fflush.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 * COPYRIGHT:   See COPYING in the top level directory
 * PROJECT:     ReactOS system libraries
 * FILE:        lib/msvcrt/stdio/fflush.c
 * PURPOSE:     Checks for keyboard hits
 * PROGRAMER:   Ariadne
 * UPDATE HISTORY:
 *              28/12/98: Created
 */
/* Copyright (C) 1998 DJ Delorie, see COPYING.DJ for details */
/* Copyright (C) 1996 DJ Delorie, see COPYING.DJ for details */
/* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
#include <precomp.h>
#include <sys/stat.h>

/*
 * @implemented
 */
int fflush(FILE *f)
{
  char *base;
  int n, rn;



  if (f == NULL)
  {
     int e = *_errno();

     __set_errno(0);
    _fwalk((void (*)(FILE *))fflush);
    if (*_errno())
      return EOF;
    __set_errno(e);
    return 0;
  }


// nothing to do if stream can not be written to

  if ( !OPEN4WRITING(f) ) {
	__set_errno (EINVAL);
	return 0;
  }

// discard any unget characters

  f->_flag &= ~_IOUNGETC;


// check for buffered dirty block

  if ( (f->_flag&(_IODIRTY|_IONBF)) ==_IODIRTY && f->_base != NULL)
  {

    base = f->_base;


// if the buffer is read ahead and dirty we will flush it entirely
// else the buffer is appended to the file to the extend it has valid bytes

    if ( (f->_flag & _IOAHEAD) == _IOAHEAD )
    	rn = n = f->_ptr - base + f->_cnt;
    else
	rn = n = f->_ptr - base;

    f->_ptr = base;

    if ((f->_flag & _IOFBF) == _IOFBF) {
     	if ( (f->_flag & _IOAHEAD) == _IOAHEAD )
 	    _lseek(_fileno(f),-rn, SEEK_CUR);
    }

    f->_flag &= ~_IOAHEAD;


    f->_cnt = (f->_flag&(_IO_LBF|_IONBF)) ? 0 : f->_bufsiz;

// how can write return less than rn without being on error ???

// possibly commit the flushed data
// better open the file in write through mode

    while (rn > 0) {
      n = _write(_fileno(f), base, rn);
      if (n <= 0) {
	    f->_flag |= _IOERR;
	    return EOF;
      }
      rn -= n;
      base += n;
    };
    f->_flag &= ~_IODIRTY;

// commit flushed data
//    _commit(_fileno(f));
  }
  if (OPEN4READING(f) && OPEN4WRITING(f) )
  {
    f->_cnt = 0;
    f->_ptr = f->_base;
  }
  return 0;
}

/*
 * @implemented
 */
int _flushall( void )
{
	return fflush(NULL);
}