Apache Portable Runtime

apr_hash.h

Go to the documentation of this file.
00001 /* Licensed to the Apache Software Foundation (ASF) under one or more
00002  * contributor license agreements.  See the NOTICE file distributed with
00003  * this work for additional information regarding copyright ownership.
00004  * The ASF licenses this file to You under the Apache License, Version 2.0
00005  * (the "License"); you may not use this file except in compliance with
00006  * the License.  You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef APR_HASH_H
00018 #define APR_HASH_H
00019 
00020 /**
00021  * @file apr_hash.h
00022  * @brief APR Hash Tables
00023  */
00024 
00025 #include "apr_pools.h"
00026 
00027 #ifdef __cplusplus
00028 extern "C" {
00029 #endif
00030 
00031 /**
00032  * @defgroup apr_hash Hash Tables
00033  * @ingroup APR 
00034  * @{
00035  */
00036 
00037 /**
00038  * When passing a key to apr_hash_set or apr_hash_get, this value can be
00039  * passed to indicate a string-valued key, and have apr_hash compute the
00040  * length automatically.
00041  *
00042  * @remark apr_hash will use strlen(key) for the length. The NUL terminator
00043  *         is not included in the hash value (why throw a constant in?).
00044  *         Since the hash table merely references the provided key (rather
00045  *         than copying it), apr_hash_this() will return the NUL-term'd key.
00046  */
00047 #define APR_HASH_KEY_STRING     (-1)
00048 
00049 /**
00050  * Abstract type for hash tables.
00051  */
00052 typedef struct apr_hash_t apr_hash_t;
00053 
00054 /**
00055  * Abstract type for scanning hash tables.
00056  */
00057 typedef struct apr_hash_index_t apr_hash_index_t;
00058 
00059 /**
00060  * Callback functions for calculating hash values.
00061  * @param key The key.
00062  * @param klen The length of the key, or APR_HASH_KEY_STRING to use the string 
00063  *             length. If APR_HASH_KEY_STRING then returns the actual key length.
00064  */
00065 typedef unsigned int (*apr_hashfunc_t)(const char *key, apr_ssize_t *klen);
00066 
00067 /**
00068  * The default hash function.
00069  */
00070 APR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *key,
00071                                                       apr_ssize_t *klen);
00072 
00073 /**
00074  * Create a hash table.
00075  * @param pool The pool to allocate the hash table out of
00076  * @return The hash table just created
00077   */
00078 APR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool);
00079 
00080 /**
00081  * Create a hash table with a custom hash function
00082  * @param pool The pool to allocate the hash table out of
00083  * @param hash_func A custom hash function.
00084  * @return The hash table just created
00085   */
00086 APR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool, 
00087                                                apr_hashfunc_t hash_func);
00088 
00089 /**
00090  * Make a copy of a hash table
00091  * @param pool The pool from which to allocate the new hash table
00092  * @param h The hash table to clone
00093  * @return The hash table just created
00094  * @remark Makes a shallow copy
00095  */
00096 APR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool,
00097                                         const apr_hash_t *h);
00098 
00099 /**
00100  * Associate a value with a key in a hash table.
00101  * @param ht The hash table
00102  * @param key Pointer to the key
00103  * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
00104  * @param val Value to associate with the key
00105  * @remark If the value is NULL the hash entry is deleted. The key is stored as is,
00106  *         and so must have a lifetime at least as long as the hash table's pool.
00107  */
00108 APR_DECLARE(void) apr_hash_set(apr_hash_t *ht, const void *key,
00109                                apr_ssize_t klen, const void *val);
00110 
00111 /**
00112  * Look up the value associated with a key in a hash table.
00113  * @param ht The hash table
00114  * @param key Pointer to the key
00115  * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
00116  * @return Returns NULL if the key is not present.
00117  */
00118 APR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, const void *key,
00119                                  apr_ssize_t klen);
00120 
00121 /**
00122  * Start iterating over the entries in a hash table.
00123  * @param p The pool to allocate the apr_hash_index_t iterator. If this
00124  *          pool is NULL, then an internal, non-thread-safe iterator is used.
00125  * @param ht The hash table
00126  * @return The iteration state
00127  * @remark  There is no restriction on adding or deleting hash entries during
00128  * an iteration (although the results may be unpredictable unless all you do
00129  * is delete the current entry) and multiple iterations can be in
00130  * progress at the same time.
00131  *
00132  * @par Example:
00133  *
00134  * @code
00135  * int sum_values(apr_pool_t *p, apr_hash_t *ht)
00136  * {
00137  *     apr_hash_index_t *hi;
00138  *     void *val;
00139  *     int sum = 0;
00140  *     for (hi = apr_hash_first(p, ht); hi; hi = apr_hash_next(hi)) {
00141  *         apr_hash_this(hi, NULL, NULL, &val);
00142  *         sum += *(int *)val;
00143  *     }
00144  *     return sum;
00145  * }
00146  * @endcode
00147  */
00148 APR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht);
00149 
00150 /**
00151  * Continue iterating over the entries in a hash table.
00152  * @param hi The iteration state
00153  * @return a pointer to the updated iteration state.  NULL if there are no more  
00154  *         entries.
00155  */
00156 APR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi);
00157 
00158 /**
00159  * Get the current entry's details from the iteration state.
00160  * @param hi The iteration state
00161  * @param key Return pointer for the pointer to the key.
00162  * @param klen Return pointer for the key length.
00163  * @param val Return pointer for the associated value.
00164  * @remark The return pointers should point to a variable that will be set to the
00165  *         corresponding data, or they may be NULL if the data isn't interesting.
00166  */
00167 APR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, const void **key, 
00168                                 apr_ssize_t *klen, void **val);
00169 
00170 /**
00171  * Get the current entry's key from the iteration state.
00172  * @param hi The iteration state
00173  * @return The pointer to the key
00174  */
00175 APR_DECLARE(const void*) apr_hash_this_key(apr_hash_index_t *hi);
00176 
00177 /**
00178  * Get the current entry's key length from the iteration state.
00179  * @param hi The iteration state
00180  * @return The key length
00181  */
00182 APR_DECLARE(apr_ssize_t) apr_hash_this_key_len(apr_hash_index_t *hi);
00183 
00184 /**
00185  * Get the current entry's value from the iteration state.
00186  * @param hi The iteration state
00187  * @return The pointer to the value
00188  */
00189 APR_DECLARE(void*) apr_hash_this_val(apr_hash_index_t *hi);
00190 
00191 /**
00192  * Get the number of key/value pairs in the hash table.
00193  * @param ht The hash table
00194  * @return The number of key/value pairs in the hash table.
00195  */
00196 APR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht);
00197 
00198 /**
00199  * Clear any key/value pairs in the hash table.
00200  * @param ht The hash table
00201  */
00202 APR_DECLARE(void) apr_hash_clear(apr_hash_t *ht);
00203 
00204 /**
00205  * Merge two hash tables into one new hash table. The values of the overlay
00206  * hash override the values of the base if both have the same key.  Both
00207  * hash tables must use the same hash function.
00208  * @param p The pool to use for the new hash table
00209  * @param overlay The table to add to the initial table
00210  * @param base The table that represents the initial values of the new table
00211  * @return A new hash table containing all of the data from the two passed in
00212  */
00213 APR_DECLARE(apr_hash_t *) apr_hash_overlay(apr_pool_t *p,
00214                                            const apr_hash_t *overlay, 
00215                                            const apr_hash_t *base);
00216 
00217 /**
00218  * Merge two hash tables into one new hash table. If the same key
00219  * is present in both tables, call the supplied merge function to
00220  * produce a merged value for the key in the new table.  Both
00221  * hash tables must use the same hash function.
00222  * @param p The pool to use for the new hash table
00223  * @param h1 The first of the tables to merge
00224  * @param h2 The second of the tables to merge
00225  * @param merger A callback function to merge values, or NULL to
00226  *  make values from h1 override values from h2 (same semantics as
00227  *  apr_hash_overlay())
00228  * @param data Client data to pass to the merger function
00229  * @return A new hash table containing all of the data from the two passed in
00230  */
00231 APR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p,
00232                                          const apr_hash_t *h1,
00233                                          const apr_hash_t *h2,
00234                                          void * (*merger)(apr_pool_t *p,
00235                                                      const void *key,
00236                                                      apr_ssize_t klen,
00237                                                      const void *h1_val,
00238                                                      const void *h2_val,
00239                                                      const void *data),
00240                                          const void *data);
00241 
00242 /**
00243  * Declaration prototype for the iterator callback function of apr_hash_do().
00244  *
00245  * @param rec The data passed as the first argument to apr_hash_[v]do()
00246  * @param key The key from this iteration of the hash table
00247  * @param klen The key length from this iteration of the hash table
00248  * @param value The value from this iteration of the hash table
00249  * @remark Iteration continues while this callback function returns non-zero.
00250  * To export the callback function for apr_hash_do() it must be declared 
00251  * in the _NONSTD convention.
00252  */
00253 typedef int (apr_hash_do_callback_fn_t)(void *rec, const void *key,
00254                                                    apr_ssize_t klen,
00255                                                    const void *value);
00256 
00257 /** 
00258  * Iterate over a hash table running the provided function once for every
00259  * element in the hash table. The @param comp function will be invoked for
00260  * every element in the hash table.
00261  *
00262  * @param comp The function to run
00263  * @param rec The data to pass as the first argument to the function
00264  * @param ht The hash table to iterate over
00265  * @return FALSE if one of the comp() iterations returned zero; TRUE if all
00266  *            iterations returned non-zero
00267  * @see apr_hash_do_callback_fn_t
00268  */
00269 APR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp,
00270                              void *rec, const apr_hash_t *ht);
00271 
00272 /**
00273  * Get a pointer to the pool which the hash table was created in
00274  */
00275 APR_POOL_DECLARE_ACCESSOR(hash);
00276 
00277 /** @} */
00278 
00279 #ifdef __cplusplus
00280 }
00281 #endif
00282 
00283 #endif  /* !APR_HASH_H */
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Defines