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• Providing downloads on ASP.net website

  - by Dave

  I need to provide downloads of large files (upwards of 2 GB) on an ASP.net website. It has been some time since I've done something like this (I've been in the thick-client world for awhile now), and was wondering on current best practices for this. Ideally, I would like: To be able to track download statistics: # of downloads is essential; actual bytes sent would be nice. To provide downloads in a way that "plays nice" with third-party download managers. Many of our users have unreliable internet connections, and being able to resume a download is a must. To allow multiple users to download the same file simultaneously. My download files are not security-sensitive, so providing a direct link ("right-click to download...") is a possibility. Is just providing a direct link sufficient, letting IIS handle it, and then using some log analyzer service (any recommendations?) to compile and report the statistics? Or do I need to intercept the download request, store some info in a database, then send a custom Response? Or is there an ASP.net user control (built-in or third party) that does this? I appreciate all suggestions.

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• Creating Binary Block from struct

  - by MOnsDaR

  I hope the title is describing the problem, i'll change it if anyone has a better idea. I'm storing information in a struct like this: struct AnyStruct { AnyStruct : testInt(20), testDouble(100.01), testBool1(true), testBool2(false), testBool3(true), testChar('x') {} int testInt; double testDouble; bool testBool1; bool testBool2; bool testBool3; char testChar; std::vector<char> getBinaryBlock() { //how to build that? } } The struct should be sent via network in a binary byte-buffer with the following structure: Bit 00- 31: testInt Bit 32- 61: testDouble most significant portion Bit 62- 93: testDouble least significant portion Bit 94: testBool1 Bit 95: testBool2 Bit 96: testBool3 Bit 97-104: testChar According to this definition the resulting std::vector should have a size of 13 bytes (char == byte) My question now is how I can form such a packet out of the different datatypes I've got. I've already read through a lot of pages and found datatypes like std::bitset or boost::dynamic_bitset, but neither seems to solve my problem. I think it is easy to see, that the above code is just an example, the original standard is far more complex and contains more different datatypes. Solving the above example should solve my problems with the complex structures too i think. One last point: The problem should be solved just by using standard, portable language-features of C++ like STL or Boost (

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• Cannot connect to Github?

  - by user2973438

  so I tried to push some updates onto my repo on github via terminal on Mac OSX 10.8.4 and it doesn't work. I've been getting the same error many times: Lillys-MacBook-Air:Yuewei Lilly$ git push origin master error: Failed connect to github.com:443; Operation timed out while accessing https://github.com/lillybeans/Yuewei.git/info/refs?service=git-receive-pack fatal: HTTP request failed Some background: I've pushed many projects onto github before using terminal (when I was in Canada). I am currently in Shanghai, China, could it be the GFW? But when I was in Beijing, I was able to push projects onto github still. when I do ping github.com: Lillys-MacBook-Air:Yuewei Lilly$ ping github.com PING github.com (192.30.252.131): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 ping: sendto: No route to host Request timeout for icmp_seq 2 ping: sendto: Host is down Request timeout for icmp_seq 3 ping: sendto: Host is down Request timeout for icmp_seq 4 ping: sendto: Host is down Request timeout for icmp_seq 5 ping: sendto: Host is down Request timeout for icmp_seq 6 ping: sendto: Host is down Request timeout for icmp_seq 7 ^C --- github.com ping statistics --- 9 packets transmitted, 0 packets received, 100.0% packet loss Lillys-MacBook-Air:Yuewei Lilly$ I have ShadowSocks (proxy) turned on. Without it I can't access github.com via browser, with it, I can. also when I do "git remote -v" I see both my pull and push remote repos correctly listed. Thank you in advance!

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• How to use linux csplit to chop up massive XML file?

  - by Fred

  Hi everyone, I have a gigantic (4GB) XML file that I am currently breaking into chunks with linux "split" function (every 25,000 lines - not by bytes). This usually works great (I end up with about 50 files), except some of the data descriptions have line breaks, and so frequently the chunk files do not have the proper closing tags - and my parser chokes halfway through processing. Example file: (note: normally each "listing" xml node is supposed to be on its own line) <?xml version="1.0" encoding="UTF-8"?> <listings> <listing><date>2009-09-22</date><desc>This is a description WITHOUT line breaks and works fine with split</desc><more_tags>stuff</more_tags></listing> <listing><date>2009-09-22</date><desc>This is a really annoying description field WITH line breaks that screw the split function</desc><more_tags>stuff</more_tags></listing> </listings> Then sometimes my split ends up like <?xml version="1.0" encoding="UTF-8"?> <listings> <listing><date>2009-09-22</date><desc>This is a description WITHOUT line breaks and works fine with split</desc><more_tags>stuff</more_tags></listing> <listing><date>2009-09-22</date><desc>This is a really annoying description field WITH line breaks ... EOF So - I have been reading about "csplit" and it sounds like it might work to solve this issue. I cant seem to get the regular expression right... Basically I want the same output of ~50ish files Something like: *csplit -k myfile.xml '/</listing>/' 25000 {50} Any help would be great Thanks!

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• Information about PTE's (Page Table Entries) in Windows

  - by Patrick

  In order to find more easily buffer overflows I am changing our custom memory allocator so that it allocates a full 4KB page instead of only the wanted number of bytes. Then I change the page protection and size so that if the caller writes before or after its allocated piece of memory, the application immediately crashes. Problem is that although I have enough memory, the application never starts up completely because it runs out of memory. This has two causes: since every allocation needs 4 KB, we probably reach the 2 GB limit very soon. This problem could be solved if I would make a 64-bit executable (didn't try it yet). even when I only need a few hundreds of megabytes, the allocations fail at a certain moment. The second problem is the biggest one, and I think it's related to the maximum number of PTE's (page table entries, which store information on how Virtual Memory is mapped to physical memory, and whether pages should be read-only or not) you can have in a process. My questions (or a cry-for-tips): Where can I find information about the maximum number of PTE's in a process? Is this different (higher) for 64-bit systems/applications or not? Can the number of PTE's be configured in the application or in Windows? Thanks, Patrick PS. note for those who will try to argument that you shouldn't write your own memory manager: My application is rather specific so I really want full control over memory management (can't give any more details) Last week we had a memory overwrite which we couldn't find using the standard C++ allocator and the debugging functionality of the C/C++ run time (it only said "block corrupt" minutes after the actual corruption") We also tried standard Windows utilities (like GFLAGS, ...) but they slowed down the application by a factor of 100, and couldn't find the exact position of the overwrite either We also tried the "Full Page Heap" functionality of Application Verifier, but then the application doesn't start up either (probably also running out of PTE's)

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• What's the best way to communicate the purpose of a string parameter in a public API?

  - by Dave

  According to the guidance published in New Recommendations for Using Strings in Microsoft .NET 2.0, the data in a string may exhibit one of the following types of behavior: A non-linguistic identifier, where bytes match exactly. A non-linguistic identifier, where case is irrelevant, especially a piece of data stored in most Microsoft Windows system services. Culturally-agnostic data, which still is linguistically relevant. Data that requires local linguistic customs. Given that, I'd like to know the best way to communicate which behavior is expected of a string parameter in a public API. I wasn't able to find an answer in the Framework Design Guidelines. Consider the following methods: f(string this_is_a_linguistic_string) g(string this_is_a_symbolic_identifier_so_use_ordinal_compares) Is variable naming and XML documentation the best I can do? Could I use attributes in some way to mark the requirements of the string? Now consider the following case: h(Dictionary<string, object> dictionary) Note that the dictionary instance is created by the caller. How do I communicate that the callee expects the IEqualityComparer<string> object held by the dictionary to perform, for example, a case-insensitive ordinal comparison?

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• Questions regarding detouring by modifying the virtual table

  - by Elliott Darfink

  I've been practicing detours using the same approach as Microsoft Detours (replace the first five bytes with a jmp and an address). More recently I've been reading about detouring by modifying the virtual table. I would appreciate if someone could shed some light on the subject by mentioning a few pros and cons with this method compared to the one previously mentioned! I'd also like to ask about patched vtables and objects on the stack. Consider the following situation: // Class definition struct Foo { virtual void Call(void) { std::cout << "FooCall\n"; } }; // If it's GCC, 'this' is passed as the first parameter void MyCall(Foo * object) { std::cout << "MyCall\n"; } // In some function Foo * foo = new Foo; // Allocated on the heap Foo foo2; // Created on the stack // Arguments: void ** vtable, uint offset, void * replacement PatchVTable(*reinterpret_cast<void***>(foo), 0, MyCall); // Call the methods foo->Call(); // Outputs: 'MyCall' foo2.Call(); // Outputs: 'FooCall' In this case foo->Call() would end up calling MyCall(Foo * object) whilst foo2.Call() call the original function (i.e Foo::Call(void) method). This is because the compiler will try to decide any virtual calls during compile time if possible (correct me if I'm wrong). Does that mean it does not matter if you patch the virtual table or not, as long as you use objects on the stack (not heap allocated)?

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• Conditional deserialization

  - by Yordan Pavlov

  I am still not sure whether the title of my question is correct and it most probably is not. However I have spent some time searching both the net and stackoverflow and I can not find a good description of the issue I am facing. Basically what I want to achieve is the ability to read some raw bytes and based on the value of some of them to interpret the rest in different ways. This is how TLV works in a way, you check the tag and depending on it - interpret the result. Of course I can always keep that logic in my C++ code, however I am looking for a solution which would move the logic out of the source code (maybe to some xml description). This would allow me to describe different encodings (protocols) more easily. I am familiar with Protocol Buffers and some other serialization libraries, however all of them solve different issue. They assume they are on both ends of the communication, while I want to describe the communication (sort of). Is such solution available, if no - why not? Are there some inherent difficulties I will face trying to implement it.

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• Read varbinary data in java

  - by masoud farahani

  I made a Java application which reads some files from SQL server. Those files are saved to a varbinary(MAX) field in SQL Server by a third party web service. My problem is that when I want to read those files with my Java application, those binary data show different content in the Java application. In fact, I read data byte by byte and I figured out that some bytes did not show the real values which were saved in the database. I found out what the problem is, but I couldn’t find a solution yet. I found out that in the web service every varbinary data is saved to database as byte data (in .Net each byte takes 0 to 255). But, when I want to read the binary data in Java, it takes different values and cause an exception with some values, because in Java a byte value takes -127 to 127. In my Java application I want to write those data to a file by OutputStream.write(byte[]) method. How can I solve this problem? I think that I have to find a way to convert c# byte[] to a Java byte[] (or binary data), but how can I do that?

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• MD5CryptoServiceProvider ComputeHash Issues between VS 2003 and VS 2008

  - by owensoroke

  I have a database application that generates a MD5 hash and compares the hash value to a value in our DB (SQL 2K). The original application was written in Visual Studio 2003 and a deployed version has been working for years. Recently, some new machines on the .NET framework 3.5 have been having unrelated issues with our runtime. This has forced us to port our code path from Visual Studio 2003 to Visual Studio 2008. Since that time the hash produced by the code is different than the values in the database. The original call to the function posted in code is: RemoveInvalidPasswordCharactersFromHashedPassword(Text_Scrub(GenerateMD5Hash(strPSW))) I am looking for expert guidance as to whether or not the MD5 methods have changed since VS 2K3 (causing this point of failure), or where other possible problems may be originating from. I realize this may not be the best method to hash, but utimately any changes to the MD5 code would force us to change some 300 values in our DB table and would cost us a lot of time. In addition, I am trying to avoid having to redeploy all of the functioning versions of this application. I am more than happy to post other code including the RemoveInvalidPasswordCharactersFromHashedPassword function, or our Text_Scrub if it is necessary to recieve appropriate feedback. Thank you in advance for your input. Public Function GenerateMD5Hash(ByVal strInput As String) As String Dim md5Provider As MD5 ' generate bytes for the input string Dim inputData() As Byte = ASCIIEncoding.ASCII.GetBytes(strInput) ' compute MD5 hash md5Provider = New MD5CryptoServiceProvider Dim hashResult() As Byte = md5Provider.ComputeHash(inputData) Return ASCIIEncoding.ASCII.GetString(hashResult) End Function

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• How do I see if an established socket is stuck on a server that's expecting input?

  - by Parker

  I have a script that scans ports for open proxy servers. Problem is if it encounters a login program (specifically telnet) then it hangs there forever since it doesn't know what to do and eventually the server closes the connection. The simple solution would be to create a bunch of cases. If telnet, do this. If SSH, do that. If something else, blah blah blah. I'd like an umbrella solution since the script is not a high priority for me. The script, as it is now, is available at http://parkrrr.net/socks/scan.phps On a small scale (the page maybe averages 15 hits/day) it's fine but on a larger scale I'd be worried about a lot of open zombie sockets. Swapping the !$strpos doesn't work since servers can return more information than what you requested (headers, ads, etc). Only accepting a fixed number of bytes (as opposed to appending until EOF, which it does now) from the $fgets also does not seem to work. I am sure this is where it gets stuck: while (!feof($fp)) { $data.=fgets($fp,512); } But what can I do? Any other suggestions/warnings would also be welcomed.

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• Querying the size of a drive on a remote server is giving me an error

  - by Testifier

  Here's what I have: public static bool DriveHasLessThanTenPercentFreeSpace(string server) { long driveSize = 0; long freeSpace = 0; var oConn = new ConnectionOptions {Username = "username", Password = Settings.Default.SQLServerAdminPassword}; var scope = new ManagementScope("\\\\" + server + "\\root\\CIMV2", oConn); //connect to the scope scope.Connect(); //construct the query var query = new ObjectQuery("SELECT FreeSpace FROM Win32_LogicalDisk where DeviceID = 'D:'"); //this class retrieves the collection of objects returned by the query var searcher = new ManagementObjectSearcher(scope, query); //this is similar to using a data adapter to fill a data set - use an instance of the ManagementObjectSearcher to get the collection from the query and store it ManagementObjectCollection queryCollection = searcher.Get(); //iterate through the object collection and get what you're looking for - in my case I want the FreeSpace of the D drive foreach (ManagementObject m in queryCollection) { //the FreeSpace value is in bytes freeSpace = Convert.ToInt64(m["FreeSpace"]); //error happens here! driveSize = Convert.ToInt64(m["Size"]); } long percentFree = ((freeSpace / driveSize) * 100); if (percentFree < 10) { return true; } return false; } This line of code is giving me an error: driveSize = Convert.ToInt64(m["Size"]); The error says: ManagementException was unhandled by user code Not found I'm assuming the query to get the drive size is wrong. Please note that I AM getting the freeSpace value at the line: freeSpace = Convert.ToInt64(m["FreeSpace"]); So I know the query IS working for freeSpace. Can anyone give me a hand?

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• Protocol specification in XML

  - by Mathijs

  Is there a way to specify a packet-based protocol in XML, so (de)serialization can happen automatically? The context is as follows. I have a device that communicates through a serial port. It sends and receives a byte stream consisting of 'packets'. A packet is a collection of elementary data types and (sometimes) other packets. Some elements of packets are conditional; their inclusion depends on earlier elements. I have a C# application that communicates with this device. Naturally, I don't want to work on a byte-level throughout my application; I want to separate the protocol from my application code. Therefore I need to translate the byte stream to structures (classes). Currently I have implemented the protocol in C# by defining a class for each packet. These classes define the order and type of elements for each packet. Making class members conditional is difficult, so protocol information ends up in functions. I imagine XML that looks like this (note that my experience designing XML is limited): <packet> <field name="Author" type="int32" /> <field name="Nickname" type="bytes" size="4"> <condition type="range"> <field>Author</field> <min>3</min> <max>6</min> </condition> </field> </packet> .NET has something called a 'binary serializer', but I don't think that's what I'm looking for. Is there a way to separate protocol and code, even if packets 'include' other packets and have conditional elements?

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• pthread_create followed by pthread_detach still results in possibly lost error in Valgrind.

  - by alesplin

  I'm having a problem with Valgrind telling me I have some memory possible lost: ==23205== 544 bytes in 2 blocks are possibly lost in loss record 156 of 265 ==23205== at 0x6022879: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==23205== by 0x540E209: allocate_dtv (in /lib/ld-2.12.1.so) ==23205== by 0x540E91D: _dl_allocate_tls (in /lib/ld-2.12.1.so) ==23205== by 0x623068D: pthread_create@@GLIBC_2.2.5 (in /lib/libpthread-2.12.1.so) ==23205== by 0x758D66: MTPCreateThreadPool (MTP.c:290) ==23205== by 0x405787: main (MServer.c:317) The code that creates these threads (MTPCreateThreadPool) basically gets an index into a block of waiting pthread_t slots, and creates a thread with that. TI becomes a pointer to a struct that has a thread index and a pthread_t. (simplified/sanitized): for (tindex = 0; tindex < NumThreads; tindex++) { int rc; TI = &TP->ThreadInfo[tindex]; TI->ThreadID = tindex; rc = pthread_create(&TI->ThreadHandle,NULL,MTPHandleRequestsLoop,TI); /* check for non-success that I've omitted */ pthread_detach(&TI->ThreadHandle); } Then we have a function MTPDestroyThreadPool that loops through all the threads we created and cancels them (since the MTPHandleRequestsLoop doesn't exit). for (tindex = 0; tindex < NumThreads; tindex++) { pthread_cancel(TP->ThreadInfo[tindex].ThreadHandle); } I've read elsewhere (including other questions here on SO) that detaching a thread explicitly would prevent this possibly lost error, but it clearly isn't. Any thoughts?

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• C++, using one byte to store two variables

  - by 2di

  Hi All I am working on representation of the chess board, and I am planning to store it in 32 bytes array, where each byte will be used to store two pieces. (That way only 4 bits are needed per piece) Doing it in that way, results in a overhead for accessing particular index of the board. Do you think that, this code can be optimised or completely different method of accessing indexes can be used? c++ char getPosition(unsigned char* c, int index){ //moving pointer c+=(index>>1); //odd number if (index & 1){ //taking right part return *c & 0xF; }else { //taking left part return *c>>4; } } void setValue(unsigned char* board, char value, int index){ //moving pointer board+=(index>>1); //odd number if (index & 1){ //replace right part //save left value only 4 bits *board = (*board & 0xF0) + value; }else { //replacing left part *board = (*board & 0xF) + (value<<4); } } int main() { char* c = (char*)malloc(32); for (int i = 0; i < 64 ; i++){ setValue((unsigned char*)c, i % 8,i); } for (int i = 0; i < 64 ; i++){ cout<<(int)getPosition((unsigned char*)c, i)<<" "; if (((i+1) % 8 == 0) && (i > 0)){ cout<<endl; } } return 0; } I am equally interested in your opinions regarding chess representations, and optimisation of the method above, as a stand alone problem. Thanks a lot

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• Time taken for memcpy decreases after certain point

  - by tss

  I ve a code which increases the size of the memory(identified by a pointer) exponentially. Instead of realloc, I use malloc followed by memcpy.. Something like this.. int size=5,newsize; int *c = malloc(size*sizeof(int)); int *temp; while(1) { newsize=2*size; //begin time temp=malloc(newsize*sizeof(int)); memcpy(temp,c,size*sizeof(int)); //end time //print time in mili seconds c=temp; size=newsize; } Thus the number of bytes getting copied is increasing exponentially. The time required for this task also increases almost linearly with the increase in size. However after certain point, the time taken abruptly reduces to a very small value and then remains constant. I recorded time for similar code, copyin data(Of my own type) 5 -> 10 - 2 ms 10 -> 20 - 2 ms . . 2560 -> 5120 - 5 ms . . 20480 -> 40960 - 30 ms 40960 -> 91920 - 58 ms 367680 -> 735360 - 2 ms 735360 -> 1470720 - 2 ms 1470720 -> 2941440 - 2 ms What is the reason for this drop in time ? Does a more optimal memcpy method get called when the size is large ?

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• Objective C: Function returning correct data for the first time of call and null for other times

  - by Kooshal Bhungy

  Hi all, Am a beginner in objective C, i am implementing a function that would query a web server and display the returning string in console. I am calling the function (getDatafromServer) repeatedly in a loop. The problem is that the first time am getting the value whereas the other times, it returns me a (null) in console... I've searched about memory management and check out on the forums but none have worked. Can you please guys tell me where am wrong in the codes below? Thanks in advance.... @implementation RequestThread +(void)startthread:(id)param{ while (true) { //NSLog(@"Test threads"); sleep(5); NSLog(@"%@",[self getDatafromServer]); } } +(NSString *) getDatafromServer{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSString *myRequestString = @"name=Hello%20&[email protected]"; NSData *myRequestData = [NSData dataWithBytes:[myRequestString UTF8String] length:[myRequestString length]]; NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString:@"http://192.168.1.32/gs/includes/widget/getcalls.php?user=asdasd&passw=asdasdasd"]]; [request setHTTPMethod:@"POST"]; [request setHTTPBody: myRequestData]; [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"]; NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]; NSString *myString = [NSString stringWithUTF8String:[returnData bytes]]; [myRequestString release]; [request release]; [returnData release]; return myString; [pool release]; } @end

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• Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

  - by kpdvx

  An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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• Complicated API issue with calling assemblies dynamically?

  - by Stefanos Tses

  I have an interesting challenge that I'm wondering if anyone here can give me some direction. I'm writing a .Net windows forms application that runs on a network and uses an SQL Server to save and pull data. I want to offer a mini "plugin" API, where developers can build their own assemblies and implement a specific interface (IDataManipulate). These assemblies then can be used by my application to call the interface functions and do something. I can create assemblies using my API, copy the file to a folder in my local hard drive and configure my application to use Reflection to call a specific function from the implemented interface (IDataManipulate.Execute). The problem: Since the application will be installed in multiple workstations in the network, is impossible to copy the plugin dlls the users will create to each machine. Solutions I tried: Solution 1 Copy the API dll to a network share. Problem: Requires AllowPartiallyTrustedCallersAttribute, which requires .Net singing, which I can't force from my users. Solution 2 (preferred) Serialize the dll object, save it to the database, deserialize it and call IDataManipulate.Execute. Problem: After deserialization, I try cast it to a IDataManipulate object but returns an error looking for the actual dll file. Solution 3 Save the dll bytes as byte[] to the database and recreate the dll at the local PC every time the user starts my application. Problem: Dll may have dependencies, which I don't know if I can detect. Any suggestions will be greatly appreciated. Thanks

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• Problem with reading and writing to binary file in C++

  - by Reem

  I need to make a file that contains "name" which is a string -array of char- and "data" which is array of bytes -array of char in C++- but the first problem I faced is how to separate the "name" from the "data"? newline character could work in this case (assuming that I don't have "\n" in the name) but I could have special characters in the "data" part so there's no way to know when it ends so I'm putting an int value in the file before the data which has the size of the "data"! I tried to do this with code as follow: if((fp = fopen("file.bin","wb")) == NULL) { return false; } char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int number[1]; number[0]=10; fwrite( number ,1,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); fclose(fp); but I didn't know if the "int" part was right, so I tried many other codes including this one: char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int size=10; fwrite( &size ,sizeof size,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); I see 4 "NULL" characters in the file when I open it instead of seeing an integer. Is that normal? The other problem I'm facing is reading that again from the file! The code I tried to read didn't work at all :( I tried it with "fread" but I'm not sure if I should use "fseek" with it or it just read the other character after it. Forgive me but I'm a beginner :(

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• How to debug JBoss out of memory problem?

  - by user561733

  Hello, I am trying to debug a JBoss out of memory problem. When JBoss starts up and runs for a while, it seems to use memory as intended by the startup configuration. However, it seems that when some unknown user action is taken (or the log file grows to a certain size) using the sole web application JBoss is serving up, memory increases dramatically and JBoss freezes. When JBoss freezes, it is difficult to kill the process or do anything because of low memory. When the process is finally killed via a -9 argument and the server is restarted, the log file is very small and only contains outputs from the startup of the newly started process and not any information on why the memory increased so much. This is why it is so hard to debug: server.log does not have information from the killed process. The log is set to grow to 2 GB and the log file for the new process is only about 300 Kb though it grows properly during normal memory circumstances. This is information on the JBoss configuration: JBoss (MX MicroKernel) 4.0.3 JDK 1.6.0 update 22 PermSize=512m MaxPermSize=512m Xms=1024m Xmx=6144m This is basic info on the system: Operating system: CentOS Linux 5.5 Kernel and CPU: Linux 2.6.18-194.26.1.el5 on x86_64 Processor information: Intel(R) Xeon(R) CPU E5420 @ 2.50GHz, 8 cores This is good example information on the system during normal pre-freeze conditions a few minutes after the jboss service startup: Running processes: 183 CPU load averages: 0.16 (1 min) 0.06 (5 mins) 0.09 (15 mins) CPU usage: 0% user, 0% kernel, 1% IO, 99% idle Real memory: 17.38 GB total, 2.46 GB used Virtual memory: 19.59 GB total, 0 bytes used Local disk space: 113.37 GB total, 11.89 GB used When JBoss freezes, system information looks like this: Running processes: 225 CPU load averages: 4.66 (1 min) 1.84 (5 mins) 0.93 (15 mins) CPU usage: 0% user, 12% kernel, 73% IO, 15% idle Real memory: 17.38 GB total, 17.18 GB used Virtual memory: 19.59 GB total, 706.29 MB used Local disk space: 113.37 GB total, 11.89 GB used

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• uploading database file in assets not returning a record

  - by Alexander

  I have a problem with a database file not being read I have added the database file in assets called mydb but when i run my code it says its not being located. It is calling this toast Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show(); This is being called because no records are being returned. This is an example form Android Application Development book. public class DatabaseActivity extends Activity { /** Called when the activity is first created. */ TextView quest, response1, response2; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView quest = (TextView) findViewById(R.id.quest); try { String destPath = "/data/data/" + getPackageName() + "/databases/MyDB"; File f = new File(destPath); if (!f.exists()) { CopyDB( getBaseContext().getAssets().open("mydb"), new FileOutputStream(destPath)); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } DBAdapter db = new DBAdapter(this); //---get a contact--- db.open(); Cursor c = db.getContact(2); if (c.moveToFirst()) DisplayContact(c); else Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show(); db.close(); } public void CopyDB(InputStream inputStream, OutputStream outputStream) throws IOException { //---copy 1K bytes at a time--- byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, length); } inputStream.close(); outputStream.close(); } public void DisplayContact(Cursor c) { quest.setText(String.valueOf(c.getString(1))); //quest.setText(String.valueOf("this is a text string")); } }

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• UIImage Object surprisingly returning null but not NSData

  - by riyaz

  i have created a sqlite db. and i have insert a few datas in my db.. UIImage * imagee=[UIImage imageNamed:@"image.png"]; NSData *mydata=[NSData dataWithData:UIImagePNGRepresentation(imagee)]; const char *dbpath = [databasePath UTF8String]; NSString *insertSQL=[NSString stringWithFormat:@"insert into CONTACTS values(\"%@\",\"%@\")",@"Mathan",mydata]; NSLog(@"mydata %@",mydata); sqlite3_stmt *addStatement; const char *insert_stmt=[insertSQL UTF8String]; if (sqlite3_open(dbpath,&contactDB)==SQLITE_OK) { sqlite3_prepare_v2(contactDB,insert_stmt,-1,&addStatement,NULL); if (sqlite3_step(addStatement)==SQLITE_DONE) { sqlite3_bind_blob(addStatement,1, [mydata bytes], [mydata length], SQLITE_TRANSIENT); NSLog(@"Data saved"); } else{ NSLog(@"Some Error occured"); } sqlite3_close(contactDB); } else{ NSLog(@"Failure"); } have written some codes to retrive the data sqlite3_stmt *statement; if (sqlite3_open([databasePath UTF8String], &contactDB) == SQLITE_OK) { NSString *sql = [NSString stringWithFormat:@"SELECT * FROM contacts"]; if (sqlite3_prepare_v2( contactDB, [sql UTF8String], -1, &statement, nil) == SQLITE_OK) { while (sqlite3_step(statement) == SQLITE_ROW) { char *field1 = (char *) sqlite3_column_text(statement, 0); NSString *field1Str = [[NSString alloc] initWithUTF8String: field1]; NSLog(@"UserName %@",field1Str); NSData *data = [[NSData alloc] initWithBytes:sqlite3_column_blob(statement, 1) length:sqlite3_column_bytes(statement, 1)]; UIImage *newImage = [[UIImage alloc]initWithData:data]; NSLog(@"Image OBJ %@",newImage); NSLog(@"Image Data %@",data); } sqlite3_close(contactDB); } } sqlite3_finalize(statement); the problem is in log, inserted NSData object and retrieved NSData Objects are different (printing in log gives different stream) moreover Image OBJ is printed null in log.. Have seen similar questions in stackoverflow. But nothing seems to help. Please give some suggestions to overcome this issue.

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• How to encrypt a RSAKey using another RSAKey?

  - by Tom Brito

  I know its not the usual thing to do. But the specification I'm implementing is discribed this way, and I cannot run out. I was trying to encrypt the modulus and exponent of the private key, but the following test code raises an exception because the byte array is 1 byte larger then the maximum allowed by RSA block: import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import javax.crypto.Cipher; import org.apache.commons.lang.ArrayUtils; public class TEST { public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, NoSuchProviderException { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(1024); return keyPairGenerator.generateKeyPair(); } public static void main(String[] args) throws Exception { KeyPair keyPair = generateKeyPair(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); System.out.println("Priv modulus len = " + privateKey.getModulus().bitLength()); System.out.println("Priv exponent len = " + privateKey.getPrivateExponent().bitLength()); System.out.println("Priv modulus toByteArray len = " + privateKey.getModulus().toByteArray().length); byte[] byteArray = privateKey.getModulus().toByteArray(); // the byte at index 0 have no value (in every generation it is always zero) byteArray = ArrayUtils.subarray(byteArray, 1, byteArray.length); System.out.println("byteArray size: " + byteArray.length); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); Cipher cipher = Cipher.getInstance("RSA", "BC"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); byte[] encryptedBytes = cipher.doFinal(byteArray); System.out.println("Success!"); } } (obs. its just a test, i would never encrypt the private key with its pair public key) The byte array is 128 bytes, the exactly maximum allowed by a RSA block, so why the exception? And how to fix it?

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• JMS message. Model to include data or pointers to data?

  - by John

  I am trying to resolve a design difference of opinion where neither of us has experience with JMS. We want to use JMS to communicate between a j2ee application and the stand-alone application when a new event occurs. We would be using a single point-to-point queue. Both sides are Java-based. The question is whether to send the event data itself in the JMS message body or to send a pointer to the data so that the stand-alone program can retrieve it. Details below. I have a j2ee application that supports data entry of new and updated persons and related events. The person records and associated events are written to an Oracle database. There are also stand-alone, separate programs that contribute new person and event records to the database. When a new event occurs through any of 5-10 different application functions, I need to notify remote systems through an outbound interface using an industry-specific standard messaging protocol. The outbound interface has been designed as a stand-alone application to support scalability through asynchronous operation and by moving it to a separate server. The j2ee application currently has most of the data in memory at the time the event is entered. The data would consist of approximately 6 different objects; a person object and some with multiple instances for an average size in the range of 3000 to 20,000 bytes. Some special cases could be many times this amount. From a performance and reliability perspective, should I model the JMS message to pass all the data needed to create the interface message, or model the JMS message to contain record keys for the data and have the stand-alone Java application retrieve the data to create the interface message?

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