101 lines
3.7 KiB
C
101 lines
3.7 KiB
C
/****************************************************************************
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* include/nuttx/hashtable.h
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_HASHTABLE_H
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#define __INCLUDE_NUTTX_HASHTABLE_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/lib/math32.h>
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#include <nuttx/nuttx.h>
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#include <nuttx/queue.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Hash function related definitions. */
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#define GOLDEN_RATIO_32 0x61C88647 /* Negative golden ratio, used by Linux. */
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#define HASH(val, bits) ((uint32_t)((val) * GOLDEN_RATIO_32) >> (32 - (bits)))
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/* Hashtable related definitions. */
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#define DECLARE_HASHTABLE(table, bits) hash_head_t table[1 << (bits)]
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#define hashtable_size(table) (sizeof(table) / sizeof((table)[0]))
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#define hashtable_bits(table) (LOG2_FLOOR(hashtable_size(table)))
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#define hashtable_init(table) \
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do \
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{ \
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int i; \
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for (i = 0; i < hashtable_size(table); i++) \
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{ \
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dq_init(&table[i]); \
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} \
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} \
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while(0)
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#define hashtable_add(table, item, key) \
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dq_addfirst(item, &table[HASH(key, hashtable_bits(table))])
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#define hashtable_delete(table, item, key) \
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dq_rem(item, &table[HASH(key, hashtable_bits(table))])
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/* Iterate over whole hashtable. */
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#define hashtable_for_every(table, item, i) \
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for ((i) = 0; (i) < hashtable_size(table); (i)++) \
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sq_for_every(&table[i], item)
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#define hashtable_for_every_safe(table, item, temp, i) \
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for ((i) = 0; (i) < hashtable_size(table); (i)++) \
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sq_for_every_safe(&table[i], item, temp)
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/* Iterate over all possible objects hashing to the same bucket. */
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#define hashtable_for_every_possible(table, item, key) \
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sq_for_every(&table[HASH(key, hashtable_bits(table))], item)
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#define hashtable_for_every_possible_safe(table, item, temp, key) \
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sq_for_every_safe(&table[HASH(key, hashtable_bits(table))], item, temp)
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/****************************************************************************
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* Public Types
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****************************************************************************/
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/* Note: Our `list` is not suitable for hashtable, because `list` will always
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* access `head` when iterating by `for_every`, but `head` may sometimes be
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* accessed by hash result, then hash function will be called on each
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* iteration. So we use `dq` instead to avoid this.
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*
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* Note: There is an optimized type `hlist` on Linux, which saves one pointer
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* in list head, we can do the same optimization to save memory (but only
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* saves a little compares to the whole hashtable).
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*/
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typedef dq_queue_t hash_head_t;
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typedef dq_entry_t hash_node_t;
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#endif /* __INCLUDE_NUTTX_HASHTABLE_H */
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