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+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef APR_HASH_H
+#define APR_HASH_H
+
+/**
+ * @file apr_hash.h
+ * @brief APR Hash Tables
+ */
+
+#include "apr_pools.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @defgroup apr_hash Hash Tables
+ * @ingroup APR
+ * @{
+ */
+
+/**
+ * When passing a key to apr_hash_set or apr_hash_get, this value can be
+ * passed to indicate a string-valued key, and have apr_hash compute the
+ * length automatically.
+ *
+ * @remark apr_hash will use strlen(key) for the length. The NUL 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), apr_hash_this() will return the NUL-term'd key.
+ */
+#define APR_HASH_KEY_STRING (-1)
+
+/**
+ * Abstract type for hash tables.
+ */
+typedef struct apr_hash_t apr_hash_t;
+
+/**
+ * Abstract type for scanning hash tables.
+ */
+typedef struct apr_hash_index_t apr_hash_index_t;
+
+/**
+ * Callback functions for calculating hash values.
+ * @param key The key.
+ * @param klen The length of the key, or APR_HASH_KEY_STRING to use the string
+ * length. If APR_HASH_KEY_STRING then returns the actual key length.
+ */
+typedef unsigned int (*apr_hashfunc_t)(const char *key, apr_ssize_t *klen);
+
+/**
+ * The default hash function.
+ */
+APR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *key,
+ apr_ssize_t *klen);
+
+/**
+ * Create a hash table.
+ * @param pool The pool to allocate the hash table out of
+ * @return The hash table just created
+ */
+APR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool);
+
+/**
+ * Create a hash table with a custom hash function
+ * @param pool The pool to allocate the hash table out of
+ * @param hash_func A custom hash function.
+ * @return The hash table just created
+ */
+APR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool,
+ apr_hashfunc_t hash_func);
+
+/**
+ * Make a copy of a hash table
+ * @param pool The pool from which to allocate the new hash table
+ * @param h The hash table to clone
+ * @return The hash table just created
+ * @remark Makes a shallow copy
+ */
+APR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool,
+ const apr_hash_t *h);
+
+/**
+ * Associate a value with a key in a hash table.
+ * @param ht The hash table
+ * @param key Pointer to the key
+ * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
+ * @param val Value to associate with the key
+ * @remark If the value is NULL the hash entry is deleted. The key is stored as is,
+ * and so must have a lifetime at least as long as the hash table's pool.
+ */
+APR_DECLARE(void) apr_hash_set(apr_hash_t *ht, const void *key,
+ apr_ssize_t klen, const void *val);
+
+/**
+ * Look up the value associated with a key in a hash table.
+ * @param ht The hash table
+ * @param key Pointer to the key
+ * @param klen Length of the key. Can be APR_HASH_KEY_STRING to use the string length.
+ * @return Returns NULL if the key is not present.
+ */
+APR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, const void *key,
+ apr_ssize_t klen);
+
+/**
+ * Start iterating over the entries in a hash table.
+ * @param p The pool to allocate the apr_hash_index_t iterator. If this
+ * pool is NULL, then an internal, non-thread-safe iterator is used.
+ * @param ht The hash table
+ * @return The iteration state
+ * @remark 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.
+ *
+ * @par Example:
+ *
+ * @code
+ * int sum_values(apr_pool_t *p, apr_hash_t *ht)
+ * {
+ * apr_hash_index_t *hi;
+ * void *val;
+ * int sum = 0;
+ * for (hi = apr_hash_first(p, ht); hi; hi = apr_hash_next(hi)) {
+ * apr_hash_this(hi, NULL, NULL, &val);
+ * sum += *(int *)val;
+ * }
+ * return sum;
+ * }
+ * @endcode
+ */
+APR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht);
+
+/**
+ * Continue iterating over the entries in a hash table.
+ * @param hi The iteration state
+ * @return a pointer to the updated iteration state. NULL if there are no more
+ * entries.
+ */
+APR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi);
+
+/**
+ * Get the current entry's details from the iteration state.
+ * @param hi The iteration state
+ * @param key Return pointer for the pointer to the key.
+ * @param klen Return pointer for the key length.
+ * @param val Return pointer for the associated value.
+ * @remark 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.
+ */
+APR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, const void **key,
+ apr_ssize_t *klen, void **val);
+
+/**
+ * Get the current entry's key from the iteration state.
+ * @param hi The iteration state
+ * @return The pointer to the key
+ */
+APR_DECLARE(const void*) apr_hash_this_key(apr_hash_index_t *hi);
+
+/**
+ * Get the current entry's key length from the iteration state.
+ * @param hi The iteration state
+ * @return The key length
+ */
+APR_DECLARE(apr_ssize_t) apr_hash_this_key_len(apr_hash_index_t *hi);
+
+/**
+ * Get the current entry's value from the iteration state.
+ * @param hi The iteration state
+ * @return The pointer to the value
+ */
+APR_DECLARE(void*) apr_hash_this_val(apr_hash_index_t *hi);
+
+/**
+ * Get the number of key/value pairs in the hash table.
+ * @param ht The hash table
+ * @return The number of key/value pairs in the hash table.
+ */
+APR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht);
+
+/**
+ * Clear any key/value pairs in the hash table.
+ * @param ht The hash table
+ */
+APR_DECLARE(void) apr_hash_clear(apr_hash_t *ht);
+
+/**
+ * Merge two hash tables into one new hash table. The values of the overlay
+ * hash override the values of the base if both have the same key. Both
+ * hash tables must use the same hash function.
+ * @param p The pool to use for the new hash table
+ * @param overlay The table to add to the initial table
+ * @param base The table that represents the initial values of the new table
+ * @return A new hash table containing all of the data from the two passed in
+ */
+APR_DECLARE(apr_hash_t *) apr_hash_overlay(apr_pool_t *p,
+ const apr_hash_t *overlay,
+ const apr_hash_t *base);
+
+/**
+ * Merge two hash tables into one new hash table. If the same key
+ * is present in both tables, call the supplied merge function to
+ * produce a merged value for the key in the new table. Both
+ * hash tables must use the same hash function.
+ * @param p The pool to use for the new hash table
+ * @param h1 The first of the tables to merge
+ * @param h2 The second of the tables to merge
+ * @param merger A callback function to merge values, or NULL to
+ * make values from h1 override values from h2 (same semantics as
+ * apr_hash_overlay())
+ * @param data Client data to pass to the merger function
+ * @return A new hash table containing all of the data from the two passed in
+ */
+APR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p,
+ const apr_hash_t *h1,
+ const apr_hash_t *h2,
+ void * (*merger)(apr_pool_t *p,
+ const void *key,
+ apr_ssize_t klen,
+ const void *h1_val,
+ const void *h2_val,
+ const void *data),
+ const void *data);
+
+/**
+ * Declaration prototype for the iterator callback function of apr_hash_do().
+ *
+ * @param rec The data passed as the first argument to apr_hash_[v]do()
+ * @param key The key from this iteration of the hash table
+ * @param klen The key length from this iteration of the hash table
+ * @param value The value from this iteration of the hash table
+ * @remark Iteration continues while this callback function returns non-zero.
+ * To export the callback function for apr_hash_do() it must be declared
+ * in the _NONSTD convention.
+ */
+typedef int (apr_hash_do_callback_fn_t)(void *rec, const void *key,
+ apr_ssize_t klen,
+ const void *value);
+
+/**
+ * Iterate over a hash table running the provided function once for every
+ * element in the hash table. The @p comp function will be invoked for
+ * every element in the hash table.
+ *
+ * @param comp The function to run
+ * @param rec The data to pass as the first argument to the function
+ * @param ht The hash table to iterate over
+ * @return FALSE if one of the comp() iterations returned zero; TRUE if all
+ * iterations returned non-zero
+ * @see apr_hash_do_callback_fn_t
+ */
+APR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp,
+ void *rec, const apr_hash_t *ht);
+
+/**
+ * Get a pointer to the pool which the hash table was created in
+ */
+APR_POOL_DECLARE_ACCESSOR(hash);
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* !APR_HASH_H */