windows-xp/Source/XPSP1/NT/base/crts/crtw32/stdio/fflush.c

/***
*fflush.c - flush a stream buffer
*
*       Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines fflush() - flush the buffer on a stream
*               _flushall() - flush all stream buffers
*
*Revision History:
*       09-01-83  RN    initial version
*       11-02-87  JCR   Multi-thread support
*       12-11-87  JCR   Added "_LOAD_DS" to declaration
*       01-13-88  JCR   Removed unnecessary calls to mthread fileno/feof/ferror
*       05-27-88  PHG   Merge DLL and normal versions
*       06-14-88  JCR   Use near pointer to reference _iob[] entries
*       08-24-88  GJF   Don't use FP_OFF() macro for the 386
*       08-17-89  GJF   Clean up, now specific to OS/2 2.0 (i.e., 386 flat
*                       model). Also fixed copyright and indents.
*       11-29-89  GJF   Added support for fflush(NULL) (per ANSI). Merged in
*                       flushall().
*       01-24-90  GJF   Fixed fflush(NULL) functionality to comply with ANSI
*                       (must only call fflush() for output streams)
*       03-16-90  GJF   Made calling type  _CALLTYPE1, added #include
*                       <cruntime.h> and removed #include <register.h>.
*       03-26-90  GJF   Made flsall() _CALLTYPE4.
*       05-09-90  SBM   _fflush_lk became _flush, added new [_]fflush[_lk]
*       07-11-90  SBM   Commit mode on a per stream basis
*       10-02-90  GJF   New-style function declarators.
*       12-12-90  GJF   Fixed mis-placed paran in ternary expr commiting the
*                       buffers.
*       01-16-91  SRW   Reversed test of _commit return value
*       01-21-91  GJF   ANSI naming.
*       06-05-91  GJF   On a successful _flush of a read/write stream in write
*                       mode, clear _IOWRT so that the next operation can be a
*                       read. ANSI requirement (C700 bug #2531).
*       07-30-91  GJF   Added support for termination scheme used on
*                       non-Cruiser targets [_WIN32_].
*       08-19-91  JCR   Added _exitflag, _endstdio
*       03-16-92  SKS   Moved _cflush to the initializer module (in assembler)
*       03-27-92  DJM   POSIX support.
*       08-26-92  GJF   Include unistd.h for POSIX build.
*       03-18-93  CFW   fflush_lk returns 0 before exit.
*       03-19-93  GJF   Revised flsall() so that, in multi-thread models,
*                       unused streams are not locked unnecessarily.
*       04-06-93  SKS   Replace _CRTAPI* with __cdecl
*       05-10-93  GJF   Purged ftell call accidently checked in 3/10/93.
*       10-29-93  GJF   Define entry for termination section (used to be in
*                       in i386\cinitstd.asm). Also, replaced MTHREAD with
*                       _MT.
*       04-05-94  GJF   #ifdef-ed out _cflush definition for msvcrt*.dll, it
*                       is unnecessary.
*       08-18-94  GJF   Moved terminator stuff (including _cflush def) to
*                       _file.c
*       02-17-95  GJF   Appended Mac version of source file (somewhat cleaned
*                       up), with appropriate #ifdef-s.
*       03-07-95  GJF   Changed flsall() to iterate over the __piob[] table.
*                       Also, changed to locks based on __piob.
*       12-28-95  GJF   Repaced reference to _NSTREAM_ with _nstream (users
*                       may change the max. number of supported streams).
*       08-01-96  RDK   Change termination pointer data type to static.
*       02-13-98  GJF   Changes for Win64: added int cast to pointer diff.
*       02-27-98  GJF   Exception-safe locking.
*       04-28-99  PML   Wrap __declspec(allocate()) in _CRTALLOC macro.
*       05-17-99  PML   Remove all Macintosh support.
*
*******************************************************************************/

#include <sect_attribs.h>
#include <cruntime.h>
#ifdef  _POSIX_
#include <unistd.h>
#include <fcntl.h>
#endif
#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:
*
*******************************************************************************/

#ifdef _MT

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_lk(stream);
        }
        __finally {
                _unlock_str(stream);
        }

        return(rc);
}


/***
*_fflush_lk() - 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_lk (
        REG1 FILE *str
        )
{

#else   /* non multi-thread */

int __cdecl fflush (
        REG1 FILE *str
        )
{

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

#endif  /* rejoin common code */

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

        /* lowio commit to ensure data is written to disk */
#ifndef _POSIX_
        if (str->_flag & _IOCOMMIT) {
                return (_commit(_fileno(str)) ? EOF : 0);
        }
#endif
        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;

#ifdef _POSIX_

        /*
         * Insure that EBADF is returned whenever the underlying
         * file descriptor is closed.
         */

        if (-1 == fcntl(fileno(stream), F_GETFL))
                return(EOF);

        /*
         * Posix ignores read streams to insure that the result of
         * ftell() is the same before and after fflush(), and to
         * avoid seeking on pipes, ttys, etc.
         */

        if ((stream->_flag & (_IOREAD | _IOWRT)) == _IOREAD) {
                return 0;
        }

#endif /* _POSIX_ */

        if ((stream->_flag & (_IOREAD | _IOWRT)) == _IOWRT && bigbuf(stream)
                && (nchar = (int)(stream->_ptr - stream->_base)) > 0)
        {
#ifdef _POSIX_
                if ( write(fileno(stream), stream->_base, nchar) == nchar ) {
#else
                if ( _write(_fileno(stream), stream->_base, nchar) == nchar ) {
#endif
                        /* 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 errcode = 0;

#ifdef  _MT
        _mlock(_IOB_SCAN_LOCK);
        __try {
#endif

        for ( i = 0 ; i < _nstream ; i++ ) {

                if ( (__piob[i] != NULL) && (inuse((FILE *)__piob[i])) ) {

#ifdef  _MT
                        /*
                         * 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]) ) {
#endif

                        if ( flushflag == FLUSHALL ) {
                                /*
                                 * FLUSHALL functionality: fflush the read or
                                 * write stream and, if successful, update the
                                 * count of flushed streams
                                 */
                                if ( _fflush_lk(__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_lk(__piob[i]) == EOF )
                                        errcode = EOF;
                        }

#ifdef  _MT
                                }
                        }
                        __finally {
                                _unlock_str2(i, __piob[i]);
                        }
#endif
                }
        }

#ifdef  _MT
        }
        __finally {
                _munlock(_IOB_SCAN_LOCK);
        }
#endif

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