Tricks of the Windows Gam…ming Gurus (2nd Edition)/Disc2.iso/vc98/crt/src/_sftbuf.c

C/C++ Source or Header | 1998-06-17 | 5.9 KB | 199 lines

/***
*_sftbuf.c - temporary buffering initialization and flushing
*
*       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       temporary buffering initialization and flushing. if stdout/err is
*       unbuffered, buffer it temporarily so that string is sent to kernel as
*       a batch of chars, not char-at-a-time. if appropriate, make buffering
*       permanent.
*
*       [NOTE 1: These routines assume that the temporary buffering is only
*       used for output.  In particular, note that _stbuf() sets _IOWRT.]
*
*       [NOTE 2: It is valid for this module to assign a value directly to
*       _flag instead of simply twiddling bits since we are initializing the
*       buffer data base.]
*
*******************************************************************************/

#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <io.h>
#include <internal.h>
#include <malloc.h>
#ifdef _MT
#include <mtdll.h>
#endif  /* _MT */
#include <dbgint.h>

/* Buffer pointers for stdout and stderr */
void *_stdbuf[2] = { NULL, NULL};

/***
*int _stbuf(stream) - set temp buffer on stdout, stdprn, stderr
*
*Purpose:
*       if stdout/stderr is still unbuffered, buffer it.
*       this function works intimately with _ftbuf, and accompanies it in
*       bracketing normally unbuffered output. these functions intended for
*       library use only.
*
*       Multi-thread: It is assumed that the caller has already aquired the
*       stream lock.
*
*Entry:
*       FILE *stream - stream to temp buffer
*
*Exit:
*       returns 1 if buffer initialized, 0 if not
*       sets fields in stdout or stderr to indicate buffering
*
*Exceptions:
*
*******************************************************************************/

int __cdecl _stbuf (
        FILE *str
        )
{
        REG1 FILE *stream;
        int index;

        _ASSERTE(str != NULL);

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

        /* do nothing if not a tty device */
        if (!_isatty(_fileno(stream)))
                return(0);

        /* Make sure stream is stdout/stderr and init _stdbuf index */
        if (stream == stdout)
                index = 0;
        else if (stream == stderr)
                index = 1;
        else
                return(0);

#ifndef CRTDLL
        /* force library pre-termination procedure */
        _cflush++;
#endif  /* CRTDLL */

        /* Make sure the stream is not already buffered. */
        if (anybuf(stream))
                return(0);

        /* Allocate a buffer for this stream if we haven't done so yet. */
        if ( (_stdbuf[index] == NULL) &&
#ifdef _WIN32
             ((_stdbuf[index]=_malloc_crt(_INTERNAL_BUFSIZ)) == NULL) ) {
#else  /* _WIN32 */
#ifdef _MAC
             ((_stdbuf[index]=_malloc_crt(BUFSIZ)) == NULL) ) {
#endif  /* _MAC */
#endif  /* _WIN32 */
                /* Cannot allocate buffer. Use _charbuf this time */
                stream->_ptr = stream->_base = (void *)&(stream->_charbuf);
#ifdef _WIN32
                stream->_cnt = stream->_bufsiz = 2;
#else  /* _WIN32 */
#ifdef _MAC
                stream->_cnt = stream->_bufsiz = 1;
#endif  /* _MAC */
#endif  /* _WIN32 */
        }
        else {
                /* Set up the buffer */
                stream->_ptr = stream->_base = _stdbuf[index];
#ifdef _WIN32
                stream->_cnt = stream->_bufsiz = _INTERNAL_BUFSIZ;
#else  /* _WIN32 */
#ifdef _MAC
                stream->_cnt = stream->_bufsiz = BUFSIZ;
#endif  /* _MAC */
#endif  /* _WIN32 */
        }

        stream->_flag |= (_IOWRT | _IOYOURBUF | _IOFLRTN);

        return(1);
}


/***
*void _ftbuf(flag, stream) - take temp buffering off a stream
*
*Purpose:
*       If stdout/stderr is being buffered and it is a device, _flush and
*       dismantle the buffer. if it's not a device, leave the buffering on.
*       This function works intimately with _stbuf, and accompanies it in
*       bracketing normally unbuffered output. these functions intended for
*       library use only
*
*       Multi-thread: It is assumed that the caller has already aquired the
*       stream lock.
*
*Entry:
*       int flag     - a flag to tell whether to dismantle temp buffering on a
*                      stream
*       FILE *stream - the stream
*
*Exit:
*       no return value
*       sets fields in stdout/stderr
*
*Exceptions:
*
*******************************************************************************/

void __cdecl _ftbuf (
        int flag,
        FILE *str
        )
{
        REG1 FILE *stream;

        _ASSERTE(flag == 0 || flag == 1);

        /* Init near stream pointers */
        stream = str;

        if (flag) {

                if (stream->_flag & _IOFLRTN) {

                        /* Flush the stream and tear down temp buffering. */
                        _flush(stream);
                        stream->_flag &= ~(_IOYOURBUF | _IOFLRTN);
                        stream->_bufsiz = 0;
                        stream->_base = stream->_ptr = NULL;
                }

                /* Note: If we expand the functionality of the _IOFLRTN bit to
                include other streams, we may want to clear that bit here under
                an 'else' clause (i.e., clear bit in the case that we leave the
                buffer permanently assigned.  Given our current use of the bit,
                the extra code is not needed. */

        } /* end flag = 1 */

#ifndef _MT
/* NOTE: Currently, writing to the same string at interrupt level does not
   work in multi-thread programs. */

/* The following code is needed if an interrupt occurs between calls
   to _stbuf/_ftbuf and the interrupt handler also calls _stbuf/_ftbuf. */

        else
                if (stream->_flag & _IOFLRTN)
                        _flush(stream);

#endif  /* _MT */

}