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  • Creating Instance of Python Extension Type in C

    - by Brad Zeis
    I am writing a simple Vector implementation as a Python extension module in C that looks mostly like this: typedef struct { PyObject_HEAD double x; double y; } Vector; static PyTypeObject Vector_Type = { ... }; It is very simple to create instances of Vector while calling from Python, but I need to create a Vector instance in the same extension module. I looked in the documentation but I couldn't find a clear answer. What's the best way to do this?

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  • status failed for LdrLoadDll

    - by kiddo
    hello all,I'am trying to work-out the LdrLoadDll function and am having no luck with that..i also googled for some examples there is no much documentation or correct example about this.I know what it exactly does..Please check the code below. //declaration function pointer for LdrLoadDll typedef NTSTATUS (_stdcall*fp_LdrLoadDll)( IN PWCHAR PathToFile OPTIONAL, IN ULONG Flags OPTIONAL, IN PUNICODE_STRING ModuleFileName, OUT PHANDLE ModuleHandle ); //calling LdrLoadDll using getprocaddress HANDLE handle; HMODULE module = LoadLibrary(L"ntdll.dll"); fp_LdrLoadDll loadDll; loadDll = (fp_LdrLoadDll)GetProcAddress(module,"LdrLoadDll"); if(loadDll == NULL) { MessageBox(0,L"Not able to load the function",L"LdrLoadDll",&handle); } UNICODE_STRING input; input.Buffer = L"C:\\Desktop\\myDll.dll"; input.Length = wcslen(input.Buffer)*2; input.MaximumLength = wcslen(input.Buffer) +2; NTSTATUS status = loadDll(NULL,LOAD_WITH_ALTERED_SEARCH_PATH,&input,0); When i execute the above am not getting the handle niether valid status.Please help me with this.

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  • JNI: dll function works ok in C++ main, but not with dll wrapper

    - by Joseph Lim
    I have an a.dll (not modifiable as i do not have the source) with a function bool openPort(DWORD mem).I wrote a c++ main, loaded this dll using LoadLibrary, and the function works well.It returns true. Now, I need to call this function from Java via JNI. I wrote another b.dll with a function like so JNIEXPORT void JNICALL Java_MyClass_openPortFunc (JNIEnv *env, jobject obj, jint pMemPhy) { hInstLibrary = LoadLibrary("a.dll"); typedef bool (*openPort)(DWORD); openPort _openPort; _openPort = (openPort)GetProcAddress(hInstLibrary, "openPort"); DWORD memAddr = 0xda000; if(_openPort(memAddr)){ cout << "ok" << endl; }else{ cout << "failed " << endl; } } This however, causes the openPort to return false despite using the same parameters. I hope someone can advise me. Thank you. :)

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  • C++ STL map.find() not finding my stuff

    - by Joe
    Hello, I have constructed a map and loaded it with data. If I iterate over all the elements I see they are all valid. However, the find method doesn't find my item. I'm sure it's something stupid I am doing. Here is snippet: // definitions // I am inserting a person class and using the firstname as the key typedef std::map<char*,Person *> mapType; mapType _myMap; mapType::iterator _mapIter; ... Person *pers = new Person(FirstName, LastName, Address, Phone); _myMap.insert(make_pair(pers->firstName, pers); ... ...later.... _mapIter = _myMap.find(firstName); // returns map.end _mapIter = _myMap.find("joe"); // returns map.end and I have no idea why :(

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  • Copy a function in memory and execute it

    - by Elinghton
    Hi everybody, I would like to know how in C in can copy the content of a function into memroy and the execute it? I'm trying to do something like this: typedef void(*FUN)(int *); char * myNewFunc; char *allocExecutablePages (int pages) { template = (char *) valloc (getpagesize () * pages); if (mprotect (template, getpagesize (), PROT_READ|PROT_EXEC|PROT_WRITE) == -1) { perror ("mprotect"); } } void f1 (int *v) { *v = 10; } // allocate enough spcae but how much ?? myNewFunc = allocExecutablePages(...) /* Copy f1 somewere else * (how? assume that i know the size of f1 having done a (nm -S foo.o)) */ ((FUN)template)(&val); printf("%i",val); Thanks for your answers

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  • [SOLVED]Port C's fread(&struct,....) to Python

    - by user287669
    Hey, I'm really struggling with this one. I'am trying to port a small piece of someone else's code to Python and this is what I have: typedef struct { uint8_t Y[LUMA_HEIGHT][LUMA_WIDTH]; uint8_t Cb[CHROMA_HEIGHT][CHROMA_WIDTH]; uint8_t Cr[CHROMA_HEIGHT][CHROMA_WIDTH]; } __attribute__((__packed__)) frame_t; frame_t frame; while (! feof(stdin)) { fread(&frame, 1, sizeof(frame), stdin); // DO SOME STUFF } Later I need to access the data like so: frame.Y[x][y] So I made a Class 'frame' in Python and inserted the corresponding variables(frame.Y, frame.Cb, frame.Cr). I have tried to sequentially map the data from Y[0][0] to Cr[MAX][MAX], even printed out the C struct in action but didn't manage to wrap my head around the method used to put the data in there. I've been struggling overnight with this and have to get back to the army tonight, so any immediate help is very welcome and appreciated. Thanks

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  • Casting to global variable from LPVOID - C

    - by Jamie Keeling
    I am trying to cast data to a struct from a parameter passed into my method, I need the data to be passed to a global variable as it is needed elsewhere in my application. I have tried the following but I get errors saying that diceResult is an undeclared identifier Here is the code itself: //Structure to hold dice data typedef struct diceData { int dice1; int dice2; }; struct diceResult; DWORD WINAPI UnpackDiceData(LPVOID sentData) { //Unpack data struct diceData unpackedData = *((struct diceData*)sentData); diceResult.dice1 = unpackedData.dice1; diceResult.dice2 = unpackedData.dice2; } I don't understand why it won't recognise it being there when it's clearly global.

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  • Why am I getting a segmentation fault with this code?

    - by gooswa
    Trying to make a simple rectangle/bin packer in C. Takes a given area and finds placement for any given size rectangle. About after 4 recursions is when I get the segmentation fault. #include <stdio.h> #include <stdlib.h> typedef struct node_type PackNode; struct node_type { int x , y; int width , height; int used; struct node_type *left; struct node_type *right; }; typedef struct point_type PackPoint; struct point_type { int x,y; }; PackNode _clone(PackNode *node) { PackNode clone; clone.used = 0; clone.x = node->x; clone.y = node->y; clone.width = node->width; clone.height= node->height; clone.left = NULL; clone.right= NULL; return clone; } PackNode root; int rcount; PackPoint* recursiveFind(PackNode *node, int w, int h) { PackPoint rp; PackPoint *p = NULL; rcount++; printf ("rcount = %u\n", rcount); //left is not null go to left, if left didn't work try right. if (node->left!=NULL) { //move down to left branch p = recursiveFind(node->left, w, h); if (p!=NULL) { return p; } else { p = recursiveFind(node->right, w, h); return p; } } else { //If used just return null and possible go to the right branch; if (node->used==1 || w > node->width || h > node->height) { return p; } //if current node is exact size and hasn't been used it return the x,y of the mid-point of the rectangle if (w==node->width && h == node->height) { node->used=1; rp.x = node->x+(w/2); rp.y = node->y+(h/2); p = &rp; return p; } //If rectangle wasn't exact fit, create branches from cloning it's parent. PackNode l_clone = _clone(node); PackNode r_clone = _clone(node); node->left = &l_clone; node->right = &r_clone; //adjust branches accordingly, split up the current unused areas if ( (node->width - w) > (node->height - h) ) { node->left->width = w; node->right->x = node->x + w; node->right->width = node->width - w; } else { node->left->height = h; node->right->y = node->y + h; node->right->height = node->height - h; } p = recursiveFind(node->left, w, h); return p; } return p; } int main(void) { root = malloc( root.x=0; root.y=0; root.used=0; root.width=1000; root.height=1000; root.left=NULL; root.right=NULL; int i; PackPoint *pnt; int rw; int rh; for (i=0;i<10;i++) { rw = random()%20+1; rh = random()%20+1; pnt = recursiveFind(&root, rw, rh); printf("pnt.x,y: %d,%d\n",pnt->x,pnt->y); } return 0; }

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  • Fault address when malloc/free pthread_t across threads

    - by scleung
    Fault address occurred when i malloc pthread_t to save a newly created thread id and free it in another thread. Codes as follows: typedef struct _TaskInfo { // int dummy_int; pthread_t tid; } TaskInfo; void* dummy_task(void* pArg) { free(pArg); return NULL; } void create_task() { TaskInfo *pInfo; pthread_attr_t attr; // set detached state stuff ... pInfo = (TaskInfo*) malloc(sizeof(TaskInfo)); pthread_create(&pInfo->tid, &attr, dummy_task, pInfo); // destroy pthread attribute stuff ... } int main() { int i; while(i < 10000) { create_task(); ++i; } return 0; } When I uncomment the member dummy_int of TaskInfo it sometimes ran successfully, but sometimes failed. My platform is VMWare + Ubuntu 9.10 + ndk r3 Thanks!

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  • winsock compile crash

    - by ioil
    The following errors are from a file with just windows and winsock2 included. C:\Users\ioil\Desktop\dm\bin>dmc sockit.c typedef struct fd_set { ^ C:\Users\ioil\Desktop\dm\bin\..\include\win32\WINSOCK2.H(85) : Error: 'fd_set' is already defined } fd_set; ^ C:\Users\ioil\Desktop\dm\bin\..\include\win32\WINSOCK2.H(88) : Error: identifier or '( declarator )' expected struct timeval { ^ C:\Users\ioil\Desktop\dm\bin\..\include\win32\WINSOCK2.H(129) : Error: 'timeval' is already defined }; ^ C:\Users\ioil\Desktop\dm\bin\..\include\win32\WINSOCK2.H(132) : Error: identifier or '( declarator )' expected struct hostent { ^ C:\Users\ioil\Desktop\dm\bin\..\include\win32\WINSOCK2.H(185) : Error: 'hostent' is already defined Fatal error: too many errors --- errorlevel 1 C:\Users\ioil\Desktop\dm\bin> What's already been tried : placing the winsock.dll file in the same directory as the compiler and program to be compiled, placing it in the system32 directory, and entering it in the registry with the regsrv32 command. Don't really know where to go from here, appreciate any advice . . .

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  • Is it a good practice to pass struct object as parameter to a function in c++?

    - by tsubasa
    I tried an example live below: typedef struct point { int x; int y; } point; void cp(point p) { cout<<p.x<<endl; cout<<p.y<<endl; } int main() { point p1; p1.x=1; p1.y=2; cp(p1); } The result thats printed out is: 1 2 which is what I expected. My question is: Does parameter p get the full copy of object p1? If so, I wonder if this is a good practice? (I assumed when the struct gets big in size, this will create a lot of copy overhead).

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  • C error expected specifier-qualifier-list before ‘time_t’

    - by ambika
    I got the error from error.c:31: /usr/include/ap/mas.h:254: error: expected specifier-qualifier-list before ‘time_t’ make: *** [error.o] Error 1 Feedback We at least need to see line 31 of error.c and line 254 of mas.h, with preferably a few lines of context around each. This error may have nothing to do with how time_t is being declared. – John Bode Then I check in error.c (line no 31) -- #include "mas.h" then I check line no 254 in mas.h. in mas.h #include <sys/types.h> typedef struct _x{ time_t time; }x; Can anybody suggest where I am going wrong?

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  • c++ to vb.net , problem with callback function

    - by johan
    I'm having a hard time here trying to find a solution for my problem. I'm trying to convert a client API funktion from C++ to VB.NET, and i think have some problems with the callback function. parts of the C++ code: typedef struct{ BYTE m_bRemoteChannel; BYTE m_bSendMode; BYTE m_nImgFormat; // =0 cif ; = 1 qcif char *m_sIPAddress; char *m_sUserName; char *m_sUserPassword; BOOL m_bUserCheck; HWND m_hShowVideo; }CLIENT_VIDEOINFO, *PCLIENT_VIDEOINFO; CPLAYER_API LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo,void(CALLBACK *ReadDataCallBack)(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize)); void CALLBACK ReadDataCallBack(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize) { TRACE("%d\n",nPacketSize); } ..... aa5.m_sUserName = "123"; aa5.m_sUserPassword="w"; aa5.m_bUserCheck = TRUE; MP4_ClientSetTTL(64); nn1 = MP4_ClientStart(&aa5,ReadDataCallBack); if (nn1 == -1) { MessageBox("error"); return; } SDK description: MP4_ClientStart This function starts a connection. The format of the call is: LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo, void(*ReadDataCallBack)(DWORD nChannel,UCHAR *pPacketBuffer,DWORD nPacketSize)) Parameters pClientinfo holds the information. of this connection. nChannel holds the channel of card. pPacketBuffer holds the pointer to the receive buffer. nPacketSize holds the length of the receive buffer. Return Values If the function succeeds the return value is the context of this connection. If the function fails the return value is -1. Remarks typedef struct{ BYTE m_bRemoteChannel; BYTE m_bSendMode; BYTE m_bImgFormat; char *m_sIPAddress; char *m_sUserName; char *m_sUserPassword; BOOL m_bUserCheck; HWND m_hShowVideo; } CLIENT_VIDEOINFO, * PCLIENT_VIDEOINFO; m_bRemoteChannel holds the channel which the client wants to connect to. m_bSendMode holds the network mode of the connection. m_bImgFormat : Image format, 0 is main channel video, 1 is sub channel video m_sIPAddress holds the IP address of the server. m_sUserName holds the user’s name. m_sUserPassword holds the user’s password. m_bUserCheck holds the value whether sends the user’s name and password or not. m_hShowVideo holds Handle for this video window. If m_hShowVideo holds NULL, the client can be record only without decoder. If m_bUserCheck is FALSE, we will send m_sUserName and m_sUserPassword as NULL, else we will send each 50 bytes. The length of m_sIPAddress and m_sUserName must be more than 50 bytes. ReadDataCallBack: When the library receives a packet from a server, this callback is called. My VB.Net code: Imports System.Runtime.InteropServices Public Class Form1 Const WM_USER = &H400 Public Structure CLIENT_VIDEOINFO Public m_bRemoteChannel As Byte Public m_bSendMode As Byte Public m_bImgFormat As Byte Public m_sIPAddress As String Public m_sUserName As String Public m_sUserPassword As String Public m_bUserCheck As Boolean Public m_hShowVideo As Long 'hWnd End Structure Public Declare Function MP4_ClientSetNetPort Lib "hikclient.dll" (ByVal dServerPort As Integer, ByVal dClientPort As Integer) As Boolean Public Declare Function MP4_ClientStartup Lib "hikclient.dll" (ByVal nMessage As UInteger, ByVal hWnd As System.IntPtr) As Boolean <DllImport("hikclient.dll")> Public Shared Function MP4_ClientStart(ByVal Clientinfo As CLIENT_VIDEOINFO, ByRef ReadDataCallBack As CALLBACKdel) As Long End Function Public Delegate Sub CALLBACKdel(ByVal nPort As Long, <MarshalAs(UnmanagedType.LPArray)> ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) Public Sub CALLBACK(ByVal nPort As Long, <MarshalAs(UnmanagedType.LPArray)> ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) End Sub Public mydel As New CALLBACKdel(AddressOf CALLBACK) Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim Clientinfo As New CLIENT_VIDEOINFO() Clientinfo.m_bRemoteChannel = 0 Clientinfo.m_bSendMode = 0 Clientinfo.m_bImgFormat = 0 Clientinfo.m_sIPAddress = "193.168.1.100" Clientinfo.m_sUserName = "1" Clientinfo.m_sUserPassword = "a" Clientinfo.m_bUserCheck = False Clientinfo.m_hShowVideo = Me.Handle 'Nothing MP4_ClientSetNetPort(850, 850) MP4_ClientStartup(WM_USER + 1, Me.Handle) MP4_ClientStart(Clientinfo, mydel) End Sub End Class here is some other examples of the code in: C# http://blog.csdn.net/nenith1981/archive/2007/09/17/1787692.aspx VB ://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/hikclient.bas__.htm ://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/Form1.frm__.htm Delphi ://read.pudn.com/downloads91/sourcecode/multimedia/streaming/349759/Delphi_client/Unit1.pas__.htm

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  • C++ Structure within itself?

    - by Douglas
    I've been trying to port this code to python, but there is something I do not quite understand in C++ (I do know a bit of C++ but this is beyond me): typedef struct huffnode_s { struct huffnode_s *zero; struct huffnode_s *one; unsigned char val; float freq; } huffnode_t; What I don't get is how huffnode_s can be within itself, I've never seen this before and don't quite understand it. What does this mean, and if someone can, what would be the python equivalent?

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  • Getting plane slices from array data

    - by umanga
    Greetings all, I read 3d grid data (from multiple TIF images) into a structure as follows : typedef struct VolumeData{ int nx; int ny; int nz; unsigned char *data; // size is nx*ny*nz } Now I want to get the plane slices from this 1-D grid data: eg: unsigned char* getXYPlaneStack(VolumeData *vol,int z); I could implement above function because the *data array stores image stack. But i am having difficult time implement along the other axes: unsigned char* getYZPlaneStack(VolumeData *vol,int x); and unsigned char* getXZPlaneStack(VolumeData *vol,int y); any easy algorithm for this? thanks in advance.

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  • C errors - Cannot combine with previous 'struct' declaration specifier && Redefinition of 'MyMIDINotifyProc' as different kind of symbol

    - by user1905634
    I'm still new to C but trying to understand it better by working my way through a small MIDI audio unit (in Xcode 4.3.3). I've been searching for an answer to this all day and still don't even understand exactly what the problem is. Here's the code in question: //MyMIDINotifyProc.h #ifndef MIDIInstrumentUnit_CallbackProcs_h #define MIDIInstrumentUnit_CallbackProcs_h void MyMIDINotifyProc (const MIDINotification *message, void *refCon); #endif //MyMIDINotifyProc.c #include <CoreMIDI/CoreMIDI.h> #include "MyMIDINotifyProc.h" void MyMIDINotifyProc (const MIDINotification *message, void *refCon) { //manage notification } In the header definition I get this: ! Cannot combine with previous 'struct' declaration specifier I've made sure the definitions match and tried renaming them and I still get this in my .c file: ! Redefinition of 'MyMIDINotifyProc' as different kind of symbol Which points to the .h definition as the 'Previous definition'. I know that MIDIServices.h in the CoreMIDI framework defines: typedef void (*MIDINotifyProc)(const MIDINotification *message, void *refCon); But I don't understand if/why that would cause an error. I would be grateful if anyone could offer some help.

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  • Auto pointer for unsigned char array?

    - by Gianluca
    I'd need a class like std::auto_ptr for an array of unsigned char*, allocated with new[]. But auto_ptr only calls delete and not delete[], so i can't use it. I also need to have a function which creates and returns the array. I came out with my own implementation within a class ArrayDeleter, which i use like in this example: #include <Utils/ArrayDeleter.hxx> typedef Utils::ArrayDeleter<unsigned char> Bytes; void f() { // Create array with new unsigned char* xBytes = new unsigned char[10]; // pass array to constructor of ArrayDeleter and // wrap it into auto_ptr return std::auto_ptr<Bytes>(new Bytes(xBytes)); } ... // usage of return value { auto_ptr<Bytes> xBytes(f()); }// unsigned char* is destroyed with delete[] in destructor of ArrayDeleter Is there a more elegant way to solve this? (Even using another "popular" library)

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  • What is the ISO C++ way to directly define a conversion function to reference to array?

    - by ben
    According to the standard, a conversion function has a function-id operator conversion-type-id, which would look like, say, operator char(&)[4] I believe. But I cannot figure out where to put the function parameter list. gcc does not accept either of operator char(&())[4] or operator char(&)[4]() or anything I can think of. Now, gcc seems to accept (&operator char ())[4] but clang does not, and I am inclined to not either, since it does not seem to fit the grammar as I understand it. I do not want to use a typedef because I want to avoid polluting the namespace with it.

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  • Constructor/Destructor involving a class and a struct

    - by Bogdan Maier
    I am working on a program and need to make an array of objects, specifically I have a 31x1 array where each position is an object, (each object is basically built out of 6 ints). Here is what I have but something is wrong and i could use some help thank you. 31x1 struct header" const int days=31; struct Arr{ int days; int *M; }; typedef Arr* Array; 31x1 matrix constructor: void constr(){ int *M; M = new Expe[31]; // Expe is the class class header: class Expe { private: //0-HouseKeeping, 1-Food, 2-Transport, 3-Clothing, 4-TelNet, 5-others int *obj; } Class object constructor: Expe::Expe() { this->obj=new int[6]; } help please... because i`m pretty lost.

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  • Segmentation fault problem (C)

    - by user228938
    I have a struct named Game with an array of levels, defined like this: typedef struct { Level levels[x]; } Game; When I compile the code, if x is 1, 2 or 3, the program runs normally. If it's any other value (4, for instance), I get a segmentation fault. I'm not accessing the array anywhere. Main is something like this at the moment (commented everything except the initialization): int main (...) { Game g; return 0; } Any clue of what this might be? Thanks in advance.

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  • a nicer way to create structs in a loop

    - by sandra
    Hi guys, I haven't coded in C++ in ages. And recently, I'm trying to work on something involving structs. Like this typedef struct{ int x; int y; } Point; Then in a loop, I'm trying to create new structs and put pointers to them them in a list. Point* p; int i, j; while (condition){ // compute values for i and j with some function... p = new Point; p* = {i, j}; //initialize my struct. list.append(p); //append this pointer to my list. } Now, my question is it possible to simplify this? I mean, the pointer variable *p outside of the loop and calling p = new Point inside the loop. Isn't there a better/nicer syntax for this?

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  • Can someone explain how pointer to pointer works?

    - by user3549560
    I don't really understand how the pointer to pointer works. Any way to do the same work without using pointer to pointer? struct customer{ char name[20]; char surname[20]; int code; float money; }; typedef struct customer customer; void inserts(customer **tmp) { *tmp = (customer*)malloc(sizeof(customer)); puts("Give me a customer name, surname code and money"); scanf("%s %s %d %f", (*tmp)->name, (*tmp)->surname, &(*tmp)->code,&(*tmp)->money); }

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  • C++ function-pointer and inheritance

    - by pingvinus
    In parent class I have function, that operates under an array of functions, declared in child-class, number of functions for every child-class may vary. But since every function uses some object-variables, I can't declare them as static. I've try to do something like this: class A { public: typedef int (A::*func)(); func * fs; void f() { /*call functions from this->fs*/ } }; class B : public A { public: int smth; B(int smth) { this->smth = smth; this->fs = new func[1]; fs[0] = &B::f; } int f() { return smth + 1; } }; But, obviously it doesn't work. Any suggestions?

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  • Designing an API with compile-time option to remove first parameter to most functions and use a glob

    - by tomlogic
    I'm trying to design a portable API in ANSI C89/ISO C90 to access a wireless networking device on a serial interface. The library will have multiple network layers, and various versions need to run on embedded devices as small as an 8-bit micro with 32K of code and 2K of data, on up to embedded devices with a megabyte or more of code and data. In most cases, the target processor will have a single network interface and I'll want to use a single global structure with all state information for that device. I don't want to pass a pointer to that structure through the network layers. In a few cases (e.g., device with more resources that needs to live on two networks) I will interface to multiple devices, each with their own global state, and will need to pass a pointer to that state (or an index to a state array) through the layers. I came up with two possible solutions, but neither one is particularly pretty. Keep in mind that the full driver will potentially be 20,000 lines or more, cover multiple files, and contain hundreds of functions. The first solution requires a macro that discards the first parameter for every function that needs to access the global state: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define foo_function( x, a, b, c) _foo_function( x, a, b, c) #define bar_function( x) _bar_function( x) #else extern dev_t DEV; #define IFACE (&DEV) #define foo_function( x, a, b, c) _foo_function( a, b, c) #define bar_function( x) _bar_function( ) #endif int bar_function( dev_t *IFACE); int foo_function( dev_t *IFACE, int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( dev_t *IFACE) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( dev_t *IFACE, int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The second solution defines macros to use in the function declarations: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define DEV_PARAM_ONLY dev_t *IFACE #define DEV_PARAM DEV_PARAM_ONLY, #else extern dev_t DEV; #define IFACE (&DEV) #define DEV_PARAM_ONLY void #define DEV_PARAM #endif int bar_function( DEV_PARAM_ONLY); // I don't like the missing comma between DEV_PARAM and arg2... int foo_function( DEV_PARAM int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( DEV_PARAM_ONLY) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( DEV_PARAM int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The C code to access either method remains the same: // multi.c - example of multiple interfaces #define IF_MULTI #include "network.h" dev_t if0, if1; int main() { foo_function( &if0, -1, 3.1415926, "public"); foo_function( &if1, 42, 3.1415926, "private"); return 0; } // single.c - example of a single interface #include "network.h" int main() { foo_function( 11, 1.0, "network"); return 0; } Is there a cleaner method that I haven't figured out? I lean toward the second since it should be easier to maintain, and it's clearer that there's some macro magic in the parameters to the function. Also, the first method requires prefixing the function names with "_" when I want to use them as function pointers. I really do want to remove the parameter in the "single interface" case to eliminate unnecessary code to push the parameter onto the stack, and to allow the function to access the first "real" parameter in a register instead of loading it from the stack. And, if at all possible, I don't want to have to maintain two separate codebases. Thoughts? Ideas? Examples of something similar in existing code? (Note that using C++ isn't an option, since some of the planned targets don't have a C++ compiler available.)

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