diff options
Diffstat (limited to 'generic/tclPreserve.c')
| -rw-r--r-- | generic/tclPreserve.c | 272 |
1 files changed, 142 insertions, 130 deletions
diff --git a/generic/tclPreserve.c b/generic/tclPreserve.c index cea5725..8281bc4 100644 --- a/generic/tclPreserve.c +++ b/generic/tclPreserve.c @@ -1,71 +1,73 @@ -/* +/* * tclPreserve.c -- * - * This file contains a collection of procedures that are used - * to make sure that widget records and other data structures - * aren't reallocated when there are nested procedures that - * depend on their existence. + * This file contains a collection of functions that are used to make + * sure that widget records and other data structures aren't reallocated + * when there are nested functions that depend on their existence. * * Copyright (c) 1991-1994 The Regents of the University of California. * Copyright (c) 1994-1998 Sun Microsystems, Inc. * - * See the file "license.terms" for information on usage and redistribution - * of this file, and for a DISCLAIMER OF ALL WARRANTIES. + * See the file "license.terms" for information on usage and redistribution of + * this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tclPreserve.c,v 1.6 2005/06/24 20:07:22 kennykb Exp $ + * RCS: @(#) $Id: tclPreserve.c,v 1.7 2005/07/24 22:56:43 dkf Exp $ */ #include "tclInt.h" /* - * The following data structure is used to keep track of all the - * Tcl_Preserve calls that are still in effect. It grows as needed - * to accommodate any number of calls in effect. + * The following data structure is used to keep track of all the Tcl_Preserve + * calls that are still in effect. It grows as needed to accommodate any + * number of calls in effect. */ typedef struct { ClientData clientData; /* Address of preserved block. */ - int refCount; /* Number of Tcl_Preserve calls in effect - * for block. */ + int refCount; /* Number of Tcl_Preserve calls in effect for + * block. */ int mustFree; /* Non-zero means Tcl_EventuallyFree was * called while a Tcl_Preserve call was in - * effect, so the structure must be freed - * when refCount becomes zero. */ - Tcl_FreeProc *freeProc; /* Procedure to call to free. */ + * effect, so the structure must be freed when + * refCount becomes zero. */ + Tcl_FreeProc *freeProc; /* Function to call to free. */ } Reference; +/* + * Global data structures used to hold the list of preserved data references. + * These variables are protected by "preserveMutex". + */ + static Reference *refArray; /* First in array of references. */ -static int spaceAvl = 0; /* Total number of structures available - * at *firstRefPtr. */ -static int inUse = 0; /* Count of structures currently in use - * in refArray. */ -#define INITIAL_SIZE 2 +static int spaceAvl = 0; /* Total number of structures available at + * *firstRefPtr. */ +static int inUse = 0; /* Count of structures currently in use in + * refArray. */ TCL_DECLARE_MUTEX(preserveMutex)/* To protect the above statics */ +#define INITIAL_SIZE 2 /* Initial number of reference slots to make */ + /* - * The following data structure is used to keep track of whether an - * arbitrary block of memory has been deleted. This is used by the - * TclHandle code to avoid the more time-expensive algorithm of - * Tcl_Preserve(). This mechanism is mainly used when we have lots of - * references to a few big, expensive objects that we don't want to live - * any longer than necessary. + * The following data structure is used to keep track of whether an arbitrary + * block of memory has been deleted. This is used by the TclHandle code to + * avoid the more time-expensive algorithm of Tcl_Preserve(). This mechanism + * is mainly used when we have lots of references to a few big, expensive + * objects that we don't want to live any longer than necessary. */ typedef struct HandleStruct { - VOID *ptr; /* Pointer to the memory block being - * tracked. This field will become NULL when - * the memory block is deleted. This field - * must be the first in the structure. */ + VOID *ptr; /* Pointer to the memory block being tracked. + * This field will become NULL when the memory + * block is deleted. This field must be the + * first in the structure. */ #ifdef TCL_MEM_DEBUG - VOID *ptr2; /* Backup copy of the abpve pointer used to + VOID *ptr2; /* Backup copy of the above pointer used to * ensure that the contents of the handle are * not changed by anyone else. */ #endif int refCount; /* Number of TclHandlePreserve() calls in * effect on this handle. */ } HandleStruct; - - /* *---------------------------------------------------------------------- @@ -102,16 +104,16 @@ TclFinalizePreserve() * * Tcl_Preserve -- * - * This procedure is used by a procedure to declare its interest - * in a particular block of memory, so that the block will not be - * reallocated until a matching call to Tcl_Release has been made. + * This function is used by a function to declare its interest in a + * particular block of memory, so that the block will not be reallocated + * until a matching call to Tcl_Release has been made. * * Results: * None. * * Side effects: - * Information is retained so that the block of memory will - * not be freed until at least the matching call to Tcl_Release. + * Information is retained so that the block of memory will not be freed + * until at least the matching call to Tcl_Release. * *---------------------------------------------------------------------- */ @@ -124,12 +126,12 @@ Tcl_Preserve(clientData) int i; /* - * See if there is already a reference for this pointer. If so, - * just increment its reference count. + * See if there is already a reference for this pointer. If so, just + * increment its reference count. */ Tcl_MutexLock(&preserveMutex); - for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) { + for (i=0, refPtr=refArray ; i<inUse ; i++, refPtr++) { if (refPtr->clientData == clientData) { refPtr->refCount++; Tcl_MutexUnlock(&preserveMutex); @@ -138,8 +140,8 @@ Tcl_Preserve(clientData) } /* - * Make a reference array if it doesn't already exist, or make it - * bigger if it is full. + * Make a reference array if it doesn't already exist, or make it bigger + * if it is full. */ if (inUse == spaceAvl) { @@ -178,17 +180,16 @@ Tcl_Preserve(clientData) * * Tcl_Release -- * - * This procedure is called to cancel a previous call to - * Tcl_Preserve, thereby allowing a block of memory to be - * freed (if no one else cares about it). + * This function is called to cancel a previous call to Tcl_Preserve, + * thereby allowing a block of memory to be freed (if no one else cares + * about it). * * Results: * None. * * Side effects: - * If Tcl_EventuallyFree has been called for clientData, and if - * no other call to Tcl_Preserve is still in effect, the block of - * memory is freed. + * If Tcl_EventuallyFree has been called for clientData, and if no other + * call to Tcl_Preserve is still in effect, the block of memory is freed. * *---------------------------------------------------------------------- */ @@ -198,48 +199,57 @@ Tcl_Release(clientData) ClientData clientData; /* Pointer to malloc'ed block of memory. */ { Reference *refPtr; - int mustFree; - Tcl_FreeProc *freeProc; int i; Tcl_MutexLock(&preserveMutex); - for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) { + for (i=0, refPtr=refArray ; i<inUse ; i++, refPtr++) { + int mustFree; + Tcl_FreeProc *freeProc; + if (refPtr->clientData != clientData) { continue; } - refPtr->refCount--; - if (refPtr->refCount == 0) { - - /* - * Must remove information from the slot before calling freeProc - * to avoid reentrancy problems if the freeProc calls Tcl_Preserve - * on the same clientData. Copy down the last reference in the - * array to overwrite the current slot. - */ - - freeProc = refPtr->freeProc; - mustFree = refPtr->mustFree; - inUse--; - if (i < inUse) { - refArray[i] = refArray[inUse]; - } - if (mustFree) { - if (freeProc == TCL_DYNAMIC) { - ckfree((char *) clientData); - } else { - Tcl_MutexUnlock(&preserveMutex); - (*freeProc)((char *) clientData); - return; - } - } + + if (--refPtr->refCount != 0) { + Tcl_MutexUnlock(&preserveMutex); + return; + } + + /* + * Must remove information from the slot before calling freeProc to + * avoid reentrancy problems if the freeProc calls Tcl_Preserve on the + * same clientData. Copy down the last reference in the array to + * overwrite the current slot. + */ + + freeProc = refPtr->freeProc; + mustFree = refPtr->mustFree; + inUse--; + if (i < inUse) { + refArray[i] = refArray[inUse]; } + + /* + * Now committed to disposing the data. But first, we've patched up + * all the global data structures so we should release the mutex now. + * Only then should we dabble around with potentially-slow memory + * managers... + */ + Tcl_MutexUnlock(&preserveMutex); + if (mustFree) { + if (freeProc == TCL_DYNAMIC) { + ckfree((char *) clientData); + } else { + (*freeProc)((char *) clientData); + } + } return; } Tcl_MutexUnlock(&preserveMutex); /* - * Reference not found. This is a bug in the caller. + * Reference not found. This is a bug in the caller. */ Tcl_Panic("Tcl_Release couldn't find reference for 0x%x", clientData); @@ -250,10 +260,9 @@ Tcl_Release(clientData) * * Tcl_EventuallyFree -- * - * Free up a block of memory, unless a call to Tcl_Preserve is in - * effect for that block. In this case, defer the free until all - * calls to Tcl_Preserve have been undone by matching calls to - * Tcl_Release. + * Free up a block of memory, unless a call to Tcl_Preserve is in effect + * for that block. In this case, defer the free until all calls to + * Tcl_Preserve have been undone by matching calls to Tcl_Release. * * Results: * None. @@ -267,14 +276,14 @@ Tcl_Release(clientData) void Tcl_EventuallyFree(clientData, freeProc) ClientData clientData; /* Pointer to malloc'ed block of memory. */ - Tcl_FreeProc *freeProc; /* Procedure to actually do free. */ + Tcl_FreeProc *freeProc; /* Function to actually do free. */ { Reference *refPtr; int i; /* - * See if there is a reference for this pointer. If so, set its - * "mustFree" flag (the flag had better not be set already!). + * See if there is a reference for this pointer. If so, set its "mustFree" + * flag (the flag had better not be set already!). */ Tcl_MutexLock(&preserveMutex); @@ -283,7 +292,8 @@ Tcl_EventuallyFree(clientData, freeProc) continue; } if (refPtr->mustFree) { - Tcl_Panic("Tcl_EventuallyFree called twice for 0x%x\n", clientData); + Tcl_Panic("Tcl_EventuallyFree called twice for 0x%x\n", + clientData); } refPtr->mustFree = 1; refPtr->freeProc = freeProc; @@ -308,31 +318,29 @@ Tcl_EventuallyFree(clientData, freeProc) * * TclHandleCreate -- * - * Allocate a handle that contains enough information to determine - * if an arbitrary malloc'd block has been deleted. This is - * used to avoid the more time-expensive algorithm of Tcl_Preserve(). + * Allocate a handle that contains enough information to determine if an + * arbitrary malloc'd block has been deleted. This is used to avoid the + * more time-expensive algorithm of Tcl_Preserve(). * * Results: * The return value is a TclHandle that refers to the given malloc'd - * block. Doubly dereferencing the returned handle will give - * back the pointer to the block, or will give NULL if the block has - * been deleted. + * block. Doubly dereferencing the returned handle will give back the + * pointer to the block, or will give NULL if the block has been deleted. * * Side effects: - * The caller must keep track of this handle (generally by storing - * it in a field in the malloc'd block) and call TclHandleFree() - * on this handle when the block is deleted. Everything else that - * wishes to keep track of whether the malloc'd block has been deleted - * should use calls to TclHandlePreserve() and TclHandleRelease() - * on the associated handle. + * The caller must keep track of this handle (generally by storing it in + * a field in the malloc'd block) and call TclHandleFree() on this handle + * when the block is deleted. Everything else that wishes to keep track + * of whether the malloc'd block has been deleted should use calls to + * TclHandlePreserve() and TclHandleRelease() on the associated handle. * *--------------------------------------------------------------------------- */ TclHandle TclHandleCreate(ptr) - VOID *ptr; /* Pointer to an arbitrary block of memory - * to be tracked for deletion. Must not be + VOID *ptr; /* Pointer to an arbitrary block of memory to + * be tracked for deletion. Must not be * NULL. */ { HandleStruct *handlePtr; @@ -351,11 +359,10 @@ TclHandleCreate(ptr) * * TclHandleFree -- * - * Called when the arbitrary malloc'd block associated with the - * handle is being deleted. Modifies the handle so that doubly - * dereferencing it will give NULL. This informs any user of the - * handle that the block of memory formerly referenced by the - * handle has been freed. + * Called when the arbitrary malloc'd block associated with the handle is + * being deleted. Modifies the handle so that doubly dereferencing it + * will give NULL. This informs any user of the handle that the block of + * memory formerly referenced by the handle has been freed. * * Results: * None. @@ -368,10 +375,10 @@ TclHandleCreate(ptr) void TclHandleFree(handle) - TclHandle handle; /* Previously created handle associated - * with a malloc'd block that is being - * deleted. The handle is modified so that - * doubly dereferencing it will give NULL. */ + TclHandle handle; /* Previously created handle associated with a + * malloc'd block that is being deleted. The + * handle is modified so that doubly + * dereferencing it will give NULL. */ { HandleStruct *handlePtr; @@ -396,25 +403,25 @@ TclHandleFree(handle) * * TclHandlePreserve -- * - * Declare an interest in the arbitrary malloc'd block associated - * with the handle. + * Declare an interest in the arbitrary malloc'd block associated with + * the handle. * * Results: * The return value is the handle argument, with its ref count * incremented. * * Side effects: - * For each call to TclHandlePreserve(), there should be a matching - * call to TclHandleRelease() when the caller is no longer interested - * in the malloc'd block associated with the handle. + * For each call to TclHandlePreserve(), there should be a matching call + * to TclHandleRelease() when the caller is no longer interested in the + * malloc'd block associated with the handle. * *--------------------------------------------------------------------------- */ TclHandle TclHandlePreserve(handle) - TclHandle handle; /* Declare an interest in the block of - * memory referenced by this handle. */ + TclHandle handle; /* Declare an interest in the block of memory + * referenced by this handle. */ { HandleStruct *handlePtr; @@ -423,8 +430,7 @@ TclHandlePreserve(handle) if (handlePtr->refCount == 0x61616161) { Tcl_Panic("using previously disposed TclHandle %x", handlePtr); } - if ((handlePtr->ptr != NULL) - && (handlePtr->ptr != handlePtr->ptr2)) { + if ((handlePtr->ptr != NULL) && (handlePtr->ptr != handlePtr->ptr2)) { Tcl_Panic("someone has changed the block referenced by the handle %x\nfrom %x to %x", handlePtr, handlePtr->ptr2, handlePtr->ptr); } @@ -439,24 +445,24 @@ TclHandlePreserve(handle) * * TclHandleRelease -- * - * This procedure is called to release an interest in the malloc'd - * block associated with the handle. + * This function is called to release an interest in the malloc'd block + * associated with the handle. * * Results: * None. * * Side effects: - * The ref count of the handle is decremented. If the malloc'd block - * has been freed and if no one is using the handle any more, the - * handle will be reclaimed. + * The ref count of the handle is decremented. If the malloc'd block has + * been freed and if no one is using the handle any more, the handle will + * be reclaimed. * *--------------------------------------------------------------------------- */ - + void TclHandleRelease(handle) - TclHandle handle; /* Unregister interest in the block of - * memory referenced by this handle. */ + TclHandle handle; /* Unregister interest in the block of memory + * referenced by this handle. */ { HandleStruct *handlePtr; @@ -465,8 +471,7 @@ TclHandleRelease(handle) if (handlePtr->refCount == 0x61616161) { Tcl_Panic("using previously disposed TclHandle %x", handlePtr); } - if ((handlePtr->ptr != NULL) - && (handlePtr->ptr != handlePtr->ptr2)) { + if ((handlePtr->ptr != NULL) && (handlePtr->ptr != handlePtr->ptr2)) { Tcl_Panic("someone has changed the block referenced by the handle %x\nfrom %x to %x", handlePtr, handlePtr->ptr2, handlePtr->ptr); } @@ -476,4 +481,11 @@ TclHandleRelease(handle) ckfree((char *) handlePtr); } } - + +/* + * Local Variables: + * mode: c + * c-basic-offset: 4 + * fill-column: 78 + * End: + */ |