1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
22 * @brief APR Hash Tables
25 #include "apr_pools.h"
32 * @defgroup apr_hash Hash Tables
38 * When passing a key to apr_hash_set or apr_hash_get, this value can be
39 * passed to indicate a string-valued key, and have apr_hash compute the
40 * length automatically.
42 * @remark apr_hash will use strlen(key) for the length. The NUL terminator
43 * is not included in the hash value (why throw a constant in?).
44 * Since the hash table merely references the provided key (rather
45 * than copying it), apr_hash_this() will return the NUL-term'd key.
47 #define APR_HASH_KEY_STRING (-1)
50 * Abstract type for hash tables.
52 typedef struct apr_hash_t apr_hash_t;
55 * Abstract type for scanning hash tables.
57 typedef struct apr_hash_index_t apr_hash_index_t;
60 * Callback functions for calculating hash values.
62 * @param klen The length of the key, or APR_HASH_KEY_STRING to use the string
63 * length. If APR_HASH_KEY_STRING then returns the actual key length.
65 typedef unsigned int (*apr_hashfunc_t)(const char *key, apr_ssize_t *klen);
68 * The default hash function.
70 APR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *key,
74 * Create a hash table.
75 * @param pool The pool to allocate the hash table out of
76 * @return The hash table just created
78 APR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool);
81 * Create a hash table with a custom hash function
82 * @param pool The pool to allocate the hash table out of
83 * @param hash_func A custom hash function.
84 * @return The hash table just created
86 APR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool,
87 apr_hashfunc_t hash_func);
90 * Make a copy of a hash table
91 * @param pool The pool from which to allocate the new hash table
92 * @param h The hash table to clone
93 * @return The hash table just created
94 * @remark Makes a shallow copy
96 APR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool,
100 * Associate a value with a key in a hash table.
101 * @param ht The hash table
102 * @param key Pointer to the key
103 * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
104 * @param val Value to associate with the key
105 * @remark If the value is NULL the hash entry is deleted.
107 APR_DECLARE(void) apr_hash_set(apr_hash_t *ht, const void *key,
108 apr_ssize_t klen, const void *val);
111 * Look up the value associated with a key in a hash table.
112 * @param ht The hash table
113 * @param key Pointer to the key
114 * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
115 * @return Returns NULL if the key is not present.
117 APR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, const void *key,
121 * Start iterating over the entries in a hash table.
122 * @param p The pool to allocate the apr_hash_index_t iterator. If this
123 * pool is NULL, then an internal, non-thread-safe iterator is used.
124 * @param ht The hash table
125 * @return The iteration state
126 * @remark There is no restriction on adding or deleting hash entries during
127 * an iteration (although the results may be unpredictable unless all you do
128 * is delete the current entry) and multiple iterations can be in
129 * progress at the same time.
134 * int sum_values(apr_pool_t *p, apr_hash_t *ht)
136 * apr_hash_index_t *hi;
139 * for (hi = apr_hash_first(p, ht); hi; hi = apr_hash_next(hi)) {
140 * apr_hash_this(hi, NULL, NULL, &val);
141 * sum += *(int *)val;
147 APR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht);
150 * Continue iterating over the entries in a hash table.
151 * @param hi The iteration state
152 * @return a pointer to the updated iteration state. NULL if there are no more
155 APR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi);
158 * Get the current entry's details from the iteration state.
159 * @param hi The iteration state
160 * @param key Return pointer for the pointer to the key.
161 * @param klen Return pointer for the key length.
162 * @param val Return pointer for the associated value.
163 * @remark The return pointers should point to a variable that will be set to the
164 * corresponding data, or they may be NULL if the data isn't interesting.
166 APR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, const void **key,
167 apr_ssize_t *klen, void **val);
170 * Get the number of key/value pairs in the hash table.
171 * @param ht The hash table
172 * @return The number of key/value pairs in the hash table.
174 APR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht);
177 * Clear any key/value pairs in the hash table.
178 * @param ht The hash table
180 APR_DECLARE(void) apr_hash_clear(apr_hash_t *ht);
183 * Merge two hash tables into one new hash table. The values of the overlay
184 * hash override the values of the base if both have the same key. Both
185 * hash tables must use the same hash function.
186 * @param p The pool to use for the new hash table
187 * @param overlay The table to add to the initial table
188 * @param base The table that represents the initial values of the new table
189 * @return A new hash table containing all of the data from the two passed in
191 APR_DECLARE(apr_hash_t *) apr_hash_overlay(apr_pool_t *p,
192 const apr_hash_t *overlay,
193 const apr_hash_t *base);
196 * Merge two hash tables into one new hash table. If the same key
197 * is present in both tables, call the supplied merge function to
198 * produce a merged value for the key in the new table. Both
199 * hash tables must use the same hash function.
200 * @param p The pool to use for the new hash table
201 * @param h1 The first of the tables to merge
202 * @param h2 The second of the tables to merge
203 * @param merger A callback function to merge values, or NULL to
204 * make values from h1 override values from h2 (same semantics as
205 * apr_hash_overlay())
206 * @param data Client data to pass to the merger function
207 * @return A new hash table containing all of the data from the two passed in
209 APR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p,
210 const apr_hash_t *h1,
211 const apr_hash_t *h2,
212 void * (*merger)(apr_pool_t *p,
221 * Declaration prototype for the iterator callback function of apr_hash_do().
223 * @param rec The data passed as the first argument to apr_hash_[v]do()
224 * @param key The key from this iteration of the hash table
225 * @param klen The key length from this iteration of the hash table
226 * @param value The value from this iteration of the hash table
227 * @remark Iteration continues while this callback function returns non-zero.
228 * To export the callback function for apr_hash_do() it must be declared
229 * in the _NONSTD convention.
231 typedef int (apr_hash_do_callback_fn_t)(void *rec, const void *key,
236 * Iterate over a hash table running the provided function once for every
237 * element in the hash table. The @param comp function will be invoked for
238 * every element in the hash table.
240 * @param comp The function to run
241 * @param rec The data to pass as the first argument to the function
242 * @param ht The hash table to iterate over
243 * @return FALSE if one of the comp() iterations returned zero; TRUE if all
244 * iterations returned non-zero
245 * @see apr_hash_do_callback_fn_t
247 APR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp,
248 void *rec, const apr_hash_t *ht);
251 * Get a pointer to the pool which the hash table was created in
253 APR_POOL_DECLARE_ACCESSOR(hash);
261 #endif /* !APR_HASH_H */