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Diffstat (limited to 'libobjc/objc/hash.h')
| -rw-r--r-- | libobjc/objc/hash.h | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/libobjc/objc/hash.h b/libobjc/objc/hash.h new file mode 100644 index 00000000000..bddb791c820 --- /dev/null +++ b/libobjc/objc/hash.h @@ -0,0 +1,206 @@ +/* Hash tables for Objective C method dispatch. + Copyright (C) 1993, 1995, 1996 Free Software Foundation, Inc. + +This file is part of GNU CC. + +GNU CC 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 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 of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU CC; see the file COPYING. If not, write to +the Free Software Foundation, 59 Temple Place - Suite 330, +Boston, MA 02111-1307, 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. */ + + +#ifndef __hash_INCLUDE_GNU +#define __hash_INCLUDE_GNU + +#include <stddef.h> +#include <objc/objc.h> + +/* + * This data structure is used to hold items + * stored in a hash table. Each node holds + * a key/value pair. + * + * Items in the cache are really of type void *. + */ +typedef struct cache_node +{ + struct cache_node *next; /* Pointer to next entry on the list. + NULL indicates end of list. */ + const void *key; /* Key used to locate the value. Used + to locate value when more than one + key computes the same hash + value. */ + void *value; /* Value stored for the key. */ +} *node_ptr; + + +/* + * This data type is the function that computes a hash code given a key. + * Therefore, the key can be a pointer to anything and the function specific + * to the key type. + * + * Unfortunately there is a mutual data structure reference problem with this + * typedef. Therefore, to remove compiler warnings the functions passed to + * hash_new will have to be casted to this type. + */ +typedef unsigned int (*hash_func_type)(void *, const void *); + +/* + * This data type is the function that compares two hash keys and returns an + * integer greater than, equal to, or less than 0, according as the first + * parameter is lexicographically greater than, equal to, or less than the + * second. + */ + +typedef int (*compare_func_type)(const void *, const void *); + + +/* + * This data structure is the cache. + * + * It must be passed to all of the hashing routines + * (except for new). + */ +typedef struct cache +{ + /* Variables used to implement the hash itself. */ + node_ptr *node_table; /* Pointer to an array of hash nodes. */ + /* Variables used to track the size of the hash table so to determine + when to resize it. */ + unsigned int size; /* Number of buckets allocated for the hash table + (number of array entries allocated for + "node_table"). Must be a power of two. */ + unsigned int used; /* Current number of entries in the hash table. */ + unsigned int mask; /* Precomputed mask. */ + + /* Variables used to implement indexing through the hash table. */ + + unsigned int last_bucket; /* Tracks which entry in the array where + the last value was returned. */ + /* Function used to compute a hash code given a key. + This function is specified when the hash table is created. */ + hash_func_type hash_func; + /* Function used to compare two hash keys to see if they are equal. */ + compare_func_type compare_func; +} *cache_ptr; + + +/* Two important hash tables. */ +extern cache_ptr module_hash_table, class_hash_table; + +/* Allocate and initialize a hash table. */ + +cache_ptr hash_new (unsigned int size, + hash_func_type hash_func, + compare_func_type compare_func); + +/* Deallocate all of the hash nodes and the cache itself. */ + +void hash_delete (cache_ptr cache); + +/* Add the key/value pair to the hash table. If the + hash table reaches a level of fullness then it will be resized. + + assert if the key is already in the hash. */ + +void hash_add (cache_ptr *cachep, const void *key, void *value); + +/* Remove the key/value pair from the hash table. + assert if the key isn't in the table. */ + +void hash_remove (cache_ptr cache, const void *key); + +/* Used to index through the hash table. Start with NULL + to get the first entry. + + Successive calls pass the value returned previously. + ** Don't modify the hash during this operation *** + + Cache nodes are returned such that key or value can + be extracted. */ + +node_ptr hash_next (cache_ptr cache, node_ptr node); + +/* Used to return a value from a hash table using a given key. */ + +void *hash_value_for_key (cache_ptr cache, const void *key); + +/* Used to determine if the given key exists in the hash table */ + +BOOL hash_is_key_in_hash (cache_ptr cache, const void *key); + +/************************************************ + + Useful hashing functions. + + Declared inline for your pleasure. + +************************************************/ + +/* Calculate a hash code by performing some + manipulation of the key pointer. (Use the lowest bits + except for those likely to be 0 due to alignment.) */ + +static inline unsigned int +hash_ptr (cache_ptr cache, const void *key) +{ + return ((size_t)key / sizeof (void *)) & cache->mask; +} + + +/* Calculate a hash code by iterating over a NULL + terminate string. */ +static inline unsigned int +hash_string (cache_ptr cache, const void *key) +{ + unsigned int ret = 0; + unsigned int ctr = 0; + + + while (*(char*)key) { + ret ^= *(char*)key++ << ctr; + ctr = (ctr + 1) % sizeof (void *); + } + + return ret & cache->mask; +} + + +/* Compare two pointers for equality. */ +static inline int +compare_ptrs (const void *k1, const void *k2) +{ + return !(k1 - k2); +} + + +/* Compare two strings. */ +static inline int +compare_strings (const void *k1, const void *k2) +{ + if (k1 == k2) + return 1; + else if (k1 == 0 || k2 == 0) + return 0; + else + return !strcmp (k1, k2); +} + + +#endif /* not __hash_INCLUDE_GNU */ |