a4bcff5ba3
When traversing entry array chains for a bisection or for retrieving an item by index we previously always started at the beginning of the chain. Since we tend to look at the same chains repeatedly, let's cache where we have been the last time, and maybe we can skip ahead with this the next time. This turns most bisections and index lookups from O(log(n)*log(n)) into O(log(n)). More importantly however, we seek around on disk much less, which is good to reduce buffer cache and seek times on rotational disks.
99 lines
3.8 KiB
C
99 lines
3.8 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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#pragma once
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <stdbool.h>
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/* Pretty straightforward hash table implementation. As a minor
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* optimization a NULL hashmap object will be treated as empty hashmap
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* for all read operations. That way it is not necessary to
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* instantiate an object for each Hashmap use. */
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typedef struct Hashmap Hashmap;
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typedef struct _IteratorStruct _IteratorStruct;
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typedef _IteratorStruct* Iterator;
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#define ITERATOR_FIRST ((Iterator) 0)
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#define ITERATOR_LAST ((Iterator) -1)
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typedef unsigned (*hash_func_t)(const void *p);
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typedef int (*compare_func_t)(const void *a, const void *b);
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unsigned string_hash_func(const void *p);
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int string_compare_func(const void *a, const void *b);
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unsigned trivial_hash_func(const void *p);
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int trivial_compare_func(const void *a, const void *b);
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unsigned uint64_hash_func(const void *p);
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int uint64_compare_func(const void *a, const void *b);
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Hashmap *hashmap_new(hash_func_t hash_func, compare_func_t compare_func);
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void hashmap_free(Hashmap *h);
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void hashmap_free_free(Hashmap *h);
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Hashmap *hashmap_copy(Hashmap *h);
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int hashmap_ensure_allocated(Hashmap **h, hash_func_t hash_func, compare_func_t compare_func);
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int hashmap_put(Hashmap *h, const void *key, void *value);
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int hashmap_update(Hashmap *h, const void *key, void *value);
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int hashmap_replace(Hashmap *h, const void *key, void *value);
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void* hashmap_get(Hashmap *h, const void *key);
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void* hashmap_get2(Hashmap *h, const void *key, void **rkey);
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bool hashmap_contains(Hashmap *h, const void *key);
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void* hashmap_remove(Hashmap *h, const void *key);
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void* hashmap_remove_value(Hashmap *h, const void *key, void *value);
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int hashmap_remove_and_put(Hashmap *h, const void *old_key, const void *new_key, void *value);
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int hashmap_remove_and_replace(Hashmap *h, const void *old_key, const void *new_key, void *value);
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int hashmap_merge(Hashmap *h, Hashmap *other);
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void hashmap_move(Hashmap *h, Hashmap *other);
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int hashmap_move_one(Hashmap *h, Hashmap *other, const void *key);
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unsigned hashmap_size(Hashmap *h);
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bool hashmap_isempty(Hashmap *h);
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void *hashmap_iterate(Hashmap *h, Iterator *i, const void **key);
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void *hashmap_iterate_backwards(Hashmap *h, Iterator *i, const void **key);
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void *hashmap_iterate_skip(Hashmap *h, const void *key, Iterator *i);
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void hashmap_clear(Hashmap *h);
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void hashmap_clear_free(Hashmap *h);
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void *hashmap_steal_first(Hashmap *h);
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void *hashmap_steal_first_key(Hashmap *h);
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void* hashmap_first(Hashmap *h);
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void* hashmap_first_key(Hashmap *h);
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void* hashmap_last(Hashmap *h);
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void *hashmap_next(Hashmap *h, const void *key);
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char **hashmap_get_strv(Hashmap *h);
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#define HASHMAP_FOREACH(e, h, i) \
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for ((i) = ITERATOR_FIRST, (e) = hashmap_iterate((h), &(i), NULL); (e); (e) = hashmap_iterate((h), &(i), NULL))
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#define HASHMAP_FOREACH_KEY(e, k, h, i) \
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for ((i) = ITERATOR_FIRST, (e) = hashmap_iterate((h), &(i), (const void**) &(k)); (e); (e) = hashmap_iterate((h), &(i), (const void**) &(k)))
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#define HASHMAP_FOREACH_BACKWARDS(e, h, i) \
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for ((i) = ITERATOR_LAST, (e) = hashmap_iterate_backwards((h), &(i), NULL); (e); (e) = hashmap_iterate_backwards((h), &(i), NULL))
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