208 lines
6.3 KiB
C
208 lines
6.3 KiB
C
/* Hash tables for Objective C method dispatch.
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Copyright (C) 1993, 1995, 1996 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, 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, 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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#ifndef __hash_INCLUDE_GNU
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#define __hash_INCLUDE_GNU
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#include <stddef.h>
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#include <string.h>
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#include <objc/objc.h>
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/*
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* This data structure is used to hold items
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* stored in a hash table. Each node holds
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* a key/value pair.
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*
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* Items in the cache are really of type void *.
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*/
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typedef struct cache_node
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{
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struct cache_node *next; /* Pointer to next entry on the list.
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NULL indicates end of list. */
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const void *key; /* Key used to locate the value. Used
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to locate value when more than one
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key computes the same hash
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value. */
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void *value; /* Value stored for the key. */
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} *node_ptr;
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/*
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* This data type is the function that computes a hash code given a key.
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* Therefore, the key can be a pointer to anything and the function specific
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* to the key type.
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*
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* Unfortunately there is a mutual data structure reference problem with this
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* typedef. Therefore, to remove compiler warnings the functions passed to
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* hash_new will have to be casted to this type.
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*/
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typedef unsigned int (*hash_func_type)(void *, const void *);
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/*
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* This data type is the function that compares two hash keys and returns an
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* integer greater than, equal to, or less than 0, according as the first
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* parameter is lexicographically greater than, equal to, or less than the
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* second.
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*/
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typedef int (*compare_func_type)(const void *, const void *);
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/*
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* This data structure is the cache.
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*
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* It must be passed to all of the hashing routines
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* (except for new).
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*/
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typedef struct cache
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{
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/* Variables used to implement the hash itself. */
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node_ptr *node_table; /* Pointer to an array of hash nodes. */
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/* Variables used to track the size of the hash table so to determine
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when to resize it. */
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unsigned int size; /* Number of buckets allocated for the hash table
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(number of array entries allocated for
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"node_table"). Must be a power of two. */
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unsigned int used; /* Current number of entries in the hash table. */
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unsigned int mask; /* Precomputed mask. */
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/* Variables used to implement indexing through the hash table. */
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unsigned int last_bucket; /* Tracks which entry in the array where
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the last value was returned. */
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/* Function used to compute a hash code given a key.
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This function is specified when the hash table is created. */
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hash_func_type hash_func;
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/* Function used to compare two hash keys to see if they are equal. */
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compare_func_type compare_func;
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} *cache_ptr;
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/* Two important hash tables. */
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extern cache_ptr module_hash_table, class_hash_table;
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/* Allocate and initialize a hash table. */
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cache_ptr hash_new (unsigned int size,
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hash_func_type hash_func,
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compare_func_type compare_func);
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/* Deallocate all of the hash nodes and the cache itself. */
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void hash_delete (cache_ptr cache);
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/* Add the key/value pair to the hash table. If the
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hash table reaches a level of fullness then it will be resized.
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assert if the key is already in the hash. */
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void hash_add (cache_ptr *cachep, const void *key, void *value);
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/* Remove the key/value pair from the hash table.
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assert if the key isn't in the table. */
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void hash_remove (cache_ptr cache, const void *key);
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/* Used to index through the hash table. Start with NULL
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to get the first entry.
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Successive calls pass the value returned previously.
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** Don't modify the hash during this operation ***
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Cache nodes are returned such that key or value can
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be extracted. */
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node_ptr hash_next (cache_ptr cache, node_ptr node);
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/* Used to return a value from a hash table using a given key. */
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void *hash_value_for_key (cache_ptr cache, const void *key);
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/* Used to determine if the given key exists in the hash table */
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BOOL hash_is_key_in_hash (cache_ptr cache, const void *key);
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/************************************************
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Useful hashing functions.
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Declared inline for your pleasure.
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************************************************/
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/* Calculate a hash code by performing some
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manipulation of the key pointer. (Use the lowest bits
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except for those likely to be 0 due to alignment.) */
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static inline unsigned int
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hash_ptr (cache_ptr cache, const void *key)
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{
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return ((size_t)key / sizeof (void *)) & cache->mask;
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}
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/* Calculate a hash code by iterating over a NULL
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terminate string. */
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static inline unsigned int
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hash_string (cache_ptr cache, const void *key)
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{
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unsigned int ret = 0;
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unsigned int ctr = 0;
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while (*(char*)key) {
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ret ^= *(char*)key++ << ctr;
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ctr = (ctr + 1) % sizeof (void *);
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}
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return ret & cache->mask;
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}
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/* Compare two pointers for equality. */
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static inline int
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compare_ptrs (const void *k1, const void *k2)
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{
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return !(k1 - k2);
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}
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/* Compare two strings. */
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static inline int
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compare_strings (const void *k1, const void *k2)
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{
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if (k1 == k2)
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return 1;
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else if (k1 == 0 || k2 == 0)
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return 0;
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else
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return !strcmp (k1, k2);
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}
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#endif /* not __hash_INCLUDE_GNU */
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