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author | Nebuleon Fumika | 2013-02-08 05:50:22 -0500 |
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committer | Nebuleon Fumika | 2013-02-08 05:50:22 -0500 |
commit | 927d456306672110870eb3386742c1c1ef8eb4f6 (patch) | |
tree | 509da9ac1727570b02572068aefb9cdf102ad75b /sdk-modifications/libsrc/fs/cache.c | |
parent | 433749b6ef1e2b070755c3bb7fc0d81b5ecaa7b1 (diff) | |
parent | d4fcf2697c9a45594e3ee0b8bf82e480ddd0b69b (diff) | |
download | snes9x2005-927d456306672110870eb3386742c1c1ef8eb4f6.tar.gz snes9x2005-927d456306672110870eb3386742c1c1ef8eb4f6.tar.bz2 snes9x2005-927d456306672110870eb3386742c1c1ef8eb4f6.zip |
Merge branch 'master' into 8bitsound
Conflicts:
source/nds/entry.cpp
Diffstat (limited to 'sdk-modifications/libsrc/fs/cache.c')
-rwxr-xr-x | sdk-modifications/libsrc/fs/cache.c | 273 |
1 files changed, 273 insertions, 0 deletions
diff --git a/sdk-modifications/libsrc/fs/cache.c b/sdk-modifications/libsrc/fs/cache.c new file mode 100755 index 0000000..2c66e1f --- /dev/null +++ b/sdk-modifications/libsrc/fs/cache.c @@ -0,0 +1,273 @@ +/* + cache.c + The cache is not visible to the user. It should be flushed + when any file is closed or changes are made to the filesystem. + + This cache implements a least-used-page replacement policy. This will + distribute sectors evenly over the pages, so if less than the maximum + pages are used at once, they should all eventually remain in the cache. + This also has the benefit of throwing out old sectors, so as not to keep + too many stale pages around. + + Copyright (c) 2006 Michael "Chishm" Chisholm + + 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. The name of the author may not be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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. +*/ + +#include <string.h> + +#include "fs_common.h" +#include "fs_cache.h" +#include "disc_io/disc.h" + +#include "mem_allocate.h" + +#define CACHE_FREE 0xFFFFFFFF + +CACHE* _FAT_cache_constructor (u32 numberOfPages, const IO_INTERFACE* discInterface) { + CACHE* cache; + u32 i; + CACHE_ENTRY* cacheEntries; + + if (numberOfPages < 2) { + numberOfPages = 2; + } + + cache = (CACHE*) _FAT_mem_allocate (sizeof(CACHE)); + if (cache == NULL) { + return NULL; + } + + cache->disc = discInterface; + cache->numberOfPages = numberOfPages; + + + cacheEntries = (CACHE_ENTRY*) _FAT_mem_allocate ( sizeof(CACHE_ENTRY) * numberOfPages); + if (cacheEntries == NULL) { + _FAT_mem_free (cache); + return NULL; + } + + for (i = 0; i < numberOfPages; i++) { + cacheEntries[i].sector = CACHE_FREE; + cacheEntries[i].count = 0; + cacheEntries[i].dirty = 0; + } + + cache->cacheEntries = cacheEntries; + + cache->pages = (u8*) _FAT_mem_allocate ( CACHE_PAGE_SIZE * numberOfPages); + if (cache->pages == NULL) { + _FAT_mem_free (cache->cacheEntries); + _FAT_mem_free (cache); + return NULL; + } + + return cache; +} + +void _FAT_cache_destructor (CACHE* cache) { + // Clear out cache before destroying it + _FAT_cache_flush(cache); + + // Free memory in reverse allocation order + _FAT_mem_free (cache->pages); + _FAT_mem_free (cache->cacheEntries); + _FAT_mem_free (cache); + + return; +} + +/* +Retrieve a sector's page from the cache. If it is not found in the cache, +load it into the cache and return the page it was loaded to. +Return CACHE_FREE on error. +*/ +static u32 _FAT_cache_getSector (CACHE* cache, u32 sector) { + u32 i; + CACHE_ENTRY* cacheEntries = cache->cacheEntries; + u32 numberOfPages = cache->numberOfPages; + + u32 leastUsed = 0; + u32 lowestCount = 0xFFFFFFFF; + + for (i = 0; (i < numberOfPages) && (cacheEntries[i].sector != sector); i++) { + // While searching for the desired sector, also search for the leased used page + if ( (cacheEntries[i].sector == CACHE_FREE) || (cacheEntries[i].count < lowestCount) ) { + leastUsed = i; + lowestCount = cacheEntries[i].count; + } + } + + // If it found the sector in the cache, return it + if ((i < numberOfPages) && (cacheEntries[i].sector == sector)) { + // Increment usage counter + cacheEntries[i].count += 1; + return i; + } + + // If it didn't, replace the least used cache page with the desired sector + if ((cacheEntries[leastUsed].sector != CACHE_FREE) && (0xC33CA55A == cacheEntries[leastUsed].dirty)) { + // Write the page back to disc if it has been written to + if (!_FAT_disc_writeSectors (cache->disc, cacheEntries[leastUsed].sector, 1, cache->pages + CACHE_PAGE_SIZE * leastUsed)) { + return CACHE_FREE; + } + cacheEntries[leastUsed].dirty = 0; + } + + // Load the new sector into the cache + if (!_FAT_disc_readSectors (cache->disc, sector, 1, cache->pages + CACHE_PAGE_SIZE * leastUsed)) { + return CACHE_FREE; + } + cacheEntries[leastUsed].sector = sector; + // Increment the usage count, don't reset it + // This creates a paging policy of least used PAGE, not sector + cacheEntries[leastUsed].count += 1; + return leastUsed; +} + +/* +Reads some data from a cache page, determined by the sector number +*/ +bool _FAT_cache_readPartialSector (CACHE* cache, void* buffer, u32 sector, u32 offset, u32 size) { + u32 page; + + if (offset + size > BYTES_PER_READ) { + return false; + } + + page = _FAT_cache_getSector (cache, sector); + if (page == CACHE_FREE) { + return false; + } + + memcpy (buffer, cache->pages + (CACHE_PAGE_SIZE * page) + offset, size); + return true; +} + +/* +Writes some data to a cache page, making sure it is loaded into memory first. +*/ +bool _FAT_cache_writePartialSector (CACHE* cache, const void* buffer, u32 sector, u32 offset, u32 size) { + u32 page; + + if (offset + size > BYTES_PER_READ) { + return false; + } + + page = _FAT_cache_getSector (cache, sector); + if (page == CACHE_FREE) { + return false; + } + + memcpy (cache->pages + (CACHE_PAGE_SIZE * page) + offset, buffer, size); + cache->cacheEntries[page].dirty = 0xC33CA55A; + + return true; +} + +/* +some where call _FAT_cache_writePartialSector to cache sector m , but later, another +place(in fwrite function) directly write data to sector m, in this case, need to +cancel the dirty state of sector m +*/ +void _FAT_cache_writePartialSector_check (CACHE* cache, u32 sector, u32 num, const void* buffer) +{ + u32 i, m; + CACHE_ENTRY* cacheEntries = cache->cacheEntries; + u32 numberOfPages = cache->numberOfPages; + + m = 0; + while(m++ < num) + { + for (i = 0; i < numberOfPages; i++) + { + if(cacheEntries[i].sector == sector) + break; + } + + if(i >= numberOfPages) + return; + + //cache the data + memcpy (cache->pages + (CACHE_PAGE_SIZE * i), buffer, CACHE_PAGE_SIZE); + //cancel the dirty state + cache->cacheEntries[i].dirty = 0; + + sector += 1; + buffer += CACHE_PAGE_SIZE; + } +} + +/* +Writes some data to a cache page, zeroing out the page first +*/ +bool _FAT_cache_eraseWritePartialSector (CACHE* cache, const void* buffer, u32 sector, u32 offset, u32 size) { + u32 page; + + if (offset + size > BYTES_PER_READ) { + return false; + } + + page = _FAT_cache_getSector (cache, sector); + if (page == CACHE_FREE) { + return false; + } + + memset (cache->pages + (CACHE_PAGE_SIZE * page), 0, CACHE_PAGE_SIZE); + memcpy (cache->pages + (CACHE_PAGE_SIZE * page) + offset, buffer, size); + cache->cacheEntries[page].dirty = 0xC33CA55A; + + return true; +} + + +/* +Flushes all dirty pages to disc, clearing the dirty flag. +Also resets all pages' page count to 0. +*/ +bool _FAT_cache_flush (CACHE* cache) { + u32 i; + + for (i = 0; i < cache->numberOfPages; i++) { + if (0xC33CA55A == cache->cacheEntries[i].dirty) { + if (!_FAT_disc_writeSectors (cache->disc, cache->cacheEntries[i].sector, 1, cache->pages + CACHE_PAGE_SIZE * i)) { + return CACHE_FREE; + } + } + cache->cacheEntries[i].count = 0; + cache->cacheEntries[i].dirty = 0; + } + + _FAT_disc_clearStatus( cache->disc ); + return true; +} + +void _FAT_cache_invalidate (CACHE* cache) { + int i; + for (i = 0; i < cache->numberOfPages; i++) { + cache->cacheEntries[i].sector = CACHE_FREE; + cache->cacheEntries[i].count = 0; + cache->cacheEntries[i].dirty = 0; + } +} + |