fflush.c

C语言库函数的原型,有用的拿去

/***
*fflush.c - flush a stream buffer
*
*       Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines fflush() - flush the buffer on a stream
*               _flushall() - flush all stream buffers
*
*******************************************************************************/

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


/* Values passed to flsall() to distinguish between _flushall() and
 * fflush(NULL) behavior
 */
#define FLUSHALL        1
#define FFLUSHNULL      0

/* Core routine for fflush(NULL) and flushall()
 */
static int __cdecl flsall(int);


/***
*int fflush(stream) - flush the buffer on a stream
*
*Purpose:
*       if file open for writing and buffered, flush the buffer. if problems
*       flushing the buffer, set the stream flag to error
*       Always flushes the stdio stream and forces a commit to disk if file
*       was opened in commit mode.
*
*Entry:
*       FILE *stream - stream to flush
*
*Exit:
*       returns 0 if flushed successfully, or no buffer to flush
*       returns EOF and sets file error flag if fails.
*       FILE struct entries affected: _ptr, _cnt, _flag.
*
*Exceptions:
*
*******************************************************************************/

int __cdecl fflush (
        REG1 FILE *stream
        )
{
    int rc;

    /* if stream is NULL, flush all streams
     */
    if ( stream == NULL )
        return(flsall(FFLUSHNULL));

    _lock_str(stream);

    __try {
        rc = _fflush_nolock(stream);
    }
    __finally {
        _unlock_str(stream);
    }

    return(rc);
}


/***
*_fflush_nolock() - Flush the buffer on a stream (stream is already locked)
*
*Purpose:
*       Core flush routine; assumes stream lock is held by caller.
*
*       [See fflush() above for more information.]
*
*Entry:
*       [See fflush()]
*Exit:
*       [See fflush()]
*
*Exceptions:
*
*******************************************************************************/

int __cdecl _fflush_nolock (
        REG1 FILE *str
        )
{

    /* if stream is NULL, flush all streams
     */
    if ( str == NULL )
        return(flsall(FFLUSHNULL));

    if (_flush(str) != 0) {
        /* _flush failed, don't attempt to commit */
        return(EOF);
    }

    /* lowio commit to ensure data is written to disk */

    if (str->_flag & _IOCOMMIT) {
            return (_commit(_fileno(str)) ? EOF : 0);
    }

    return 0;
}


/***
*int _flush(stream) - flush the buffer on a single stream
*
*Purpose:
*       If file open for writing and buffered, flush the buffer.  If
*       problems flushing the buffer, set the stream flag to error.
*       Multi-thread version assumes stream lock is held by caller.
*
*Entry:
*       FILE* stream - stream to flush
*
*Exit:
*       Returns 0 if flushed successfully, or if no buffer to flush.,
*       Returns EOF and sets file error flag if fails.
*       File struct entries affected: _ptr, _cnt, _flag.
*
*Exceptions:
*
*******************************************************************************/

int __cdecl _flush (
        FILE *str
        )
{
        REG1 FILE *stream;
        REG2 int rc = 0; /* assume good return */
        REG3 int nchar;

        /* Init pointer to stream */
        stream = str;


        if ((stream->_flag & (_IOREAD | _IOWRT)) == _IOWRT && bigbuf(stream)
                && (nchar = (int)(stream->_ptr - stream->_base)) > 0)
        {
                if ( _write(_fileno(stream), stream->_base, nchar) == nchar ) {
                        /* if this is a read/write file, clear _IOWRT so that
                         * next operation can be a read
                         */
                        if ( _IORW & stream->_flag )
                                stream->_flag &= ~_IOWRT;
                }
                else {
                        stream->_flag |= _IOERR;
                        rc = EOF;
                }
        }

        stream->_ptr = stream->_base;
        stream->_cnt = 0;

        return(rc);
}


/***
*int _flushall() - flush all output buffers
*
*Purpose:
*       flushes all the output buffers to the file, clears all input buffers.
*
*Entry:
*       None.
*
*Exit:
*       returns number of open streams
*
*Exceptions:
*
*******************************************************************************/

int __cdecl _flushall (
        void
        )
{
        return(flsall(FLUSHALL));
}


/***
*static int flsall(flushflag) - flush all output buffers
*
*Purpose:
*       Flushes all the output buffers to the file and, if FLUSHALL is passed,
*       clears all input buffers. Core routine for both fflush(NULL) and
*       flushall().
*
*       MTHREAD Note: All the locking/unlocking required for both fflush(NULL)
*       and flushall() is performed in this routine.
*
*Entry:
*       int flushflag - flag indicating the exact semantics, there are two
*                       legal values: FLUSHALL and FFLUSHNULL
*
*Exit:
*       if flushflag == FFLUSHNULL then flsbuf returns:
                0, if successful
*               EOF, if an error occurs while flushing one of the streams
*
*       if flushflag == FLUSHALL then flsbuf returns the number of streams
*       successfully flushed
*
*Exceptions:
*
*******************************************************************************/

static int __cdecl flsall (
        int flushflag
        )
{
   REG1 int i;
   int count = 0;
   int err = 0;

   _mlock(_IOB_SCAN_LOCK);
   __try {
        for ( i = 0 ; i < _nstream ; i++ ) {
            if ( (__piob[i] != NULL) && (inuse((FILE *)__piob[i])) ) {
                /*
                 * lock the stream. this is not done until testing
                 * the stream is in use to avoid unnecessarily creating
                 * a lock for every stream. the price is having to
                 * retest the stream after the lock has been asserted.
                 */
                _lock_str2(i, __piob[i]);

                __try {
                    /*
                     * if the stream is STILL in use (it may have been
                     * closed before the lock was asserted), see about
                     * flushing it.
                     */
                    if ( inuse((FILE *)__piob[i]) ) {
                        if ( flushflag == FLUSHALL ) {
                            /*
                             * FLUSHALL functionality: fflush the read or
                             * write stream and, if successful, update the
                             * count of flushed streams
                             */
                            if ( _fflush_nolock(__piob[i]) != EOF )
                                /* update count of successfully flushed
                                 * streams
                                 */
                                count++;
                        }
                        else if ( (flushflag == FFLUSHNULL) &&
                                  (((FILE *)__piob[i])->_flag & _IOWRT) ) {
                            /*
                             * FFLUSHNULL functionality: fflush the write
                             * stream and kept track of the error, if one
                             * occurs
                             */
                            if ( _fflush_nolock(__piob[i]) == EOF )
                                err = EOF;
                        }
                    }
                }
                __finally {
                        _unlock_str2(i, __piob[i]);
                }
            }
        }
    }
    __finally {
        _munlock(_IOB_SCAN_LOCK);
    }

    if ( flushflag == FLUSHALL )
        return(count);
    else
        return(err);
}