Дискуссия о распределении памяти в ОС

#include <Windows.h>
#include <stdio.h>
 
WCHAR GetDriveWithMaxFreeSpace(ULARGE_INTEGER *pTotalAvailable);
 
int main() {
    ULARGE_INTEGER uMaxAvailable;
    LARGE_INTEGER szSwapSize;
    WCHAR chDrive,
          pszSwapFile[] = L"A:\\swap.map";
    HANDLE hFile = NULL,
           hMap = NULL;
    PBYTE pbData = NULL;
    int iRet = 0;
 
    if ((chDrive = GetDriveWithMaxFreeSpace(&uMaxAvailable)) == NULL) {
        printf("Unable to get drive\r\n"); iRet = 1;
        goto CleanUp;
    }
 
    pszSwapFile[0] = chDrive;
 
    if ((hFile = CreateFile(pszSwapFile, GENERIC_READ | GENERIC_WRITE, 0, NULL, 
                            CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) == INVALID_HANDLE_VALUE) {
        printf("Unable to create swap file\r\n"); iRet = 2;
        goto CleanUp;
    }
    
    if (uMaxAvailable.QuadPart < 0x1900000000) {
 
        szSwapSize.QuadPart = uMaxAvailable.QuadPart;
        printf("Available max %I64u bytes\r\n", szSwapSize.QuadPart);
 
    } else {
        szSwapSize.QuadPart = 0x1900000000;
    }
 
    if (!SetFilePointerEx(hFile, szSwapSize, NULL, FILE_BEGIN)) {
        printf("Unable to set file pointer\r\n"); iRet = 3;
        goto CleanUp;
    }
 
    if (!SetEndOfFile(hFile)) {
        printf("Unable to expand file\r\n"); iRet = 4;
        goto CleanUp;
    }
 
    if ((hMap = CreateFileMapping(hFile, NULL, PAGE_READWRITE, 0, 0, NULL)) == NULL) {
        printf("Unable to create file mapping\r\n"); iRet = 5;
        goto CleanUp;
    }
 
 
    if ((pbData = (PBYTE)MapViewOfFile(hMap, FILE_MAP_WRITE, 0, 0, 0)) == NULL) {
        printf("Unable to map mapping\r\n"); iRet = 6;
        goto CleanUp;
    }
 
    printf("Memory filling in progress...\r\n");
 
    for (UINT64 i = 0; i < szSwapSize.QuadPart; i++)
        pbData[i] = 1;
    
    printf("Done\r\n");
    getchar();
 
CleanUp:
 
    if (pbData)
        UnmapViewOfFile(pbData);
 
    if (hMap)
        CloseHandle(hMap);
 
    if (hFile)
        CloseHandle(hFile);
 
    return iRet;
}
 
WCHAR GetDriveWithMaxFreeSpace( 
      ULARGE_INTEGER *pTotalAvailable) {
    DWORD dwMask = GetLogicalDrives();
    DWORD dwDrive = 1;
    WCHAR chName = 'A',
          chRet = '\0';
    ULARGE_INTEGER uSize = {0, 0};
    
    while (dwMask) {
        
        if (dwMask & dwDrive) {
 
            WCHAR pszDrive[4] = L"A:\\";
            ULARGE_INTEGER uCurSize;
 
            pszDrive[0] = chName;
 
            if (GetDiskFreeSpaceEx(pszDrive, &uCurSize, NULL, NULL)) {
                if (uCurSize.QuadPart > uSize.QuadPart) {
                    uSize = uCurSize; chRet = chName;
                }
            }
 
            dwMask ^= dwDrive;
 
        }
 
        chName++;
        dwDrive <<= 1;
    
    }
 
    *pTotalAvailable = uSize;
    return chRet;
 
}