160 lines
4.9 KiB
C
160 lines
4.9 KiB
C
/***
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*stream.c - find a stream not in use
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*
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* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines _getstream() - find a stream not in use
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*
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*Revision History:
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* 09-02-83 RN initial version
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* 11-01-87 JCR Multi-thread support
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* 05-24-88 PHG Merged DLL and normal versions
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* 06-10-88 JCR Use near pointer to reference _iob[] entries
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* 08-17-89 GJF Removed _NEAR_, fixed copyright and indenting.
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* 02-16-90 GJF Fixed copyright
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* 03-19-90 GJF Made calling type _CALLTYPE1, added #include
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* <cruntime.h> and removed #include <register.h>.
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* 10-03-90 GJF New-style function declarator.
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* 12-31-91 GJF Improved multi-thread lock usage [_WIN32_].
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* 04-06-93 SKS Replace _CRTAPI* with __cdecl
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 03-07-95 GJF Changes to manage streams via __piob[], rather than
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* _iob[].
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* 05-12-95 CFW Bug fix: set _tmpfname field to NULL.
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* 03-02-98 GJF Exception-safe locking.
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* 05-13-99 PML Remove Win32s
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* 05-17-99 PML Remove all Macintosh support.
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* 10-14-99 PML Replace InitializeCriticalSection with wrapper function
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* __crtInitCritSecAndSpinCount
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* 02-20-01 PML vs7#172586 Avoid _RT_LOCK by preallocating all locks
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* that will be required, and returning failure back on
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* inability to allocate a lock.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <windows.h>
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#include <malloc.h>
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#include <stdio.h>
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#include <file2.h>
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#include <internal.h>
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#include <mtdll.h>
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#include <dbgint.h>
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/***
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*FILE *_getstream() - find a stream not in use
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*
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*Purpose:
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* Find a stream not in use and make it available to caller. Intended
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* for use inside library only
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*
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*Entry:
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* None. Scans __piob[]
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*
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*Exit:
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* Returns a pointer to a free stream, or NULL if all are in use. A
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* stream becomes allocated if the caller decided to use it by setting
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* any r, w, r/w mode.
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*
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* [Multi-thread note: If a free stream is found, it is returned in a
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* LOCKED state. It is the caller's responsibility to unlock the stream.]
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*
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*Exceptions:
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*
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*******************************************************************************/
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FILE * __cdecl _getstream (
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void
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)
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{
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REG2 FILE *retval = NULL;
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REG1 int i;
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#ifdef _MT
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/* Get the iob[] scan lock */
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_mlock(_IOB_SCAN_LOCK);
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__try {
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#endif
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/*
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* Loop through the __piob table looking for a free stream, or the
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* first NULL entry.
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*/
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for ( i = 0 ; i < _nstream ; i++ ) {
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if ( __piob[i] != NULL ) {
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/*
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* if the stream is not inuse, return it.
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*/
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if ( !inuse( (FILE *)__piob[i] ) ) {
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#ifdef _MT
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/*
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* Allocate the FILE lock, in case it hasn't already been
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* allocated (only necessary for the first _IOB_ENTRIES
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* locks, not including stdin/stdout/stderr). Return
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* failure if lock can't be allocated.
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*/
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if ( i > 2 && i < _IOB_ENTRIES )
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if ( !_mtinitlocknum( _STREAM_LOCKS + i ) )
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break;
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_lock_str2(i, __piob[i]);
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if ( inuse( (FILE *)__piob[i] ) ) {
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_unlock_str2(i, __piob[i]);
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continue;
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}
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#endif
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retval = (FILE *)__piob[i];
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break;
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}
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}
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else {
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/*
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* allocate a new _FILEX, set _piob[i] to it and return a
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* pointer to it.
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*/
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if ( (__piob[i] = _malloc_crt( sizeof(_FILEX) )) != NULL ) {
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#if defined(_MT)
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if ( !__crtInitCritSecAndSpinCount(
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&(((_FILEX *)__piob[i])->lock), _CRT_SPINCOUNT ))
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{
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/*
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* Failed to initialize the critical section because
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* of lack of memory, clean up and return failure.
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*/
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_free_crt( __piob[i] );
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__piob[i] = NULL;
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break;
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}
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EnterCriticalSection( &(((_FILEX *)__piob[i])->lock) );
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#endif
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retval = (FILE *)__piob[i];
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}
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break;
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}
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}
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/*
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* Initialize the return stream.
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*/
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if ( retval != NULL ) {
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retval->_flag = retval->_cnt = 0;
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retval->_tmpfname = retval->_ptr = retval->_base = NULL;
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retval->_file = -1;
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}
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#ifdef _MT
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}
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__finally {
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_munlock(_IOB_SCAN_LOCK);
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}
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#endif
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return(retval);
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}
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