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/* Arduino SdFat Library
* Copyright (C) 2009 by William Greiman
*
* This file is part of the Arduino SdFat Library
*
* This Library is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This Library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the Arduino SdFat Library. If not, see
* <http://www.gnu.org/licenses/>.
*/
#include <SdFat.h>
//------------------------------------------------------------------------------
// raw block cache
// init cacheBlockNumber_to invalid SD block number
uint32_t SdVolume::cacheBlockNumber_ = 0XFFFFFFFF;
cache_t SdVolume::cacheBuffer_; // 512 byte cache for Sd2Card
Sd2Card* SdVolume::sdCard_; // pointer to SD card object
uint8_t SdVolume::cacheDirty_ = 0; // cacheFlush() will write block if true
uint32_t SdVolume::cacheMirrorBlock_ = 0; // mirror block for second FAT
//------------------------------------------------------------------------------
// find a contiguous group of clusters
uint8_t SdVolume::allocContiguous(uint32_t count, uint32_t* curCluster) {
// start of group
uint32_t bgnCluster;
// flag to save place to start next search
uint8_t setStart;
// set search start cluster
if (*curCluster) {
// try to make file contiguous
bgnCluster = *curCluster + 1;
// don't save new start location
setStart = false;
} else {
// start at likely place for free cluster
bgnCluster = allocSearchStart_;
// save next search start if one cluster
setStart = 1 == count;
}
// end of group
uint32_t endCluster = bgnCluster;
// last cluster of FAT
uint32_t fatEnd = clusterCount_ + 1;
// search the FAT for free clusters
for (uint32_t n = 0;; n++, endCluster++) {
// can't find space checked all clusters
if (n >= clusterCount_) return false;
// past end - start from beginning of FAT
if (endCluster > fatEnd) {
bgnCluster = endCluster = 2;
}
uint32_t f;
if (!fatGet(endCluster, &f)) return false;
if (f != 0) {
// cluster in use try next cluster as bgnCluster
bgnCluster = endCluster + 1;
} else if ((endCluster - bgnCluster + 1) == count) {
// done - found space
break;
}
}
// mark end of chain
if (!fatPutEOC(endCluster)) return false;
// link clusters
while (endCluster > bgnCluster) {
if (!fatPut(endCluster - 1, endCluster)) return false;
endCluster--;
}
if (*curCluster != 0) {
// connect chains
if (!fatPut(*curCluster, bgnCluster)) return false;
}
// return first cluster number to caller
*curCluster = bgnCluster;
// remember possible next free cluster
if (setStart) allocSearchStart_ = bgnCluster + 1;
return true;
}
//------------------------------------------------------------------------------
uint8_t SdVolume::cacheFlush(void) {
if (cacheDirty_) {
if (!sdCard_->writeBlock(cacheBlockNumber_, cacheBuffer_.data)) {
return false;
}
// mirror FAT tables
if (cacheMirrorBlock_) {
if (!sdCard_->writeBlock(cacheMirrorBlock_, cacheBuffer_.data)) {
return false;
}
cacheMirrorBlock_ = 0;
}
cacheDirty_ = 0;
}
return true;
}
//------------------------------------------------------------------------------
uint8_t SdVolume::cacheRawBlock(uint32_t blockNumber, uint8_t action) {
if (cacheBlockNumber_ != blockNumber) {
if (!cacheFlush()) return false;
if (!sdCard_->readBlock(blockNumber, cacheBuffer_.data)) return false;
cacheBlockNumber_ = blockNumber;
}
cacheDirty_ |= action;
return true;
}
//------------------------------------------------------------------------------
// cache a zero block for blockNumber
uint8_t SdVolume::cacheZeroBlock(uint32_t blockNumber) {
if (!cacheFlush()) return false;
// loop take less flash than memset(cacheBuffer_.data, 0, 512);
for (uint16_t i = 0; i < 512; i++) {
cacheBuffer_.data[i] = 0;
}
cacheBlockNumber_ = blockNumber;
cacheSetDirty();
return true;
}
//------------------------------------------------------------------------------
// return the size in bytes of a cluster chain
uint8_t SdVolume::chainSize(uint32_t cluster, uint32_t* size) const {
uint32_t s = 0;
do {
if (!fatGet(cluster, &cluster)) return false;
s += 512UL << clusterSizeShift_;
} while (!isEOC(cluster));
*size = s;
return true;
}
//------------------------------------------------------------------------------
// Fetch a FAT entry
uint8_t SdVolume::fatGet(uint32_t cluster, uint32_t* value) const {
if (cluster > (clusterCount_ + 1)) return false;
uint32_t lba = fatStartBlock_;
lba += fatType_ == 16 ? cluster >> 8 : cluster >> 7;
if (lba != cacheBlockNumber_) {
if (!cacheRawBlock(lba, CACHE_FOR_READ)) return false;
}
if (fatType_ == 16) {
*value = cacheBuffer_.fat16[cluster & 0XFF];
} else {
*value = cacheBuffer_.fat32[cluster & 0X7F] & FAT32MASK;
}
return true;
}
//------------------------------------------------------------------------------
// Store a FAT entry
uint8_t SdVolume::fatPut(uint32_t cluster, uint32_t value) {
// error if reserved cluster
if (cluster < 2) return false;
// error if not in FAT
if (cluster > (clusterCount_ + 1)) return false;
// calculate block address for entry
uint32_t lba = fatStartBlock_;
lba += fatType_ == 16 ? cluster >> 8 : cluster >> 7;
if (lba != cacheBlockNumber_) {
if (!cacheRawBlock(lba, CACHE_FOR_READ)) return false;
}
// store entry
if (fatType_ == 16) {
cacheBuffer_.fat16[cluster & 0XFF] = value;
} else {
cacheBuffer_.fat32[cluster & 0X7F] = value;
}
cacheSetDirty();
// mirror second FAT
if (fatCount_ > 1) cacheMirrorBlock_ = lba + blocksPerFat_;
return true;
}
//------------------------------------------------------------------------------
// free a cluster chain
uint8_t SdVolume::freeChain(uint32_t cluster) {
// clear free cluster location
allocSearchStart_ = 2;
do {
uint32_t next;
if (!fatGet(cluster, &next)) return false;
// free cluster
if (!fatPut(cluster, 0)) return false;
cluster = next;
} while (!isEOC(cluster));
return true;
}
//------------------------------------------------------------------------------
/**
* Initialize a FAT volume.
*
* \param[in] dev The SD card where the volume is located.
*
* \param[in] part The partition to be used. Legal values for \a part are
* 1-4 to use the corresponding partition on a device formatted with
* a MBR, Master Boot Record, or zero if the device is formatted as
* a super floppy with the FAT boot sector in block zero.
*
* \return The value one, true, is returned for success and
* the value zero, false, is returned for failure. Reasons for
* failure include not finding a valid partition, not finding a valid
* FAT file system in the specified partition or an I/O error.
*/
uint8_t SdVolume::init(Sd2Card* dev, uint8_t part) {
uint32_t volumeStartBlock = 0;
sdCard_ = dev;
// if part == 0 assume super floppy with FAT boot sector in block zero
// if part > 0 assume mbr volume with partition table
if (part) {
if (part > 4)return false;
if (!cacheRawBlock(volumeStartBlock, CACHE_FOR_READ)) return false;
part_t* p = &cacheBuffer_.mbr.part[part-1];
if ((p->boot & 0X7F) !=0 ||
p->totalSectors < 100 ||
p->firstSector == 0) {
// not a valid partition
return false;
}
volumeStartBlock = p->firstSector;
}
if (!cacheRawBlock(volumeStartBlock, CACHE_FOR_READ)) return false;
bpb_t* bpb = &cacheBuffer_.fbs.bpb;
if (bpb->bytesPerSector != 512 ||
bpb->fatCount == 0 ||
bpb->reservedSectorCount == 0 ||
bpb->sectorsPerCluster == 0) {
// not valid FAT volume
return false;
}
fatCount_ = bpb->fatCount;
blocksPerCluster_ = bpb->sectorsPerCluster;
// determine shift that is same as multiply by blocksPerCluster_
clusterSizeShift_ = 0;
while (blocksPerCluster_ != (1 << clusterSizeShift_)) {
// error if not power of 2
if (clusterSizeShift_++ > 7) return false;
}
blocksPerFat_ = bpb->sectorsPerFat16 ?
bpb->sectorsPerFat16 : bpb->sectorsPerFat32;
fatStartBlock_ = volumeStartBlock + bpb->reservedSectorCount;
// count for FAT16 zero for FAT32
rootDirEntryCount_ = bpb->rootDirEntryCount;
// directory start for FAT16 dataStart for FAT32
rootDirStart_ = fatStartBlock_ + bpb->fatCount * blocksPerFat_;
// data start for FAT16 and FAT32
dataStartBlock_ = rootDirStart_ + ((32 * bpb->rootDirEntryCount + 511)/512);
// total blocks for FAT16 or FAT32
uint32_t totalBlocks = bpb->totalSectors16 ?
bpb->totalSectors16 : bpb->totalSectors32;
// total data blocks
clusterCount_ = totalBlocks - (dataStartBlock_ - volumeStartBlock);
// divide by cluster size to get cluster count
clusterCount_ >>= clusterSizeShift_;
// FAT type is determined by cluster count
if (clusterCount_ < 4085) {
fatType_ = 12;
} else if (clusterCount_ < 65525) {
fatType_ = 16;
} else {
rootDirStart_ = bpb->fat32RootCluster;
fatType_ = 32;
}
return true;
}
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