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Diffstat (limited to 'generic/tclHash.c')
| -rw-r--r-- | generic/tclHash.c | 1079 |
1 files changed, 1079 insertions, 0 deletions
diff --git a/generic/tclHash.c b/generic/tclHash.c new file mode 100644 index 0000000..78ad514 --- /dev/null +++ b/generic/tclHash.c @@ -0,0 +1,1079 @@ +/* + * tclHash.c -- + * + * Implementation of in-memory hash tables for Tcl and Tcl-based + * applications. + * + * Copyright (c) 1991-1993 The Regents of the University of California. + * Copyright (c) 1994 Sun Microsystems, Inc. + * + * See the file "license.terms" for information on usage and redistribution of + * this file, and for a DISCLAIMER OF ALL WARRANTIES. + */ + +#include "tclInt.h" + +/* + * Prevent macros from clashing with function definitions. + */ + +#undef Tcl_FindHashEntry +#undef Tcl_CreateHashEntry + +/* + * When there are this many entries per bucket, on average, rebuild the hash + * table to make it larger. + */ + +#define REBUILD_MULTIPLIER 3 + +/* + * The following macro takes a preliminary integer hash value and produces an + * index into a hash tables bucket list. The idea is to make it so that + * preliminary values that are arbitrarily similar will end up in different + * buckets. The hash function was taken from a random-number generator. + */ + +#define RANDOM_INDEX(tablePtr, i) \ + ((((i)*1103515245L) >> (tablePtr)->downShift) & (tablePtr)->mask) + +/* + * Prototypes for the array hash key methods. + */ + +static Tcl_HashEntry * AllocArrayEntry(Tcl_HashTable *tablePtr, void *keyPtr); +static int CompareArrayKeys(void *keyPtr, Tcl_HashEntry *hPtr); +static TCL_HASH_TYPE HashArrayKey(Tcl_HashTable *tablePtr, void *keyPtr); + +/* + * Prototypes for the one word hash key methods. Not actually declared because + * this is a critical path that is implemented in the core hash table access + * function. + */ + +#if 0 +static Tcl_HashEntry * AllocOneWordEntry(Tcl_HashTable *tablePtr, + void *keyPtr); +static int CompareOneWordKeys(void *keyPtr, Tcl_HashEntry *hPtr); +static unsigned int HashOneWordKey(Tcl_HashTable *tablePtr, void *keyPtr); +#endif + +/* + * Prototypes for the string hash key methods. + */ + +static Tcl_HashEntry * AllocStringEntry(Tcl_HashTable *tablePtr, + void *keyPtr); +static int CompareStringKeys(void *keyPtr, Tcl_HashEntry *hPtr); +static TCL_HASH_TYPE HashStringKey(Tcl_HashTable *tablePtr, void *keyPtr); + +/* + * Function prototypes for static functions in this file: + */ + +static Tcl_HashEntry * BogusFind(Tcl_HashTable *tablePtr, const char *key); +static Tcl_HashEntry * BogusCreate(Tcl_HashTable *tablePtr, const char *key, + int *newPtr); +static Tcl_HashEntry * CreateHashEntry(Tcl_HashTable *tablePtr, const char *key, + int *newPtr); +static Tcl_HashEntry * FindHashEntry(Tcl_HashTable *tablePtr, const char *key); +static void RebuildTable(Tcl_HashTable *tablePtr); + +const Tcl_HashKeyType tclArrayHashKeyType = { + TCL_HASH_KEY_TYPE_VERSION, /* version */ + TCL_HASH_KEY_RANDOMIZE_HASH, /* flags */ + HashArrayKey, /* hashKeyProc */ + CompareArrayKeys, /* compareKeysProc */ + AllocArrayEntry, /* allocEntryProc */ + NULL /* freeEntryProc */ +}; + +const Tcl_HashKeyType tclOneWordHashKeyType = { + TCL_HASH_KEY_TYPE_VERSION, /* version */ + 0, /* flags */ + NULL, /* HashOneWordKey, */ /* hashProc */ + NULL, /* CompareOneWordKey, */ /* compareProc */ + NULL, /* AllocOneWordKey, */ /* allocEntryProc */ + NULL /* FreeOneWordKey, */ /* freeEntryProc */ +}; + +const Tcl_HashKeyType tclStringHashKeyType = { + TCL_HASH_KEY_TYPE_VERSION, /* version */ + 0, /* flags */ + HashStringKey, /* hashKeyProc */ + CompareStringKeys, /* compareKeysProc */ + AllocStringEntry, /* allocEntryProc */ + NULL /* freeEntryProc */ +}; + +/* + *---------------------------------------------------------------------- + * + * Tcl_InitHashTable -- + * + * Given storage for a hash table, set up the fields to prepare the hash + * table for use. + * + * Results: + * None. + * + * Side effects: + * TablePtr is now ready to be passed to Tcl_FindHashEntry and + * Tcl_CreateHashEntry. + * + *---------------------------------------------------------------------- + */ + +void +Tcl_InitHashTable( + register Tcl_HashTable *tablePtr, + /* Pointer to table record, which is supplied + * by the caller. */ + int keyType) /* Type of keys to use in table: + * TCL_STRING_KEYS, TCL_ONE_WORD_KEYS, or an + * integer >= 2. */ +{ + /* + * Use a special value to inform the extended version that it must not + * access any of the new fields in the Tcl_HashTable. If an extension is + * rebuilt then any calls to this function will be redirected to the + * extended version by a macro. + */ + + Tcl_InitCustomHashTable(tablePtr, keyType, (const Tcl_HashKeyType *) -1); +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_InitCustomHashTable -- + * + * Given storage for a hash table, set up the fields to prepare the hash + * table for use. This is an extended version of Tcl_InitHashTable which + * supports user defined keys. + * + * Results: + * None. + * + * Side effects: + * TablePtr is now ready to be passed to Tcl_FindHashEntry and + * Tcl_CreateHashEntry. + * + *---------------------------------------------------------------------- + */ + +void +Tcl_InitCustomHashTable( + register Tcl_HashTable *tablePtr, + /* Pointer to table record, which is supplied + * by the caller. */ + int keyType, /* Type of keys to use in table: + * TCL_STRING_KEYS, TCL_ONE_WORD_KEYS, + * TCL_CUSTOM_TYPE_KEYS, TCL_CUSTOM_PTR_KEYS, + * or an integer >= 2. */ + const Tcl_HashKeyType *typePtr) /* Pointer to structure which defines the + * behaviour of this table. */ +{ +#if (TCL_SMALL_HASH_TABLE != 4) + Tcl_Panic("Tcl_InitCustomHashTable: 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->downShift = 28; + tablePtr->mask = 3; + tablePtr->keyType = keyType; + tablePtr->findProc = FindHashEntry; + tablePtr->createProc = CreateHashEntry; + + if (typePtr == NULL) { + /* + * The caller has been rebuilt so the hash table is an extended + * version. + */ + } else if (typePtr != (Tcl_HashKeyType *) -1) { + /* + * The caller is requesting a customized hash table so it must be an + * extended version. + */ + + tablePtr->typePtr = typePtr; + } else { + /* + * The caller has not been rebuilt so the hash table is not extended. + */ + } +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_FindHashEntry -- + * + * Given a hash table 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. + * + *---------------------------------------------------------------------- + */ + +Tcl_HashEntry * +Tcl_FindHashEntry( + Tcl_HashTable *tablePtr, /* Table in which to lookup entry. */ + const void *key) /* Key to use to find matching entry. */ +{ + return (*((tablePtr)->findProc))(tablePtr, key); +} + +static Tcl_HashEntry * +FindHashEntry( + Tcl_HashTable *tablePtr, /* Table in which to lookup entry. */ + const char *key) /* Key to use to find matching entry. */ +{ + return CreateHashEntry(tablePtr, key, NULL); +} + + +/* + *---------------------------------------------------------------------- + * + * Tcl_CreateHashEntry -- + * + * 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. + * + *---------------------------------------------------------------------- + */ + +Tcl_HashEntry * +Tcl_CreateHashEntry( + Tcl_HashTable *tablePtr, /* Table in which to lookup entry. */ + const void *key, /* Key to use to find or create matching + * entry. */ + int *newPtr) /* Store info here telling whether a new entry + * was created. */ +{ + return (*((tablePtr)->createProc))(tablePtr, key, newPtr); +} + +static Tcl_HashEntry * +CreateHashEntry( + 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. */ +{ + register Tcl_HashEntry *hPtr; + const Tcl_HashKeyType *typePtr; + unsigned int hash; + int index; + + if (tablePtr->keyType == TCL_STRING_KEYS) { + typePtr = &tclStringHashKeyType; + } else if (tablePtr->keyType == TCL_ONE_WORD_KEYS) { + typePtr = &tclOneWordHashKeyType; + } else if (tablePtr->keyType == TCL_CUSTOM_TYPE_KEYS + || tablePtr->keyType == TCL_CUSTOM_PTR_KEYS) { + typePtr = tablePtr->typePtr; + } else { + typePtr = &tclArrayHashKeyType; + } + + if (typePtr->hashKeyProc) { + hash = typePtr->hashKeyProc(tablePtr, (void *) key); + if (typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) { + index = RANDOM_INDEX(tablePtr, hash); + } else { + index = hash & tablePtr->mask; + } + } else { + hash = PTR2UINT(key); + index = RANDOM_INDEX(tablePtr, hash); + } + + /* + * Search all of the entries in the appropriate bucket. + */ + + if (typePtr->compareKeysProc) { + Tcl_CompareHashKeysProc *compareKeysProc = typePtr->compareKeysProc; + + for (hPtr = tablePtr->buckets[index]; hPtr != NULL; + hPtr = hPtr->nextPtr) { + if (hash != PTR2UINT(hPtr->hash)) { + continue; + } + if (((void *) key == hPtr) || compareKeysProc((void *) key, hPtr)) { + if (newPtr) { + *newPtr = 0; + } + return hPtr; + } + } + } else { + for (hPtr = tablePtr->buckets[index]; hPtr != NULL; + hPtr = hPtr->nextPtr) { + if (hash != PTR2UINT(hPtr->hash)) { + continue; + } + if (key == hPtr->key.oneWordValue) { + if (newPtr) { + *newPtr = 0; + } + return hPtr; + } + } + } + + if (!newPtr) { + return NULL; + } + + /* + * Entry not found. Add a new one to the bucket. + */ + + *newPtr = 1; + if (typePtr->allocEntryProc) { + hPtr = typePtr->allocEntryProc(tablePtr, (void *) key); + } else { + hPtr = ckalloc(sizeof(Tcl_HashEntry)); + hPtr->key.oneWordValue = (char *) key; + hPtr->clientData = 0; + } + + hPtr->tablePtr = tablePtr; + hPtr->hash = UINT2PTR(hash); + hPtr->nextPtr = tablePtr->buckets[index]; + tablePtr->buckets[index] = 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; +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_DeleteHashEntry -- + * + * Remove a single entry from a hash table. + * + * Results: + * None. + * + * Side effects: + * The entry given by entryPtr is deleted from its table and should never + * again be used by the caller. It is up to the caller to free the + * clientData field of the entry, if that is relevant. + * + *---------------------------------------------------------------------- + */ + +void +Tcl_DeleteHashEntry( + Tcl_HashEntry *entryPtr) +{ + register Tcl_HashEntry *prevPtr; + const Tcl_HashKeyType *typePtr; + Tcl_HashTable *tablePtr; + Tcl_HashEntry **bucketPtr; + int index; + + tablePtr = entryPtr->tablePtr; + + if (tablePtr->keyType == TCL_STRING_KEYS) { + typePtr = &tclStringHashKeyType; + } else if (tablePtr->keyType == TCL_ONE_WORD_KEYS) { + typePtr = &tclOneWordHashKeyType; + } else if (tablePtr->keyType == TCL_CUSTOM_TYPE_KEYS + || tablePtr->keyType == TCL_CUSTOM_PTR_KEYS) { + typePtr = tablePtr->typePtr; + } else { + typePtr = &tclArrayHashKeyType; + } + + if (typePtr->hashKeyProc == NULL + || typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) { + index = RANDOM_INDEX(tablePtr, PTR2INT(entryPtr->hash)); + } else { + index = PTR2UINT(entryPtr->hash) & tablePtr->mask; + } + + bucketPtr = &tablePtr->buckets[index]; + + if (*bucketPtr == entryPtr) { + *bucketPtr = entryPtr->nextPtr; + } else { + for (prevPtr = *bucketPtr; ; prevPtr = prevPtr->nextPtr) { + if (prevPtr == NULL) { + Tcl_Panic("malformed bucket chain in Tcl_DeleteHashEntry"); + } + if (prevPtr->nextPtr == entryPtr) { + prevPtr->nextPtr = entryPtr->nextPtr; + break; + } + } + } + + tablePtr->numEntries--; + if (typePtr->freeEntryProc) { + typePtr->freeEntryProc(entryPtr); + } else { + ckfree(entryPtr); + } +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_DeleteHashTable -- + * + * Free up everything associated with a hash table except for the record + * for the table itself. + * + * Results: + * None. + * + * Side effects: + * The hash table is no longer useable. + * + *---------------------------------------------------------------------- + */ + +void +Tcl_DeleteHashTable( + register Tcl_HashTable *tablePtr) /* Table to delete. */ +{ + register Tcl_HashEntry *hPtr, *nextPtr; + const Tcl_HashKeyType *typePtr; + int i; + + if (tablePtr->keyType == TCL_STRING_KEYS) { + typePtr = &tclStringHashKeyType; + } else if (tablePtr->keyType == TCL_ONE_WORD_KEYS) { + typePtr = &tclOneWordHashKeyType; + } else if (tablePtr->keyType == TCL_CUSTOM_TYPE_KEYS + || tablePtr->keyType == TCL_CUSTOM_PTR_KEYS) { + typePtr = tablePtr->typePtr; + } else { + typePtr = &tclArrayHashKeyType; + } + + /* + * Free up all the entries in the table. + */ + + for (i = 0; i < tablePtr->numBuckets; i++) { + hPtr = tablePtr->buckets[i]; + while (hPtr != NULL) { + nextPtr = hPtr->nextPtr; + if (typePtr->freeEntryProc) { + typePtr->freeEntryProc(hPtr); + } else { + ckfree(hPtr); + } + hPtr = nextPtr; + } + } + + /* + * Free up the bucket array, if it was dynamically allocated. + */ + + if (tablePtr->buckets != tablePtr->staticBuckets) { + if (typePtr->flags & TCL_HASH_KEY_SYSTEM_HASH) { + TclpSysFree((char *) tablePtr->buckets); + } else { + ckfree(tablePtr->buckets); + } + } + + /* + * Arrange for panics if the table is used again without + * re-initialization. + */ + + tablePtr->findProc = BogusFind; + tablePtr->createProc = BogusCreate; +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_FirstHashEntry -- + * + * Locate the first entry in a hash table and set up a record that can be + * used to step through all the remaining entries of the table. + * + * Results: + * The return value is a pointer to the first entry in tablePtr, or NULL + * if tablePtr has no entries in it. The memory at *searchPtr is + * initialized so that subsequent calls to Tcl_NextHashEntry will return + * all of the entries in the table, one at a time. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +Tcl_HashEntry * +Tcl_FirstHashEntry( + Tcl_HashTable *tablePtr, /* Table to search. */ + Tcl_HashSearch *searchPtr) /* Place to store information about progress + * through the table. */ +{ + searchPtr->tablePtr = tablePtr; + searchPtr->nextIndex = 0; + searchPtr->nextEntryPtr = NULL; + return Tcl_NextHashEntry(searchPtr); +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_NextHashEntry -- + * + * Once a hash table enumeration has been initiated by calling + * Tcl_FirstHashEntry, this function may be called to return successive + * elements of the table. + * + * Results: + * The return value is the next entry in the hash table being enumerated, + * or NULL if the end of the table is reached. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +Tcl_HashEntry * +Tcl_NextHashEntry( + register Tcl_HashSearch *searchPtr) + /* Place to store information about progress + * through the table. Must have been + * initialized by calling + * Tcl_FirstHashEntry. */ +{ + Tcl_HashEntry *hPtr; + Tcl_HashTable *tablePtr = searchPtr->tablePtr; + + while (searchPtr->nextEntryPtr == NULL) { + if (searchPtr->nextIndex >= tablePtr->numBuckets) { + return NULL; + } + searchPtr->nextEntryPtr = + tablePtr->buckets[searchPtr->nextIndex]; + searchPtr->nextIndex++; + } + hPtr = searchPtr->nextEntryPtr; + searchPtr->nextEntryPtr = hPtr->nextPtr; + return hPtr; +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_HashStats -- + * + * 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 * +Tcl_HashStats( + Tcl_HashTable *tablePtr) /* Table for which to produce stats. */ +{ +#define NUM_COUNTERS 10 + int count[NUM_COUNTERS], overflow, i, j; + double average, tmp; + register Tcl_HashEntry *hPtr; + char *result, *p; + + /* + * Compute a histogram of bucket usage. + */ + + 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 (hPtr = tablePtr->buckets[i]; hPtr != NULL; hPtr = hPtr->nextPtr) { + j++; + } + if (j < NUM_COUNTERS) { + count[j]++; + } else { + overflow++; + } + tmp = j; + if (tablePtr->numEntries != 0) { + average += (tmp+1.0)*(tmp/tablePtr->numEntries)/2.0; + } + } + + /* + * Print out the histogram and a few other pieces of information. + */ + + result = ckalloc((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; +} + +/* + *---------------------------------------------------------------------- + * + * AllocArrayEntry -- + * + * Allocate space for a Tcl_HashEntry containing the array key. + * + * Results: + * The return value is a pointer to the created entry. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static Tcl_HashEntry * +AllocArrayEntry( + Tcl_HashTable *tablePtr, /* Hash table. */ + void *keyPtr) /* Key to store in the hash table entry. */ +{ + int *array = (int *) keyPtr; + register int *iPtr1, *iPtr2; + Tcl_HashEntry *hPtr; + int count; + unsigned int size; + + count = tablePtr->keyType; + + size = sizeof(Tcl_HashEntry) + (count*sizeof(int)) - sizeof(hPtr->key); + if (size < sizeof(Tcl_HashEntry)) { + size = sizeof(Tcl_HashEntry); + } + hPtr = ckalloc(size); + + for (iPtr1 = array, iPtr2 = hPtr->key.words; + count > 0; count--, iPtr1++, iPtr2++) { + *iPtr2 = *iPtr1; + } + hPtr->clientData = 0; + + return hPtr; +} + +/* + *---------------------------------------------------------------------- + * + * CompareArrayKeys -- + * + * Compares two array keys. + * + * Results: + * The return value is 0 if they are different and 1 if they are the + * same. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static int +CompareArrayKeys( + void *keyPtr, /* New key to compare. */ + Tcl_HashEntry *hPtr) /* Existing key to compare. */ +{ + register const int *iPtr1 = (const int *) keyPtr; + register const int *iPtr2 = (const int *) hPtr->key.words; + Tcl_HashTable *tablePtr = hPtr->tablePtr; + int count; + + for (count = tablePtr->keyType; ; count--, iPtr1++, iPtr2++) { + if (count == 0) { + return 1; + } + if (*iPtr1 != *iPtr2) { + break; + } + } + return 0; +} + +/* + *---------------------------------------------------------------------- + * + * HashArrayKey -- + * + * Compute a one-word summary of an array, 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 TCL_HASH_TYPE +HashArrayKey( + Tcl_HashTable *tablePtr, /* Hash table. */ + void *keyPtr) /* Key from which to compute hash value. */ +{ + register const int *array = (const int *) keyPtr; + register unsigned int result; + int count; + + for (result = 0, count = tablePtr->keyType; count > 0; + count--, array++) { + result += *array; + } + return (TCL_HASH_TYPE) result; +} + +/* + *---------------------------------------------------------------------- + * + * AllocStringEntry -- + * + * Allocate space for a Tcl_HashEntry containing the string key. + * + * Results: + * The return value is a pointer to the created entry. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static Tcl_HashEntry * +AllocStringEntry( + Tcl_HashTable *tablePtr, /* Hash table. */ + void *keyPtr) /* Key to store in the hash table entry. */ +{ + const char *string = (const char *) keyPtr; + Tcl_HashEntry *hPtr; + unsigned int size, allocsize; + + allocsize = size = strlen(string) + 1; + if (size < sizeof(hPtr->key)) { + allocsize = sizeof(hPtr->key); + } + hPtr = ckalloc(TclOffset(Tcl_HashEntry, key) + allocsize); + memcpy(hPtr->key.string, string, size); + hPtr->clientData = 0; + return hPtr; +} + +/* + *---------------------------------------------------------------------- + * + * CompareStringKeys -- + * + * Compares two string keys. + * + * Results: + * The return value is 0 if they are different and 1 if they are the + * same. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static int +CompareStringKeys( + void *keyPtr, /* New key to compare. */ + Tcl_HashEntry *hPtr) /* Existing key to compare. */ +{ + register const char *p1 = (const char *) keyPtr; + register const char *p2 = (const char *) hPtr->key.string; + + return !strcmp(p1, p2); +} + +/* + *---------------------------------------------------------------------- + * + * HashStringKey -- + * + * 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 TCL_HASH_TYPE +HashStringKey( + Tcl_HashTable *tablePtr, /* Hash table. */ + void *keyPtr) /* Key from which to compute hash value. */ +{ + register const char *string = keyPtr; + register unsigned int result; + register char c; + + /* + * 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, but isn't strong against maliciously-chosen + * keys. + * + * Note that this function is very weak against malicious strings; it's + * very easy to generate multiple keys that have the same hashcode. On the + * other hand, that hardly ever actually occurs and this function *is* + * very cheap, even by comparison with industry-standard hashes like FNV. + * If real strength of hash is required though, use a custom hash based on + * Bob Jenkins's lookup3(), but be aware that it's significantly slower. + * Since Tcl command and namespace names are usually reasonably-named (the + * main use for string hashes in modern Tcl) speed is far more important + * than strength. + * + * See also HashString in tclLiteral.c. + * See also TclObjHashKey in tclObj.c. + * + * See [tcl-Feature Request #2958832] + */ + + if ((result = UCHAR(*string)) != 0) { + while ((c = *++string) != 0) { + result += (result << 3) + UCHAR(c); + } + } + return (TCL_HASH_TYPE) result; +} + +/* + *---------------------------------------------------------------------- + * + * BogusFind -- + * + * This function is invoked when Tcl_FindHashEntry is called on a + * table that has been deleted. + * + * Results: + * If Tcl_Panic returns (which it shouldn't) this function returns NULL. + * + * Side effects: + * Generates a panic. + * + *---------------------------------------------------------------------- + */ + + /* ARGSUSED */ +static Tcl_HashEntry * +BogusFind( + Tcl_HashTable *tablePtr, /* Table in which to lookup entry. */ + const char *key) /* Key to use to find matching entry. */ +{ + Tcl_Panic("called %s on deleted table", "Tcl_FindHashEntry"); + return NULL; +} + +/* + *---------------------------------------------------------------------- + * + * BogusCreate -- + * + * This function is invoked when Tcl_CreateHashEntry is called on a + * table that has been deleted. + * + * Results: + * If panic returns (which it shouldn't) this function returns NULL. + * + * Side effects: + * Generates a panic. + * + *---------------------------------------------------------------------- + */ + + /* ARGSUSED */ +static Tcl_HashEntry * +BogusCreate( + 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_Panic("called %s on deleted table", "Tcl_CreateHashEntry"); + return NULL; +} + +/* + *---------------------------------------------------------------------- + * + * RebuildTable -- + * + * This function is invoked when the ratio of entries to hash buckets + * becomes too large. It creates a new table with a larger bucket array + * and moves all of the entries into the new table. + * + * Results: + * None. + * + * Side effects: + * Memory gets reallocated and entries get re-hashed to new buckets. + * + *---------------------------------------------------------------------- + */ + +static void +RebuildTable( + register Tcl_HashTable *tablePtr) /* Table to enlarge. */ +{ + int oldSize, count, index; + Tcl_HashEntry **oldBuckets; + register Tcl_HashEntry **oldChainPtr, **newChainPtr; + register Tcl_HashEntry *hPtr; + const Tcl_HashKeyType *typePtr; + + if (tablePtr->keyType == TCL_STRING_KEYS) { + typePtr = &tclStringHashKeyType; + } else if (tablePtr->keyType == TCL_ONE_WORD_KEYS) { + typePtr = &tclOneWordHashKeyType; + } else if (tablePtr->keyType == TCL_CUSTOM_TYPE_KEYS + || tablePtr->keyType == TCL_CUSTOM_PTR_KEYS) { + typePtr = tablePtr->typePtr; + } else { + typePtr = &tclArrayHashKeyType; + } + + 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; + if (typePtr->flags & TCL_HASH_KEY_SYSTEM_HASH) { + tablePtr->buckets = (Tcl_HashEntry **) TclpSysAlloc((unsigned) + (tablePtr->numBuckets * sizeof(Tcl_HashEntry *)), 0); + } else { + tablePtr->buckets = + ckalloc(tablePtr->numBuckets * sizeof(Tcl_HashEntry *)); + } + for (count = tablePtr->numBuckets, newChainPtr = tablePtr->buckets; + count > 0; count--, newChainPtr++) { + *newChainPtr = NULL; + } + tablePtr->rebuildSize *= 4; + tablePtr->downShift -= 2; + 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 (hPtr = *oldChainPtr; hPtr != NULL; hPtr = *oldChainPtr) { + *oldChainPtr = hPtr->nextPtr; + if (typePtr->hashKeyProc == NULL + || typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) { + index = RANDOM_INDEX(tablePtr, PTR2INT(hPtr->hash)); + } else { + index = PTR2UINT(hPtr->hash) & tablePtr->mask; + } + hPtr->nextPtr = tablePtr->buckets[index]; + tablePtr->buckets[index] = hPtr; + } + } + + /* + * Free up the old bucket array, if it was dynamically allocated. + */ + + if (oldBuckets != tablePtr->staticBuckets) { + if (typePtr->flags & TCL_HASH_KEY_SYSTEM_HASH) { + TclpSysFree((char *) oldBuckets); + } else { + ckfree(oldBuckets); + } + } +} + +/* + * Local Variables: + * mode: c + * c-basic-offset: 4 + * fill-column: 78 + * End: + */ |