For example, I would like to declare a boost::ptr_list< TYPE > in a Traits class without dragging the entire Boost library into every file that includes the traits. I would like to declare namespace boost { template<class T> class ptr_list< T >; }, but that doesn't work because it doesn't exactly match the true class declaration: template < class T, class CloneAllocator = heap_clone_allocator, class Allocator = std::allocator<void*> > class ptr_list { ... }; Are my options only to live with it or to specify boost::ptr_list< TYPE, boost::heap_clone_allocator, std::allocator<void*> in my traits class? (If I use the latter, I'll also have to forward declare boost::heap_clone_allocator and include <memory>, I suppose.) I've looked through Stroustrup's book, SO, and the rest of the internet and haven't found a solution. Usually people are concerned about not including STL, and the solution is "just include the STL headers." However, Boost is a much more massive and compiler-intensive library, so I'd prefer to leave it out unless I absolutely have to.

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  • MySQL Query Error

    - by Nano HE
    I am debug my php forum. Before the error,I modified the DB table name from cdb_sessions to imc_forum_sessions successfully. I tried my best to debug with NetBeans but can't find the reason. Could you please have a look at my post below. Thank you. // It will run to else during debug if($sid) { if($discuz_uid) { $query = $db->query("SELECT s.sid, s.styleid, s.groupid='6' AS ipbanned, s.pageviews AS spageviews, s.lastolupdate, s.seccode, $membertablefields FROM {$tablepre}sessions s, {$tablepre}members m WHERE m.uid=s.uid AND s.sid='$sid' AND CONCAT_WS('.',s.ip1,s.ip2,s.ip3,s.ip4)='$onlineip' AND m.uid='$discuz_uid' AND m.password='$discuz_pw' AND m.secques='$discuz_secques'"); } else { $query = $db->query("SELECT sid, uid AS sessionuid, groupid, groupid='6' AS ipbanned, pageviews AS spageviews, styleid, lastolupdate, seccode FROM {$tablepre}sessions WHERE sid='$sid' AND CONCAT_WS('.',ip1,ip2,ip3,ip4)='$onlineip'"); } } MySQL data table exported as below CREATE TABLE IF NOT EXISTS `imc_forum_sessions` ( `sid` char(6) NOT NULL DEFAULT '', `ip1` tinyint(3) unsigned NOT NULL DEFAULT '0', `ip2` tinyint(3) unsigned NOT NULL DEFAULT '0', `ip3` tinyint(3) unsigned NOT NULL DEFAULT '0', `ip4` tinyint(3) unsigned NOT NULL DEFAULT '0', `uid` mediumint(8) unsigned NOT NULL DEFAULT '0', `username` char(15) NOT NULL DEFAULT '', `groupid` smallint(6) unsigned NOT NULL DEFAULT '0', `styleid` smallint(6) unsigned NOT NULL DEFAULT '0', `invisible` tinyint(1) NOT NULL DEFAULT '0', `action` tinyint(1) unsigned NOT NULL DEFAULT '0', `lastactivity` int(10) unsigned NOT NULL DEFAULT '0', `lastolupdate` int(10) unsigned NOT NULL DEFAULT '0', `pageviews` smallint(6) unsigned NOT NULL DEFAULT '0', `seccode` mediumint(6) unsigned NOT NULL DEFAULT '0', `fid` smallint(6) unsigned NOT NULL DEFAULT '0', `tid` mediumint(8) unsigned NOT NULL DEFAULT '0', `bloguid` mediumint(8) unsigned NOT NULL DEFAULT '0', UNIQUE KEY `sid` (`sid`), KEY `uid` (`uid`), KEY `bloguid` (`bloguid`) ) ENGINE=MEMORY DEFAULT CHARSET=utf8 MAX_ROWS=5000; -- -- Dumping data for table `imc_forum_sessions` -- INSERT INTO `imc_forum_sessions` (`sid`, `ip1`, `ip2`, `ip3`, `ip4`, `uid`, `username`, `groupid`, `styleid`, `invisible`, `action`, `lastactivity`, `lastolupdate`, `pageviews`, `seccode`, `fid`, `tid`, `bloguid`) VALUES ('NYC4r7', 127, 0, 0, 1, 0, '', 6, 5, 0, 3, 1271372018, 0, 0, 939015, 51, 303, 0); And the IE error showed, Time: 2010-4-16 7:12am Script: /forum/index.php SQL: SELECT sid, uid AS sessionuid, groupid, groupid='6' AS ipbanned, pageviews AS spageviews, styleid, lastolupdate, seccode FROM [Table]sessions WHERE sid='NYC4r7' AND CONCAT_WS('.',ip1,ip2,ip3,ip4)='127.0.0.1' Error: Table 'dbbbs.[Table]sessions' doesn't exist Errno.: 1146 Similar error report has beed dispatched to administrator before.

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  • NHibernate IQueryable Collection as Property of Root

    - by Khalid Abuhakmeh
    Hello and thank you for taking the time to read this. I have a root object that has a property that is a collection. For example : I have a Shelf object that has Books. // now public class Shelf { public ICollection<Book> Books {get; set;} } // want public class Shelf { public IQueryable<Book> Books {get;set;} } What I want to accomplish is to return a collection that is IQueryable so that I can run paging and filtering off of the collection directly from the the parent. var shelf = shelfRepository.Get(1); var filtered = from book in shelf.Books where book.Name == "The Great Gatsby" select book; I want to have that query executed specifically by NHibernate and not a get all to load a whole collection and then parse it in memory (which is what currently happens when I use ICollection). The reasoning behind this is that my collection could be huge, tens of thousands of records, and a get all query could bash my database. I would like to do this implicitly so that when NHibernate sees and IQueryable on my class it knows what to do. I have looked at NHibernates Linq provider and currently I am making the decision to take large collections and split them into their own repository so that I can make explicit calls for filtering and paging. Linq To SQL offers something similar to what I'm talking about.

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  • Quickest algorithm for finding sets with high intersection

    - by conradlee
    I have a large number of user IDs (integers), potentially millions. These users all belong to various groups (sets of integers), such that there are on the order of 10 million groups. To simplify my example and get to the essence of it, let's assume that all groups contain 20 user IDs (i.e., all integer sets have a cardinality of 100). I want to find all pairs of integer sets that have an intersection of 15 or greater. Should I compare every pair of sets? (If I keep a data structure that maps userIDs to set membership, this would not be necessary.) What is the quickest way to do this? That is, what should my underlying data structure be for representing the integer sets? Sorted sets, unsorted---can hashing somehow help? And what algorithm should I use to compute set intersection)? I prefer answers that relate C/C++ (especially STL), but also any more general, algorithmic insights are welcome. Update Also, note that I will be running this in parallel in a shared memory environment, so ideas that cleanly extend to a parallel solution are preferred.

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  • What are practical guidelines for evaluating a language's "Turing Completeness"?

    - by AShelly
    I've read "what-is-turing-complete" and the wikipedia page, but I'm less interested in a formal proof than in the practical implications of being Turing Complete. What I'm actually trying to decide is if the toy language I've just designed could be used as a general-purpose language. I know I can prove it is if I can write a Turing machine with it. But I don't want to go through that exercise until I'm fairly certain of success. Is there a minimum set of features without which Turing Completeness is impossible? Is there a set of features which virtually guarantees completeness? (My guess is that conditional branching and a readable/writeable memory store will get me most of the way there) EDIT: I think I've gone off on a tangent by saying "Turing Complete". I'm trying to guess with reasonable confidence that a newly invented language with a certain feature set (or alternately, a VM with a certain instruction set) would be able to compute anything worth computing. I know proving you can building a Turing machine with it is one way, but not the only way. What I was hoping for was a set of guidelines like: "if it can do X,Y,and Z, it can probably do anything".

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  • Error while compiling Hello world program for CUDA

    - by footy
    I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA: #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ __global__ void kernel(void) { } /* MAIN PROGRAM BEGINS */ int main(void) { /* Dg = 1; Db = 1; Ns = 0; S = 0 */ kernel<<<1,1>>>(); /* PRINT 'HELLO, WORLD!' TO THE SCREEN */ printf("\n Hello, World!\n\n"); /* INDICATE THE TERMINATION OF THE PROGRAM */ return 0; } /* MAIN PROGRAM ENDS */ The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main': /home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil': /usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1': /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary' /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)': /usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch' collect2: ld returned 1 exit status I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)

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  • Reasons for & against a Database

    - by dbemerlin
    Hi, i had a discussion with a coworker about the architecture of a program i'm writing and i'd like some more opinions. The Situation: The Program should update at near-realtime (+/- 1 Minute). It involves the movement of objects on a coordinate system. There are some events that occur at regular intervals (i.e. creation of the objects). Movements can change at any time through user input. My solution was: Build a server that runs continously and stores the data internally. The server dumps a state-of-the-program at regular intervals to protect against powerfailures and/or crashes. He argued that the program requires a Database and i should use cronjobs to update the data. I can store movement information by storing startpoint, endpoint and speed and update the position in the cronjob (and calculate collisions with other objects there) by calculating direction and speed. His reasons: Requires more CPU & Memory because it runs constantly. Powerfailures/Crashes might destroy data. Databases are faster. My reasons against this are mostly: Not very precise as events can only occur at full minutes (wouldn't be that bad though). Requires (possibly costly) transformation of data on every run from relational data to objects. RDBMS are a general solution for a specialized problem so a specialized solution should be more efficient. Powerfailures (or other crashes) can leave the Data in an undefined state with only partially updated data unless (possibly costly) precautions (like transactions) are taken. What are your opinions about that? Which arguments can you add for any side?

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  • Maintaining a pool of DAO Class instances vs doing new operator

    - by Fazal
    we have been trying to benchmark our application performance in multiple way for sometime now. I always believed that object creation in java using Class.newInstance() was not slow (at least after 1.4 version of java). But we anyways did a test to use newInstance method vs mainitain an object pool of 1000 objects. We did about 200K iterations of loading data from DB using JDBC and populating these objects. I was amazed (even shocked) to see that newInstance code compared to object pool code was almost 10 times slower. These objects represent tables with about 50 fields and all string type. Can someone share there thoughts on this issue as now I am more confused if object pooling of atleast some DAO instances is a better option. The pool size as I see right now should be large enough to meet size of average requests. There is a flip side as my memory footprint will go up but I am beginning to wonder if this kind of idea makes sense atleast for some of the DAO entities representing tables of about 50 or more columns Please share your ideas and let me know if this has been tried by someone or am I missing some point here

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  • NSArray/NSMutableArray : Passed by ref or by value???

    - by wgpubs
    Totally confused here. I have a PARENT UIViewController that needs to pass an NSMutableArray to a CHILD UIViewController. I'm expecting it to be passed by reference so that changes made in the CHILD will be reflected in the PARENT and vice-versa. But that is not the case. Both have a property declared as .. @property (nonatomic, retain) NSMutableArray *photos; Example: In PARENT: self.photos = [[NSMutableArray alloc] init]; ChildViewController *c = [[ChildViewController alloc] init ...]; c.photos = self.photos; ... ... ... In CHILD: [self.photos addObject:obj1]; [self.photos addObject:obj2]; NSLog(@"Count:%d", [self.photos count]) // Equals 2 as expected ... Back in PARENT: NSLog(@"Count:%d", [self.photos count]) // Equals 0 ... NOT EXPECTED I thought they'd both be accessing the same memory. Is this not the case? If it isn't ... how do I keep the two NSMutableArrays in sync?

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  • Question about creating device-compatible bitmaps in C#

    - by MusiGenesis
    I am storing bitmap-like data in a two-dimensional int array. To convert this array into a GDI-compatible bitmap (for use with BitBlt), I am using this function: public IntPtr GetGDIBitmap(int[,] data) { int w = data.GetLength(0); int h = data.GetLength(1); IntPtr ret = IntPtr.Zero; using (Bitmap bmp = new Bitmap(w, h)) { for (int x = 0; x < w; x++) { for (int y = 0; y < h; y++) { Color color = Color.FromArgb(data[x, y]); bmp.SetPixel(x, y, color); } } ret = bmp.GetHbitmap(); } return ret; } This works as expected, but the call to bmp.GetHbitmap() has to allocate memory for the returned bitmap. I'd like to modify this method in two (probably related) ways: I'd like to remove the intermediate Bitmap from the above code entirely, and go directly from my int[,] array to the device-compatible bitmap (i.e. the IntPtr). I presume this would involve calling CreateCompatibleBitmap, but I don't know how to go from that call to actually manipulating the pixel values. This should logically follow from the answer to the first, but I'd also like my method to re-use existing GDI bitmap handles (instead of creating a new bitmap each time). How can I do this? NOTE: I don't really use Bitmap.SetPixel(), as its performance could best be described as "glacial". The code is just for illustration.

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  • Collecting high-volume video viewing data

    - by DanK
    I want to add tracking to our Flash-based media player so that we can provide analytics that show what sections of videos are being watched (at the moment, we just register a view when a video starts playing) For example, if a viewer watches the first 30 seconds of a video and then clicks away to something else, we want the data to reflect that. Likewise, if someone watches the first 10 seconds, then scrubs the timeline to the last minute of the video and watches that, we want to register viewing on the parts watched and not the middle section. My first thought was to collect up the viewing data in the player and send it all to the server at the end of a viewing session. Unfortunately, Flash does not seem to have an event that you can hook into when a viewer clicks away from the page the movie is on (probably a good thing - it would be open to abuse) So, it looks like we're going to have to make regular requests to the server as the video is playing. This is obviously going to lead to a high volume of requests when there are large numbers of simultaneous viewers. The simple approach of dumping all these 'heartbeat' events from clients to a database feels like it will quickly become unmanageable so I'm wondering whether I should be taking an approach where viewing sessions are cached in memory and flushed to database when they become inactive (based on a timeout). That way, the data could be stored as time spans rather than individual heartbeats. So, to the question - what is the best way to approach dealing with this kind of high-volume viewing data? Are there any good existing architectures/patterns? Thanks, Dan.

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  • Issue on maven 2.2.1

    - by Dawit
    I wrote a small maven plugin and everything seems to work well with prior version of maven (2.0.9) but my build fails on version 2.2.1 The stack trace does not show anything from my end of the code and was wondering if anyone has encountered this issue. .... .... [ERROR] FATAL ERROR [INFO] ------------------------------------------------------------------------ [INFO] null [INFO] ------------------------------------------------------------------------ [INFO] Trace java.lang.NullPointerException at java.util.Hashtable.put(Hashtable.java:396) at java.util.Properties.setProperty(Properties.java:128) at org.apache.maven.project.ModelUtils.cloneProperties(ModelUtils.java:1264) at org.apache.maven.project.ModelUtils.cloneModelBaseFields(ModelUtils.java:318) at org.apache.maven.project.ModelUtils.cloneModel(ModelUtils.java:953) at org.apache.maven.project.DefaultMavenProjectBuilder.calculateConcreteStateInternal(DefaultMavenProjectBuilder.java:1855) at org.apache.maven.project.DefaultMavenProjectBuilder.calculateConcreteState(DefaultMavenProjectBuilder.java:1814) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.calculateConcreteState(DefaultLifecycleExecutor.java:779) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:575) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:540) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:519) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:371) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:332) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:181) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:356) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:137) at org.apache.maven.cli.MavenCli.main(MavenCli.java:362) at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:41) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:592) at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315) at org.codehaus.classworlds.Launcher.launch(Launcher.java:255) at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430) at org.codehaus.classworlds.Launcher.main(Launcher.java:375) [INFO] ------------------------------------------------------------------------ [INFO] Total time: 17 seconds [INFO] Finished at: Thu May 27 16:18:40 CDT 2010 [INFO] Final Memory: 35M/63M

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  • To what degree should I use Marshal.ReleaseComObject with Excel Interop objects?

    - by DanM
    I've seen several examples where Marshal.ReleaseComObject() is used with Excel Interop objects (i.e., objects from namespace Microsoft.Office.Interop.Excel), but I've seen it used to various degrees. I'm wondering if I can get away with something like this: var application = new ApplicationClass(); try { // do work with application, workbooks, worksheets, cells, etc. } finally { Marashal.ReleaseComObject(application) } Or if I need to release every single object created, as in this method: public void CreateExcelWorkbookWithSingleSheet() { var application = new ApplicationClass(); var workbook = application.Workbooks.Add(_missing); var worksheets = workbook.Worksheets; for (var worksheetIndex = 1; worksheetIndex < worksheets.Count; worksheetIndex++) { var worksheet = (WorksheetClass)worksheets[worksheetIndex]; worksheet.Delete(); Marshal.ReleaseComObject(worksheet); } workbook.SaveAs( WorkbookPath, _missing, _missing, _missing, _missing, _missing, XlSaveAsAccessMode.xlExclusive, _missing, _missing, _missing, _missing, _missing); workbook.Close(true, _missing, _missing); application.Quit(); Marshal.ReleaseComObject(worksheets); Marshal.ReleaseComObject(workbook); Marshal.ReleaseComObject(application); } What prompted me to ask this question is that, being the LINQ devotee I am, I really want to do something like this: var worksheetNames = worksheets.Cast<Worksheet>().Select(ws => ws.Name); ...but I'm concerned I'll end up with memory leaks or ghost processes if I don't release each worksheet (ws) object. Any insight on this would be appreciated.

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  • C pointers and addresses

    - by yCalleecharan
    Hi, I always thought that *&p = p = &*p in C. I tried this code: #include <stdio.h> #include <stdlib.h> char a[] = "programming"; char *ap = &a[4]; int main(void) { printf("%x %x %x\n", ap, &*(ap), *&(ap)); /* line 13 */ printf("%x %x %x\n\n", ap+1, &*(ap+1), *&(ap+1)); /* line 14 */ } The first printf line (line 13) gives me the addresses: 40b0a8 40b0a8 40b0a8 which are the same as expected. But when I added the second printf line, Borland complains: "first.c": E2027 Must take address of a memory location in function main at line 14 I was expecting to get: 40b0a9 40b0a9 40b0a9. It seems that the expression *&(ap+1) on line 14 is the culprit here. I thought all three pointer expressions on line 14 are equivalent. Why am I thinking wrong? A second related question: The line char *ap = a; points to the first element of array a. I used char *ap = &a[4]; to point to the 5th element of array a. Is the expression char *ap = a; same as the expression char *ap = &a[0]; Is the last expression only more verbose than the previous one? Thanks a lot...

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  • How is a relative JMP (x86) implemented in an Assembler?

    - by Pindatjuh
    While building my assembler for the x86 platform I encountered some problems with encoding the JMP instruction: enc inst size in bytes EB cb JMP rel8 2 E9 cw JMP rel16 4 (because of 0x66 16-bit prefix) E9 cd JMP rel32 5 ... (from my favourite x86 instruction website, http://siyobik.info/index.php?module=x86&id=147) All are relative jumps, where the size of each encoding (operation + operand) is in the third column. Now my original (and thus fault because of this) design reserved the maximum (5 bytes) space for each instruction. The operand is not yet known, because it's a jump to a yet unknown location. So I've implemented a "rewrite" mechanism, that rewrites the operands in the correct location in memory, if the location of the jump is known, and fills the rest with NOPs. This is a somewhat serious concern in tight-loops. Now my problem is with the following situation: b: XXX c: JMP a e: XXX ... XXX d: JMP b a: XXX (where XXX is any instruction, depending on the to-be assembled program) The problem is that I want the smallest possible encoding for a JMP instruction (and no NOP filling). I have to know the size of the instruction at c before I can calculate the relative distance between a and b for the operand at d. The same applies for the JMP at c: it needs to know the size of d before it can calculate the relative distance between e and a. How do existing assemblers implement this, or how would you implement this? This is what I am thinking which solves the problem: First encode all the instructions to opcodes between the JMP and it's target, and if this region contains a variable-sized opcode, use the maximum size, i.e. 5 for JMP. Then in some conditions, the JMP is oversized (because it may fit in a smaller encoding): so another pass will search for oversized JMPs, shrink them, and move all instructions ahead), and set absolute branching instructions (i.e. external CALLs) after this pass is completed. I wonder, perhaps this is an over-engineered solution, that's why I ask this question.

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  • How can I make this method more Scalalicious

    - by Neil Chambers
    I have a function that calculates the left and right node values for some collection of treeNodes given a simple node.id, node.parentId association. It's very simple and works well enough...but, well, I am wondering if there is a more idiomatic approach. Specifically is there a way to track the left/right values without using some externally tracked value but still keep the tasty recursion. /* * A tree node */ case class TreeNode(val id:String, val parentId: String){ var left: Int = 0 var right: Int = 0 } /* * a method to compute the left/right node values */ def walktree(node: TreeNode) = { /* * increment state for the inner function */ var c = 0 /* * A method to set the increment state */ def increment = { c+=1; c } // poo /* * the tasty inner method * treeNodes is a List[TreeNode] */ def walk(node: TreeNode): Unit = { node.left = increment /* * recurse on all direct descendants */ treeNodes filter( _.parentId == node.id) foreach (walk(_)) node.right = increment } walk(node) } walktree(someRootNode) Edit - The list of nodes is taken from a database. Pulling the nodes into a proper tree would take too much time. I am pulling a flat list into memory and all I have is an association via node id's as pertains to parents and children. Adding left/right node values allows me to get a snapshop of all children (and childrens children) with a single SQL query. The calculation needs to run very quickly in order to maintain data integrity should parent-child associations change (which they do very frequently). In addition to using the awesome Scala collections I've also boosted speed by using parallel processing for some pre/post filtering on the tree nodes. I wanted to find a more idiomatic way of tracking the left/right node values. After looking at the answers listed I have settled on this synthesised version: def walktree(node: TreeNode) = { def walk(node: TreeNode, counter: Int): Int = { node.left = counter node.right = treeNodes .filter( _.parentId == node.id) .foldLeft(counter+1) { (counter, curnode) => walk(curnode, counter) + 1 } node.right } walk(node,1) }

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  • use startActivityForResult from non-activity

    - by rayman
    Hi, I have MainActivity which is an Activity and other class(which is a simple java class), we`ll call it "SimpleClass". now i want to run from that class the command startActivityForResult. now i though that i could pass that class(SimpleClass), only MainActivity's context, problem is that, u cant run context.startActivityForResult(...); so the only way making SimpleClass to use 'startActivityForResult; is to pass the reference of MainActivity as an Activity variable to the SimpleClass something like that: inside the MainActivity class i create the instance of SimpleClass this way: SimpleClass simpleClass=new SimpleClass(MainActivity.this); now this is how SimpleClass looks like: public Class SimpleClass { Activity myMainActivity; public SimpleClass(Activity mainActivity) { super(); this.myMainActivity=mainActivity; } .... } public void someMethod(...) { myMainActivity.startActivityForResult(...); } now its working, but isnt a proper way of doing this? I`am afraid i could have some memory leaks in the future. thanks. ray.

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  • Need to call original function from detoured function

    - by peachykeen
    I'm using Detours to hook into an executable's message function, but I need to run my own code and then call the original code. From what I've seen in the Detours docs, it definitely sounds like that should happen automatically. The original function prints a message to the screen, but as soon as I attach a detour it starts running my code and stops printing. The original function code is roughly: void CGuiObject::AppendMsgToBuffer(classA, unsigned long, unsigned long, int, classB); My function is: void CGuiObject_AppendMsgToBuffer( [same params, with names] ); I know the memory position the original function resides in, so using: DWORD OrigPos = 0x0040592C; DetourAttach( (void*)OrigPos, CGuiObject_AppendMsgToBuffer); gets me into the function. This code works almost perfectly: my function is called with the proper parameters. However, execution leaves my function and the original code is not called. I've tried jmping back in, but that crashes the program (I'm assuming the code Detours moved to fit the hook is responsible for the crash). Edit: I've managed to fix the first issue, with no returning to program execution. By calling the OrigPos value as a function, I'm able to go to the "trampoline" function and from there on to the original code. However, somewhere along the lines the registers are changing and that is causing the program to crash with a segfault as soon as I get back into the original code.

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