rewind.c

来自「C语言库函数的原型,有用的拿去」· C语言 代码 · 共 75 行

/***
*rewind.c - rewind a stream
*
*       Copyright (c) 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
*
*Exceptions:
*
*******************************************************************************/

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

    _VALIDATE_RETURN_VOID( (str != NULL), EINVAL);

    /* Init stream pointer */
    stream = str;

    fd = _fileno(stream);

    /* Lock the file */
    _lock_str(stream);
    __try {
        /* Flush the stream */
        _flush(stream);

        /* Clear errors */
        stream->_flag &= ~(_IOERR|_IOEOF);
        _osfile_safe(fd) &= ~(FEOFLAG);

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

       /* Position to beginning of file */
        if (_lseek(fd,0L,0)==-1)
        {
            stream->_flag |= _IOERR;
        }
    }
    __finally {
        /* unlock stream */
        _unlock_str(stream);
    }
}