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/* haptable.h
Scalable hash table of happings.
Bertrand, August 1990
Copyright 1990 NeXT, Inc.
*/
#ifndef _OBJC_HAPTABLE_H_
#define _OBJC_HAPTABLE_H_
#import <objc/objc.h>
#import <objc/zone.h>
/*************** Definitions ***************/
/* This module allows hashing of arbitrary associations [key -> key]. Keys must be pointers or integers, and client is responsible for allocating/deallocating this data. A deallocation call-back is provided.
NX_HAPNOTAKEY (-1) is used internally as a marker, and therefore keys must always be different from -1.
As well-behaved scalable data structures, hash tables double in size when they start becoming full, thus guaranteeing both average constant time access and linear size. */
typedef struct _NXHapTable {
/* private data structure; may change */
const struct _NXHapTablePrototype *prototype;
unsigned count;
unsigned nbBuckets;
void *buckets;
} NXHapTable;
typedef struct _NXHapTablePrototype {
unsigned (*hash)(NXHapTable *, const void *key);
int (*isEqual)(NXHapTable *, const void *key1, const void *key2);
void (*free)(NXHapTable *, void *key);
int style; /* reserved for future expansion; currently 0 */
} NXHapTablePrototype;
/* invariants assumed by the implementation:
A - key != -1
B - key1 == key2 => hash(key1) == hash(key2)
when key varies over time, hash(key) must remain invariant
e.g. if string key, the string must not be changed
C - isEqual(key1, key2) => key1 == key2
*/
#define NX_HAPNOTAKEY ((void *)(-1))
/*************** Functions ***************/
extern NXHapTable *NXCreateHapTableFromZone(NXHapTablePrototype prototype, unsigned capacity, NXZone *zone);
extern NXHapTable *NXCreateHapTable(NXHapTablePrototype prototype, unsigned capacity);
/* capacity is only a hint; 0 creates a small table */
extern void NXFreeHapTable(NXHapTable *table);
/* call free for each pair, and recovers table */
extern void NXResetHapTable(NXHapTable *table);
/* free each pair; keep current capacity */
extern BOOL NXCompareHapTables(NXHapTable *table1, NXHapTable *table2);
/* Returns YES if the two sets are equal (each member of table1 in table2, and table have same size) */
extern unsigned NXCountHapTable(NXHapTable *table);
/* current number of data in table */
extern void *NXHapMember(NXHapTable *table, const void *key);
/* return original table key or NX_HAPNOTAKEY. */
extern void *NXHapGet(NXHapTable *table, const void *key);
extern void *NXHapInsert(NXHapTable *table, const void *key);
/* override preexisting pair; Return previous key or NULL. */
extern void *NXHapRemove(NXHapTable *table, const void *key);
/* previous key or NULL is returned */
/* Iteration over all elements of a table consists in setting up an iteration state and then to progress until all entries have been visited. An example of use for counting elements in a table is:
unsigned count = 0;
const MyKey *key;
NXHapState state = NXInitHapState(table);
while(NXNextHapState(table, &state, &key)) {
count++;
}
*/
typedef struct {int index;} NXHapState;
/* callers should not rely on actual contents of the struct */
extern NXHapState NXInitHapState(NXHapTable *table);
extern int NXNextHapState(NXHapTable *table, NXHapState *state, const void **key);
/* returns 0 when all elements have been visited */
/*************** Conveniences ***************/
extern const NXHapTablePrototype NXPtrValueHapPrototype;
/* hashing is pointer/integer hashing;
isEqual is identity;
free is no-op. */
extern const NXHapTablePrototype NXStrValueHapPrototype;
/* hashing is string hashing;
isEqual is strcmp;
free is no-op. */
extern const NXHapTablePrototype NXObjectHapPrototype;
/* for objects; uses methods: hash, isEqual:, free, all for key. */
#endif /* _OBJC_HAPTABLE_H_ */
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