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/*
* Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _DCDR_CACHE_H_
#define _DCDR_CACHE_H_
#include <sys/types.h>
/*
* A drive cache descriptor (DCD) describes a logical
* block within a storage medium and is chained with
* other DCDs. Logical block coalescing is a method
* to optimize caching by combining adjacent logical block
* pairs that are infrequently invalidated into a single
* DCD.
*
* If the lbc bit is set, this block is coalesced with
* the next.
*/
struct dcd {
off_t lba; /* Starting LBA */
void *data; /* Driver specific data */
void *block; /* Cached data from described block */
uint8_t lbc : 1; /* Set if coalesced */
uint32_t hit_count; /* Number of hits */
struct dcd *next; /* Next ptr for DCD chaining */
struct dcd *prev; /* Prev ptr for DCD chaining */
};
/*
* This structure describes a drive cache descriptor
* ring and contains basic information like the size
* of each block.
*/
struct dcdr {
size_t bsize; /* Block size */
size_t cap; /* Capacity (in entries) */
size_t size; /* Size (in entries) */
struct dcd *head; /* Ring head */
struct dcd *tail; /* Ring tail */
};
/*
* Result from DCDR lookup.
*/
struct dcdr_lookup {
struct dcd *dcd_res;
void *buf;
off_t lba;
};
struct dcdr *dcdr_alloc(size_t bsize, size_t cap);
struct dcd *dcdr_cachein(struct dcdr *dcdr, void *block, off_t lba);
struct dcd *dcdr_lbc_cachein(struct dcdr *dcdr, void *block, off_t lba);
int dcdr_lookup(struct dcdr *dcdr, off_t lba, struct dcdr_lookup *res);
int dcdr_invldcd(struct dcdr *dcdr, off_t lba);
#endif /* !_DCDR_CACHE_H_ */
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