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/* Hash tables for Objective C internal structures
Copyright (C) 1993, 1996, 1997, 2004, 2009 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<>. */
#include "assert.h"
#include "objc/hash.h"
#include "objc/runtime.h" /* for DEBUG_PRINTF */
/* These two macros determine when a hash table is full and
by how much it should be expanded respectively.
These equations are percentages. */
#define FULLNESS(cache) \
((((cache)->size * 75) / 100) <= (cache)->used)
#define EXPANSION(cache) \
((cache)->size * 2)
objc_hash_new (unsigned int size, hash_func_type hash_func,
compare_func_type compare_func)
cache_ptr cache;
/* Pass me a value greater than 0 and a power of 2. */
assert (size);
assert (! (size & (size - 1)));
/* Allocate the cache structure. calloc insures
its initialization for default values. */
cache = (cache_ptr) objc_calloc (1, sizeof (struct cache));
assert (cache);
/* Allocate the array of buckets for the cache.
calloc initializes all of the pointers to NULL. */
= (node_ptr *) objc_calloc (size, sizeof (node_ptr));
assert (cache->node_table);
cache->size = size;
/* This should work for all processor architectures? */
cache->mask = (size - 1);
/* Store the hashing function so that codes can be computed. */
cache->hash_func = hash_func;
/* Store the function that compares hash keys to
determine if they are equal. */
cache->compare_func = compare_func;
return cache;
objc_hash_delete (cache_ptr cache)
node_ptr node;
node_ptr next_node;
unsigned int i;
/* Purge all key/value pairs from the table. */
/* Step through the nodes one by one and remove every node WITHOUT
using objc_hash_next. this makes objc_hash_delete much more efficient. */
for (i = 0;i < cache->size;i++) {
if ((node = cache->node_table[i])) {
/* an entry in the hash table has been found, now step through the
nodes next in the list and free them. */
while ((next_node = node->next)) {
objc_hash_remove (cache,node->key);
node = next_node;
objc_hash_remove (cache,node->key);
/* Release the array of nodes and the cache itself. */
objc_hash_add (cache_ptr *cachep, const void *key, void *value)
size_t indx = (*(*cachep)->hash_func)(*cachep, key);
node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node));
assert (node);
/* Initialize the new node. */
node->key = key;
node->value = value;
node->next = (*cachep)->node_table[indx];
/* Debugging.
Check the list for another key. */
#ifdef DEBUG
{ node_ptr node1 = (*cachep)->node_table[indx];
while (node1) {
assert (node1->key != key);
node1 = node1->next;
/* Install the node as the first element on the list. */
(*cachep)->node_table[indx] = node;
/* Bump the number of entries in the cache. */
/* Check the hash table's fullness. We're going
to expand if it is above the fullness level. */
if (FULLNESS (*cachep)) {
/* The hash table has reached its fullness level. Time to
expand it.
I'm using a slow method here but is built on other
primitive functions thereby increasing its
correctness. */
node_ptr node1 = NULL;
cache_ptr new = objc_hash_new (EXPANSION (*cachep),
DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n",
(int) *cachep, (*cachep)->size, new->size);
/* Copy the nodes from the first hash table to the new one. */
while ((node1 = objc_hash_next (*cachep, node1)))
objc_hash_add (&new, node1->key, node1->value);
/* Trash the old cache. */
objc_hash_delete (*cachep);
/* Return a pointer to the new hash table. */
*cachep = new;
objc_hash_remove (cache_ptr cache, const void *key)
size_t indx = (*cache->hash_func)(cache, key);
node_ptr node = cache->node_table[indx];
/* We assume there is an entry in the table. Error if it is not. */
assert (node);
/* Special case. First element is the key/value pair to be removed. */
if ((*cache->compare_func)(node->key, key)) {
cache->node_table[indx] = node->next;
} else {
/* Otherwise, find the hash entry. */
node_ptr prev = node;
BOOL removed = NO;
do {
if ((*cache->compare_func)(node->key, key)) {
prev->next = node->next, removed = YES;
} else
prev = node, node = node->next;
} while (! removed && node);
assert (removed);
/* Decrement the number of entries in the hash table. */
objc_hash_next (cache_ptr cache, node_ptr node)
/* If the scan is being started then reset the last node
visitied pointer and bucket index. */
if (! node)
cache->last_bucket = 0;
/* If there is a node visited last then check for another
entry in the same bucket; Otherwise step to the next bucket. */
if (node) {
if (node->next)
/* There is a node which follows the last node
returned. Step to that node and retun it. */
return node->next;
/* If the list isn't exhausted then search the buckets for
other nodes. */
if (cache->last_bucket < cache->size) {
/* Scan the remainder of the buckets looking for an entry
at the head of the list. Return the first item found. */
while (cache->last_bucket < cache->size)
if (cache->node_table[cache->last_bucket])
return cache->node_table[cache->last_bucket];
/* No further nodes were found in the hash table. */
return NULL;
} else
return NULL;
/* Given KEY, return corresponding value for it in CACHE.
Return NULL if the KEY is not recorded. */
void *
objc_hash_value_for_key (cache_ptr cache, const void *key)
node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
void *retval = NULL;
if (node)
do {
if ((*cache->compare_func)(node->key, key)) {
retval = node->value;
} else
node = node->next;
} while (! retval && node);
return retval;
/* Given KEY, return YES if it exists in the CACHE.
Return NO if it does not */
objc_hash_is_key_in_hash (cache_ptr cache, const void *key)
node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
if (node)
do {
if ((*cache->compare_func)(node->key, key))
return YES;
node = node->next;
} while (node);
return NO;