/* Hash tables for Objective C method dispatch.   Copyright (C) 1992 Free Software Foundation, Inc.This file is part of GNU CC.GNU CC is free software; you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 2, or (at your option)any later version.GNU CC is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See theGNU General Public License for more details.You should have received a copy of the GNU General Public Licensealong with GNU CC; see the file COPYING.  If not, write tothe Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  *//* As a special exception, if you link this library with files   compiled with GCC to produce an executable, this does not cause   the resulting executable to be covered by the GNU General Public License.   This exception does not however invalidate any other reasons why   the executable file might be covered by the GNU General Public License.  */#include "tconfig.h"#include "gstddef.h"#include "gstdarg.h"#include "assert.h"#include "hash.h"#include "objc.h"#include "objc-proto.h"/* 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)cache_ptrhash_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) calloc (1, sizeof (struct cache));  assert (cache);  /* Allocate the array of buckets for the cache.     calloc initializes all of the pointers to NULL.  */  cache->node_table    = (node_ptr *) 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;}voidhash_delete (cache_ptr cache){  node_ptr node;  /* Purge all key/value pairs from the table.  */  while (node = hash_next (cache, NULL))    hash_remove (cache, node->key);  /* Release the array of nodes and the cache itself.  */  free (cache->node_table);  free (cache);}voidhash_add (cache_ptr *cachep, const void *key, void *value){  size_t indx = (*(*cachep)->hash_func)(*cachep, key);  node_ptr node = (node_ptr) 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;    }  }#endif  /* Install the node as the first element on the list.  */  (*cachep)->node_table[indx] = node;  /* Bump the number of entries in the cache.  */  ++(*cachep)->used;  /* 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 = hash_new (EXPANSION (*cachep),			      (*cachep)->hash_func,			      (*cachep)->compare_func);    DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n",		  *cachep, (*cachep)->size, new->size);    /* Copy the nodes from the first hash table to the new one.  */    while (node1 = hash_next (*cachep, node1))      hash_add (&new, node1->key, node1->value);    /* Trash the old cache.  */    hash_delete (*cachep);    /* Return a pointer to the new hash table.  */    *cachep = new;  }}voidhash_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;    free (node);  } 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;        free (node);      } else        prev = node, node = node->next;    } while (!removed && node);    assert (removed);  }  /* Decrement the number of entries in the hash table.  */  --cache->used;}node_ptrhash_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;    else      ++cache->last_bucket;  }  /* 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];      else        ++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 *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;}