479 lines
13 KiB
C
479 lines
13 KiB
C
/*
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* $Id$
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*/
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/*
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* Harbour Project source code:
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* The garbage collector for Harbour
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*
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* Copyright 1999 Ryszard Glab <rglab@imid.med.pl>
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* www - http://www.harbour-project.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this software; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA (or visit the web site http://www.gnu.org/).
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*
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* As a special exception, the Harbour Project gives permission for
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* additional uses of the text contained in its release of Harbour.
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*
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* The exception is that, if you link the Harbour libraries with other
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* files to produce an executable, this does not by itself cause the
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* resulting executable to be covered by the GNU General Public License.
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* Your use of that executable is in no way restricted on account of
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* linking the Harbour library code into it.
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*
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* This exception does not however invalidate any other reasons why
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* the executable file might be covered by the GNU General Public License.
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*
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* This exception applies only to the code released by the Harbour
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* Project under the name Harbour. If you copy code from other
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* Harbour Project or Free Software Foundation releases into a copy of
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* Harbour, as the General Public License permits, the exception does
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* not apply to the code that you add in this way. To avoid misleading
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* anyone as to the status of such modified files, you must delete
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* this exception notice from them.
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*
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* If you write modifications of your own for Harbour, it is your choice
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* whether to permit this exception to apply to your modifications.
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* If you do not wish that, delete this exception notice.
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*
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*/
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#include "hbapi.h"
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#include "hbstack.h"
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#include "hbapiitm.h"
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#include "hbapierr.h"
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#include "hbvm.h"
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#include "error.ch"
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/* holder of memory block information */
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/* NOTE: USHORT is used intentionally to fill up the structure to
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* full 16 bytes (on 16/32 bit environment)
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*/
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typedef struct HB_GARBAGE_
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{
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struct HB_GARBAGE_ *pNext; /* next memory block */
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struct HB_GARBAGE_ *pPrev; /* previous memory block */
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HB_GARBAGE_FUNC_PTR pFunc; /* cleanup function called before memory releasing */
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USHORT locked; /* locking counter */
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USHORT used; /* used/unused block */
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} HB_GARBAGE, *HB_GARBAGE_PTR;
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/* status of memory block */
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#define HB_GC_UNLOCKED 0
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#define HB_GC_LOCKED 1 /* do not collect a memory block */
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#define HB_GC_USED_FLAG 2 /* the bit for used/unused flag */
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#define HB_GC_DELETE 4 /* item will be deleted during finalization */
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/* pointer to memory block that will be checked in next step */
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static HB_GARBAGE_PTR s_pCurrBlock = NULL;
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/* memory blocks are stored in linked list with a loop */
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/* pointer to locked memory blocks */
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static HB_GARBAGE_PTR s_pLockedBlock = NULL;
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/* marks if block releasing is requested during garbage collecting */
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static BOOL s_bCollecting = FALSE;
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/* flag for used/unused blocks - the meaning of the HB_GC_USED_FLAG bit
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* is reversed on every collecting attempt
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*/
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static USHORT s_uUsedFlag = HB_GC_USED_FLAG;
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/* we may use a cache later */
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#define HB_GARBAGE_NEW( ulSize ) ( HB_GARBAGE_PTR )hb_xgrab( ulSize )
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#define HB_GARBAGE_FREE( pAlloc ) hb_xfree( (void *)(pAlloc) )
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static void hb_gcLink( HB_GARBAGE_PTR *pList, HB_GARBAGE_PTR pAlloc )
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{
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if( *pList )
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{
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/* add new block at the logical end of list */
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pAlloc->pNext = *pList;
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pAlloc->pPrev = (*pList)->pPrev;
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pAlloc->pPrev->pNext = pAlloc;
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(*pList)->pPrev = pAlloc;
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}
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else
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{
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*pList = pAlloc->pNext = pAlloc->pPrev = pAlloc;
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}
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}
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static void hb_gcUnlink( HB_GARBAGE_PTR *pList, HB_GARBAGE_PTR pAlloc )
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{
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pAlloc->pPrev->pNext = pAlloc->pNext;
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pAlloc->pNext->pPrev = pAlloc->pPrev;
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if( *pList == pAlloc )
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*pList = pAlloc->pNext;
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if( ( pAlloc->pNext == pAlloc->pPrev ) && ( *pList == pAlloc ) )
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*pList = NULL; /* this was the last block */
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}
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/* allocates a memory block */
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void * hb_gcAlloc( ULONG ulSize, HB_GARBAGE_FUNC_PTR pCleanupFunc )
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{
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HB_GARBAGE_PTR pAlloc;
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pAlloc = HB_GARBAGE_NEW( ulSize + sizeof( HB_GARBAGE ) );
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if( pAlloc )
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{
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hb_gcLink( &s_pCurrBlock, pAlloc );
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pAlloc->pFunc = pCleanupFunc;
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pAlloc->locked = 0;
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pAlloc->used = s_uUsedFlag;
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return (void *)( pAlloc + 1 ); /* hide the internal data */
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}
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else
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return NULL;
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}
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/* release a memory block allocated with hb_gcAlloc() */
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void hb_gcFree( void *pBlock )
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{
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if( pBlock )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pBlock;
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--pAlloc;
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if( !( pAlloc->used & HB_GC_DELETE ) )
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{
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/* Don't release the block that will be deleted during finalization */
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if( pAlloc->locked )
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hb_gcUnlink( &s_pLockedBlock, pAlloc );
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else
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hb_gcUnlink( &s_pCurrBlock, pAlloc );
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HB_GARBAGE_FREE( pAlloc );
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}
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}
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else
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{
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hb_errInternal( HB_EI_XFREENULL, NULL, NULL, NULL );
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}
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}
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static HB_GARBAGE_FUNC( hb_gcGripRelease )
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{
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/* Item was already released in hb_gcGripDrop() - then we have nothing
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* to do here
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*/
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HB_SYMBOL_UNUSED( Cargo );
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}
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HB_ITEM_PTR hb_gcGripGet( HB_ITEM_PTR pOrigin )
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{
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HB_GARBAGE_PTR pAlloc;
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pAlloc = HB_GARBAGE_NEW( sizeof( HB_ITEM ) + sizeof( HB_GARBAGE ) );
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if( pAlloc )
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{
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HB_ITEM_PTR pItem = ( HB_ITEM_PTR )( pAlloc + 1 );
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hb_gcLink( &s_pLockedBlock, pAlloc );
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pAlloc->pFunc = hb_gcGripRelease;
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pAlloc->locked = 1;
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pAlloc->used = s_uUsedFlag;
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if( pOrigin )
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{
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pItem->type = HB_IT_NIL;
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hb_itemCopy( pItem, pOrigin );
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}
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else
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{
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memset( pItem, 0, sizeof( HB_ITEM ) );
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pItem->type = HB_IT_NIL;
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}
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return pItem;
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}
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else
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return NULL;
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}
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void hb_gcGripDrop( HB_ITEM_PTR pItem )
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{
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if( pItem )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pItem;
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--pAlloc;
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hb_itemClear( pItem ); /* clear value stored in this item */
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hb_gcUnlink( &s_pLockedBlock, pAlloc );
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HB_GARBAGE_FREE( pAlloc );
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}
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}
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/* Lock a memory pointer so it will not be released if stored
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outside of harbour variables
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*/
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void * hb_gcLock( void * pBlock )
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{
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if( pBlock )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pBlock;
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--pAlloc;
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if( ! pAlloc->locked )
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{
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hb_gcUnlink( &s_pCurrBlock, pAlloc );
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hb_gcLink( &s_pLockedBlock, pAlloc );
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}
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++pAlloc->locked;
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}
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return pBlock;
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}
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/* Unlock a memory pointer so it can be released if there is no
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references inside of harbour variables
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*/
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void *hb_gcUnlock( void *pBlock )
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{
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if( pBlock )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pBlock;
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--pAlloc;
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if( pAlloc->locked )
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{
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if( --pAlloc->locked == 0 )
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{
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hb_gcUnlink( &s_pLockedBlock, pAlloc );
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hb_gcLink( &s_pCurrBlock, pAlloc );
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pAlloc->used = s_uUsedFlag;
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}
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}
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}
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return pBlock;
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}
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/* Mark a passed item as used so it will be not released by the GC
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*/
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void hb_gcItemRef( HB_ITEM_PTR pItem )
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{
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if( HB_IS_BYREF( pItem ) )
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pItem = hb_itemUnRef( pItem );
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if( HB_IS_ARRAY( pItem ) )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pItem->item.asArray.value;
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--pAlloc;
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/* Check this array only if it was not checked yet */
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if( pAlloc->used == s_uUsedFlag )
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{
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ULONG ulSize = pItem->item.asArray.value->ulLen;
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/* mark this block as used so it will be no re-checked from
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* other references
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*/
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pAlloc->used ^= HB_GC_USED_FLAG;
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/* mark also all array elements */
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pItem = pItem->item.asArray.value->pItems;
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while( ulSize )
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{
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hb_gcItemRef( pItem++ );
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--ulSize;
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}
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}
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}
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else if( HB_IS_BLOCK( pItem ) )
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{
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HB_GARBAGE_PTR pAlloc = ( HB_GARBAGE_PTR ) pItem->item.asBlock.value;
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--pAlloc;
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if( pAlloc->used == s_uUsedFlag )
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{
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HB_CODEBLOCK_PTR pCBlock = pItem->item.asBlock.value;
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USHORT ui = 1;
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pAlloc->used ^= HB_GC_USED_FLAG; /* mark this codeblock as used */
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/* mark as used all detached variables in a codeblock */
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while( ui <= pCBlock->uiLocals )
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{
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hb_gcItemRef( &pCBlock->pLocals[ ui ] );
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++ui;
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}
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}
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}
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/* all other data types don't need the GC */
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}
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void hb_gcCollect( void )
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{
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/* TODO: decrease the amount of time spend collecting */
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hb_gcCollectAll();
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}
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/* Check all memory block if they can be released
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*/
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void hb_gcCollectAll( void )
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{
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if( s_pCurrBlock && !s_bCollecting )
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{
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HB_GARBAGE_PTR pAlloc, pDelete;
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s_bCollecting = TRUE;
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/* Step 1 - mark */
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/* All blocks are already marked because we are flipping
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* the used/unused flag
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*/
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/* Step 2 - sweep */
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/* check all known places for blocks they are referring */
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hb_vmIsLocalRef();
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hb_vmIsStaticRef();
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hb_memvarsIsMemvarRef();
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hb_gcItemRef( &hb_stack.Return );
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hb_clsIsClassRef();
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/* check list of locked block for blocks referenced from
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* locked block
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*/
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if( s_pLockedBlock )
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{
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pAlloc = s_pLockedBlock;
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do
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{ /* it is not very elegant method but it works well */
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if( pAlloc->pFunc == hb_gcGripRelease )
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{
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hb_gcItemRef( ( HB_ITEM_PTR ) ( pAlloc + 1 ) );
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}
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pAlloc = pAlloc->pNext;
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} while ( s_pLockedBlock != pAlloc );
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}
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/* Step 3 - finalize */
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/* Release all blocks that are still marked as unused */
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pAlloc = s_pCurrBlock;
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do
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{
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if( s_pCurrBlock->used == s_uUsedFlag )
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{
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/* call a cleanup function */
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s_pCurrBlock->used |= HB_GC_DELETE;
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if( s_pCurrBlock->pFunc )
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{
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( s_pCurrBlock->pFunc )( ( void *)( s_pCurrBlock + 1 ) );
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}
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}
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s_pCurrBlock = s_pCurrBlock->pNext;
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} while ( s_pCurrBlock && (pAlloc != s_pCurrBlock) );
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pAlloc = s_pCurrBlock;
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do
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{
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NewTopBlock:
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if( s_pCurrBlock->used & HB_GC_DELETE )
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{
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pDelete = s_pCurrBlock;
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hb_gcUnlink( &s_pCurrBlock, s_pCurrBlock );
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/*
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Releasing the top block in the list, so we must mark the new top into pAlloc
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but we still need to process this new top. Without this goto, the while
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condition will immediatly fail. Using extra flags, and new conditions
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will adversly effect performance.
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*/
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if( pDelete == pAlloc )
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{
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pAlloc = s_pCurrBlock;
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HB_GARBAGE_FREE( pDelete );
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if( s_pCurrBlock )
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{
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goto NewTopBlock;
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}
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}
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else
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{
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HB_GARBAGE_FREE( pDelete );
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}
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}
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else
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{
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s_pCurrBlock = s_pCurrBlock->pNext;
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}
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} while ( s_pCurrBlock && ( pAlloc != s_pCurrBlock ) );
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s_bCollecting = FALSE;
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s_pCurrBlock = pAlloc;
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/* Step 4 - flip flag */
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/* Reverse used/unused flag so we don't have to mark all blocks
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* during next collecting
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*/
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s_uUsedFlag ^= HB_GC_USED_FLAG;
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}
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}
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void hb_gcReleaseAll( void )
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{
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if( s_pCurrBlock )
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{
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HB_GARBAGE_PTR pAlloc, pDelete;
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s_bCollecting = TRUE;
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pAlloc = s_pCurrBlock;
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do
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{
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/* call a cleanup function */
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if( s_pCurrBlock->pFunc )
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{
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HB_TRACE( HB_TR_INFO, ( "Cleanup, %p", s_pCurrBlock ) );
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( s_pCurrBlock->pFunc )( ( void *)( s_pCurrBlock + 1 ) );
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}
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s_pCurrBlock = s_pCurrBlock->pNext;
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} while ( s_pCurrBlock && pAlloc != s_pCurrBlock );
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do
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{
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HB_TRACE( HB_TR_INFO, ( "Release %p", s_pCurrBlock ) );
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pDelete = s_pCurrBlock;
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hb_gcUnlink( &s_pCurrBlock, s_pCurrBlock );
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HB_GARBAGE_FREE( pDelete );
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} while ( s_pCurrBlock );
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}
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s_bCollecting = FALSE;
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}
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/* service a single garbage collector step
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* Check a single memory block if it can be released
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*/
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HB_FUNC( HB_GCSTEP )
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{
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hb_gcCollect();
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}
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/* Check all memory blocks if they can be released
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*/
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HB_FUNC( HB_GCALL )
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{
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hb_gcCollectAll();
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}
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