在 C++ 中直接文件访问？

Question

有没有办法在c++中直接写入磁盘而不使用缓存？ 目前我正在使用：

int open(fileout, O_CREATE | O_WRONLY | O_DIRECT);  
FILE *fh = fdopen(fileout_dev, "wb");

是否有跨平台库允许这样做？

谢谢阿曼。

Answer 1

如果您正在谈论缓冲，那么您可以使用 setbuf 或 setvbuf

/* setbuf example */
#include <stdio.h>

int main ()
{
  char buffer[BUFSIZ];
  FILE *pFile1, *pFile2;

  pFile1=fopen ("myfile.txt","w");
  pFile2=fopen ("myfile2.txt","a");

  setbuf ( pFile1 , buffer );
  fputs ("This is sent to a buffered stream",pFile1);
  fflush (pFile1);

  setbuf ( pFile2 , NULL );
  fputs ("This is sent to an unbuffered stream",pFile2);

  fclose (pFile1);
  fclose (pFile2);

  return 0;
}


/* setvbuf example */
#include <stdio.h>

int main ()
{
  FILE *pFile;

  pFile=fopen ("myfile.txt","w");

  // _IONBF disables buffering
  setvbuf (pFile , NULL , _IONBF, 0);

  // File operations here

  fclose (pFile);

  return 0;
}