内存映射文件初步学习

最新推荐文章于 2023-06-08 19:25:32 发布

jyytest

最新推荐文章于 2023-06-08 19:25:32 发布

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文章标签： null file

本文链接：https://blog.youkuaiyun.com/jyytest/article/details/4051581

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HANDLE hFile = NULL;
HANDLE hFileMaping = NULL;
SYSTEM_INFO sysInfo;
GetSystemInfo(&sysInfo);
DWORD dwPageSize = sysInfo.dwAllocationGranularity;

do
{
  hFile = CreateFileW(L"D://pfsvoddata.bbv", GENERIC_READ,
       FILE_SHARE_READ, NULL, OPEN_ALWAYS,
       FILE_ATTRIBUTE_NORMAL, NULL);

  if (INVALID_HANDLE_VALUE == hFile)
  {
   break;
  }

  hFileMaping = CreateFileMappingW(hFile, NULL, PAGE_READONLY, 0, 0,
           L"jyytest");
  if (NULL == hFileMaping)
  {
   break;
  }
  CloseHandle(hFile);
  hFile = NULL;

  DWORD dwFileHight = 0;;
  __int64 n64FileSize = GetFileSize(hFile, &dwFileHight);
  n64FileSize += ((__int64) dwFileHight) << 32;
  __int64 n64FileMapOffSet = 0;

  do
  {
   DWORD dwMapSize = dwPageSize;
   if (dwMapSize > n64FileSize)
   {
    dwMapSize = (DWORD) n64FileSize;
   }

DWORD dwOffsetLow =(DWORD) (n64FileMapOffSet & 0x00000000FFFFFFFF);
DWORD dwOffsetHight = (DWORD) ((n64FileMapOffSet & 0xFFFFFFFF00000000) >> 32);

   int *pValue = (int *) MapViewOfFile(hFileMaping, FILE_SHARE_READ,
            dwOffsetHight, dwOffsetLow, dwMapSize); //特别要注意一次的偏移为64K的整数倍
   if (NULL == pValue)
   {
    UnmapViewOfFile(pValue);

break;
}

n64FileMapOffSet += dwMapSize;
n64FileSize -= dwMapSize;

UnmapViewOfFile(pValue);

} while (n64FileSize > 0);

} while (0);

getchar();