C / C++ / MFC

// process1.c
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>

#define BUF_SIZE 2048

char *szName = "Global\MyFileMappingObject";
char *pSharedBuffer;

int addMsg(char *msg, char *buffer)
{
    long msgCount, curMsgIndex, curMsgLen;
    char *newStrPos;

    // get count of messages stored
    memcpy(&msgCount, buffer, sizeof(long));

    // first message begins after sizeof(long) bytes - since we stored the num of messages as a long
    newStrPos = (char*) (long)buffer + sizeof(long);

    // step through the buffer, until we find the next free space to insert a new message
    for (curMsgIndex=0; curMsgIndex<msgCount; curMsgIndex++)
    {
        curMsgLen = strlen(newStrPos);
        newStrPos += curMsgLen + 1;
    }

    // copy the message
    strcpy(newStrPos, msg);

    // update the message count
    msgCount++;
    memcpy(buffer, &msgCount, sizeof(long));

    return 0;
}

int main()
{
    HANDLE handleMappedFile;
    LPVOID lpMsgBuf;

    handleMappedFile = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, HIWORD(BUF_SIZE), LOWORD(BUF_SIZE), szName);
    if (handleMappedFile == NULL)
    {
        printf("Could not create file mapping object.\n");
        LocalFree( lpMsgBuf );
        return 1;
    }

    pSharedBuffer = (char*)MapViewOfFile(handleMappedFile, FILE_MAP_ALL_ACCESS, 0, 0, BUF_SIZE);
    if (pSharedBuffer == NULL)
    {
        printf("Could not map view of file.\n");
        CloseHandle(handleMappedFile);
        return 1;
    }

    // initialize the shared mem
    memset((PVOID)pSharedBuffer, 0, sizeof(char) * BUF_SIZE);

    addMsg("This is msg 1", pSharedBuffer);
    addMsg("This is msg 2", pSharedBuffer);
    addMsg("This is msg 3", pSharedBuffer);

//    // code used to write mapped mem to a disk file for debugging purposes.
//    FILE *fp;
//    char *fName = "buffData.dat";
//    fp = fopen(fName, "wb");
//    fwrite(pSharedBuffer, 1, BUF_SIZE, fp);
//    fclose(fp);

    getch();
    UnmapViewOfFile(pSharedBuffer);
    printf("File unmapped\n");

    CloseHandle(handleMappedFile);
    printf("handle closed.\n");

    return 0;
}

// process2.c
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>

#define BUF_SIZE 2048
char *szName1= "Global\MyFileMappingObject";
char *pSharedBuffer;

int main()
{
    HANDLE hMappedFile;

    hMappedFile = OpenFileMapping(ILE_MAP_ALL_ACCESS, FALSE, szName1); // name of mapping object
    if (hMappedFile == NULL)
    {
        printf("Could not open file mapping object (%d).\n",GetLastError());
        return 1;
    }

    pSharedBuffer = MapViewOfFile(hMappedFile, FILE_MAP_ALL_ACCESS, 0, 0, BUF_SIZE);
    if (pSharedBuffer == NULL)
    {
        printf("Could not map view of file (%d).\n", GetLastError());
        CloseHandle(hMappedFile);
        return 1;
    }

    long msgCount, curMsgNum;
    char *curMsg;
    memcpy(&msgCount, pSharedBuffer, sizeof(long));
    printf("---- Messages retrieved: %d ----\n", msgCount);
    curMsg = (char*)pSharedBuffer + sizeof(long);
    for (curMsgNum=0; curMsgNum<msgCount; curMsgNum++)
    {
        printf("msg(%d): %s\n", curMsgNum, curMsg);
        curMsg += strlen(curMsg) + 1;
    }

    UnmapViewOfFile(pSharedBuffer);
    CloseHandle(hMappedFile);
    getch();
    return 0;
}

m_StVector.clear()

struct TestStruct {
   TestStruct() : tchTemp(0) {} // constructor initializes string pointer to 0
   ~TestStruct() { delete [] tchTemp; } // destructor frees string if needed
   void set(const TCHAR* stringvalue) {
      delete [] tchTemp; // release previously allocated memory
      if (stringvalue != 0) {
         // create a copy
         tchTemp = new TCHAR[_tcslen(stringvalue)+1];
         _tcscpy(stringvalue, tchTemp);
      }
      else {
         // reset pointer to 0
         tchTemp = 0;
      }
   }
   TCHAR* tchTemp;
};

void test() {
   std::vector<TestStruct> struct_vect;
   // now fill vector and work with it
   // ...
   struct_vect.clear(); // will delete and deconstruct all objects
}

Madan Chauhan wrote:

All the nodes become free but one that is very first node in the list does not free.

Madan Chauhan wrote:

Please give me some idea...

void main( void )
{
    for (int i = 0; i < 2; i++)
    {
        TEST_STRUCT *ptrCurrent;
        TEST_VECTORST wVectorSt = {0};
        wVectorSt.nVal = i + 1;
   
        for (int j = 0; j < 10; j++)
        {
            TEST_STRUCT *ptrTemp = (TEST_STRUCT *) calloc(1, sizeof(TEST_STRUCT));
            _tcscpy_s(ptrTemp->_tchTemp, _countof(ptrTemp->_tchTemp), _T(""));
            ptrTemp->dwTemp = 10 + j;
            ptrTemp->i64Temp = 100 + j;
            ptrTemp->Next = NULL;
  
            if (wVectorSt.m_ListInVector == NULL)
                wVectorSt.m_ListInVector = ptrTemp;
            else
                ptrCurrent->Next = ptrTemp;
  
            ptrCurrent = ptrTemp;
        }
  
        m_StVector.push_back(wVectorSt);
    }
  
    for (unsigned int i = 0; i < m_StVector.size(); i++)
    {
        TEST_STRUCT *ptrList = m_StVector[i].m_ListInVector;
        while (ptrList != NULL)
        {
            TEST_STRUCT *ptrTemp = ptrList;
            ptrList = ptrList->Next;
            free(ptrTemp);
        }
    } 
}