hash_map.h File Reference

Hash map implementation. More...

#include "map.h"

Go to the source code of this file.

Data Structures
struct	cx_hash_map_s
	Internal structure for a hash map. More...

Macros
#define	cxHashMapCreateSimple(itemsize)    cxHashMapCreate(cxDefaultAllocator, itemsize, 0)
	Creates a new hash map with a default number of buckets.

Functions
CxMap *	cxHashMapCreate (CxAllocator const *allocator, size_t itemsize, size_t buckets)
	Creates a new hash map with the specified number of buckets.
int	cxMapRehash (CxMap *map)
	Increases the number of buckets, if necessary.

Detailed Description

Hash map implementation.

Author

Mike Becker

Olaf Wintermann

Version

3.0

Copyright

2-Clause BSD License

Macro Definition Documentation

cxHashMapCreateSimple

#define cxHashMapCreateSimple

(

itemsize

)

cxHashMapCreate(cxDefaultAllocator, itemsize, 0)

Creates a new hash map with a default number of buckets.

If item_size is CX_STORE_POINTERS, the created map will be created as if cxMapStorePointers() was called immediately after creation.

Note

Iterators provided by this hash map implementation provide the remove operation. The index value of an iterator is incremented when the iterator advanced without removal. In other words, when the iterator is finished, index==size .

Parameters

itemsize

the size of one element

Returns

a pointer to the new hash map

Function Documentation

cxHashMapCreate()

CxMap * cxHashMapCreate	(	CxAllocator const *	allocator,
		size_t	itemsize,
		size_t	buckets
	)

Creates a new hash map with the specified number of buckets.

If buckets is zero, an implementation defined default will be used.

If item_size is CX_STORE_POINTERS, the created map will be created as if cxMapStorePointers() was called immediately after creation.

Note

Iterators provided by this hash map implementation provide the remove operation. The index value of an iterator is incremented when the iterator advanced without removal. In other words, when the iterator is finished, index==size .

Parameters

allocator	the allocator to use
itemsize	the size of one element
buckets	the initial number of buckets in this hash map

Returns

a pointer to the new hash map

cxMapRehash()

int cxMapRehash

(

CxMap *

map

)

Increases the number of buckets, if necessary.

The load threshold is 0.75*buckets. If the element count exceeds the load threshold, the map will be rehashed. Otherwise, no action is performed and this function simply returns 0.

The rehashing process ensures, that the number of buckets is at least 2.5 times the element count. So there is enough room for additional elements without the need of another soon rehashing.

You can use this function after filling a map to increase access performance.

Note

If the specified map is not a hash map, the behavior is undefined.

Parameters

map	the map to rehash

Returns

zero on success, non-zero if a memory allocation error occurred