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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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src
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stream.c
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C/C++ Source or Header
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1998-06-17
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4KB
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131 lines
/***
*stream.c - find a stream not in use
*
* Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines _getstream() - find a stream not in use
*
*******************************************************************************/
#include <cruntime.h>
#ifdef _WIN32
#include <windows.h>
#endif /* _WIN32 */
#include <malloc.h>
#include <stdio.h>
#include <file2.h>
#include <internal.h>
#include <mtdll.h>
#include <dbgint.h>
/***
*FILE *_getstream() - find a stream not in use
*
*Purpose:
* Find a stream not in use and make it available to caller. Intended
* for use inside library only
*
*Entry:
* None. Scans __piob[]
*
*Exit:
* Returns a pointer to a free stream, or NULL if all are in use. A
* stream becomes allocated if the caller decided to use it by setting
* any r, w, r/w mode.
*
* [Multi-thread note: If a free stream is found, it is returned in a
* LOCKED state. It is the caller's responsibility to unlock the stream.]
*
*Exceptions:
*
*******************************************************************************/
FILE * __cdecl _getstream (
void
)
{
REG2 FILE *retval = NULL;
#ifdef _WIN32
REG1 int i;
/* Get the iob[] scan lock */
_mlock(_IOB_SCAN_LOCK);
/*
* Loop through the __piob table looking for a free stream, or the
* first NULL entry.
*/
for ( i = 0 ; i < _nstream ; i++ ) {
if ( __piob[i] != NULL ) {
/*
* if the stream is not inuse, return it.
*/
if ( !inuse( (FILE *)__piob[i] ) ) {
#ifdef _MT
_lock_str2(i, __piob[i]);
if ( inuse( (FILE *)__piob[i] ) ) {
_unlock_str2(i, __piob[i]);
continue;
}
#endif /* _MT */
retval = (FILE *)__piob[i];
break;
}
}
else {
/*
* allocate a new _FILEX, set _piob[i] to it and return a
* pointer to it.
*/
if ( (__piob[i] = _malloc_crt( sizeof(_FILEX) )) != NULL ) {
#if defined (_MT)
InitializeCriticalSection( &(((_FILEX *)__piob[i])->lock) );
EnterCriticalSection( &(((_FILEX *)__piob[i])->lock) );
#endif /* defined (_MT) */
retval = (FILE *)__piob[i];
}
break;
}
}
/*
* Initialize the return stream.
*/
if ( retval != NULL ) {
retval->_flag = retval->_cnt = 0;
retval->_tmpfname = retval->_ptr = retval->_base = NULL;
retval->_file = -1;
}
_munlock(_IOB_SCAN_LOCK);
#else /* _WIN32 */
#if defined (_M_MPPC) || defined (_M_M68K)
REG1 FILE *stream = _iob;
/* Loop through the _iob table looking for a free stream.*/
for (; stream <= _lastiob; stream++) {
if ( !inuse(stream) ) {
stream->_flag = stream->_cnt = 0;
stream->_tmpfname = stream->_ptr = stream->_base = NULL;
stream->_file = -1;
retval = stream;
break;
}
}
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
#endif /* _WIN32 */
return(retval);
}