pwrite.c

来自「Newlib 嵌入式 C库 标准实现代码」· C语言 代码 · 共 47 行

/* Linux version of pwrite so we can have a weak alias */

#include <_ansi.h>
#include <unistd.h>
#include <reent.h>
#include <machine/weakalias.h>

ssize_t
_DEFUN (_pwrite_r, (rptr, fd, buf, n, off),
     struct _reent *rptr _AND
     int fd _AND
     _CONST _PTR buf _AND
     size_t n _AND
     off_t off)
{
  off_t cur_pos;
  _READ_WRITE_RETURN_TYPE num_written;
  
  if ((cur_pos = _lseek_r (rptr, fd, 0, SEEK_CUR)) == (off_t)-1)
    return -1;

  if (_lseek_r (rptr, fd, off, SEEK_SET) == (off_t)-1)
    return -1;

  num_written = _write_r (rptr, fd, buf, n);

  if (_lseek_r (rptr, fd, cur_pos, SEEK_SET) == (off_t)-1)
    return -1;

  return (ssize_t)num_written;
}

#ifndef _REENT_ONLY

ssize_t
_DEFUN (__libc_pwrite, (fd, buf, n, off),
     int fd _AND
     _CONST _PTR buf _AND
     size_t n _AND
     off_t off)
{
  return _pwrite_r (_REENT, fd, buf, n, off);
}
weak_alias(__libc_pwrite,pwrite)

#endif