Memory-Mapped File Copy

#include <windows.h>
#include <stdio.h>
#include <errno.h>

int main (int argc, char *argv [])
{
  HANDLE hInFile, hOutFile;
  HANDLE hInMap, hOutMap;
  const void *pIn;
  void *pOut;
  DWORD dwSize;
  if (argc != 3) {
    printf ("Usage: cp file1 file2\n");
    return 1;
  }
  if ((hInFile=CreateFile(argv[1],
        GENERIC_READ,
        FILE_SHARE_READ,
        NULL,
        OPEN_EXISTING,
        FILE_FLAG_NO_BUFFERING,
        0))==INVALID_HANDLE_VALUE) {
    printf ("Error opening input file: %s. Error Number: %d",
          argv [1], GetLastError());
    return 2;
  }
  if ((dwSize=GetFileSize(hInFile, NULL))==0xffffffff) {
    printf ("Error getting input file size: %s. Error Number: %d",
          argv [1], GetLastError());
    return 2;
  }
  if ((hInMap=CreateFileMapping(hInFile,
        NULL,
        PAGE_READONLY,
        0,
        dwSize,
        NULL))==NULL) {
    printf ("Error creating input file mapping: %s. Error Number: %d",
          argv [1], GetLastError());
    return 2;
  }
  if ((pIn=MapViewOfFile(
      hInMap,
      FILE_MAP_READ,
      0, 0, dwSize))==NULL) {
    printf ("Error mapping view of input file: %s. Error Number: %d",
          argv [1], GetLastError());
    return 2;
  }
  if ((hOutFile=CreateFile(argv[2],
        GENERIC_READ|GENERIC_WRITE,
        0,
        NULL,
        CREATE_ALWAYS,
        FILE_FLAG_NO_BUFFERING,
        0))==INVALID_HANDLE_VALUE) {
    printf ("Error opening output file: %s. Error Number: %d",
          argv [2], GetLastError());
    return 2;
  }

  if ((hOutMap=CreateFileMapping(hOutFile,
        NULL,
        PAGE_READWRITE,
        0,
        dwSize,
        NULL))==NULL) {
    printf ("Error creating output file mapping. %s: Error Number: %d",
          argv [2], GetLastError());
    return 2;
  }
  if ((pOut=MapViewOfFile(
      hOutMap,
      FILE_MAP_WRITE,
      0, 0, dwSize))==NULL) {
    printf ("Error mapping view of output file. %s: Error Number: %d",
          argv [2], GetLastError());
    return 2;
  }
  CopyMemory(pOut, pIn, dwSize); /* Alternative to C library memcpy */
  UnmapViewOfFile (pIn);
  UnmapViewOfFile (pOut);
  CloseHandle (hInMap);
  CloseHandle (hOutMap);
  CloseHandle (hInFile);
  CloseHandle (hOutFile);
  return 0;
}

 500M 정도의 파일을 복사 했을때,

MFC의 CFile나 fopen/fread/fwrite 보다 20% 이상의 성능 향상을 볼수 있다.

진행상태를 나타내기 위해서 잘라서 읽을려면

CopyMemory 부분만 살짝 손대면 된다.

어차피 IO처리라서 큰 차이가 없을것으로 생각했는데..

생각보다 큰 성능 차이를 보여 준다.