321 lines
9.0 KiB
C
321 lines
9.0 KiB
C
/* Copyright (C) 1989, 1992 Free Software Foundation, Inc.
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This file is part of GNU CC.
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GNU CC is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU CC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU CC; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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/* As a special exception, if you link this library with files
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compiled with GCC to produce an executable, this does not cause
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the resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why
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the executable file might be covered by the GNU General Public License. */
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/*
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$Header: /home/fsf/rms/c-runtime/dispatch/RCS/hash.c,v 0.15 1992/09/02 02:04:32 rms Exp rms $
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$Author: rms $
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$Date: 1992/09/02 02:04:32 $
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$Log: hash.c,v $
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* Revision 0.15 1992/09/02 02:04:32 rms
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* Changed some decls.
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*
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* Revision 0.14 1992/08/31 21:09:15 dglattin
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* minor documentation changes.
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*
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* Revision 0.13 1992/08/18 04:46:58 dglattin
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* Saving a working version before release.
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*
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* Revision 0.12 1992/04/13 11:43:08 dennisg
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* Check in after array version of run-time works.
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* Expect more changes as hash version and other changes are made.
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*
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* Revision 0.11 1992/01/03 02:55:03 dennisg
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* modified to handle new initialization scheme.
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* fixed code structure.
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*
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* Revision 0.10 1991/12/10 12:05:28 dennisg
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* Cleaned up file format for a distribution.
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*
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* Revision 0.9 1991/12/03 02:01:23 dennisg
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* fixed assert macro.
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* added memory allocation adjustment macro for hash size allocation.
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*
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* Revision 0.8 1991/11/24 01:20:02 dennisg
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* changed shorts back to ints.
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* the efficiency gained didn't out weight the grossness of the code.
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*
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* Revision 0.7 1991/11/23 22:18:29 dennisg
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* deleted hashIndex and moved it to hash-inline.h
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* converted hash_value_for_key to a inline and moved it to hash-inline.h.
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*
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* Revision 0.6 1991/11/21 22:27:06 dennisg
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* changed hash value calculation.
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* func name changed from hashValue to hashIndex. the
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* func really calculated a index anyway.
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* changed hash func impl. essentially it was calculating a hash value
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* from a hash value. this is a implementation thing.
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*
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* Revision 0.5 1991/11/20 23:29:20 dennisg
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* converted hashIndex to a inline.
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*
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* Revision 0.4 1991/11/19 12:34:41 dennisg
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* bug in hash_delete. It was using void* to obtain nodes to
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* pass to hash_remove. The value passed to hash_removed is a
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* entry from the node structure rather than the node itself. Using
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* void* removed compiler checking.
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* Modified to implement cache expansion.
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*
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* Revision 0.3 1991/11/07 23:23:40 dennisg
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* implemented hash table expansion as suggested by rms.
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*
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* Revision 0.2 1991/11/07 22:30:54 dennisg
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* added copyleft
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*
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* Revision 0.1 1991/10/24 00:45:39 dennisg
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* Initial check in. Preliminary development stage.
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*
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*/
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#include "config.h"
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#include "hash.h"
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#include "objc.h"
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#include "objcP.h"
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#include "objc-protoP.h"
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#include "assert.h"
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/* These two macros determine when a hash table is full and
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by how much it should be expanded respectively.
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These equations are percentages. */
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#define FULLNESS(cache) \
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((((cache)->size * 75) / 100) <= (cache)->used)
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#define EXPANSION(cache) \
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((cache)->size * 2)
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cache_ptr
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hash_new (u_int size, hash_func_type hash_func, compare_func_type compare_func)
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{
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cache_ptr cache;
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/* Pass me a value greater than 0 and a power of 2. */
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assert (size);
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assert (!(size & (size - 1)));
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/* Allocate the cache structure. calloc insures
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its initialization for default values. */
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cache = (cache_ptr) calloc (1, sizeof (struct cache));
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assert (cache);
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/* Allocate the array of buckets for the cache.
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calloc initializes all of the pointers to NULL. */
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cache->node_table
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= (node_ptr *) calloc (size, sizeof (node_ptr));
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assert (cache->node_table);
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cache->size = size;
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/* This should work for all processor architectures? */
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cache->mask = (size - 1);
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/* Store the hashing function so that codes can be computed. */
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cache->hash_func = hash_func;
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/* Store the function that compares hash keys to
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determine if they are equal. */
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cache->compare_func = compare_func;
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return cache;
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}
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void
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hash_delete (cache_ptr cache)
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{
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node_ptr node;
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/* Purge all key/value pairs from the table. */
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while (node = hash_next (cache, NULL))
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hash_remove (cache, node->key);
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/* Release the array of nodes and the cache itself. */
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free (cache->node_table);
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free (cache);
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}
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void
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hash_add (cache_ptr *cachep, void *key, void *value)
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{
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u_int indx = (*(*cachep)->hash_func)(*cachep, key);
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node_ptr node = (node_ptr) calloc (1, sizeof (struct cache_node));
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assert (node);
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/* Initialize the new node. */
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node->key = key;
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node->value = value;
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node->next = (*(*cachep)->node_table)[indx];
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/* Debugging.
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Check the list for another key. */
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#ifdef DEBUG
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{ node_ptr node1 = (*(*cachep)->node_table)[indx];
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while (node1) {
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assert (node1->key != key);
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node1 = node1->next;
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}
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}
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#endif
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/* Install the node as the first element on the list. */
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(*(*cachep)->node_table)[indx] = node;
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/* Bump the number of entries in the cache. */
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++(*cachep)->used;
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/* Check the hash table's fullness. We're going
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to expand if it is above the fullness level. */
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if (FULLNESS (*cachep)) {
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/* The hash table has reached its fullness level. Time to
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expand it.
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I'm using a slow method here but is built on other
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primitive functions thereby increasing its
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correctness. */
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node_ptr node1 = NULL;
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cache_ptr new = hash_new (EXPANSION (*cachep),
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(*cachep)->hash_func,
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(*cachep)->compare_func);
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DEBUG_PRINTF (stderr, "Expanding cache %#x from %d to %d\n",
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*cachep, (*cachep)->size, new->size);
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/* Copy the nodes from the first hash table to the new one. */
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while (node1 = hash_next (*cachep, node1))
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hash_add (&new, node1->key, node1->value);
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/* Trash the old cache. */
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hash_delete (*cachep);
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/* Return a pointer to the new hash table. */
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*cachep = new;
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}
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}
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void
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hash_remove (cache_ptr cache, void *key)
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{
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u_int indx = (*cache->hash_func)(cache, key);
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node_ptr node = (*cache->node_table)[indx];
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/* We assume there is an entry in the table. Error if it is not. */
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assert (node);
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/* Special case. First element is the key/value pair to be removed. */
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if ((*cache->compare_func)(node->key, key)) {
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(*cache->node_table)[indx] = node->next;
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free (node);
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} else {
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/* Otherwise, find the hash entry. */
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node_ptr prev = node;
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BOOL removed = NO;
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do {
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if ((*cache->compare_func)(node->key, key)) {
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prev->next = node->next, removed = YES;
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free (node);
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} else
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prev = node, node = node->next;
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} while (!removed && node);
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assert (removed);
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}
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/* Decrement the number of entries in the hash table. */
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--cache->used;
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}
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node_ptr
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hash_next (cache_ptr cache, node_ptr node)
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{
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/* If the scan is being started then reset the last node
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visitied pointer and bucket index. */
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if (!node)
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cache->last_bucket = 0;
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/* If there is a node visited last then check for another
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entry in the same bucket; Otherwise step to the next bucket. */
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if (node) {
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if (node->next)
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/* There is a node which follows the last node
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returned. Step to that node and retun it. */
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return node->next;
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else
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++cache->last_bucket;
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}
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/* If the list isn't exhausted then search the buckets for
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other nodes. */
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if (cache->last_bucket < cache->size) {
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/* Scan the remainder of the buckets looking for an entry
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at the head of the list. Return the first item found. */
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while (cache->last_bucket < cache->size)
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if ((*cache->node_table)[cache->last_bucket])
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return (*cache->node_table)[cache->last_bucket];
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else
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++cache->last_bucket;
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/* No further nodes were found in the hash table. */
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return NULL;
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} else
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return NULL;
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}
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/*
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* Given key, return its value. Return NULL if the
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* key/value pair isn't in the hash.
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*/
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void *
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hash_value_for_key (cache_ptr cache, void *key)
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{
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node_ptr node
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= (*cache->node_table)[(*cache->hash_func)(cache, key)];
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void *retval = NULL;
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if (node)
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do {
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if ((*cache->compare_func)(node->key, key))
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retval = node->value;
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else
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node = node->next;
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} while (!retval && node);
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return retval;
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}
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