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59 lines
2.8 KiB
C
59 lines
2.8 KiB
C
#ifndef CACHETABLE_H
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#define CACHETABLE_H
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#include <fcntl.h>
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/* Implement the cache table. */
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typedef long long CACHEKEY;
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typedef struct cachetable *CACHETABLE;
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typedef struct cachefile *CACHEFILE;
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/* Maintain a cache mapping from cachekeys to values (void*)
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* Some of the keys can be pinned. Don't pin too many or for too long.
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* If the cachetable is too full, it will call the flush_callback() function with the key, the value, and the otherargs
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and then remove the key-value pair from the cache.
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* The callback won't be any of the currently pinned keys.
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* Also when flushing an object, the cachetable drops all references to it,
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* so you may need to free() it.
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* Note: The cachetable should use a common pool of memory, flushing things across cachetables.
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* (The first implementation doesn't)
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* If you pin something twice, you must unpin it twice.
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*/
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int create_cachetable (CACHETABLE */*result*/, int /*n_entries*/);
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int cachetable_openf (CACHEFILE *,CACHETABLE, const char */*fname*/, int flags, mode_t mode);
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/* Error if already present. On success, pin the value. */
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int cachetable_put (CACHEFILE, CACHEKEY, void*/*value*/,
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void(*flush_callback)(CACHEFILE, CACHEKEY key, void*value, int write_me, int keep_me),
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int(*fetch_callback)(CACHEFILE, CACHEKEY key, void**value,void*extraargs), /* If we are asked to fetch something, get it by calling this back. */
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void*extraargs
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);
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int cachetable_get_and_pin (CACHEFILE, CACHEKEY, void**/*value*/,
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void(*flush_callback)(CACHEFILE,CACHEKEY,void*,int write_me, int keep_me),
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int(*fetch_callback)(CACHEFILE, CACHEKEY key, void**value,void*extraargs), /* If we are asked to fetch something, get it by calling this back. */
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void*extraargs
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);
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/* If the the item is already in memory, then return 0 and store it in the void**.
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* If the item is not in memory, then return nonzero. */
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int cachetable_maybe_get_and_pin (CACHEFILE, CACHEKEY, void**);
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int cachetable_unpin (CACHEFILE, CACHEKEY, int dirty); /* Note whether it is dirty when we unpin it. */
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int cachetable_remove (CACHEFILE, CACHEKEY, int /*write_me*/); /* Removing something already present is OK. */
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int cachetable_assert_all_unpinned (CACHETABLE);
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int cachefile_assert_all_unpinned (CACHEFILE);
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//int cachetable_fsync_all (CACHETABLE); /* Flush everything to disk, but keep it in cache. */
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int cachetable_close (CACHETABLE); /* Flushes everything to disk, and destroys the cachetable. */
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int cachefile_close (CACHEFILE);
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//int cachefile_flush (CACHEFILE); /* Flush everything related to the VOID* to disk and free all memory. Don't destroy the cachetable. */
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// Return on success (different from pread and pwrite)
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//int cachefile_pwrite (CACHEFILE, const void *buf, size_t count, off_t offset);
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//int cachefile_pread (CACHEFILE, void *buf, size_t count, off_t offset);
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int cachefile_fd (CACHEFILE);
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#endif
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