rewind.c

C标准库源代码,能提高对C的理解,不错的哦

/***
*rewind.c - rewind a stream
*
*       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines rewind() - rewinds a stream to the beginning.
*
*
*******************************************************************************/

#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <dbgint.h>
#include <io.h>
#include <mtdll.h>
#include <msdos.h>
#include <internal.h>

/***
*void rewind(stream) - rewind a string
*
*Purpose:
*       Back up a stream to the beginning (if not terminal).  First flush it.
*       If read/write, allow next i/o operation to set mode.
*
*Entry:
*       FILE *stream - file to rewind
*
*Exit:
*       returns 0 if success
*       returns -1 if fails
*
*Exceptions:
*
*******************************************************************************/

void __cdecl rewind (
        FILE *str
        )
{
        REG1 FILE *stream;
        REG2 int fd;

        _ASSERTE(str != NULL);

        /* Init stream pointer */
        stream = str;

        fd = _fileno(stream);

        /* Lock the file */
        _lock_str(stream);

        /* Flush the stream */
        _flush(stream);

        /* Clear errors */
        stream->_flag &= ~(_IOERR|_IOEOF);
#ifdef _WIN32
        _osfile_safe(fd) &= ~(FEOFLAG);
#else  /* _WIN32 */
        _osfile[fd] &= ~(FEOFLAG);
#endif  /* _WIN32 */

        /* Set flags */
        /* [note: _flush set _cnt=0 and _ptr=_base] */
        if (stream->_flag & _IORW)
                stream->_flag &= ~(_IOREAD|_IOWRT);

        /* Position to beginning of file */
        _lseek(fd,0L,0);

        /* unlock stream */
        _unlock_str(stream);
}