tclLiteral.c Go to the documentation of this file. /* * tclLiteral.c -- * * Implementation of the global and ByteCode-local literal tables used to * manage the Tcl objects created for literal values during compilation * of Tcl scripts. This implementation borrows heavily from the more * general hashtable implementation of Tcl hash tables that appears in * tclHash.c. * * Copyright (c) 1997-1998 Sun Microsystems, Inc. * Copyright (c) 2004 by Kevin B. Kenny. All rights reserved. * * See the file "license.terms" for information on usage and redistribution of * this file, and for a DISCLAIMER OF ALL WARRANTIES. * * RCS: @(#) $Id: tclLiteral.c,v 1.33 2007/12/13 15:23:19 dgp Exp $ */ #include "tclInt.h" #include "tclCompile.h" /* * When there are this many entries per bucket, on average, rebuild a * literal's hash table to make it larger. */ #define REBUILD_MULTIPLIER 3 /* * Function prototypes for static functions in this file: */ static int AddLocalLiteralEntry(CompileEnv *envPtr, Tcl_Obj *objPtr, int localHash); static void ExpandLocalLiteralArray(CompileEnv *envPtr); static unsigned int HashString(const char *bytes, int length); static void RebuildLiteralTable(LiteralTable *tablePtr);  /* *---------------------------------------------------------------------- * * TclInitLiteralTable -- * * This function is called to initialize the fields of a literal table * structure for either an interpreter or a compilation's CompileEnv * structure. * * Results: * None. * * Side effects: * The literal table is made ready for use. * *---------------------------------------------------------------------- */ void TclInitLiteralTable( register LiteralTable *tablePtr) /* Pointer to table structure, which is * supplied by the caller. */ { #if (TCL_SMALL_HASH_TABLE != 4) Tcl_Panic("TclInitLiteralTable: TCL_SMALL_HASH_TABLE is %d, not 4", TCL_SMALL_HASH_TABLE); #endif tablePtr->buckets = tablePtr->staticBuckets; tablePtr->staticBuckets[0] = tablePtr->staticBuckets[1] = 0; tablePtr->staticBuckets[2] = tablePtr->staticBuckets[3] = 0; tablePtr->numBuckets = TCL_SMALL_HASH_TABLE; tablePtr->numEntries = 0; tablePtr->rebuildSize = TCL_SMALL_HASH_TABLE * REBUILD_MULTIPLIER; tablePtr->mask = 3; }  /* *---------------------------------------------------------------------- * * TclCleanupLiteralTable -- * * This function frees the internal representation of every literal in a * literal table. It is called prior to deleting an interp, so that * variable refs will be cleaned up properly. * * Results: * None. * * Side effects: * Each literal in the table has its internal representation freed. * *---------------------------------------------------------------------- */ void TclCleanupLiteralTable( Tcl_Interp *interp, /* Interpreter containing literals to purge */ LiteralTable *tablePtr) /* Points to the literal table being * cleaned. */ { int i; LiteralEntry* entryPtr; /* Pointer to the current entry in the hash * table of literals. */ LiteralEntry* nextPtr; /* Pointer to the next entry in the bucket. */ Tcl_Obj* objPtr; /* Pointer to a literal object whose internal * rep is being freed. */ const Tcl_ObjType* typePtr; /* Pointer to the object's type. */ int didOne; /* Flag for whether we've removed a literal in * the current bucket. */ #ifdef TCL_COMPILE_DEBUG TclVerifyGlobalLiteralTable((Interp *) interp); #endif /* TCL_COMPILE_DEBUG */ for (i=0 ; i<tablePtr->numBuckets ; i++) { /* * It is tempting simply to walk each hash bucket once and delete the * internal representations of each literal in turn. It's also wrong. * The problem is that freeing a literal's internal representation can * delete other literals to which it refers, making nextPtr invalid. * So each time we free an internal rep, we start its bucket over * again. */ do { didOne = 0; entryPtr = tablePtr->buckets[i]; while (entryPtr != NULL) { objPtr = entryPtr->objPtr; nextPtr = entryPtr->nextPtr; typePtr = objPtr->typePtr; if ((typePtr != NULL) && (typePtr->freeIntRepProc != NULL)) { if (objPtr->bytes == NULL) { Tcl_Panic( "literal without a string rep" ); } objPtr->typePtr = NULL; typePtr->freeIntRepProc(objPtr); didOne = 1; } else { entryPtr = nextPtr; } } } while (didOne); } }  /* *---------------------------------------------------------------------- * * TclDeleteLiteralTable -- * * This function frees up everything associated with a literal table * except for the table's structure itself. It is called when the * interpreter is deleted. * * Results: * None. * * Side effects: * Each literal in the table is released: i.e., its reference count in * the global literal table is decremented and, if it becomes zero, the * literal is freed. In addition, the table's bucket array is freed. * *---------------------------------------------------------------------- */ void TclDeleteLiteralTable( Tcl_Interp *interp, /* Interpreter containing shared literals * referenced by the table to delete. */ LiteralTable *tablePtr) /* Points to the literal table to delete. */ { LiteralEntry *entryPtr, *nextPtr; Tcl_Obj *objPtr; int i; /* * Release remaining literals in the table. Note that releasing a literal * might release other literals, modifying the table, so we restart the * search from the bucket chain we last found an entry. */ #ifdef TCL_COMPILE_DEBUG TclVerifyGlobalLiteralTable((Interp *) interp); #endif /*TCL_COMPILE_DEBUG*/ /* * We used to call TclReleaseLiteral for each literal in the table, which * is rather inefficient as it causes one lookup-by-hash for each * reference to the literal. We now rely at interp-deletion on each * bytecode object to release its references to the literal Tcl_Obj * without requiring that it updates the global table itself, and deal * here only with the table. */ for (i=0 ; i<tablePtr->numBuckets ; i++) { entryPtr = tablePtr->buckets[i]; while (entryPtr != NULL) { objPtr = entryPtr->objPtr; TclDecrRefCount(objPtr); nextPtr = entryPtr->nextPtr; ckfree((char *) entryPtr); entryPtr = nextPtr; } } /* * Free up the table's bucket array if it was dynamically allocated. */ if (tablePtr->buckets != tablePtr->staticBuckets) { ckfree((char *) tablePtr->buckets); } }  /* *---------------------------------------------------------------------- * * TclCreateLiteral -- * * Find, or if necessary create, an object in the interpreter's literal * table that has a string representation matching the argument * string. If nsPtr!=NULL then only literals stored for the namespace are * considered. * * Results: * The literal object. If it was created in this call *newPtr is set to * 1, else 0. NULL is returned if newPtr==NULL and no literal is found. * * Side effects: * Increments the ref count of the global LiteralEntry since the caller * now holds a reference. * If LITERAL_ON_HEAP is set in flags, this function is given ownership * of the string: if an object is created then its string representation * is set directly from string, otherwise the string is freed. Typically, * a caller sets LITERAL_ON_HEAP if "string" is an already heap-allocated * buffer holding the result of backslash substitutions. * *---------------------------------------------------------------------- */ Tcl_Obj * TclCreateLiteral( Interp *iPtr, char *bytes, int length, unsigned int hash, /* The string's hash. If -1, it will be computed here */ int *newPtr, Namespace *nsPtr, int flags, LiteralEntry **globalPtrPtr) { LiteralTable *globalTablePtr = &(iPtr->literalTable); LiteralEntry *globalPtr; int globalHash; Tcl_Obj *objPtr; /* * Is it in the interpreter's global literal table? */ if (hash == (unsigned int) -1) { hash = HashString(bytes, length); } globalHash = (hash & globalTablePtr->mask); for (globalPtr=globalTablePtr->buckets[globalHash] ; globalPtr!=NULL; globalPtr = globalPtr->nextPtr) { objPtr = globalPtr->objPtr; if ((globalPtr->nsPtr == nsPtr) && (objPtr->length == length) && ((length == 0) || ((objPtr->bytes[0] == bytes[0]) && (memcmp(objPtr->bytes, bytes, (unsigned) length) == 0)))) { /* * A literal was found: return it */ if (newPtr) { *newPtr = 0; } if (globalPtrPtr) { *globalPtrPtr = globalPtr; } if (flags & LITERAL_ON_HEAP) { ckfree(bytes); } globalPtr->refCount++; return objPtr; } } if (!newPtr) { if (flags & LITERAL_ON_HEAP) { ckfree(bytes); } return NULL; } /* * The literal is new to the interpreter. Add it to the global literal * table. */ TclNewObj(objPtr); Tcl_IncrRefCount(objPtr); if (flags & LITERAL_ON_HEAP) { objPtr->bytes = bytes; objPtr->length = length; } else { TclInitStringRep(objPtr, bytes, length); } #ifdef TCL_COMPILE_DEBUG if (TclLookupLiteralEntry((Tcl_Interp *) iPtr, objPtr) != NULL) { Tcl_Panic("TclRegisterLiteral: literal \"%.*s\" found globally but shouldn't be", (length>60? 60 : length), bytes); } #endif globalPtr = (LiteralEntry *) ckalloc((unsigned) sizeof(LiteralEntry)); globalPtr->objPtr = objPtr; globalPtr->refCount = 1; globalPtr->nsPtr = nsPtr; globalPtr->nextPtr = globalTablePtr->buckets[globalHash]; globalTablePtr->buckets[globalHash] = globalPtr; globalTablePtr->numEntries++; /* * If the global literal table has exceeded a decent size, rebuild it with * more buckets. */ if (globalTablePtr->numEntries >= globalTablePtr->rebuildSize) { RebuildLiteralTable(globalTablePtr); } #ifdef TCL_COMPILE_DEBUG TclVerifyGlobalLiteralTable(iPtr); { LiteralEntry *entryPtr; int found, i; found = 0; for (i=0 ; i<globalTablePtr->numBuckets ; i++) { for (entryPtr=globalTablePtr->buckets[i]; entryPtr!=NULL ; entryPtr=entryPtr->nextPtr) { if ((entryPtr == globalPtr) && (entryPtr->objPtr == objPtr)) { found = 1; } } } if (!found) { Tcl_Panic("TclRegisterLiteral: literal \"%.*s\" wasn't global", (length>60? 60 : length), bytes); } } #endif /*TCL_COMPILE_DEBUG*/ #ifdef TCL_COMPILE_STATS iPtr->stats.numLiteralsCreated++; iPtr->stats.totalLitStringBytes += (double) (length + 1); iPtr->stats.currentLitStringBytes += (double) (length + 1); iPtr->stats.literalCount[TclLog2(length)]++; #endif /*TCL_COMPILE_STATS*/ if (globalPtrPtr) { *globalPtrPtr = globalPtr; } *newPtr = 1; return objPtr; }  /* *---------------------------------------------------------------------- * * TclRegisterLiteral -- * * Find, or if necessary create, an object in a CompileEnv literal array * that has a string representation matching the argument string. * * Results: * The index in the CompileEnv's literal array that references a shared * literal matching the string. The object is created if necessary. * * Side effects: * To maximize sharing, we look up the string in the interpreter's global * literal table. If not found, we create a new shared literal in the * global table. We then add a reference to the shared literal in the * CompileEnv's literal array. * * If LITERAL_ON_HEAP is set in flags, this function is given ownership * of the string: if an object is created then its string representation * is set directly from string, otherwise the string is freed. Typically, * a caller sets LITERAL_ON_HEAP if "string" is an already heap-allocated * buffer holding the result of backslash substitutions. * *---------------------------------------------------------------------- */ int TclRegisterLiteral( CompileEnv *envPtr, /* Points to the CompileEnv in whose object * array an object is found or created. */ register char *bytes, /* Points to string for which to find or * create an object in CompileEnv's object * array. */ int length, /* Number of bytes in the string. If < 0, the * string consists of all bytes up to the * first null character. */ int flags) /* If LITERAL_ON_HEAP then the caller already * malloc'd bytes and ownership is passed to * this function. If LITERAL_NS_SCOPE then * the literal shouldnot be shared accross * namespaces. */ { Interp *iPtr = envPtr->iPtr; LiteralTable *localTablePtr = &(envPtr->localLitTable); LiteralEntry *globalPtr, *localPtr; Tcl_Obj *objPtr; unsigned int hash; int localHash, objIndex, new; Namespace *nsPtr; if (length < 0) { length = (bytes ? strlen(bytes) : 0); } hash = HashString(bytes, length); /* * Is the literal already in the CompileEnv's local literal array? If so, * just return its index. */ localHash = (hash & localTablePtr->mask); for (localPtr=localTablePtr->buckets[localHash] ; localPtr!=NULL; localPtr = localPtr->nextPtr) { objPtr = localPtr->objPtr; if ((objPtr->length == length) && ((length == 0) || ((objPtr->bytes[0] == bytes[0]) && (memcmp(objPtr->bytes, bytes, (unsigned) length) == 0)))) { if (flags & LITERAL_ON_HEAP) { ckfree(bytes); } objIndex = (localPtr - envPtr->literalArrayPtr); #ifdef TCL_COMPILE_DEBUG TclVerifyLocalLiteralTable(envPtr); #endif /*TCL_COMPILE_DEBUG*/ return objIndex; } } /* * The literal is new to this CompileEnv. Should it be shared accross * namespaces? If it is a fully qualified name, the namespace * specification is not needed to avoid sharing. */ if ((flags & LITERAL_NS_SCOPE) && iPtr->varFramePtr && ((length <2) || (bytes[0] != ':') || (bytes[1] != ':'))) { nsPtr = iPtr->varFramePtr->nsPtr; } else { nsPtr = NULL; } /* * Is it in the interpreter's global literal table? If not, create it. */ objPtr = TclCreateLiteral(iPtr, bytes, length, hash, &new, nsPtr, flags, &globalPtr); objIndex = AddLocalLiteralEntry(envPtr, objPtr, localHash); #ifdef TCL_COMPILE_DEBUG if (globalPtr->refCount < 1) { Tcl_Panic("TclRegisterLiteral: global literal \"%.*s\" had bad refCount %d", (length>60? 60 : length), bytes, globalPtr->refCount); } TclVerifyLocalLiteralTable(envPtr); #endif /*TCL_COMPILE_DEBUG*/ return objIndex; }  /* *---------------------------------------------------------------------- * * TclLookupLiteralEntry -- * * Finds the LiteralEntry that corresponds to a literal Tcl object * holding a literal. * * Results: * Returns the matching LiteralEntry if found, otherwise NULL. * * Side effects: * None. * *---------------------------------------------------------------------- */ LiteralEntry * TclLookupLiteralEntry( Tcl_Interp *interp, /* Interpreter for which objPtr was created to * hold a literal. */ register Tcl_Obj *objPtr) /* Points to a Tcl object holding a literal * that was previously created by a call to * TclRegisterLiteral. */ { Interp *iPtr = (Interp *) interp; LiteralTable *globalTablePtr = &(iPtr->literalTable); register LiteralEntry *entryPtr; char *bytes; int length, globalHash; bytes = TclGetStringFromObj(objPtr, &length); globalHash = (HashString(bytes, length) & globalTablePtr->mask); for (entryPtr=globalTablePtr->buckets[globalHash] ; entryPtr!=NULL; entryPtr=entryPtr->nextPtr) { if (entryPtr->objPtr == objPtr) { return entryPtr; } } return NULL; }  /* *---------------------------------------------------------------------- * * TclHideLiteral -- * * Remove a literal entry from the literal hash tables, leaving it in the * literal array so existing references continue to function. This makes * it possible to turn a shared literal into a private literal that * cannot be shared. * * Results: * None. * * Side effects: * Removes the literal from the local hash table and decrements the * global hash entry's reference count. * *---------------------------------------------------------------------- */ void TclHideLiteral( Tcl_Interp *interp, /* Interpreter for which objPtr was created to * hold a literal. */ register CompileEnv *envPtr,/* Points to CompileEnv whose literal array * contains the entry being hidden. */ int index) /* The index of the entry in the literal * array. */ { LiteralEntry **nextPtrPtr, *entryPtr, *lPtr; LiteralTable *localTablePtr = &(envPtr->localLitTable); int localHash, length; char *bytes; Tcl_Obj *newObjPtr; lPtr = &(envPtr->literalArrayPtr[index]); /* * To avoid unwanted sharing we need to copy the object and remove it from * the local and global literal tables. It still has a slot in the literal * array so it can be referred to by byte codes, but it will not be * matched by literal searches. */ newObjPtr = Tcl_DuplicateObj(lPtr->objPtr); Tcl_IncrRefCount(newObjPtr); TclReleaseLiteral(interp, lPtr->objPtr); lPtr->objPtr = newObjPtr; bytes = TclGetStringFromObj(newObjPtr, &length); localHash = (HashString(bytes, length) & localTablePtr->mask); nextPtrPtr = &localTablePtr->buckets[localHash]; for (entryPtr=*nextPtrPtr ; entryPtr!=NULL ; entryPtr=*nextPtrPtr) { if (entryPtr == lPtr) { *nextPtrPtr = lPtr->nextPtr; lPtr->nextPtr = NULL; localTablePtr->numEntries--; break; } nextPtrPtr = &entryPtr->nextPtr; } }  /* *---------------------------------------------------------------------- * * TclAddLiteralObj -- * * Add a single literal object to the literal array. This function does * not add the literal to the local or global literal tables. The caller * is expected to add the entry to whatever tables are appropriate. * * Results: * The index in the CompileEnv's literal array that references the * literal. Stores the pointer to the new literal entry in the location * referenced by the localPtrPtr argument. * * Side effects: * Expands the literal array if necessary. Increments the refcount on the * literal object. * *---------------------------------------------------------------------- */ int TclAddLiteralObj( register CompileEnv *envPtr,/* Points to CompileEnv in whose literal array * the object is to be inserted. */ Tcl_Obj *objPtr, /* The object to insert into the array. */ LiteralEntry **litPtrPtr) /* The location where the pointer to the new * literal entry should be stored. May be * NULL. */ { register LiteralEntry *lPtr; int objIndex; if (envPtr->literalArrayNext >= envPtr->literalArrayEnd) { ExpandLocalLiteralArray(envPtr); } objIndex = envPtr->literalArrayNext; envPtr->literalArrayNext++; lPtr = &(envPtr->literalArrayPtr[objIndex]); lPtr->objPtr = objPtr; Tcl_IncrRefCount(objPtr); lPtr->refCount = -1; /* i.e., unused */ lPtr->nextPtr = NULL; if (litPtrPtr) { *litPtrPtr = lPtr; } return objIndex; }  /* *---------------------------------------------------------------------- * * AddLocalLiteralEntry -- * * Insert a new literal into a CompileEnv's local literal array. * * Results: * The index in the CompileEnv's literal array that references the * literal. * * Side effects: * Expands the literal array if necessary. May rebuild the hash bucket * array of the CompileEnv's literal array if it becomes too large. * *---------------------------------------------------------------------- */ static int AddLocalLiteralEntry( register CompileEnv *envPtr,/* Points to CompileEnv in whose literal array * the object is to be inserted. */ Tcl_Obj *objPtr, /* The literal to add to the CompileEnv. */ int localHash) /* Hash value for the literal's string. */ { register LiteralTable *localTablePtr = &(envPtr->localLitTable); LiteralEntry *localPtr; int objIndex; objIndex = TclAddLiteralObj(envPtr, objPtr, &localPtr); /* * Add the literal to the local table. */ localPtr->nextPtr = localTablePtr->buckets[localHash]; localTablePtr->buckets[localHash] = localPtr; localTablePtr->numEntries++; /* * If the CompileEnv's local literal table has exceeded a decent size, * rebuild it with more buckets. */ if (localTablePtr->numEntries >= localTablePtr->rebuildSize) { RebuildLiteralTable(localTablePtr); } #ifdef TCL_COMPILE_DEBUG TclVerifyLocalLiteralTable(envPtr); { char *bytes; int length, found, i; found = 0; for (i=0 ; i<localTablePtr->numBuckets ; i++) { for (localPtr=localTablePtr->buckets[i] ; localPtr!=NULL ; localPtr=localPtr->nextPtr) { if (localPtr->objPtr == objPtr) { found = 1; } } } if (!found) { bytes = Tcl_GetStringFromObj(objPtr, &length); Tcl_Panic("AddLocalLiteralEntry: literal \"%.*s\" wasn't found locally", (length>60? 60 : length), bytes); } } #endif /*TCL_COMPILE_DEBUG*/ return objIndex; }  /* *---------------------------------------------------------------------- * * ExpandLocalLiteralArray -- * * Function that uses malloc to allocate more storage for a CompileEnv's * local literal array. * * Results: * None. * * Side effects: * The literal array in *envPtr is reallocated to a new array of double * the size, and if envPtr->mallocedLiteralArray is non-zero the old * array is freed. Entries are copied from the old array to the new one. * The local literal table is updated to refer to the new entries. * *---------------------------------------------------------------------- */ static void ExpandLocalLiteralArray( register CompileEnv *envPtr)/* Points to the CompileEnv whose object array * must be enlarged. */ { /* * The current allocated local literal entries are stored between elements * 0 and (envPtr->literalArrayNext - 1) [inclusive]. */ LiteralTable *localTablePtr = &(envPtr->localLitTable); int currElems = envPtr->literalArrayNext; size_t currBytes = (currElems * sizeof(LiteralEntry)); LiteralEntry *currArrayPtr = envPtr->literalArrayPtr; LiteralEntry *newArrayPtr; int i; if (envPtr->mallocedLiteralArray) { newArrayPtr = (LiteralEntry *) ckrealloc( (char *)currArrayPtr, 2 * currBytes); } else { /* * envPtr->literalArrayPtr isn't a ckalloc'd pointer, so we must * code a ckrealloc equivalent for ourselves */ newArrayPtr = (LiteralEntry *) ckalloc(2 * currBytes); memcpy(newArrayPtr, currArrayPtr, currBytes); envPtr->mallocedLiteralArray = 1; } /* * Update the local literal table's bucket array. */ if (currArrayPtr != newArrayPtr) { for (i=0 ; i<currElems ; i++) { if (newArrayPtr[i].nextPtr != NULL) { newArrayPtr[i].nextPtr = newArrayPtr + (newArrayPtr[i].nextPtr - currArrayPtr); } } for (i=0 ; i<localTablePtr->numBuckets ; i++) { if (localTablePtr->buckets[i] != NULL) { localTablePtr->buckets[i] = newArrayPtr + (localTablePtr->buckets[i] - currArrayPtr); } } } envPtr->literalArrayPtr = newArrayPtr; envPtr->literalArrayEnd = (2 * currElems); }  /* *---------------------------------------------------------------------- * * TclReleaseLiteral -- * * This function releases a reference to one of the shared Tcl objects * that hold literals. It is called to release the literals referenced by * a ByteCode that is being destroyed, and it is also called by * TclDeleteLiteralTable. * * Results: * None. * * Side effects: * The reference count for the global LiteralTable entry that corresponds * to the literal is decremented. If no other reference to a global * literal object remains, it is freed. * *---------------------------------------------------------------------- */ void TclReleaseLiteral( Tcl_Interp *interp, /* Interpreter for which objPtr was created to * hold a literal. */ register Tcl_Obj *objPtr) /* Points to a literal object that was * previously created by a call to * TclRegisterLiteral. */ { Interp *iPtr = (Interp *) interp; LiteralTable *globalTablePtr = &(iPtr->literalTable); register LiteralEntry *entryPtr, *prevPtr; char *bytes; int length, index; bytes = TclGetStringFromObj(objPtr, &length); index = (HashString(bytes, length) & globalTablePtr->mask); /* * Check to see if the object is in the global literal table and remove * this reference. The object may not be in the table if it is a hidden * local literal. */ for (prevPtr=NULL, entryPtr=globalTablePtr->buckets[index]; entryPtr!=NULL ; prevPtr=entryPtr, entryPtr=entryPtr->nextPtr) { if (entryPtr->objPtr == objPtr) { entryPtr->refCount--; /* * If the literal is no longer being used by any ByteCode, delete * the entry then remove the reference corresponding to the global * literal table entry (decrement the ref count of the object). */ if (entryPtr->refCount == 0) { if (prevPtr == NULL) { globalTablePtr->buckets[index] = entryPtr->nextPtr; } else { prevPtr->nextPtr = entryPtr->nextPtr; } ckfree((char *) entryPtr); globalTablePtr->numEntries--; TclDecrRefCount(objPtr); #ifdef TCL_COMPILE_STATS iPtr->stats.currentLitStringBytes -= (double) (length + 1); #endif /*TCL_COMPILE_STATS*/ } break; } } /* * Remove the reference corresponding to the local literal table entry. */ Tcl_DecrRefCount(objPtr); }  /* *---------------------------------------------------------------------- * * HashString -- * * Compute a one-word summary of a text string, which can be used to * generate a hash index. * * Results: * The return value is a one-word summary of the information in string. * * Side effects: * None. * *---------------------------------------------------------------------- */ static unsigned int HashString( register const char *bytes, /* String for which to compute hash value. */ int length) /* Number of bytes in the string. */ { register unsigned int result; register int i; /* * I tried a zillion different hash functions and asked many other people * for advice. Many people had their own favorite functions, all * different, but no-one had much idea why they were good ones. I chose * the one below (multiply by 9 and add new character) because of the * following reasons: * * 1. Multiplying by 10 is perfect for keys that are decimal strings, and * multiplying by 9 is just about as good. * 2. Times-9 is (shift-left-3) plus (old). This means that each * character's bits hang around in the low-order bits of the hash value * for ever, plus they spread fairly rapidly up to the high-order bits * to fill out the hash value. This seems works well both for decimal * and non-decimal strings. */ result = 0; for (i=0 ; i<length ; i++) { result += (result<<3) + bytes[i]; } return result; }  /* *---------------------------------------------------------------------- * * RebuildLiteralTable -- * * This function is invoked when the ratio of entries to hash buckets * becomes too large in a local or global literal table. It allocates a * larger bucket array and moves the entries into the new buckets. * * Results: * None. * * Side effects: * Memory gets reallocated and entries get rehashed into new buckets. * *---------------------------------------------------------------------- */ static void RebuildLiteralTable( register LiteralTable *tablePtr) /* Local or global table to enlarge. */ { LiteralEntry **oldBuckets; register LiteralEntry **oldChainPtr, **newChainPtr; register LiteralEntry *entryPtr; LiteralEntry **bucketPtr; char *bytes; int oldSize, count, index, length; oldSize = tablePtr->numBuckets; oldBuckets = tablePtr->buckets; /* * Allocate and initialize the new bucket array, and set up hashing * constants for new array size. */ tablePtr->numBuckets *= 4; tablePtr->buckets = (LiteralEntry **) ckalloc((unsigned) (tablePtr->numBuckets * sizeof(LiteralEntry *))); for (count=tablePtr->numBuckets, newChainPtr=tablePtr->buckets; count>0 ; count--, newChainPtr++) { *newChainPtr = NULL; } tablePtr->rebuildSize *= 4; tablePtr->mask = (tablePtr->mask << 2) + 3; /* * Rehash all of the existing entries into the new bucket array. */ for (oldChainPtr=oldBuckets ; oldSize>0 ; oldSize--,oldChainPtr++) { for (entryPtr=*oldChainPtr ; entryPtr!=NULL ; entryPtr=*oldChainPtr) { bytes = TclGetStringFromObj(entryPtr->objPtr, &length); index = (HashString(bytes, length) & tablePtr->mask); *oldChainPtr = entryPtr->nextPtr; bucketPtr = &(tablePtr->buckets[index]); entryPtr->nextPtr = *bucketPtr; *bucketPtr = entryPtr; } } /* * Free up the old bucket array, if it was dynamically allocated. */ if (oldBuckets != tablePtr->staticBuckets) { ckfree((char *) oldBuckets); } }  #ifdef TCL_COMPILE_STATS /* *---------------------------------------------------------------------- * * TclLiteralStats -- * * Return statistics describing the layout of the hash table in its hash * buckets. * * Results: * The return value is a malloc-ed string containing information about * tablePtr. It is the caller's responsibility to free this string. * * Side effects: * None. * *---------------------------------------------------------------------- */ char * TclLiteralStats( LiteralTable *tablePtr) /* Table for which to produce stats. */ { #define NUM_COUNTERS 10 int count[NUM_COUNTERS], overflow, i, j; double average, tmp; register LiteralEntry *entryPtr; char *result, *p; /* * Compute a histogram of bucket usage. For each bucket chain i, j is the * number of entries in the chain. */ for (i=0 ; i<NUM_COUNTERS ; i++) { count[i] = 0; } overflow = 0; average = 0.0; for (i=0 ; i<tablePtr->numBuckets ; i++) { j = 0; for (entryPtr=tablePtr->buckets[i] ; entryPtr!=NULL; entryPtr=entryPtr->nextPtr) { j++; } if (j < NUM_COUNTERS) { count[j]++; } else { overflow++; } tmp = j; average += (tmp+1.0)*(tmp/tablePtr->numEntries)/2.0; } /* * Print out the histogram and a few other pieces of information. */ result = (char *) ckalloc((unsigned) ((NUM_COUNTERS*60) + 300)); sprintf(result, "%d entries in table, %d buckets\n", tablePtr->numEntries, tablePtr->numBuckets); p = result + strlen(result); for (i=0 ; i<NUM_COUNTERS ; i++) { sprintf(p, "number of buckets with %d entries: %d\n", i, count[i]); p += strlen(p); } sprintf(p, "number of buckets with %d or more entries: %d\n", NUM_COUNTERS, overflow); p += strlen(p); sprintf(p, "average search distance for entry: %.1f", average); return result; } #endif /*TCL_COMPILE_STATS*/  #ifdef TCL_COMPILE_DEBUG /* *---------------------------------------------------------------------- * * TclVerifyLocalLiteralTable -- * * Check a CompileEnv's local literal table for consistency. * * Results: * None. * * Side effects: * Tcl_Panic if problems are found. * *---------------------------------------------------------------------- */ void TclVerifyLocalLiteralTable( CompileEnv *envPtr) /* Points to CompileEnv whose literal table is * to be validated. */ { register LiteralTable *localTablePtr = &(envPtr->localLitTable); register LiteralEntry *localPtr; char *bytes; register int i; int length, count; count = 0; for (i=0 ; i<localTablePtr->numBuckets ; i++) { for (localPtr=localTablePtr->buckets[i] ; localPtr!=NULL; localPtr=localPtr->nextPtr) { count++; if (localPtr->refCount != -1) { bytes = Tcl_GetStringFromObj(localPtr->objPtr, &length); Tcl_Panic("TclVerifyLocalLiteralTable: local literal \"%.*s\" had bad refCount %d", (length>60? 60 : length), bytes, localPtr->refCount); } if (TclLookupLiteralEntry((Tcl_Interp *) envPtr->iPtr, localPtr->objPtr) == NULL) { bytes = Tcl_GetStringFromObj(localPtr->objPtr, &length); Tcl_Panic("TclVerifyLocalLiteralTable: local literal \"%.*s\" is not global", (length>60? 60 : length), bytes); } if (localPtr->objPtr->bytes == NULL) { Tcl_Panic("TclVerifyLocalLiteralTable: literal has NULL string rep"); } } } if (count != localTablePtr->numEntries) { Tcl_Panic("TclVerifyLocalLiteralTable: local literal table had %d entries, should be %d", count, localTablePtr->numEntries); } }  /* *---------------------------------------------------------------------- * * TclVerifyGlobalLiteralTable -- * * Check an interpreter's global literal table literal for consistency. * * Results: * None. * * Side effects: * Tcl_Panic if problems are found. * *---------------------------------------------------------------------- */ void TclVerifyGlobalLiteralTable( Interp *iPtr) /* Points to interpreter whose global literal * table is to be validated. */ { register LiteralTable *globalTablePtr = &(iPtr->literalTable); register LiteralEntry *globalPtr; char *bytes; register int i; int length, count; count = 0; for (i=0 ; i<globalTablePtr->numBuckets ; i++) { for (globalPtr=globalTablePtr->buckets[i] ; globalPtr!=NULL; globalPtr=globalPtr->nextPtr) { count++; if (globalPtr->refCount < 1) { bytes = Tcl_GetStringFromObj(globalPtr->objPtr, &length); Tcl_Panic("TclVerifyGlobalLiteralTable: global literal \"%.*s\" had bad refCount %d", (length>60? 60 : length), bytes, globalPtr->refCount); } if (globalPtr->objPtr->bytes == NULL) { Tcl_Panic("TclVerifyGlobalLiteralTable: literal has NULL string rep"); } } } if (count != globalTablePtr->numEntries) { Tcl_Panic("TclVerifyGlobalLiteralTable: global literal table had %d entries, should be %d", count, globalTablePtr->numEntries); } } #endif /*TCL_COMPILE_DEBUG*/  /* * Local Variables: * mode: c * c-basic-offset: 4 * fill-column: 78 * End: */

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