/*
* 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.
*
* RCS: @(#) $Id: tclHash.c,v 1.33.2.1 2008/11/18 07:02:17 nijtmans Exp $
*/
#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) \
(((((long) (i))*1103515245) >> (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 unsigned int HashArrayKey(Tcl_HashTable *tablePtr, VOID *keyPtr);
/*
* Prototypes for the one word hash key methods.
*/
#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 unsigned int 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 void RebuildTable(Tcl_HashTable *tablePtr);
Tcl_HashKeyType tclArrayHashKeyType = {
TCL_HASH_KEY_TYPE_VERSION, /* version */
TCL_HASH_KEY_RANDOMIZE_HASH, /* flags */
HashArrayKey, /* hashKeyProc */
CompareArrayKeys, /* compareKeysProc */
AllocArrayEntry, /* allocEntryProc */
NULL /* freeEntryProc */
};
Tcl_HashKeyType tclOneWordHashKeyType = {
TCL_HASH_KEY_TYPE_VERSION, /* version */
0, /* flags */
NULL, /* HashOneWordKey, */ /* hashProc */
NULL, /* CompareOneWordKey, */ /* compareProc */
NULL, /* AllocOneWordKey, */ /* allocEntryProc */
NULL /* FreeOneWordKey, */ /* freeEntryProc */
};
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.
*
*----------------------------------------------------------------------
*/
#undef Tcl_InitHashTable
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, (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. */
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 = Tcl_FindHashEntry;
tablePtr->createProc = Tcl_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 char *key) /* Key to use to find matching entry. */
{
return Tcl_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 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 TCL_HASH_KEY_STORE_HASH
if (hash != PTR2UINT(hPtr->hash)) {
continue;
}
#endif
if (compareKeysProc((VOID *) key, hPtr)) {
if (newPtr) {
*newPtr = 0;
}
return hPtr;
}
}
} else {
for (hPtr = tablePtr->buckets[index]; hPtr != NULL;
hPtr = hPtr->nextPtr) {
#if TCL_HASH_KEY_STORE_HASH
if (hash != PTR2UINT(hPtr->hash)) {
continue;
}
#endif
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 = (Tcl_HashEntry *) ckalloc((unsigned) sizeof(Tcl_HashEntry));
hPtr->key.oneWordValue = (char *) key;
hPtr->clientData = 0;
}
hPtr->tablePtr = tablePtr;
#if TCL_HASH_KEY_STORE_HASH
hPtr->hash = UINT2PTR(hash);
hPtr->nextPtr = tablePtr->buckets[index];
tablePtr->buckets[index] = hPtr;
#else
hPtr->bucketPtr = &(tablePtr->buckets[index]);
hPtr->nextPtr = *hPtr->bucketPtr;
*hPtr->bucketPtr = hPtr;
#endif
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;
#if TCL_HASH_KEY_STORE_HASH
int index;
#endif
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 TCL_HASH_KEY_STORE_HASH
if (typePtr->hashKeyProc == NULL
|| typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) {
index = RANDOM_INDEX (tablePtr, entryPtr->hash);
} else {
index = PTR2UINT(entryPtr->hash) & tablePtr->mask;
}
bucketPtr = &(tablePtr->buckets[index]);
#else
bucketPtr = entryPtr->bucketPtr;
#endif
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((char *) 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((char *) 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((char *) 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;
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;
}
/*
* 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.
*/
if (typePtr->flags & TCL_HASH_KEY_SYSTEM_HASH) {
result = (char *) TclpSysAlloc((unsigned) (NUM_COUNTERS*60) + 300, 0);
} else {
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;
}
/*
*----------------------------------------------------------------------
*
* 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 = (Tcl_HashEntry *) 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 unsigned int
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 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;
size = sizeof(Tcl_HashEntry) + strlen(string) + 1 - sizeof(hPtr->key);
if (size < sizeof(Tcl_HashEntry)) {
size = sizeof(Tcl_HashEntry);
}
hPtr = (Tcl_HashEntry *) ckalloc(size);
strcpy(hPtr->key.string, string);
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 unsigned int
HashStringKey(
Tcl_HashTable *tablePtr, /* Hash table. */
VOID *keyPtr) /* Key from which to compute hash value. */
{
register const char *string = (const char *) keyPtr;
register unsigned int result;
register int 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.
*/
result = 0;
for (c=*string++ ; c ; c=*string++) {
result += (result<<3) + c;
}
return result;
}
/*
*----------------------------------------------------------------------
*
* BogusFind --
*
* This function is invoked when an 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 an 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 = (Tcl_HashEntry **) ckalloc((unsigned)
(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 TCL_HASH_KEY_STORE_HASH
if (typePtr->hashKeyProc == NULL
|| typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) {
index = RANDOM_INDEX (tablePtr, hPtr->hash);
} else {
index = PTR2UINT(hPtr->hash) & tablePtr->mask;
}
hPtr->nextPtr = tablePtr->buckets[index];
tablePtr->buckets[index] = hPtr;
#else
VOID *key = (VOID *) Tcl_GetHashKey(tablePtr, hPtr);
if (typePtr->hashKeyProc) {
unsigned int hash;
hash = typePtr->hashKeyProc(tablePtr, key);
if (typePtr->flags & TCL_HASH_KEY_RANDOMIZE_HASH) {
index = RANDOM_INDEX (tablePtr, hash);
} else {
index = hash & tablePtr->mask;
}
} else {
index = RANDOM_INDEX (tablePtr, key);
}
hPtr->bucketPtr = &(tablePtr->buckets[index]);
hPtr->nextPtr = *hPtr->bucketPtr;
*hPtr->bucketPtr = hPtr;
#endif
}
}
/*
* 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((char *) oldBuckets);
}
}
}
/*
* Local Variables:
* mode: c
* c-basic-offset: 4
* fill-column: 78
* End:
*/
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