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/***
*stream.c - find a stream not in use
*
* Copyright (c) 1985-1992, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines _getstream() - find a stream not in use
*
*Revision History:
* 09-02-83 RN initial version
* 11-01-87 JCR Multi-thread support
* 05-24-88 PHG Merged DLL and normal versions
* 06-10-88 JCR Use near pointer to reference _iob[] entries
* 08-17-89 GJF Removed _NEAR_, fixed copyright and indenting.
* 02-16-90 GJF Fixed copyright
* 03-19-90 GJF Made calling type _CALLTYPE1, added #include
* <cruntime.h> and removed #include <register.h>.
* 10-03-90 GJF New-style function declarator.
* 12-31-91 GJF Improved multi-thread lock usage [_WIN32_].
*
*******************************************************************************/
#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <internal.h>
#include <os2dll.h>
/***
*FILE *_getstream() - find a stream not in use
*
*Purpose:
* find a stream not in use and make it available to caller. _lastiob is
* the last FILE address. intended for use inside library only
*
*Entry:
* None. Reads _iob.
*
*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.
*
* Note: Optimized the code to use a near pointer for the stream. This
* is especially helpful in large model. However, the drawback is that we
* need another temporary 'retval' so that when we return NULL, we return
* 0:0, not DS:0.
*
* [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 * _CALLTYPE1 _getstream (
void
)
{
REG1 FILE *stream = _iob;
REG2 FILE *retval = NULL;
#ifdef MTHREAD
int index;
#endif
/* Get the iob[] scan lock */
_mlock(_IOB_SCAN_LOCK);
/* Loop through the _iob table looking for a free stream.*/
for (; stream <= _lastiob; stream++) {
if ( !inuse(stream) ) {
#ifdef MTHREAD
index = _iob_index(stream);
_lock_str(index);
/* make sure the _iob entry is still free */
if ( inuse(stream) ) {
/* no longer free! release the lock and
continue looping */
_unlock_str(index);
continue;
}
#endif
stream->_flag = stream->_cnt = 0;
stream->_ptr = stream->_base = NULL;
stream->_file = -1;
retval = stream;
break;
}
}
_munlock(_IOB_SCAN_LOCK);
return(retval);
}
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