/*
* Copyright © 2008 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
/**
* \file hash_table.h
* \brief Implementation of a generic, opaque hash table data type.
*
* \author Ian Romanick <ian.d.romanick@intel.com>
*/
#ifndef HASH_TABLE_H
#define HASH_TABLE_H
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <assert.h>
struct string_to_uint_map;
#ifdef __cplusplus
extern "C" {
#endif
struct hash_table;
typedef unsigned (*hash_func_t)(const void *key);
typedef int (*hash_compare_func_t)(const void *key1, const void *key2);
/**
* Hash table constructor
*
* Creates a hash table with the specified number of buckets. The supplied
* \c hash and \c compare routines are used when adding elements to the table
* and when searching for elements in the table.
*
* \param num_buckets Number of buckets (bins) in the hash table.
* \param hash Function used to compute hash value of input keys.
* \param compare Function used to compare keys.
*/
extern struct hash_table *hash_table_ctor(unsigned num_buckets,
hash_func_t hash, hash_compare_func_t compare);
/**
* Release all memory associated with a hash table
*
* \warning
* This function cannot release memory occupied either by keys or data.
*/
extern void hash_table_dtor(struct hash_table *ht);
/**
* Flush all entries from a hash table
*
* \param ht Table to be cleared of its entries.
*/
extern void hash_table_clear(struct hash_table *ht);
/**
* Search a hash table for a specific element
*
* \param ht Table to be searched
* \param key Key of the desired element
*
* \return
* The \c data value supplied to \c hash_table_insert when the element with
* the matching key was added. If no matching key exists in the table,
* \c NULL is returned.
*/
extern void *hash_table_find(struct hash_table *ht, const void *key);
/**
* Add an element to a hash table
*
* \warning
* If \c key is already in the hash table, it will be added again. Future
* calls to \c hash_table_find and \c hash_table_remove will return or remove,
* repsectively, the most recently added instance of \c key.
*
* \warning
* The value passed by \c key is kept in the hash table and is used by later
* calls to \c hash_table_find.
*
* \sa hash_table_replace
*/
extern void hash_table_insert(struct hash_table *ht, void *data,
const void *key);
/**
* Add an element to a hash table with replacement
*
* \return
* 1 if it did replace the the value (in which case the old key is kept), 0 if
* it did not replace the value (in which case the new key is kept).
*
* \warning
* If \c key is already in the hash table, \c data will \b replace the most
* recently inserted \c data (see the warning in \c hash_table_insert) for
* that key.
*
* \sa hash_table_insert
*/
extern bool hash_table_replace(struct hash_table *ht, void *data,
const void *key);
/**
* Remove a specific element from a hash table.
*/
extern void hash_table_remove(struct hash_table *ht, const void *key);
/**
* Compute hash value of a string
*
* Computes the hash value of a string using the DJB2 algorithm developed by
* Professor Daniel J. Bernstein. It was published on comp.lang.c once upon
* a time. I was unable to find the original posting in the archives.
*
* \param key Pointer to a NUL terminated string to be hashed.
*
* \sa hash_table_string_compare
*/
extern unsigned hash_table_string_hash(const void *key);
/**
* Compare two strings used as keys
*
* This is just a macro wrapper around \c strcmp.
*
* \sa hash_table_string_hash
*/
#define hash_table_string_compare ((hash_compare_func_t) strcmp)
/**
* Compute hash value of a pointer
*
* \param key Pointer to be used as a hash key
*
* \note
* The memory pointed to by \c key is \b never accessed. The value of \c key
* itself is used as the hash key
*
* \sa hash_table_pointer_compare
*/
unsigned
hash_table_pointer_hash(const void *key);
/**
* Compare two pointers used as keys
*
* \sa hash_table_pointer_hash
*/
int
hash_table_pointer_compare(const void *key1, const void *key2);
void
hash_table_call_foreach(struct hash_table *ht,
void (*callback)(const void *key,
void *data,
void *closure),
void *closure);
struct string_to_uint_map *
string_to_uint_map_ctor();
void
string_to_uint_map_dtor(struct string_to_uint_map *);
#ifdef __cplusplus
}
/**
* Map from a string (name) to an unsigned integer value
*
* \note
* Because of the way this class interacts with the \c hash_table
* implementation, values of \c UINT_MAX cannot be stored in the map.
*/
struct string_to_uint_map {
public:
string_to_uint_map()
{
this->ht = hash_table_ctor(0, hash_table_string_hash,
hash_table_string_compare);
}
~string_to_uint_map()
{
hash_table_call_foreach(this->ht, delete_key, NULL);
hash_table_dtor(this->ht);
}
/**
* Remove all mappings from this map.
*/
void clear()
{
hash_table_call_foreach(this->ht, delete_key, NULL);
hash_table_clear(this->ht);
}
/**
* Get the value associated with a particular key
*
* \return
* If \c key is found in the map, \c true is returned. Otherwise \c false
* is returned.
*
* \note
* If \c key is not found in the table, \c value is not modified.
*/
bool get(unsigned &value, const char *key)
{
const intptr_t v =
(intptr_t) hash_table_find(this->ht, (const void *) key);
if (v == 0)
return false;
value = (unsigned)(v - 1);
return true;
}
void put(unsigned value, const char *key)
{
/* The low-level hash table structure returns NULL if key is not in the
* hash table. However, users of this map might want to store zero as a
* valid value in the table. Bias the value by +1 so that a
* user-specified zero is stored as 1. This enables ::get to tell the
* difference between a user-specified zero (returned as 1 by
* hash_table_find) and the key not in the table (returned as 0 by
* hash_table_find).
*
* The net effect is that we can't store UINT_MAX in the table. This is
* because UINT_MAX+1 = 0.
*/
assert(value != UINT_MAX);
char *dup_key = strdup(key);
bool result = hash_table_replace(this->ht,
(void *) (intptr_t) (value + 1),
dup_key);
if (result)
free(dup_key);
}
private:
static void delete_key(const void *key, void *data, void *closure)
{
(void) data;
(void) closure;
free((char *)key);
}
struct hash_table *ht;
};
#endif /* __cplusplus */
#endif /* HASH_TABLE_H */