PARTITION* _FAT_partition_constructor (const DISC_INTERFACE* disc, uint32_t cacheSize, sec_t startSector) {
PARTITION* partition;
int i;
uint8_t sectorBuffer[BYTES_PER_READ] = {0};
// Read first sector of disc
if (!_FAT_disc_readSectors (disc, startSector, 1, sectorBuffer)) {
return NULL;
}
// Make sure it is a valid MBR or boot sector
if ( (sectorBuffer[BPB_bootSig_55] != 0x55) || (sectorBuffer[BPB_bootSig_AA] != 0xAA)) {
return NULL;
}
if (startSector != 0) {
// We're told where to start the partition, so just accept it
} else if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
// Check if there is a FAT string, which indicates this is a boot sector
startSector = 0;
} else if (!memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
// Check for FAT32
startSector = 0;
} else {
// This is an MBR
// Find first valid partition from MBR
// First check for an active partition
for (i=0x1BE; (i < 0x1FE) && (sectorBuffer[i] != 0x80); i+= 0x10);
// If it didn't find an active partition, search for any valid partition
if (i == 0x1FE) {
for (i=0x1BE; (i < 0x1FE) && (sectorBuffer[i+0x04] == 0x00); i+= 0x10);
}
if ( i != 0x1FE) {
// Go to first valid partition
startSector = u8array_to_u32(sectorBuffer, 0x8 + i);
// Load the BPB
if (!_FAT_disc_readSectors (disc, startSector, 1, sectorBuffer)) {
return NULL;
}
// Make sure it is a valid BPB
if ( (sectorBuffer[BPB_bootSig_55] != 0x55) || (sectorBuffer[BPB_bootSig_AA] != 0xAA)) {
return NULL;
}
} else {
// No partition found, assume this is a MBR free disk
startSector = 0;
}
}
// Now verify that this is indeed a FAT partition
if (memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG)) &&
memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG)))
{
return NULL;
}
partition = (PARTITION*) _FAT_mem_allocate (sizeof(PARTITION));
if (partition == NULL) {
return NULL;
}
// Init the partition lock
_FAT_lock_init(&partition->lock);
// Set partition's disc interface
partition->disc = disc;
// Store required information about the file system
partition->fat.sectorsPerFat = u8array_to_u16(sectorBuffer, BPB_sectorsPerFAT);
if (partition->fat.sectorsPerFat == 0) {
partition->fat.sectorsPerFat = u8array_to_u32( sectorBuffer, BPB_FAT32_sectorsPerFAT32);
}
partition->numberOfSectors = u8array_to_u16( sectorBuffer, BPB_numSectorsSmall);
if (partition->numberOfSectors == 0) {
partition->numberOfSectors = u8array_to_u32( sectorBuffer, BPB_numSectors);
}
partition->bytesPerSector = BYTES_PER_READ; // Sector size is redefined to be 512 bytes
partition->sectorsPerCluster = sectorBuffer[BPB_sectorsPerCluster] * u8array_to_u16(sectorBuffer, BPB_bytesPerSector) / BYTES_PER_READ;
partition->bytesPerCluster = partition->bytesPerSector * partition->sectorsPerCluster;
partition->fat.fatStart = startSector + u8array_to_u16(sectorBuffer, BPB_reservedSectors);
partition->rootDirStart = partition->fat.fatStart + (sectorBuffer[BPB_numFATs] * partition->fat.sectorsPerFat);
partition->dataStart = partition->rootDirStart +
(( u8array_to_u16(sectorBuffer, BPB_rootEntries) * DIR_ENTRY_DATA_SIZE) / partition->bytesPerSector);
partition->totalSize = ((uint64_t)partition->numberOfSectors - (partition->dataStart - startSector)) * (uint64_t)partition->bytesPerSector;
// Store info about FAT
partition->fat.lastCluster = (partition->numberOfSectors - (uint32_t)(partition->dataStart - startSector)) / partition->sectorsPerCluster;
partition->fat.firstFree = CLUSTER_FIRST;
if (partition->fat.lastCluster < CLUSTERS_PER_FAT12) {
partition->filesysType = FS_FAT12; // FAT12 volume
} else if (partition->fat.lastCluster < CLUSTERS_PER_FAT16) {
partition->filesysType = FS_FAT16; // FAT16 volume
} else {
partition->filesysType = FS_FAT32; // FAT32 volume
}
if (partition->filesysType != FS_FAT32) {
partition->rootDirCluster = FAT16_ROOT_DIR_CLUSTER;
} else {
// Set up for the FAT32 way
partition->rootDirCluster = u8array_to_u32(sectorBuffer, BPB_FAT32_rootClus);
// Check if FAT mirroring is enabled
if (!(sectorBuffer[BPB_FAT32_extFlags] & 0x80)) {
// Use the active FAT
partition->fat.fatStart = partition->fat.fatStart + ( partition->fat.sectorsPerFat * (sectorBuffer[BPB_FAT32_extFlags] & 0x0F));
}
}
// Create a cache to use
partition->cache = _FAT_cache_constructor (cacheSize, partition->disc);
// Set current directory to the root
partition->cwdCluster = partition->rootDirCluster;
// Check if this disc is writable, and set the readOnly property appropriately
partition->readOnly = !(_FAT_disc_features(disc) & FEATURE_MEDIUM_CANWRITE);
// There are currently no open files on this partition
partition->openFileCount = 0;
partition->firstOpenFile = NULL;
return partition;
}
PARTITION* _FAT_partition_constructor_buf (const DISC_INTERFACE* disc, uint32_t cacheSize, uint32_t sectorsPerPage, sec_t startSector, uint8_t *sectorBuffer)
{
PARTITION* partition;
// Read first sector of disc
if (!_FAT_disc_readSectors (disc, startSector, 1, sectorBuffer)) {
return NULL;
}
// Make sure it is a valid MBR or boot sector
if ( (sectorBuffer[BPB_bootSig_55] != 0x55) || (sectorBuffer[BPB_bootSig_AA] != 0xAA && sectorBuffer[BPB_bootSig_AA] != 0xAB)) {
return NULL;
}
if (startSector != 0) {
// We're told where to start the partition, so just accept it
} else if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
// Check if there is a FAT string, which indicates this is a boot sector
startSector = 0;
} else if (!memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
// Check for FAT32
startSector = 0;
} else {
startSector = FindFirstValidPartition_buf(disc, sectorBuffer);
if (!_FAT_disc_readSectors (disc, startSector, 1, sectorBuffer)) {
return NULL;
}
}
if (!isValidMBR(sectorBuffer))
{
return NULL;
}
partition = (PARTITION*) _FAT_mem_allocate (sizeof(PARTITION));
if (partition == NULL) {
return NULL;
}
// Init the partition lock
_FAT_lock_init(&partition->lock);
if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG)))
strncpy(partition->label, (char*)(sectorBuffer + BPB_FAT16_volumeLabel), 11);
else
strncpy(partition->label, (char*)(sectorBuffer + BPB_FAT32_volumeLabel), 11);
partition->label[11] = '\0';
// Set partition's disc interface
partition->disc = disc;
// Store required information about the file system
partition->fat.sectorsPerFat = u8array_to_u16(sectorBuffer, BPB_sectorsPerFAT);
if (partition->fat.sectorsPerFat == 0) {
partition->fat.sectorsPerFat = u8array_to_u32( sectorBuffer, BPB_FAT32_sectorsPerFAT32);
}
partition->numberOfSectors = u8array_to_u16( sectorBuffer, BPB_numSectorsSmall);
if (partition->numberOfSectors == 0) {
partition->numberOfSectors = u8array_to_u32( sectorBuffer, BPB_numSectors);
}
partition->bytesPerSector = u8array_to_u16(sectorBuffer, BPB_bytesPerSector);
if(partition->bytesPerSector < MIN_SECTOR_SIZE || partition->bytesPerSector > MAX_SECTOR_SIZE) {
// Unsupported sector size
_FAT_mem_free(partition);
return NULL;
}
partition->sectorsPerCluster = sectorBuffer[BPB_sectorsPerCluster];
partition->bytesPerCluster = partition->bytesPerSector * partition->sectorsPerCluster;
partition->fat.fatStart = startSector + u8array_to_u16(sectorBuffer, BPB_reservedSectors);
partition->rootDirStart = partition->fat.fatStart + (sectorBuffer[BPB_numFATs] * partition->fat.sectorsPerFat);
partition->dataStart = partition->rootDirStart +
(( u8array_to_u16(sectorBuffer, BPB_rootEntries) * DIR_ENTRY_DATA_SIZE) / partition->bytesPerSector);
partition->totalSize = ((uint64_t)partition->numberOfSectors - (partition->dataStart - startSector)) * (uint64_t)partition->bytesPerSector;
//FS info sector
partition->fsInfoSector = startSector + (u8array_to_u16(sectorBuffer, BPB_FAT32_fsInfo) ? u8array_to_u16(sectorBuffer, BPB_FAT32_fsInfo) : 1);
// Store info about FAT
uint32_t clusterCount = (partition->numberOfSectors - (uint32_t)(partition->dataStart - startSector)) / partition->sectorsPerCluster;
partition->fat.lastCluster = clusterCount + CLUSTER_FIRST - 1;
partition->fat.firstFree = CLUSTER_FIRST;
partition->fat.numberFreeCluster = 0;
partition->fat.numberLastAllocCluster = 0;
if (clusterCount < CLUSTERS_PER_FAT12) {
partition->filesysType = FS_FAT12; // FAT12 volume
} else if (clusterCount < CLUSTERS_PER_FAT16) {
partition->filesysType = FS_FAT16; // FAT16 volume
} else {
partition->filesysType = FS_FAT32; // FAT32 volume
}
if (partition->filesysType != FS_FAT32) {
partition->rootDirCluster = FAT16_ROOT_DIR_CLUSTER;
} else {
// Set up for the FAT32 way
partition->rootDirCluster = u8array_to_u32(sectorBuffer, BPB_FAT32_rootClus);
// Check if FAT mirroring is enabled
if (!(sectorBuffer[BPB_FAT32_extFlags] & 0x80)) {
// Use the active FAT
partition->fat.fatStart = partition->fat.fatStart + ( partition->fat.sectorsPerFat * (sectorBuffer[BPB_FAT32_extFlags] & 0x0F));
}
}
// Create a cache to use
partition->cache = _FAT_cache_constructor (cacheSize, sectorsPerPage, partition->disc, startSector+partition->numberOfSectors, partition->bytesPerSector);
// Set current directory to the root
partition->cwdCluster = partition->rootDirCluster;
// Check if this disc is writable, and set the readOnly property appropriately
partition->readOnly = !(_FAT_disc_features(disc) & FEATURE_MEDIUM_CANWRITE);
// There are currently no open files on this partition
partition->openFileCount = 0;
partition->firstOpenFile = NULL;
_FAT_partition_readFSinfo(partition);
return partition;
}
