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find the first valid fat partition (rodries)

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tantricity 2009-06-30 08:01:04 +00:00
parent 8ad45f1556
commit d09577c51a
1 changed files with 62 additions and 24 deletions
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86
source/partition.c
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@ -96,9 +96,67 @@ enum BPB {
static const char FAT_SIG[3] = {'F', 'A', 'T'}; static const char FAT_SIG[3] = {'F', 'A', 'T'};
sec_t FindFirstValidPartition(const DISC_INTERFACE* disc)
{
uint8_t part_table[16*4];
uint8_t *ptr;
int i;
uint8_t sectorBuffer[BYTES_PER_READ] = {0};
// Read first sector of disc
if (!_FAT_disc_readSectors (disc, 0, 1, sectorBuffer)) {
return 0;
}
memcpy(part_table,sectorBuffer+0x1BE,16*4);
ptr = part_table;
for(i=0;i<4;i++,ptr+=16) {
sec_t part_lba = u8array_to_u32(ptr, 0x8);
if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG)) ||
!memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
return part_lba;
}
if(ptr[4]==0) continue;
if(ptr[4]==0x0F) {
sec_t part_lba2=part_lba;
sec_t next_lba2=0;
int n;
for(n=0;n<8;n++) // max 8 logic partitions
{
if(!_FAT_disc_readSectors (disc, part_lba+next_lba2, 1, sectorBuffer)) return 0;
part_lba2 = part_lba + next_lba2 + u8array_to_u32(sectorBuffer, 0x1C6) ;
next_lba2 = u8array_to_u32(sectorBuffer, 0x1D6);
if(!_FAT_disc_readSectors (disc, part_lba2, 1, sectorBuffer)) return 0;
if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG)) ||
!memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG)))
{
return part_lba2;
}
if(next_lba2==0) break;
}
} else {
if(!_FAT_disc_readSectors (disc, part_lba, 1, sectorBuffer)) return 0;
if (!memcmp(sectorBuffer + BPB_FAT16_fileSysType, FAT_SIG, sizeof(FAT_SIG)) ||
!memcmp(sectorBuffer + BPB_FAT32_fileSysType, FAT_SIG, sizeof(FAT_SIG))) {
return part_lba;
}
}
}
return 0;
}
PARTITION* _FAT_partition_constructor (const DISC_INTERFACE* disc, uint32_t cacheSize, uint32_t sectorsPerPage, sec_t startSector) { PARTITION* _FAT_partition_constructor (const DISC_INTERFACE* disc, uint32_t cacheSize, uint32_t sectorsPerPage, sec_t startSector) {
PARTITION* partition; PARTITION* partition;
int i;
uint8_t sectorBuffer[BYTES_PER_READ] = {0}; uint8_t sectorBuffer[BYTES_PER_READ] = {0};
// Read first sector of disc // Read first sector of disc
@ -120,29 +178,9 @@ PARTITION* _FAT_partition_constructor (const DISC_INTERFACE* disc, uint32_t cach
// Check for FAT32 // Check for FAT32
startSector = 0; startSector = 0;
} else { } else {
// This is an MBR startSector = FindFirstValidPartition(disc);
// Find first valid partition from MBR if (!_FAT_disc_readSectors (disc, startSector, 1, sectorBuffer)) {
// First check for an active partition return NULL;
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;
} }
} }