| 1 | /*
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| 2 | * Copyright (C) 2008-2010 Timothy D. Morgan
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| 3 | *
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| 4 | * This program is free software; you can redistribute it and/or modify
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| 5 | * it under the terms of the GNU General Public License as published by
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| 6 | * the Free Software Foundation; version 3 of the License.
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| 7 | *
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| 8 | * This program is distributed in the hope that it will be useful,
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| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 11 | * GNU General Public License for more details.
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| 12 | *
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| 13 | * You should have received a copy of the GNU General Public License
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| 14 | * along with this program; if not, write to the Free Software
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| 15 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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| 16 | *
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| 17 | * $Id: lru_cache.h 201 2010-06-05 04:45:05Z tim $
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| 18 | */
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| 19 |
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| 20 | /**
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| 21 | * @file
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| 22 | *
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| 23 | * A data structure which approximates a least recently used (LRU) cache.
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| 24 | * Implemented as a basic randomized hash table.
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| 25 | */
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| 26 |
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| 27 |
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| 28 | #ifndef LRU_CACHE_H
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| 29 | #define LRU_CACHE_H
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| 30 |
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| 31 | #include <stdbool.h>
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| 32 | #include <stdint.h>
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| 33 | #include <stdlib.h>
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| 34 | #include <stdio.h>
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| 35 | #include <string.h>
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| 36 | #include <unistd.h>
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| 37 | #include <talloc.h>
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| 38 |
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| 39 | /* GCC-specific macro for library exports */
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| 40 | #ifdef _EXPORT
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| 41 | #undef _EXPORT
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| 42 | #endif
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| 43 | #define _EXPORT __attribute__((visibility("default")))
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| 44 |
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| 45 | struct lru_cache_element;
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| 46 | typedef struct lru_cache_element lru_cache_element;
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| 47 |
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| 48 | struct lru_cache_element
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| 49 | {
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| 50 | void* index;
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| 51 | uint32_t index_len;
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| 52 | void* data;
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| 53 | lru_cache_element* next;
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| 54 | lru_cache_element* older;
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| 55 | lru_cache_element* newer;
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| 56 | };
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| 57 |
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| 58 |
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| 59 | /** XXX: document this. */
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| 60 | typedef struct _lru_cache
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| 61 | {
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| 62 | uint32_t secret;
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| 63 | uint32_t num_keys;
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| 64 | uint32_t num_buckets;
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| 65 | uint32_t max_keys;
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| 66 | lru_cache_element* oldest;
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| 67 | lru_cache_element* newest;
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| 68 | lru_cache_element** table;
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| 69 | bool talloc_data;
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| 70 | } lru_cache;
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| 71 |
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| 72 |
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| 73 | /**
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| 74 | * XXX: finish documenting.
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| 75 | */
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| 76 | _EXPORT
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| 77 | lru_cache* lru_cache_create(uint32_t max_keys, uint32_t secret);
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| 78 |
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| 79 |
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| 80 | /**
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| 81 | * XXX: finish documenting.
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| 82 | */
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| 83 | _EXPORT
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| 84 | lru_cache* lru_cache_create_ctx(void* talloc_ctx, uint32_t max_keys,
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| 85 | uint32_t secret, bool talloc_data);
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| 86 |
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| 87 |
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| 88 | /**
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| 89 | * XXX: finish documenting.
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| 90 | */
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| 91 | _EXPORT
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| 92 | void lru_cache_destroy(lru_cache* ht);
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| 93 |
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| 94 |
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| 95 | /**
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| 96 | * XXX: finish documenting.
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| 97 | */
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| 98 | _EXPORT
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| 99 | bool lru_cache_update(lru_cache* ht, const void* index,
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| 100 | uint32_t index_len, void* data);
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| 101 |
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| 102 | /**
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| 103 | * XXX: finish documenting.
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| 104 | *
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| 105 | * @return A pointer to data previously stored at index.
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| 106 | * If no data was found at index, NULL is returned.
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| 107 | */
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| 108 | _EXPORT
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| 109 | void* lru_cache_find(lru_cache* ht, const void* index,
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| 110 | uint32_t index_len);
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| 111 |
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| 112 | /**
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| 113 | * XXX: finish documenting.
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| 114 | *
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| 115 | * Removes entry from table at index.
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| 116 | *
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| 117 | * @return A pointer to data that was there previously or NULL if no entry is
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| 118 | * at index.
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| 119 | */
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| 120 | _EXPORT
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| 121 | bool lru_cache_remove(lru_cache* ht, const void* index,
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| 122 | uint32_t index_len);
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| 123 |
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| 124 | #endif
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