diff options
Diffstat (limited to 'generic/tclHash.c')
| -rw-r--r-- | generic/tclHash.c | 251 |
1 files changed, 248 insertions, 3 deletions
diff --git a/generic/tclHash.c b/generic/tclHash.c index 973c003..374f0e5 100644 --- a/generic/tclHash.c +++ b/generic/tclHash.c @@ -10,7 +10,7 @@ * See the file "license.terms" for information on usage and redistribution * of this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tclHash.c,v 1.3 1999/04/16 00:46:46 stanton Exp $ + * RCS: @(#) $Id: tclHash.c,v 1.4 2000/06/24 00:26:09 ericm Exp $ */ #include "tclInt.h" @@ -56,6 +56,11 @@ static Tcl_HashEntry * OneWordFind _ANSI_ARGS_((Tcl_HashTable *tablePtr, CONST char *key)); static Tcl_HashEntry * OneWordCreate _ANSI_ARGS_((Tcl_HashTable *tablePtr, CONST char *key, int *newPtr)); +static unsigned int HashObj _ANSI_ARGS_((Tcl_Obj *objPtr)); +static Tcl_HashEntry * ObjFind _ANSI_ARGS_((Tcl_HashTable *tablePtr, + CONST char *key)); +static Tcl_HashEntry * ObjCreate _ANSI_ARGS_((Tcl_HashTable *tablePtr, + CONST char *key, int *newPtr)); /* *---------------------------------------------------------------------- @@ -97,7 +102,10 @@ Tcl_InitHashTable(tablePtr, keyType) tablePtr->downShift = 28; tablePtr->mask = 3; tablePtr->keyType = keyType; - if (keyType == TCL_STRING_KEYS) { + if (keyType == TCL_OBJ_KEYS) { + tablePtr->findProc = ObjFind; + tablePtr->createProc = ObjCreate; + } else if (keyType == TCL_STRING_KEYS) { tablePtr->findProc = StringFind; tablePtr->createProc = StringCreate; } else if (keyType == TCL_ONE_WORD_KEYS) { @@ -147,6 +155,10 @@ Tcl_DeleteHashEntry(entryPtr) } } } + + if (entryPtr->tablePtr->keyType == TCL_OBJ_KEYS) { + Tcl_DecrRefCount (entryPtr->key.objPtr); + } entryPtr->tablePtr->numEntries--; ckfree((char *) entryPtr); } @@ -183,6 +195,9 @@ Tcl_DeleteHashTable(tablePtr) hPtr = tablePtr->buckets[i]; while (hPtr != NULL) { nextPtr = hPtr->nextPtr; + if (tablePtr->keyType == TCL_OBJ_KEYS) { + Tcl_DecrRefCount (hPtr->key.objPtr); + } ckfree((char *) hPtr); hPtr = nextPtr; } @@ -844,6 +859,234 @@ BogusCreate(tablePtr, key, newPtr) /* *---------------------------------------------------------------------- * + * HashObj -- + * + * Compute a one-word summary of the string representation of the + * Tcl_Obj, which can be used to generate a hash index. + * + * Results: + * The return value is a one-word summary of the information in + * the string representation of the Tcl_Obj. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static unsigned int +HashObj(objPtr) + Tcl_Obj *objPtr; +{ + register CONST char *string; + register int length; + register unsigned int result; + register int c; + + string = Tcl_GetStringFromObj (objPtr, NULL); + length = objPtr->length; + + /* + * 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; + while (length) { + c = *string; + string++; + length--; + if (length == 0) { + break; + } + result += (result<<3) + c; + } + return result; +} + +/* + *---------------------------------------------------------------------- + * + * ObjFind -- + * + * Given a hash table with string keys, and a string key, find + * the entry with a matching key. + * + * Results: + * The return value is a token for the matching entry in the + * hash table, or NULL if there was no matching entry. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static Tcl_HashEntry * +ObjFind(tablePtr, key) + Tcl_HashTable *tablePtr; /* Table in which to lookup entry. */ + CONST char *key; /* Key to use to find matching entry. */ +{ + Tcl_Obj *objPtr = (Tcl_Obj *) key; + register Tcl_HashEntry *hPtr; + register CONST char *p1, *p2; + register int l1, l2; + int index; + + index = HashObj(objPtr) & tablePtr->mask; + + /* + * Search all of the entries in the appropriate bucket. + */ + + for (hPtr = tablePtr->buckets[index]; hPtr != NULL; + hPtr = hPtr->nextPtr) { + /* + * If the object pointers are the same then they match. + */ + if (objPtr == hPtr->key.objPtr) { + return hPtr; + } + + p1 = Tcl_GetStringFromObj (objPtr, (int *) 0); + l1 = objPtr->length; + p2 = Tcl_GetStringFromObj (hPtr->key.objPtr, (int *) 0); + l2 = hPtr->key.objPtr->length; + + /* + * If the lengths are different then they do not match. + */ + if (l1 != l2) { + continue; + } + + for (;; p1++, p2++, l1--) { + if (*p1 != *p2) { + break; + } + if (l1 == 0) { + return hPtr; + } + } + } + return NULL; +} + +/* + *---------------------------------------------------------------------- + * + * ObjCreate -- + * + * Given a hash table with string keys, and a string key, find + * the entry with a matching key. If there is no matching entry, + * then create a new entry that does match. + * + * Results: + * The return value is a pointer to the matching entry. If this + * is a newly-created entry, then *newPtr will be set to a non-zero + * value; otherwise *newPtr will be set to 0. If this is a new + * entry the value stored in the entry will initially be 0. + * + * Side effects: + * A new entry may be added to the hash table. + * + *---------------------------------------------------------------------- + */ + +static Tcl_HashEntry * +ObjCreate(tablePtr, key, newPtr) + Tcl_HashTable *tablePtr; /* Table in which to lookup entry. */ + CONST char *key; /* Key to use to find or create matching + * entry. */ + int *newPtr; /* Store info here telling whether a new + * entry was created. */ +{ + Tcl_Obj *objPtr = (Tcl_Obj *) key; + register Tcl_HashEntry *hPtr; + register CONST char *p1, *p2; + register int l1, l2; + int index; + + index = HashObj(objPtr) & tablePtr->mask; + + /* + * Search all of the entries in this bucket. + */ + + for (hPtr = tablePtr->buckets[index]; hPtr != NULL; + hPtr = hPtr->nextPtr) { + /* + * If the object pointers are the same then they match. + */ + if (objPtr == hPtr->key.objPtr) { + *newPtr = 0; + return hPtr; + } + + p1 = Tcl_GetStringFromObj (objPtr, (int *) 0); + l1 = objPtr->length; + p2 = Tcl_GetStringFromObj (hPtr->key.objPtr, (int *) 0); + l2 = hPtr->key.objPtr->length; + + /* + * If the lengths are different then they do not match. + */ + if (l1 != l2) { + continue; + } + + for (;; p1++, p2++, l1--) { + if (*p1 != *p2) { + break; + } + if (l1 == 0) { + *newPtr = 0; + return hPtr; + } + } + } + + /* + * Entry not found. Add a new one to the bucket. + */ + + *newPtr = 1; + hPtr = (Tcl_HashEntry *) + Tcl_Alloc((unsigned) sizeof(Tcl_HashEntry)); + hPtr->tablePtr = tablePtr; + hPtr->bucketPtr = &(tablePtr->buckets[index]); + hPtr->nextPtr = *hPtr->bucketPtr; + hPtr->clientData = 0; + hPtr->key.objPtr = objPtr; + Tcl_IncrRefCount (objPtr); + *hPtr->bucketPtr = hPtr; + tablePtr->numEntries++; + + /* + * If the table has exceeded a decent size, rebuild it with many + * more buckets. + */ + + if (tablePtr->numEntries >= tablePtr->rebuildSize) { + RebuildTable(tablePtr); + } + return hPtr; +} + +/* + *---------------------------------------------------------------------- + * * RebuildTable -- * * This procedure is invoked when the ratio of entries to hash @@ -896,7 +1139,9 @@ RebuildTable(tablePtr) for (oldChainPtr = oldBuckets; oldSize > 0; oldSize--, oldChainPtr++) { for (hPtr = *oldChainPtr; hPtr != NULL; hPtr = *oldChainPtr) { *oldChainPtr = hPtr->nextPtr; - if (tablePtr->keyType == TCL_STRING_KEYS) { + if (tablePtr->keyType == TCL_OBJ_KEYS) { + index = HashObj(hPtr->key.objPtr) & tablePtr->mask; + } else if (tablePtr->keyType == TCL_STRING_KEYS) { index = HashString(hPtr->key.string) & tablePtr->mask; } else if (tablePtr->keyType == TCL_ONE_WORD_KEYS) { index = RANDOM_INDEX(tablePtr, hPtr->key.oneWordValue); |