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• iTunes Visualizer Plugin in C# - Energy Function

  - by James D

  Hi, iTunes Visualizer plugin in C#. Easiest way to compute the "energy level" for a particular sample? I looked at this writeup on beat detection over at GameDev and have had some success with it (I'm not doing beat detection per se, but it's relevant). But ultimately I'm looking for a stupid-as-possible, quick-and-dirty approach for demo purposes. For those who aren't familiar with how iTunes structures visualization data, basically you're given this: struct VisualPluginData { /* SNIP */ RenderVisualData renderData; UInt32 renderTimeStampID; UInt8 minLevel[kVisualMaxDataChannels]; // 0-128 UInt8 maxLevel[kVisualMaxDataChannels]; // 0-128 }; struct RenderVisualData { UInt8 numWaveformChannels; UInt8 waveformData[kVisualMaxDataChannels][kVisualNumWaveformEntries]; // 512-point FFT UInt8 numSpectrumChannels; UInt8 spectrumData[kVisualMaxDataChannels][kVisualNumSpectrumEntries]; }; Ideally, I'd like an approach that a beginning programmer with little to no DSP experience could grasp and improve on. Any ideas? Thanks!

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• MinGW Doesn't Generate an Object File When Compiling

  - by Nathan Campos

  I've just bought a new laptop for me on the travel, then on my free time, I've started to test MinGW on it by trying to compile my own OS that is written in C++, then I've created all the files needed and the kernel.cpp: extern "C" void _main(struct multiboot_data* mbd, unsigned int magic); void _main( struct multiboot_data* mbd, unsigned int magic ) { char * boot_loader_name =(char*) ((long*)mbd)[16]; /* Print a letter to screen to see everything is working: */ unsigned char *videoram = (unsigned char *) 0xb8000; videoram[0] = 65; /* character 'A' */ videoram[1] = 0x07; /* forground, background color. */ } And tried to compile it with g++ G: g++ -o C:\kernel.o -c kernel.cpp -Wall -Wextra -Werror -nostdlib -nostartfiles -nodefaultlibs kernel.cpp: In function `void _main(multiboot_data*, unsigned int)': kernel.cpp:8: warning: unused variable 'boot_loader_name' kernel.cpp: At global scope: kernel.cpp:4: warning: unused parameter 'magic' G: But it don't create any binary file at C:/. What can I do?

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• Multiple constructors in C

  - by meepz

  Hello, I am making a string class in C as a homework and I was wondering how I can make multiple constructors with the same name given the parameter. The commented out area is what I tried to do with results from a few searches but that gives me errors. Pretty much I have some cases where I want to create my new string without any parameter then in other cases create a string with a pointer to character. Here is mystring.h #include <stdio.h> #include <stdlib.h> typedef struct mystring { char * c; int length; int (*sLength)(void * s); char (*charAt)(void * s, int i); int (*compareTo)(void * s1, void * s2); struct mystring * (*concat)(void * s1, void * s2); struct mystring * (*subString)(void * s, int begin, int end); void (*printS)(void * s); } string_t; typedef string_t * String; String newString(char * c); String newString2(); int slength(void * s); char charat(void * S, int i); int compareto(void * s1, void * s2); String concat(void * s1, void * s2); String substring(void * S, int begin, int end); void printstring(void * s); And here is mystring.c #include "mystring.h" String newString(){ } String newString(char * input){ //String newString::newString(char * input) { String s; s = (string_t *) malloc(sizeof(string_t)); s->c = (char *) malloc(sizeof(char) * 20); int i = 0; if (input == NULL){ s->c[0] = '\0'; return s; } while (input[i] != '\0') { s->c[i] = input[i]; i++; } //functions s->sLength = slength; s->charAt = charat; s->compareTo = compareto; s->concat = concat; s->subString = substring; s->printS = printstring; return s; }

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• Convert "this" to a reference-to-pointer

  - by Austin Hyde

  Just stumbled onto this problem. (title says it all) Let's say I have a struct struct Foo { void bar () { do_baz(this); } void do_baz(Foo*& pFoo) { pFoo->p_sub_foo = new Foo; // for example } Foo* p_sub_foo; } GCC tells me that temp.cpp: In member function ‘void Foo::bar()’: temp.cpp:3: error: no matching function for call to ‘Foo::do_baz(Foo* const)’ temp.cpp:5: note: candidates are: void Foo::do_baz(Foo*&) So, how do I convert what is apparently a const Foo* to a Foo*&?

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• typedef of a template with a template type as its parameter

  - by bryan sammon

  Im having a problem with a typedef below, I can seem to get it right: template <typename T> struct myclass1 { static const int member1 = T::GetSomeInt(); }; template <int I> struct myclass2 { typedef myclass1< myclass2<I> > anotherclass; static int GetSomeInt(); }; anotherclass MyObj1; // ERROR here not instantiating the class When I try and initialize a anotherclass object, it gives me an error. Any idea what I am doing wrong? There seems to be a problem with my typedef. Any help is appreciated, Thanks Bryan

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• Memory leak using shared_ptr

  - by nabulke

  Both code examples compile and run without problems. Using the second variant results in a memory leak. Any ideas why? Thanks in advance for any help. Variant 1: typedef boost::shared_ptr<ParameterTabelle> SpParameterTabelle; struct ParTabSpalteData { ParTabSpalteData(const SpParameterTabelle& tabelle, const string& id) :Tabelle(tabelle), Id(id) { } const SpParameterTabelle& Tabelle; string Id; }; Variant 2: struct ParTabSpalteData { ParTabSpalteData(const SpParameterTabelle& tabelle, const string& id) :Id(id) { // causes memory leak Tabelle2 = tabelle; } SpParameterTabelle Tabelle2; string Id; };

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• WebOrb - Serializing an object as a string

  - by Robert Wagner

  We have an Adobe Flex client talking to a .NET server using WebORB. Simplifying things, on the .NET side of things we have a struct that wraps a ulong like this: public struct MyStruct { private ulong _val; public override string ToString() { return _val.ToString("x16"); } // Parse method } I want the Flex client to treat this as a string. So that for the following server method: public void DoStuff(int i, MyStruct b); It can call it as DoStuff(1, "1234567890ABCDEF") I've tried playing with custom WebORB serializers, but the documentation is a bit scarce. Is this possible? If so how?

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• How can I create a JTable where the first column is always in the JScrollPane viewport?

  - by voodoogiant

  What's the best way to set up a table in a JScrollPane such that the first column is always on the screen in the same position regardless of horizontal scrolling and overlaps columns that pass underneath? When the scrollbar is at the farthest left, the columns look normal, but as the user scrolls to the right, the secondary columns (2 and on) move underneath the first until the last column appears on the far right of the viewport? I found a sample taken from Eckstein's "Java Swing" book that sort of does this, but it doesn't allow resizing of the first column. I was thinking of some scheme where one JPanel held a horizontal struct and a table holding the secondary columns and another JPanel which floated over them (fixed regardless of scrolling). The struct would be to keep the viewport range constant as the first column floated around. Ideally I could do it with two tables using the same model, but I'm not sure if the whole idea is a naive solution.

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• unable to cuda code

  - by cuda-dev

  I'm getting an error when i try to compile and build cuda code Error 1 error C2065: 'threadIdx' : undeclared identifier Error 2 error C2228: left of '.x' must have class/struct/union

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• Listing all shared memory segments used by a process on AIX5.3+

  - by Frank Meerkötter

  I would like to find all shared memory segments used by a given process. I am especially interested in figuring out the shmid so i can use it in calls to shmctl(). On Solaris i would just read /proc/$PID/map to figure out that information (field pr_shmid). The contents of that file are defined by struct prmap_t in sys/procfs. AIX also has a /proc/$PID/map file. There is also a struct prmap but unfortunately it is missing the pr_shmid field. Any ideas how i can achieve this on AIX5.3+?

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• Trouble using opaque pointers in Objective C++

  - by morgancodes

  The answer to this quesion explains that opaque pointers are a good way to include C++ member variables in an Objective C++ header. I'm getting compile errors when trying to follow the example. Here's the relevant code from my header, with the corresponding compiler errors shown as comments: struct ADSR_opaque; // error: forward declaration of 'struct ADSR_opaque' @interface LoopyPulser : NSObject{ float _pulseRate; UInt32 tickInterval; UInt32 step; InMemoryAudioFile * audioFilePlayer; ADSR_opaque* env; // error: expected specifier-qualifier-list before 'ADSR_opaque' Pattern * pattern; float loopLengthRatio; float volume; } Is there something simple I'm doing wrong here?

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• How to handle value types when embedding IronPython in C#?

  - by kloffy

  There is a well known issue when it comes to using .NET value types in IronPython. This has recently caused me a headache when trying to use Python as an embedded scripting language in C#. The problem can be summed up as follows: Given a C# struct such as: struct Vector { public float x; public float y; } And a C# class such as: class Object { public Vector position; } The following will happen in IronPython: obj = Object() print obj.position.x # prints ‘0’ obj.position.x = 1 print obj.position.x # still prints ‘0’ As the article states, this means that value types are mostly immutable. However, this is a problem as I was planning on using a vector library that is implemented as seen above. Are there any workarounds for working with existing libraries that rely on value types? Modifying the library would be the very last resort, but I'd rather avoid that.

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• About variadic templates

  - by chedi

  Hi, I'm currently experiencing with the new c++0x variadic templates, and it's quit fun, Although I have a question about the process of member instanciation. in this example, I'm trying to emulate the strongly typed enum with the possibility of choose a random valid strong enum (this is used for unit testing). #include<vector> #include<iostream> using namespace std; template<unsigned... values> struct sp_enum; /* this is the solution I found, declaring a globar var vector<unsigned> _data; and it work just fine */ template<> struct sp_enum<>{ static const unsigned _count = 0; static vector<unsigned> _data; }; vector<unsigned> sp_enum<>::_data; template<unsigned T, unsigned... values> struct sp_enum<T, values...> : private sp_enum<values...>{ static const unsigned _count = sp_enum<values...>::_count+1; static vector<unsigned> _data; sp_enum( ) : sp_enum<values...>(values...) {_data.push_back(T);} sp_enum(unsigned v ) {_data.push_back(v);} sp_enum(unsigned v, unsigned...) : sp_enum<values...>(values...) {_data.push_back(v);} }; template<unsigned T, unsigned... values> vector<unsigned> sp_enum<T, values...>::_data; int main(){ enum class t:unsigned{Default = 5, t1, t2}; sp_enum<t::Default, t::t1, t::t2> test; cout <<test._count << endl << test._data.size() << endl; for(auto i= test._data.rbegin();i != test._data.rend();++i){cout<< *i<< ":";} } the result I'm getting with this code is : 3 1 5: can someone point me what I'm messing here ??? Ps: using gcc 4.4.3

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• Marshal.PtrToStructure (and back again) and generic solution for endianness swapping

  - by cgyDeveloper

  I have a system where a remote agent sends serialized structures (from and embedded C system) for me to read and store via IP/UDP. In some cases I need to send back the same structure types. I thought I had a nice setup using Marshal.PtrToStructure (receive) and Marshal.StructureToPtr (send). However, a small gotcha is that the network big endian integers need to be converted to my x86 little endian format to be used locally. When I'm sending them off again, big endian is the way to go. Here are the functions in question: private static T BytesToStruct<T>(ref byte[] rawData) where T: struct { T result = default(T); GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); result = (T)Marshal.PtrToStructure(rawDataPtr, typeof(T)); } finally { handle.Free(); } return result; } private static byte[] StructToBytes<T>(T data) where T: struct { byte[] rawData = new byte[Marshal.SizeOf(data)]; GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); Marshal.StructureToPtr(data, rawDataPtr, false); } finally { handle.Free(); } return rawData; } And a quick example structure that might be used like this: byte[] data = this.sock.Receive(ref this.ipep); Request request = BytesToStruct<Request>(ref data); Where the structure in question looks like: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)] private struct Request { public byte type; public short sequence; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] public byte[] address; } What (generic) way can I swap the endianness when marshalling the structures? My need is such that the locally stored 'public short sequence' in this example will be little-endian for displaying to the user. I don't want to have to swap the endianness on a structure-specific way. My first thought was to use Reflection, but I'm not very familiar with that feature. Also, I hoped that there would be a better solution out there that somebody could point me towards. Thanks in advance :)

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• How to write a cctor and op= for a factory class with ptr to abstract member field?

  - by Kache4

  I'm extracting files from zip and rar archives into raw buffers. I created the following to wrap minizip and unrarlib: Archive.hpp #include "ArchiveBase.hpp" #include "ArchiveDerived.hpp" class Archive { public: Archive(string path) { /* logic here to determine type */ switch(type) { case RAR: archive_ = new ArchiveRar(path); break; case ZIP: archive_ = new ArchiveZip(path); break; case UNKNOWN_ARCHIVE: throw; break; } } Archive(Archive& other) { archive_ = // how do I copy an abstract class? } ~Archive() { delete archive_; } void passThrough(ArchiveBase::Data& data) { archive_->passThrough(data); } Archive& operator = (Archive& other) { if (this == &other) return *this; ArchiveBase* newArchive = // can't instantiate.... delete archive_; archive_ = newArchive; return *this; } private: ArchiveBase* archive_; } ArchiveBase.hpp class ArchiveBase { public: // Is there any way to put this struct in Archive instead, // so that outside classes instantiating one could use // Archive::Data instead of ArchiveBase::Data? struct Data { int field; }; virtual void passThrough(Data& data) = 0; /* more methods */ } ArchiveDerived.hpp "Derived" being "Zip" or "Rar" #include "ArchiveBase.hpp" class ArchiveDerived : public ArchiveBase { public: ArchiveDerived(string path); void passThrough(ArchiveBase::Data& data); private: /* fields needed by minizip/unrarlib */ // example zip: unzFile zipFile_; // example rar: RARHANDLE rarFile_; } ArchiveDerived.cpp #include "ArchiveDerived.hpp" ArchiveDerived::ArchiveDerived(string path) { //implement } ArchiveDerived::passThrough(ArchiveBase::Data& data) { //implement } Somebody had suggested I use this design so that I could do: Archive archiveFile(pathToZipOrRar); archiveFile.passThrough(extractParams); // yay polymorphism! How do I write a cctor for Archive? What about op= for Archive? What can I do about "renaming" ArchiveBase::Data to Archive::Data? (Both minizip and unrarlib use such structs for input and output. Data is generic for Zip & Rar and later is used to create the respective library's struct.)

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• How to Obtain Data to Pre-Populate Forms.

  - by Stan

  The objective is to have a form reflect user's defined constraints on a search. At first, I relied entirely upon server-side scripting to achieve this; recently I tried to shift the functionality to JavaScript. On the server side, the search parameters are stored in a ColdFusion struct which makes it particularly convenient to have the data JSON'ed and sent to the client. Then it's just a matter of separately iterating over 'checkable' and text fields to reflect the user's search parameters; jQuery proved to be exceptionally effective in simplifying the workload. One observable difference lies in performance. The second method appeared to be somewhat slower and didn't work in IE8. Evidently, the returned JSON'ed struct was seen as an empty object. I'm sure it can be fixed, though before spending any more time with it, I'm curious to hear how others would approach the task. I'd gladly appreciate any suggestions. --Stan

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• No Binary File Generation

  - by Nathan Campos

  I've just bought a new laptop for me on the travel, then on my free time, I've started to test MinGW on it by trying to compile my own OS that is written in C++, then I've created all the files needed and the kernel.cpp: extern "C" void _main(struct multiboot_data* mbd, unsigned int magic); void _main( struct multiboot_data* mbd, unsigned int magic ) { char * boot_loader_name =(char*) ((long*)mbd)[16]; /* Print a letter to screen to see everything is working: */ unsigned char *videoram = (unsigned char *) 0xb8000; videoram[0] = 65; /* character 'A' */ videoram[1] = 0x07; /* forground, background color. */ } And tried to compile it with g++ G: g++ -o C:\kernel.o -c kernel.cpp -Wall -Wextra -Werror -nostdlib -nostartfiles -nodefaultlibs kernel.cpp: In function `void _main(multiboot_data*, unsigned int)': kernel.cpp:8: warning: unused variable 'boot_loader_name' kernel.cpp: At global scope: kernel.cpp:4: warning: unused parameter 'magic' G: But it don't create any binary file at C:/, what can I do?

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• UDP checksum calculation

  - by Deepak Konidena

  Hi, The UDP header struct defined at /usr/include/netinet/udp.h is as follows struct udphdr { u_int16_t source; u_int16_t dest; u_int16_t len; u_int16_t check; }; What value is stored in the check field of the header? How to verify if the checksum is correct? I meant on what data is the checksum computed? (Is it just the udp header or udp header plus the payload that follows it?) Thanks.

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• How to free member (i.e BSTR, SAFEARRAY, VARIANT) of an IDL User Defined Structure which is encapsul

  - by Picaro De Vosio

  Hi, I have a structure defined in IDL. This structure has following members: { BSTR m_sFirst; BSTR m_sSecond; VARIANT m_vChildStruct; //This member encapsulate a sub structure SAFEARRAY __RPC_FAR * m_saArray; }CustomINFO; I am allocating the memory for the structs using CoTaskMemAlloc and encapsulating it in Variant as follows: vV-vt = VT_RECORD; vV-pvRecord = pStruct; //Pointer of sturct vV-pRecInfo = pRI; //RecordInfo Interface Is it enough to call VariantClear to deallocate the memory of struct and its members? Will it also release the IRecordInfo interface? Or i have to manually get the encapsulated struct and deallocate each member myself and then use CoTaskMemFree to deallocate sturct. Thanks Picaro De Vosio

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• Avoiding improper std::string initialization with NULL const char* using g++

  - by pachanga

  A there any g++ options which can detect improper initialization of std::string with NULL const char*? I was in the process of turning some int fields into std::string ones, i.e: struct Foo { int id; Foo() : id(0) {} }; ...turned into: struct Foo { std::string id; Foo() : id(0) {} //oooops! }; I completely overlooked bad 'id' initialization with 0 and g++ gave me no warnings at all. This error was detected in the run time(std::string constructor threw an exception) but I'd really like to detect such stuff in the compile time. Is there any way?

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• Sening a file from memory (rather than disk) over HTTP using libcurl

  - by cinek1lol

  Hi! I would like to send pictures via a program written in C + +. - OK WinExec("C:\\curl\\curl.exe -H Expect: -F \"fileupload=@C:\\curl\\ok.jpg\" -F \"xml=yes\" -# \"http://www.imageshack.us/index.php\" -o data.txt -A \"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1\" -e \"http://www.imageshack.us\"", NULL); It works, but I would like to send the pictures from pre-loaded carrier to a variable char (you know what I mean? First off, I load the pictures into a variable and then send the variable), cause now I have to specify the path of the picture on a disk. I wanted to write this program in c++ by using the curl library, not through exe. extension. I have also found such a program (which has been modified by me a bit) #include <stdio.h> #include <string.h> #include <iostream> #include <curl/curl.h> #include <curl/types.h> #include <curl/easy.h> int main(int argc, char *argv[]) { CURL *curl; CURLcode res; struct curl_httppost *formpost=NULL; struct curl_httppost *lastptr=NULL; struct curl_slist *headerlist=NULL; static const char buf[] = "Expect:"; curl_global_init(CURL_GLOBAL_ALL); /* Fill in the file upload field */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "send", CURLFORM_FILE, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "nowy.jpg", CURLFORM_COPYCONTENTS, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "submit", CURLFORM_COPYCONTENTS, "send", CURLFORM_END); curl = curl_easy_init(); headerlist = curl_slist_append(headerlist, buf); if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "http://www.imageshack.us/index.php"); if ( (argc == 2) && (!strcmp(argv[1], "xml=yes")) ) curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist); curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost); res = curl_easy_perform(curl); curl_easy_cleanup(curl); curl_formfree(formpost); curl_slist_free_all (headerlist); } system("pause"); return 0; }

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• Compiler warning when passing NSError ** as a method parameter

  - by splicer

  I've been scratching my head about this for the last 4 hours, trying out all kinds of little experiments, but I can't seem to figure out what's going wrong. Could this be a compiler bug? Test.m: - (id)initWithContentsOfURL:(NSURL *)aURL error:(NSError **)error { if (!(self = [super init])) { return nil; } return self; } main.m: NSError *error; Test *t = [[Test alloc] initWithContentsOfURL:[NSURL fileURLWithPath:@"/"] error:&error]; Here's the compiler warning (from main.m): warning: incompatible Objective-C types 'struct NSError **', expected 'struct NSDictionary **' when passing argument 2 of 'initWithContentsOfURL:error:' from distinct Objective-C type I'm using the latest versions of Xcode and Snow Leopard.

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• Why is a fixed size buffers (arrays) must be unsafe?

  - by brickner

  Let's say I want to have a value type of 7 bytes (or 3 or 777). I can define it like that: public struct Buffer71 { public byte b0; public byte b1; public byte b2; public byte b3; public byte b4; public byte b5; public byte b6; } A simpler way to define it is using a fixed buffer public struct Buffer72 { public unsafe fixed byte bs[7]; } Of course the second definition is simpler. The problem lies with the unsafe keyword that must be provided for fixed buffers. I understand that this is implemented using pointers and hence unsafe. My question is why does it have to be unsafe? Why can't C# provide arbitrary constant length arrays and keep them as a value type instead of making it a C# reference type array or unsafe buffers?

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• Exception_Record in python2.5 problem

  - by amir

  I'm using Python2.5 & the following code produce 2 errors. Can any body help me? class EXCEPTION_RECORD(Structure): _fields_ = [ ("ExceptionCode", DWORD), ("ExceptionFlags", DWORD), ("ExceptionRecord", POINTER(EXCEPTION_RECORD)), ("ExceptionAddress", LPVOID), ("NumberParameters", DWORD), ("ExceptionInformation", ULONG_PTR * EXCEPTION_MAXIMUM_PARAMETERS)] Python Error: Traceback (most recent call last): File "E:\Python25\my_debugger_defines.py", line 70, in <module> class EXCEPTION_RECORD(Structure): File "E:\Python25\my_debugger_defines.py", line 74, in EXCEPTION_RECORD ("ExceptionRecord", POINTER(EXCEPTION_RECORD)), NameError: name 'EXCEPTION_RECORD' is not defined Microsoft Document: The EXCEPTION_RECORD structure describes an exception. typedef struct _EXCEPTION_RECORD { // exr DWORD ExceptionCode; DWORD ExceptionFlags; struct _EXCEPTION_RECORD *ExceptionRecord; PVOID ExceptionAddress; DWORD NumberParameters; DWORD ExceptionInformation[EXCEPTION_MAXIMUM_PARAMETERS]; } EXCEPTION_RECORD; Thanks in advance

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• What is a convenient base for a bignum library & primality testing algorithm?

  - by nn

  Hi, I am to program the Solovay-Strassen primality test presented in the original paper on RSA. Additionally I will need to write a small bignum library, and so when searching for a convenient representation for bignum I came across this [specification][1]: struct { int sign; int size; int *tab; } bignum; I will also be writing a multiplication routine using the Karatsuba method. So, for my question: What base would be convenient to store integer data in the bignum struct? Note: I am not allowed to use third party or built-in implementations for bignum such as GMP. Thank you.

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