terom@30: #ifndef CACHE_ENGINE_H
terom@30: #define CACHE_ENGINE_H
terom@30: 
terom@30: struct cache_engine {
terom@30:     /*
terom@30:      * Allocate a `struct cache`-compatible struct and return it via cache_ptr.
terom@30:      */
terom@31:     int (*fn_init) (struct cache_engine *, struct cache **);
terom@30:     
terom@30:     /*
terom@30:      * Allocate a `struct cache_op`-compatible struct and return it via cache_ptr.
terom@30:      *
terom@30:      * Begin the index lookup.
terom@30:      */
terom@31:     int (*fn_op_start) (struct cache *, struct cache_op **, struct cache_key *);
terom@33:     
terom@33:     /*
terom@33:      * Return some information about the available data.
terom@33:      */
terom@36:     int (*fn_op_available) (struct cache_op *, size_t *size, size_t *offset);
terom@36:     
terom@36:     /*
terom@36:      * Prepare to read from this cache entry.
terom@36:      */
terom@36:     int (*fn_op_begin_read) (struct cache_op *);
terom@31: 
terom@31:     /*
terom@36:      * Prepare to write to this cache entry.
terom@31:      *
terom@31:      * size_hint, if nonzero, provides a guess at the size of the cache entry that can be used to optimize stuff
terom@31:      */
terom@31:     int (*fn_op_begin_write) (struct cache_op *, size_t size_hint);
terom@33:     
terom@33:     /*
terom@33:      * Read some data from the given fd into this cache entry. Size may contain a non-zero value to hint at how many
terom@33:      * bytes should be read, or zero to just read a suitable amount. Should be updated to how many bytes were actually
terom@33:      * written (may be zero if writes are currently paused).
terom@33:      */
terom@36:     int (*fn_op_push) (struct cache_op *, int fd, size_t *size);
terom@37:     
terom@37:     /*
terom@37:      * Write some data into the given fd from this cache entry. Size either specifies how many bytes to read (and
terom@37:      * should not be more than is available), or zero to read as much as possible. Offset is the offset from the
terom@37:      * beginning of the cache entry, and should be updated to what the next unread byte would be. Size should be
terom@37:      * updated to how many bytes was read.
terom@37:      */
terom@37:     int (*fn_op_pull) (struct cache_op *, int fd, size_t *offset, size_t *size);
terom@31: 
terom@33:     /*
terom@33:      * No more calls to fn_op_push will take place. The cache entry now contains the complete data.
terom@33:      */
terom@36:     int (*fn_op_done) (struct cache_op *);
terom@33: 
terom@33:     /*
terom@33:      * The op is not needed for any operations anymore. Free any resources and memory associated with this op,
terom@33:      * including the op itself.
terom@33:      */
terom@36:     int (*fn_op_close) (struct cache_op *);
terom@30: };
terom@30: 
terom@30: #endif /* CACHE_ENGINE_H */
terom@30: