DWORD FATDrive::read_FAT(DWORD cluster, bool& ok) //@@ use exception handling
{
DWORD nClus;
Buffer* FATBuf;
DWORD nclus = (_boot_sector.Sectors32? _boot_sector.Sectors32: _boot_sector.Sectors16) / _boot_sector.SectorsPerCluster; ///@todo cache result
if (cluster > nclus) {
ok = false;
return (DWORD)-1;
}
if (nclus >= 65536) { // FAT32
DWORD FATsec = cluster / (_boot_sector.BytesPerSector/4);
DWORD z = (cluster - _boot_sector.BytesPerSector/4 * FATsec)*4;
FATsec += _boot_sector.ReservedSectors;
if (!read_cache(FATsec, &FATBuf))
ok = false;
nClus = dpeek(&FATBuf->dat[z]);
} else if (nclus >= 4096) { // 16 Bit-FAT
DWORD FATsec = cluster / (_boot_sector.BytesPerSector/2);
DWORD z = (cluster - _boot_sector.BytesPerSector/2 * FATsec)*2;
FATsec += _boot_sector.ReservedSectors;
if (!read_cache(FATsec, &FATBuf))
ok = false;
nClus = wpeek(&FATBuf->dat[z]);
if (nClus >= 0xfff0)
nClus |= 0x0fff0000;
} else { // 12 Bit-FAT
DWORD FATsec = cluster*3 / (_boot_sector.BytesPerSector*2);
DWORD z = (cluster*3 - _boot_sector.BytesPerSector*2*FATsec)/2;
FATsec += _boot_sector.ReservedSectors;
if (!read_cache(FATsec,&FATBuf))
ok = false;
BYTE a = FATBuf->dat[z++];
if (z >= _boot_sector.BytesPerSector)
if (!read_cache(FATsec+1,&FATBuf))
ok = false;
z = 0;
BYTE b = FATBuf->dat[z];
if (cluster & 1)
nClus = (a>>4) | (b<<4);
else
nClus = a | ((b & 0xf)<<8);
if (nClus >= 0xff0)
nClus |= 0x0ffff000;
}
inline cell factor_vm::unbox_array_size()
{
cell obj = dpeek();
if(TAG(obj) == FIXNUM_TYPE)
{
fixnum n = untag_fixnum(obj);
if(n >= 0 && n < (fixnum)array_size_max)
{
dpop();
return n;
}
}
return unbox_array_size_slow();
}
inline cell dpop()
{
cell value = dpeek();
ds -= sizeof(cell);
return value;
}
