src/sortedcache.h

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7 #ifndef INCLUDE_sorted_cache_h__
   8 #define INCLUDE_sorted_cache_h__
   9
  10 #include "util.h"
  11 #include "fileops.h"
  12 #include "vector.h"
  13 #include "thread-utils.h"
  14 #include "pool.h"
  15 #include "strmap.h"
  16
  17 /*
  18  * The purpose of this data structure is to cache the parsed contents of a
  19  * file (a.k.a. the backing file) where each item in the file can be
  20  * identified by a key string and you want to both look them up by name
  21  * and traverse them in sorted order.  Each item is assumed to itself end
  22  * in a GIT_FLEX_ARRAY.
  23  */
  24
  25 typedef void (*git_sortedcache_free_item_fn)(void *payload, void *item);
  26
  27 typedef struct {
  28         git_refcount rc;
  29         git_rwlock   lock;
  30         size_t       item_path_offset;
  31         git_sortedcache_free_item_fn free_item;
  32         void         *free_item_payload;
  33         git_pool     pool;
  34         git_vector   items;
  35         git_strmap   *map;
  36         git_futils_filestamp stamp;
  37         char         path[GIT_FLEX_ARRAY];
  38 } git_sortedcache;
  39
  40 /* Create a new sortedcache
  41  *
  42  * Even though every sortedcache stores items with a GIT_FLEX_ARRAY at
  43  * the end containing their key string, you have to provide the item_cmp
  44  * sorting function because the sorting function doesn't get a payload
  45  * and therefore can't know the offset to the item key string. :-(
  46  *
  47  * @param out The allocated git_sortedcache
  48  * @param item_path_offset Offset to the GIT_FLEX_ARRAY item key in the
  49  *        struct - use offsetof(struct mine, key-field) to get this
  50  * @param free_item Optional callback to free each item
  51  * @param free_item_payload Optional payload passed to free_item callback
  52  * @param item_cmp Compare the keys of two items
  53  * @param path The path to the backing store file for this cache; this
  54  *        may be NULL.  The cache makes it easy to load this and check
  55  *        if it has been modified since the last load and/or write.
  56  */
  57 int git_sortedcache_new(
  58         git_sortedcache **out,
  59         size_t item_path_offset, /* use offsetof(struct, path-field) macro */
  60         git_sortedcache_free_item_fn free_item,
  61         void *free_item_payload,
  62         git_vector_cmp item_cmp,
  63         const char *path);
  64
  65 /* Copy a sorted cache
  66  *
  67  * - `copy_item` can be NULL to just use memcpy
  68  * - if `lock`, grabs read lock on `src` during copy and releases after
  69  */
  70 int git_sortedcache_copy(
  71         git_sortedcache **out,
  72         git_sortedcache *src,
  73         bool lock,
  74         int (*copy_item)(void *payload, void *tgt_item, void *src_item),
  75         void *payload);
  76
  77 /* Free sorted cache (first calling `free_item` callbacks)
  78  *
  79  * Don't call on a locked collection - it may acquire a write lock
  80  */
  81 void git_sortedcache_free(git_sortedcache *sc);
  82
  83 /* Increment reference count - balance with call to free */
  84 void git_sortedcache_incref(git_sortedcache *sc);
  85
  86 /* Get the pathname associated with this cache at creation time */
  87 const char *git_sortedcache_path(git_sortedcache *sc);
  88
  89 /*
  90  * CACHE WRITE FUNCTIONS
  91  *
  92  * The following functions require you to have a writer lock to make the
  93  * modification.  Some of the functions take a `wlock` parameter and
  94  * will optionally lock and unlock for you if that is passed as true.
  95  *
  96  */
  97
  98 /* Lock sortedcache for write */
  99 int git_sortedcache_wlock(git_sortedcache *sc);
 100
 101 /* Unlock sorted cache when done with write */
 102 void git_sortedcache_wunlock(git_sortedcache *sc);
 103
 104 /* Lock cache and load backing file into a buffer.
 105  *
 106  * This grabs a write lock on the cache then looks at the modification
 107  * time and size of the file on disk.
 108  *
 109  * If the file appears to have changed, this loads the file contents into
 110  * the buffer and returns a positive value leaving the cache locked - the
 111  * caller should parse the file content, update the cache as needed, then
 112  * release the lock.  NOTE: In this case, the caller MUST unlock the cache.
 113  *
 114  * If the file appears to be unchanged, then this automatically releases
 115  * the lock on the cache, clears the buffer, and returns 0.
 116  *
 117  * @return 0 if up-to-date, 1 if out-of-date, <0 on error
 118  */
 119 int git_sortedcache_lockandload(git_sortedcache *sc, git_buf *buf);
 120
 121 /* Refresh file timestamp after write completes
 122  * You should already be holding the write lock when you call this.
 123  */
 124 void git_sortedcache_updated(git_sortedcache *sc);
 125
 126 /* Release all items in sorted cache
 127  *
 128  * If `wlock` is true, grabs write lock and releases when done, otherwise
 129  * you should already be holding a write lock when you call this.
 130  */
 131 int git_sortedcache_clear(git_sortedcache *sc, bool wlock);
 132
 133 /* Find and/or insert item, returning pointer to item data.
 134  * You should already be holding the write lock when you call this.
 135  */
 136 int git_sortedcache_upsert(
 137         void **out, git_sortedcache *sc, const char *key);
 138
 139 /* Removes entry at pos from cache
 140  * You should already be holding the write lock when you call this.
 141  */
 142 int git_sortedcache_remove(git_sortedcache *sc, size_t pos);
 143
 144 /*
 145  * CACHE READ FUNCTIONS
 146  *
 147  * The following functions access items in the cache.  To prevent the
 148  * results from being invalidated before they can be used, you should be
 149  * holding either a read lock or a write lock when using these functions.
 150  *
 151  */
 152
 153 /* Lock sortedcache for read */
 154 int git_sortedcache_rlock(git_sortedcache *sc);
 155
 156 /* Unlock sorted cache when done with read */
 157 void git_sortedcache_runlock(git_sortedcache *sc);
 158
 159 /* Lookup item by key - returns NULL if not found */
 160 void *git_sortedcache_lookup(const git_sortedcache *sc, const char *key);
 161
 162 /* Get how many items are in the cache
 163  *
 164  * You can call this function without holding a lock, but be aware
 165  * that it may change before you use it.
 166  */
 167 size_t git_sortedcache_entrycount(const git_sortedcache *sc);
 168
 169 /* Lookup item by index - returns NULL if out of range */
 170 void *git_sortedcache_entry(git_sortedcache *sc, size_t pos);
 171
 172 /* Lookup index of item by key - returns GIT_ENOTFOUND if not found */
 173 int git_sortedcache_lookup_index(
 174         size_t *out, git_sortedcache *sc, const char *key);
 175
 176 #endif