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  • boost::Spirit Grammar for unsorted schema

    - by Hassan Syed
    I have a section of a schema for a model that I need to parse. Lets say it looks like the following. { type = "Standard"; hostname="x.y.z"; port="123"; } The properties are: The elements may appear unordered. All elements that are part of the schema must appear, and no other. All of the elements' synthesised attributes go into a struct. (optional) The schema might in the future depend on the type field -- i.e., different fields based on type -- however I am not concerned about this at the moment.

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  • PHP/Java Bridge - Access Java objects in PHP

    - by Omer Hassan
    I have a Red5 application which defines some public Java methods. When I start the server, an object of the application class gets created. I am trying to call the public methods of the application class from PHP using the existing instance of the Java application class. So here's my Java application: public class App extends org.red5.server.adapter.ApplicationAdapter { public boolean appStart(IScope app) { // This method gets called when the application starts // and an object of this App class is created. return true; } // This is the method I would like to call from PHP. public void f() { } } From PHP, I would like to get access to the App object that is created and call the method f() on it. I have tried playing around with this thing called "context". So in the Java method App.appStart(), I did this: // Save a reference to this App object to be retrieved later in PHP. new PhpScriptContextFactory().getContext().put("x", this); And in PHP, I tried to access the saved object like this: require_once("http://localhost:5080/JavaBridge/java/Java.inc"); var_dump(java_is_null(java_context()->get("x"))); Unfortunately, the java_is_null() function in PHP returns true. I also tried saving the App object in a static variable of App class but when I access that variable in PHP, its value is null.

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  • Loading and storing encryption keys from a config source

    - by Hassan Syed
    I am writing an application which has an authenticity mechanism, using HMAC-sha1, plus a CBC-blowfish pass over the data for good measure. This requires 2 keys and one ivec. I have looked at Crypto++ but the documentation is very poor (for example the HMAC documentation). So I am going oldschool and use Openssl. Whats the best way to generate and load these keys using library functions and tools ? I don't require a secure-socket therefore a x.509 certificate probably does not make sense, unless, of-course, I am missing something. So, do I need to write my own config file, or is there any infrastructure in openssl for this ? If so, could you direct me to some documentation or examples for this.

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  • Thread Local Memory, Using std::string's internal buffer for c-style Scratch Memory.

    - by Hassan Syed
    I am using Protocol Buffers and OpensSSL to generate, HMACs and then CBC encrypt the two fields to obfuscate the session cookies -- similar Kerberos tokens. Protocol Buffers' API communicates with std::strings and has a buffer caching mechanism; I exploit the caching mechanism, for successive calls in the the same thread, by placing it in thread local memory; additionally the OpenSSL HMAC and EVP CTX's are also placed in the same thread local memory structure ( see this question for some detail on why I use thread local memory and the massive amount of speedup it enables even with a single thread). The generation and deserialization, "my algorithms", of these cookie strings uses intermediary void *s and std::strings and since Protocol Buffers has an internal memory retention mechanism I want these characteristics for "my algorithms". So how do I implement a common scratch memory ? I don't know much about the rdbuf(streambuf - strinbuf ??) of the std::string object. I would presumeably need to grow it to the lowest common size ever encountered during the execution of "my algorithms". Thoughts ? My question I guess would be: " is the internal buffer of a string re-usable, and if so, how ?" Edit: See comments to Vlad's answer please.

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • How does a portable Thread Specific Storage Mechanism's Naming Scheme Generate Thread Relative Uniqu

    - by Hassan Syed
    A portable thread specific storage reference/identity mechanism, of which boost/thread/tss.hpp is an instance, needs a way to generate a unique keys for itself. This key is unique in the scope of a thread, and is subsequently used to retrieve the object it references. This mechanism is used in code written in a thread neutral manner. Since boost is a portable example of this concept, how specifically does such a mechanism work ?

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  • Accidental Complexity in OpenSSL HMAC functions

    - by Hassan Syed
    SSL Documentation Analaysis This question is pertaining the usage of the HMAC routines in OpenSSL. Since Openssl documentation is a tad on the weak side in certain areas, profiling has revealed that using the: unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len, const unsigned char *d, int n, unsigned char *md, unsigned int *md_len); From here, shows 40% of my library runtime is devoted to creating and taking down **HMAC_CTX's behind the scenes. There are also two additional function to create and destroy a HMAC_CTX explicetly: HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_cleanup() erases the key and other data from the HMAC_CTX and releases any associated resources. It must be called when an HMAC_CTX is no longer required. These two function calls are prefixed with: The following functions may be used if the message is not completely stored in memory My data fits entirely in memory, so I choose the HMAC function -- the one whose signature is shown above. The context, as described by the man page, is made use of by using the following two functions: HMAC_Update() can be called repeatedly with chunks of the message to be authenticated (len bytes at data). HMAC_Final() places the message authentication code in md, which must have space for the hash function output. The Scope of the Application My application generates a authentic (HMAC, which is also used a nonce), CBC-BF encrypted protocol buffer string. The code will be interfaced with various web-servers and frameworks Windows / Linux as OS, nginx, Apache and IIS as webservers and Python / .NET and C++ web-server filters. The description above should clarify that the library needs to be thread safe, and potentially have resumeable processing state -- i.e., lightweight threads sharing a OS thread (which might leave thread local memory out of the picture). The Question How do I get rid of the 40% overhead on each invocation in a (1) thread-safe / (2) resume-able state way ? (2) is optional since I have all of the source-data present in one go, and can make sure a digest is created in place without relinquishing control of the thread mid-digest-creation. So, (1) can probably be done using thread local memory -- but how do I resuse the CTX's ? does the HMAC_final() call make the CTX reusable ?. (2) optional: in this case I would have to create a pool of CTX's. (3) how does the HMAC function do this ? does it create a CTX in the scope of the function call and destroy it ? Psuedocode and commentary will be useful.

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  • How to Capture a live stream from Windows Media Server 2008

    - by Hummad Hassan
    I want to capture the live stream from windows media server to filesystem on my pc I have tried with my own media server with the following code. but when i have checked the out put file i have found this in it. FileStream fs = null; try { HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://mywmsserver/test"); CookieContainer ci = new CookieContainer(1000); req.Timeout = 60000; req.Method = "Get"; req.KeepAlive = true; req.MaximumAutomaticRedirections = 99; req.UseDefaultCredentials = true; req.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3"; req.ReadWriteTimeout = 90000000; req.CookieContainer = ci; //req.MediaType = "video/x-ms-asf"; req.AllowWriteStreamBuffering = true; HttpWebResponse resp = (HttpWebResponse)req.GetResponse(); Stream resps = resp.GetResponseStream(); fs = new FileStream("d:\\dump.wmv", FileMode.Create, FileAccess.ReadWrite); byte[] buffer = new byte[1024]; int bytesRead = 0; while ((bytesRead = resps.Read(buffer, 0, buffer.Length)) > 0) { fs.Write(buffer, 0, bytesRead); } } catch (Exception ex) { } finally { if (fs != null) fs.Close(); }

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  • How to Capture a live stream from Windows Media Server 2008 using c#.net

    - by Hummad Hassan
    I want to capture the live stream from windows media server to filesystem on my pc I have tried with my own media server with the following code. but when i have checked the out put file i have found this in it. please help me with this. Thanks [Reference] Ref1=http://mywindowsmediaserver/test?MSWMExt=.asf Ref2=http://mywindowsmediaserver/test?MSWMExt=.asf FileStream fs = null; try { HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://mywmsserver/test"); CookieContainer ci = new CookieContainer(1000); req.Timeout = 60000; req.Method = "Get"; req.KeepAlive = true; req.MaximumAutomaticRedirections = 99; req.UseDefaultCredentials = true; req.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3"; req.ReadWriteTimeout = 90000000; req.CookieContainer = ci; //req.MediaType = "video/x-ms-asf"; req.AllowWriteStreamBuffering = true; HttpWebResponse resp = (HttpWebResponse)req.GetResponse(); Stream resps = resp.GetResponseStream(); fs = new FileStream("d:\\dump.wmv", FileMode.Create, FileAccess.ReadWrite); byte[] buffer = new byte[1024]; int bytesRead = 0; while ((bytesRead = resps.Read(buffer, 0, buffer.Length)) > 0) { fs.Write(buffer, 0, bytesRead); } } catch (Exception ex) { } finally { if (fs != null) fs.Close(); }

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  • postgres store with composite value type, or a better way of attributing an inverted index

    - by Hassan Syed
    can't seem to figure out the syntax for populating a hstore with a value of composite type -- note: I do not want to convert a record to a hstore. select hstore('hello => ROW(1,2)'); I know it's something simple; However, google is not my friend today. use case : custom inverted index. The data is modelling an inverted index of lexemes, the composite data types are various probabilities related to the lexemes which I will use to implement document clustering. Does anyone know a better way of doing this ? I'm open to using an external system if it allows attaching attributes to key-posting pairs in the inverted index. I'd use something external if it had solid support for what I am trying to do, I suspect that sticking 3-10k lexemes per tuple and then doing batch processing on them is gonna be nasty as the whole hstore will have to be parsed and converted .

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  • readUTF timeout

    - by Hassan Voyeau
    I am getting a timeout with the following code at readUTF. Any idea why? hc = (HttpConnection) Connector.open("http://twitter.com/statuses/user_timeline/" + username + ".json"); int rc = hc.getResponseCode(); if (rc != HttpConnection.HTTP_OK) { throw new IOException("HTTP response code: " + rc); } DataInputStream dataInputStream = hc.openDataInputStream(); String list = dataInputStream.readUTF();

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  • Conventions for modelling c programs.

    - by Hassan Syed
    I'm working with a source base written almost entirely in straight-c (nginx). It does, however, make use of rich high level programming techniques such as compile-time metaprogramming, and OOP - including run-time dispatch. I want to draw ER diagrams, UML class diagrams and UML sequence diagrams. However to have a clean mapping between the two, consistent conventions must be applied. So, I am hopping someone has some references to material that establishes or applies such conventions to similar style c-code.

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  • openssl crypto library - base64 conversion

    - by Hassan Syed
    I'm using openssl BIO objects to convert a binary string into a base64 string. The code is as follows: void ToBase64(std::string & s_in) { BIO * b_s = BIO_new( BIO_s_mem() ); BIO * b64_f = BIO_new( BIO_f_base64() ); b_s = BIO_push( b64_f , b_s); std::cout << "IN::" << s_in.length(); BIO_write(b_s, s_in.c_str(), s_in.length()); char * pp; int sz = BIO_get_mem_data(b_s, &pp); std::cout << "OUT::" << sz << endl; s_in.assign(pp,sz); //std::cout << sz << " " << std::string(pp,sz) << std::endl; BIO_free (b64_f); // TODO ret error potential BIO_free (b_s); // } The in length is either 64 or 72. However the output is always 65, which is incorrect it should be much larger than that. The documentation isn't the best in the world, AFAIK the bio_s_mem object is supposed to grow dynamically. What am I doing wrong ?

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  • Vim: yank and replace -- the same yanked input -- multiple times, and two other questions

    - by Hassan Syed
    Now that I am using vim for everything I type, rather then just for configuring servers, I wan't to sort out the following trivialities. I tried to formulate Google search queries but the results didn't address my questions :D. Question one: How do I yank and replace multiple times ? Once I have something in the yank history (if that is what its called) and then highlight and use the 'p' char in command mode the replaced text is put at the front of the yank history; therefore subsequent replace operations do not use the the text I intended. I imagine this to be a usefull feature under certain circumstances but I do not have a need for it in my workflow. Question two: How do I type text without causing the line to ripple forward ? I use hard-tab stops to allign my code in a certain way -- e.g., FunctionNameX ( lala * land ); FunctionNameProto ( ); When I figure out what needs to go into the second function, how do I insert it without move the text up ? Question three Is there a way of having a uniform yank history across gvim instances on the same machine ? I have 1 monitors. Just wondering, atm I am using highlight + mouse middle click.

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  • Thread Local Memory for Scratch Memory.

    - by Hassan Syed
    I am using Protocol Buffers and OpensSSL to generate, HMACs and then CBC encrypt the two fields to obfuscate the session cookies -- similar Kerberos tokens. Protocol Buffers' API communicates with std::strings and has a buffer caching mechanism; I exploit the caching mechanism, for successive calls in the the same thread, by placing it in thread local memory; additionally the OpenSSL HMAC and EVP CTX's are also placed in the same thread local memory structure ( see this question for some detail on why I use thread local memory and the massive amount of speedup it enables even with a single thread). The generation and deserialization, "my algorithms", of these cookie strings uses intermediary void *s and std::strings and since Protocol Buffers has an internal memory retention mechanism I want these characteristics for "my algorithms". So how do I implement a common scratch memory ? I don't know much about the rdbuf of the std::string object. I would presumeably need to grow it to the lowest common size ever encountered during the execution of "my algorithms". Thoughts ?

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  • Check server response in javascript.

    - by Mujtaba Hassan
    I want to check server response in javascript. For example I have a server A which will host the script. On excuting the script it will check if the server B is responding or not. If yest continue other wise redirect to server C. Is this possible with Javascript/Jquery? If not what could be a possible solution in PHP?

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  • C++ iterators, default initialization and what to use as an uninitialized sentinel.

    - by Hassan Syed
    The Context I have a custom template container class put together from a map and vector. The map resolves a string to an ordinal, and the vector resolves an ordinal (only an initial string to ordinal lookup is done, future references are to the vector) to the entry. The entries are modified intrusively to contain a a bool "assigned" and an iterator_type which is a const_iterator to the container class's map. My container class will use RCF's serialization code (which models boost::serialization) to serialize my container classes to nodes in a network. Serializing iterator's is not possible, or a can of worms, and I can easily regenerate them onces the vectors and maps are serialized on the remote site. The Question I need to default initialize, and be able to test that the iterator has not been assigned to (if it is assigned it is valid, if not it is invalid). Since map iterators are not invalidated upon operations performed on it (unless of course items are removed :D) am I to assume that map<x,y>::end() is a valid sentinel (regardless of the state of the map -- i.e., it could be empty) to initialize to ? I will always have access to the parent map, I'm just unsure wheather end() is the same as the map contents change. I don't want to use another level of indirection (--i.e., boost::optional) to achieve my goal, I'd rather forego compiler checks to correct logic, but it would be nice if I didn't need to. Misc This question exists, but most of its content seems non-sense. Assigning a NULL to an iterator is invalid according to g++ and clang++. This is another similar question, but it focuses on the common use-cases of iterators, which generally tends to be using the iterator to iterate, ofcourse in this use-case the state of the container isn't meant to change whilst iteration is going on.

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  • Endianness and C API's: Specifically OpenSSL.

    - by Hassan Syed
    I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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  • Postgres : Post statement (or insert) asynchronous, non-blocking processing.

    - by Hassan Syed
    I'm wondering if it is possible, that after a collection of rows is inserted, to initiate an operation that is executed asynchronously, is non-blocking, and doesn't need to inform the originator of the request - of the result. I am working with large amounts of events and I can guarantee that the post-insert logic will not fail -- I just want to have a single insert thread in my event-sources, and I want this thread to keep flying without blocking, and without being responsible for any post-delivery book-keeping. I can tell you that I would potentially have a 100 of these jobs executing concurrently and each job might operate on 5 tables with anywhere between 200-1000 inserts on each of these tables. A hint in the right direction should be enough.

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  • Multiple webservice calls

    - by Mujtaba Hassan
    I have a webservice (ASP.NET) deployed on a webfarm. A client application consumes it on daily basis. The problem is that some of its calls are duplicated (with difference of milliseconds). For example I have a function Foo(string a,string b). The client app calls this webmethod as Foo('test1','test2') once but my log shows that it is being called twice or sometimes 3 or 4 times randomly. Is this anything wrong with the webfarm or the code? Note that the webmethod has simple straighfarward insert and update statements.

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  • Get row id datatables

    - by Syed Haider Hassan
    ok. i have searched the internet and tried many things but nothing seems to work for me.. i am now getting upset of this datatables. I found 1 way which some ppl on net says works for them and it is giving me strange problem. if you see the image, when i use the function fnGetPosition, it just cross out.. i don't know why other users over net have no issue on it.. All i am trying to get is FormID, if there is any other way please help me get the ID.

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  • How to get comma-separated values in Linq?

    - by Mujtaba Hassan
    I have the query below: var users = (from a in dc.UserRoles join u in dc.Users on a.intUserId equals u.ID join r in dc.Roles on a.intRoleId equals r.ID where r.intClientId == clientID select new UserRoleDetail { ID = a.ID, intUserId = a.intUserId, intRoleId = a.intRoleId, Name =u.FullName, //Here I need comma separated values. intAssignedById = a.intAssignedById, RoleName = r.vchName, Function = u.vchFunction }); I require all the values of "Name =u.FullName" to be comma-separated in a single record group by intRoleId. I mean for every role I need all the usernames in a sigle record comma separated. Any suggestion?

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  • Getting meaningful error messages from fstream's in C++

    - by Hassan Syed
    What is the best way to get meaningful file access error messages, in a portable way from std::fstreams ? The primitiveness of badbits and failbits is getting to be bit annoying. I have written my own exception hierarchies against win32 and POSIX before, and that was far more flexible than the way the STL does it. I am getting "basic::ios_clear" as an error message from the what method of a downcasted catch (std::exception) of a fstream which has exceptions enabled. This doesn't mean much to me, although I do know what the problem is I'd like my program to be a tad more informative so that when I start deployment a few months later my life will be easier. Is there anything in Boost to extract meaningful messages out of the ofstream's implementation cross platform and cross STL implementation ?

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