Hash Tables
[mod_cache]

マクロ定義
#define	CACHE_HASH_KEY_STRING   (-1)
型定義
typedef cache_hash_t	cache_hash_t
typedef cache_hash_index_t	cache_hash_index_t
関数
cache_hash_t *	cache_hash_make (apr_size_t size)
void	cache_hash_free (cache_hash_t *ht)
void *	cache_hash_set (cache_hash_t *ht, const void *key, apr_ssize_t klen, const void *val)
void *	cache_hash_get (cache_hash_t *ht, const void *key, apr_ssize_t klen)
cache_hash_index_t *	cache_hash_first (cache_hash_t *ht)
cache_hash_index_t *	cache_hash_next (cache_hash_index_t *hi)
void	cache_hash_this (cache_hash_index_t *hi, const void **key, apr_ssize_t *klen, void **val)
int	cache_hash_count (cache_hash_t *ht)

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マクロ定義

#define CACHE_HASH_KEY_STRING   (-1)

When passing a key to cache_hash_set or cache_hash_get, this value can be passed to indicate a string-valued key, and have cache_hash compute the length automatically.

意見:

cache_hash will use strlen(key) for the length. The null-terminator is not included in the hash value (why throw a constant in?). Since the hash table merely references the provided key (rather than copying it), cache_hash_this() will return the null-term'd key.

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型定義

typedef struct cache_hash_index_t cache_hash_index_t

Abstract type for scanning hash tables.

typedef struct cache_hash_t cache_hash_t

Abstract type for hash tables.

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関数

int cache_hash_count

(

cache_hash_t *

ht

)

Get the number of key/value pairs in the hash table.

引数:

ht

The hash table

戻り値:

The number of key/value pairs in the hash table.

cache_hash_index_t* cache_hash_first

(

cache_hash_t *

ht

)

     int sum_values(cache_hash_t *ht)
     {
         cache_hash_index_t *hi;
 	   void *val;
 	   int sum = 0;
 	   for (hi = cache_hash_first(ht); hi; hi = cache_hash_next(hi)) {
 	       cache_hash_this(hi, NULL, NULL, &val);
 	       sum += *(int *)val;
 	   }
 	   return sum;
     }

 There is no restriction on adding or deleting hash entries during an
 iteration (although the results may be unpredictable unless all you do
 is delete the current entry) and multiple iterations can be in
 progress at the same time.
 

void cache_hash_free

(

cache_hash_t *

ht

)

Create a hash table.

引数:

*ht

Pointer to the hash table to be freed.

戻り値:

void

意見:

The caller should ensure that all objects have been removed from the cache prior to calling cache_hash_free(). Objects not removed from the cache prior to calling cache_hash_free() will be unaccessable.

void* cache_hash_get	(	cache_hash_t *	ht,
		const void *	key,
		apr_ssize_t	klen
	)

Look up the value associated with a key in a hash table.

引数:

	ht	The hash table
	key	Pointer to the key
	klen	Length of the key. Can be CACHE_HASH_KEY_STRING to use the string length.

戻り値:

Returns NULL if the key is not present.

cache_hash_t* cache_hash_make

(

apr_size_t

size

)

Create a hash table.

引数:

size

戻り値:

The hash table just created

cache_hash_index_t* cache_hash_next

(

cache_hash_index_t *

hi

)

Continue iterating over the entries in a hash table.

引数:

hi

The iteration state

戻り値:

a pointer to the updated iteration state. NULL if there are no more entries.

void* cache_hash_set	(	cache_hash_t *	ht,
		const void *	key,
		apr_ssize_t	klen,
		const void *	val
	)

Associate a value with a key in a hash table.

引数:

	ht	The hash table
	key	Pointer to the key
	klen	Length of the key. Can be CACHE_HASH_KEY_STRING to use the string length.
	val	Value to associate with the key

意見:

If the value is NULL the hash entry is deleted.

戻り値:

The value of the deleted cache entry (so the caller can clean it up).

void cache_hash_this	(	cache_hash_index_t *	hi,
		const void **	key,
		apr_ssize_t *	klen,
		void **	val
	)

Get the current entry's details from the iteration state.

引数:

	hi	The iteration state
	key	Return pointer for the pointer to the key.
	klen	Return pointer for the key length.
	val	Return pointer for the associated value.

意見:

The return pointers should point to a variable that will be set to the corresponding data, or they may be NULL if the data isn't interesting.

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