workbench/fs/fat/cache.h

   1 /*
   2  * Disk buffer cache
   3  *
   4  * Copyright © 2007 Robert Norris
   5  * Copyright © 2008 Pavel Fedin
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the same terms as AROS itself.
   9  *
  10  * $Id$
  11  */
  12
  13 #ifndef CACHE_H
  14 #define CACHE_H 1
  15
  16 #include <exec/types.h>
  17 #include <exec/io.h>
  18
  19 struct cache_block {
  20     struct cache_block  *hash_next;     /* next block in this hash bucket */
  21     struct cache_block  *hash_prev;     /* previous block in this hash bucket */
  22
  23     struct cache_block  *free_next;     /* next block on free list */
  24     struct cache_block  *free_prev;     /* previous block on free list */
  25
  26     struct cache_block  *dirty_next;    /* next block on dirty list */
  27
  28     ULONG               use_count;      /* number of users of this block */
  29     BOOL                is_dirty;       /* does the block need to be written? */
  30
  31     ULONG               num;            /* block number */
  32
  33     UBYTE               *data;          /* actual block data */
  34 };
  35
  36 struct cache {
  37     ULONG               hash_size;      /* size of hash table */
  38     ULONG               hash_mask;      /* mask applied to block number to find correct hash bucket */
  39
  40     ULONG               num_blocks;     /* number of blocks allocated */
  41     ULONG               block_size;     /* size of block */
  42
  43     ULONG               flags;          /* cache options */
  44
  45     struct cache_block  **blocks;       /* big list of all the blocks */
  46     ULONG               num_in_use;     /* number of blocks currently in use (ie not on the free list) */
  47
  48     struct cache_block  **hash;         /* the hash table itself */
  49
  50     struct cache_block  *free_head;     /* first block in the free list */
  51     struct cache_block  *free_tail;     /* last block in the free list */
  52
  53     struct cache_block  *dirty;         /* list of dirty blocks */
  54
  55     ULONG               hits;           /* number of hits, for stats */
  56     ULONG               misses;         /* number of misses */
  57 };
  58
  59 /* flags for cache_new */
  60 #define CACHE_WRITETHROUGH  (1<<0)      /* write immediately */
  61 #define CACHE_WRITEBACK     (1<<1)      /* defer writes */
  62
  63 struct cache *cache_new(ULONG hash_size, ULONG num_blocks, ULONG block_size, ULONG flags);
  64 void cache_free(struct cache *c);
  65
  66 ULONG cache_get_block(struct cache *c, ULONG num, ULONG flags, struct cache_block **rb);
  67 ULONG cache_put_block(struct cache *c, struct cache_block *b, ULONG flags);
  68
  69 ULONG cache_get_blocks(struct cache *c, ULONG num, ULONG nblocks, ULONG flags, struct cache_block **rb);
  70 ULONG cache_put_blocks(struct cache *c, struct cache_block **b, ULONG nblocks, ULONG flags);
  71
  72 ULONG cache_mark_block_dirty(struct cache *c, struct cache_block *b);
  73 ULONG cache_mark_blocks_dirty(struct cache *c, struct cache_block **b, ULONG nblocks);
  74
  75 ULONG cache_flush(struct cache *c);
  76
  77 void cache_stats(struct cache *c);
  78
  79 #endif