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131 lines
4.8 KiB
C
131 lines
4.8 KiB
C
/*
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cache.h
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The cache is not visible to the user. It should be flushed
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when any file is closed or changes are made to the filesystem.
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This cache implements a least-used-page replacement policy. This will
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distribute sectors evenly over the pages, so if less than the maximum
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pages are used at once, they should all eventually remain in the cache.
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This also has the benefit of throwing out old sectors, so as not to keep
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too many stale pages around.
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Copyright (c) 2006 Michael "Chishm" Chisholm
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation and/or
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other materials provided with the distribution.
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3. The name of the author may not be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _CACHE_H
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#define _CACHE_H
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#include "common.h"
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#include "disc.h"
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#define PAGE_SECTORS 64
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#define CACHE_PAGE_SIZE (BYTES_PER_READ * PAGE_SECTORS)
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typedef struct {
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sec_t sector;
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unsigned int count;
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unsigned int last_access;
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bool dirty;
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uint8_t* cache;
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} CACHE_ENTRY;
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typedef struct {
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const DISC_INTERFACE* disc;
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sec_t endOfPartition;
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unsigned int numberOfPages;
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unsigned int sectorsPerPage;
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CACHE_ENTRY* cacheEntries;
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} CACHE;
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/*
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Read data from a sector in the cache
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If the sector is not in the cache, it will be swapped in
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offset is the position to start reading from
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size is the amount of data to read
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Precondition: offset + size <= BYTES_PER_READ
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*/
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bool _FAT_cache_readPartialSector (CACHE* cache, void* buffer, sec_t sector, unsigned int offset, size_t size);
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bool _FAT_cache_readLittleEndianValue (CACHE* cache, uint32_t *value, sec_t sector, unsigned int offset, int num_bytes);
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/*
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Write data to a sector in the cache
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If the sector is not in the cache, it will be swapped in.
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When the sector is swapped out, the data will be written to the disc
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offset is the position to start writing to
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size is the amount of data to write
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Precondition: offset + size <= BYTES_PER_READ
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*/
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bool _FAT_cache_writePartialSector (CACHE* cache, const void* buffer, sec_t sector, unsigned int offset, size_t size);
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bool _FAT_cache_writeLittleEndianValue (CACHE* cache, const uint32_t value, sec_t sector, unsigned int offset, int num_bytes);
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/*
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Write data to a sector in the cache, zeroing the sector first
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If the sector is not in the cache, it will be swapped in.
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When the sector is swapped out, the data will be written to the disc
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offset is the position to start writing to
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size is the amount of data to write
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Precondition: offset + size <= BYTES_PER_READ
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*/
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bool _FAT_cache_eraseWritePartialSector (CACHE* cache, const void* buffer, sec_t sector, unsigned int offset, size_t size);
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/*
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Read several sectors from the cache
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*/
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bool _FAT_cache_readSectors (CACHE* cache, sec_t sector, sec_t numSectors, void* buffer);
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/*
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Read a full sector from the cache
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*/
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static inline bool _FAT_cache_readSector (CACHE* cache, void* buffer, sec_t sector) {
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return _FAT_cache_readPartialSector (cache, buffer, sector, 0, BYTES_PER_READ);
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}
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/*
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Write a full sector to the cache
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*/
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static inline bool _FAT_cache_writeSector (CACHE* cache, const void* buffer, sec_t sector) {
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return _FAT_cache_writePartialSector (cache, buffer, sector, 0, BYTES_PER_READ);
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}
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bool _FAT_cache_writeSectors (CACHE* cache, sec_t sector, sec_t numSectors, const void* buffer);
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/*
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Write any dirty sectors back to disc and clear out the contents of the cache
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*/
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bool _FAT_cache_flush (CACHE* cache);
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/*
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Clear out the contents of the cache without writing any dirty sectors first
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*/
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void _FAT_cache_invalidate (CACHE* cache);
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CACHE* _FAT_cache_constructor (unsigned int numberOfPages, unsigned int sectorsPerPage, const DISC_INTERFACE* discInterface, sec_t endOfPartition);
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void _FAT_cache_destructor (CACHE* cache);
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#endif // _CACHE_H
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