iris/source/fat.ccp

#pypp 0
#include <iris.hh>
#include <devices.hh>

#define SECTOR_BITS 9
#define BLOCK_MASK (~((1 << SECTOR_BITS) - 1))
#define ROOT_CLUSTER 0x7fffffff

static unsigned _free
extern unsigned _end

void init_alloc ():
	_free = ((unsigned)&_end + PAGE_SIZE - 1) & PAGE_MASK

char *alloc_space (unsigned pages):
	unsigned ret = (_free + PAGE_SIZE - 1) & PAGE_MASK
	_free = ret + (pages << PAGE_BITS)
	return (char *)ret

void *operator new[] (unsigned size):
	//kdebug ("new ")
	void *ret = (void *)_free
	size = (size + 3) & ~3
	unsigned rest = PAGE_SIZE - (((_free - 1) & ~PAGE_MASK) + 1)
	if rest < size:
		unsigned pages = ((size - rest) + PAGE_SIZE - 1) >> PAGE_BITS
		for unsigned p = 0; p < pages; ++p:
			Iris::Page page = Iris::my_memory.create_page ()
			page.set_flags (Iris::Page::PAYING | Iris::Page::FRAME)
			Iris::my_memory.map (page, _free + rest + (p << PAGE_BITS))
			Iris::free_cap (page)
	_free += size
	//kdebug_num ((unsigned)ret)
	//kdebug ("+")
	//kdebug_num (size)
	//kdebug ("\n")
	return ret

void *operator new (unsigned size):
	return new char[size]

static Iris::WString dev
static Iris::Num device_size
static Iris::Page page
static char *data
static Iris::Num current_block
static void read_block (Iris::Num idx, Iris::Page p = page, unsigned size = 1 << SECTOR_BITS, unsigned offset = 0):
	if p.code == page.code:
		if idx.value () == current_block.value () && offset == 0 && size == 1 << SECTOR_BITS:
			return
		current_block = idx
	//kdebug ("fat getting block: ")
	//kdebug_num (idx.h)
	//kdebug (":")
	//kdebug_num (idx.l)
	//kdebug ("+")
	//kdebug_num (size)
	//kdebug ("@")
	//kdebug_num (offset)
	//kdebug ("\n")
	dev.get_block (idx, size, offset, p)

struct Fat:
	char oem[8]
	unsigned sector_size_bits
	unsigned sectors_per_cluster_bits
	unsigned reserved_sectors
	unsigned num_fats
	unsigned root_entries
	unsigned sectors
	unsigned media
	unsigned sectors_per_fat
	unsigned sectors_per_track
	unsigned heads
	unsigned hidden_sectors
	unsigned active_fat
	bool write_all_fats
	unsigned fs_version
	unsigned root_cluster
	unsigned fsinfo_sector
	unsigned boot_backup_sector
	unsigned drive
	unsigned current_head
	unsigned volume_id
	char label[0xb]

	unsigned bits
	unsigned clusters
	unsigned cluster_size_bits
	unsigned root_sectors
	unsigned header_sectors
	unsigned bad_clusters

	unsigned free_clusters
	unsigned last_alloced

	unsigned *fat
	unsigned first_free_cluster, first_bad_cluster

	void print_num (char const *pre, unsigned data):
		kdebug ("\t")
		kdebug (pre)
		unsigned bytes = 1
		while bytes < 8 && data >> (bytes * 4):
			++bytes
		kdebug_num (data, bytes)
		kdebug ("\n")

	void print_br ():
		kdebug ("\tOEM: '")
		for unsigned i = 0; i < 8; ++i:
			kdebug_char (oem[i])
		kdebug ("'\n")
		print_num ("bytes per sector: ", 1 << sector_size_bits)
		print_num ("sectors per cluster: ", 1 << sectors_per_cluster_bits)
		print_num ("reserved sectors: ", reserved_sectors)
		print_num ("number of fats: ", num_fats)
		print_num ("entries in root directory: ", root_entries)
		print_num ("sectors: ", sectors)
		print_num ("media descriptor: ", media)
		print_num ("sectors per fat: ", sectors_per_fat)
		print_num ("sectors per track: ", sectors_per_track)
		print_num ("heads: ", heads)
		print_num ("hidden sectors: ", hidden_sectors)
		print_num ("active_fat: ", active_fat)
		kdebug ("\twrite all: ")
		kdebug (write_all_fats ? "yes\n" : "no\n")
		print_num ("fs version: ", fs_version)
		print_num ("root cluster: ", root_cluster)
		print_num ("fsinfo sector: ", fsinfo_sector)
		print_num ("boot sector backup sector: ", boot_backup_sector)
		print_num ("drive: ", drive)
		print_num ("current head: ", current_head)
		print_num ("volume id: ", volume_id)
		kdebug ("\tlabel: '")
		for unsigned i = 0; i < 0xb; ++i:
			kdebug_char (label[i])
		kdebug ("'\n")
		print_num ("bits: ", bits)
		print_num ("clusters: ", clusters)
		print_num ("header sectors: ", header_sectors)

	unsigned read_num (char *data, unsigned bytes):
		unsigned ret = 0
		for unsigned i = 0; i < bytes; ++i:
			ret |= (data[i] & 0xff) << (i * 8)
		return ret

	void map_fat_cluster (unsigned c, unsigned offset = 0):
		//unsigned b = current_block.l
		read_block ((reserved_sectors + ((c * bits + 8 * offset) >> (sector_size_bits + 3))) << sector_size_bits)
		//if b != current_block.l:
			//for unsigned i = 0; i < 0x20; ++i:
				//kdebug (" ")
				//kdebug_num (data[i], 2)
			//kdebug ("\n")
	
	unsigned make_bits (unsigned orig):
		unsigned ret
		for ret = 0; ret < 32; ++ret:
			if orig == 1 << ret:
				return ret
		//Iris::panic (orig, "non-power of 2")
		kdebug ("not a power of two, using 16\n")
		return 16

	void reset ():
		read_block (0)
		if data[0x1fe] != 0x55 || (data[0x1ff] & 0xff) != 0xaa:
			kdebug ("invalid boot record signature in fat device\n")
		for unsigned i = 0; i < 8; ++i:
			oem[i] = data[3 + i]
		sector_size_bits = make_bits (read_num (data + 0xb, 2))
		sectors_per_cluster_bits = make_bits (read_num (data + 0xd, 1))
		cluster_size_bits = sector_size_bits + sectors_per_cluster_bits
		reserved_sectors = read_num (data + 0xe, 2)
		num_fats = read_num (data + 0x10, 1)
		root_entries = read_num (data + 0x11, 2)
		sectors = read_num (data + 0x13, 2)
		media = read_num (data + 0x15, 1)
		sectors_per_fat = read_num (data + 0x16, 2)
		sectors_per_track = read_num (data + 0x18, 2)
		heads = read_num (data + 0x1a, 2)
		hidden_sectors = read_num (data + 0x1c, 4)
		if !sectors:
			sectors = read_num (data + 0x20, 4)
		if Iris::Num (sectors).value () << sector_size_bits > device_size.value ():
			sectors = device_size.value () >> sector_size_bits
			kdebug ("warning: limiting sectors because of limited device size\n")

		root_sectors = (root_entries * 32 + (1 << sector_size_bits) - 1) >> sector_size_bits
		header_sectors = reserved_sectors + sectors_per_fat * num_fats + root_sectors
		clusters = (sectors - header_sectors) >> sectors_per_cluster_bits
		unsigned skip
		if clusters >= 65525:
			bits = 32
			sectors_per_fat = read_num (data + 0x24, 4)
			active_fat = read_num (data + 0x28, 2)
			write_all_fats = active_fat & 0x80
			active_fat &= 0xf
			fs_version = read_num (data + 0x2a, 2)
			root_cluster = read_num (data + 0x2c, 4)
			fsinfo_sector = read_num (data + 0x30, 2)
			boot_backup_sector = read_num (data + 0x32, 2)
			skip = 0x40 - 0x24
		else:
			if clusters < 4085:
				bits = 12
			else:
				bits = 16
			skip = 0
			active_fat = 0
			write_all_fats = true
			fs_version = 0
			root_cluster = 0
			fsinfo_sector = 0
			boot_backup_sector = 0
		unsigned fat_entries_per_sector = (8 << sector_size_bits) / bits
		unsigned fat_entries = sectors_per_fat * fat_entries_per_sector
		if clusters + 2 > fat_entries:
			clusters = fat_entries - 2
			kdebug ("warning: limiting clusters because of limited sector count\n")
		drive = read_num (data + skip + 0x24, 1)
		current_head = read_num (data + skip + 0x25, 1)
		if data[skip + 0x26] == 0x29:
			volume_id = read_num (data + skip + 0x27, 4)
			for unsigned i = 0; i < 0xb; ++i:
				label[i] = data[skip + 0x2b + i]
			char *id = data + skip + 0x36
			if id[0] != 'F' || id[1] != 'A' || id[2] != 'T' || id[5] != ' ' || id[6] != ' ' || id[7] != ' ':
				kdebug ("warning: file system type field was not 'FATxx   '\n")
			else:
				switch bits:
					case 12:
						if id[3] != '1' || id[4] != '2':
							kdebug ("warning: id for fat12 is not FAT12\n")
						break
					case 16:
						if id[3] != '1' || id[4] != '6':
							kdebug ("warning: id for fat16 is not FAT16\n")
						break
					case 32:
						if id[3] != '3' || id[4] != '2':
							kdebug ("warning: id for fat32 wat not FAT32")
						break
		else:
			volume_id = 0
			for unsigned i = 0; i < 0xb; ++i:
				label[i] = 0
		if fsinfo_sector:
			read_block (fsinfo_sector << sector_size_bits)
			if (data[0] & 0xff) != 0x52 || (data[1] & 0xff) != 0x52 || (data[2] & 0xff) != 0x6a || (data[3] & 0xff) != 0x41 || (data[0x1e4] & 0xff) != 0x72 || (data[0x1e5] & 0xff) != 0x72 || (data[0x1e6] & 0xff) != 0x4a || (data[0x1e7] & 0xff) != 0x61 || (data[0x1fe] & 0xff) != 0x55 || (data[0x1ff] & 0xff) != 0xaa:
				kdebug ("invalid signature in fsinfo structure\n")
			free_clusters = read_num (data + 0x1e8, 4)
			last_alloced = read_num (data + 0x1ec, 4)
		else:
			free_clusters = ~0
			last_alloced = ~0

		// Now read the FAT.
		bad_clusters = 0
		fat = new unsigned[clusters]
		unsigned counted_free_clusters = 0
		first_free_cluster = ~0
		for unsigned c = 0; c < clusters; ++c:
			// reduced cluster.
			unsigned rc = c & (1 << sector_size_bits) - 1
			// The next line does nothing most of the time.
			map_fat_cluster (c)
			switch bits:
				case 12:
					fat[c] = data[(rc + 2) * 2] & 0xff
					// There may be a sector boundary in the middle of the entry, so optionally reread.
					map_fat_cluster (c, 1)
					fat[c] |= (data[(rc + 2) * 2 + 1] & 0xff) << 8
					if c & 1:
						fat[c] >>= 4
					else:
						fat[c] &= 0xfff
					break
				case 16:
					fat[c] = read_num (data + (rc + 2) * 2, 2)
					break
				case 32:
					fat[c] = read_num (data + (rc + 2) * 4, 4)
					break
			// Correct for the crazy +2 offset, and keep a list of bad and free clusters.
			if fat[c] == 0:
				// Free cluster.
				fat[c] = first_free_cluster
				first_free_cluster = c
				++counted_free_clusters
			else if fat[c] == 1:
				// Invalid value.
				Iris::panic (0, "entry is '1' in fat.")
			else if bits == 12 && fat[c] == 0xfff || bits == 16 && fat[c] == 0xffff || bits == 32 && fat[c] == 0xfffffff:
				// Last cluster in chain.
				fat[c] = ~0
				//kdebug ("last cluster: ")
				//kdebug_num (c)
				//kdebug ("\n")
			else if bits == 12 && fat[c] == 0xff7 || bits == 16 && fat[c] == 0xfff7 || bits == 32 && fat[c] == 0xffffff7:
				// Bad cluster.
				fat[c] = first_bad_cluster
				first_bad_cluster = c
				++bad_clusters
			else:
				// Non-last cluster in chain.
				fat[c] -= 2
				//kdebug_num (c)
				//kdebug (" -> ")
				//kdebug_num (fat[c])
				//kdebug ("\n")
	unsigned fat_lookup (unsigned first_cluster, unsigned cluster):
		//kdebug ("looking up ")
		//kdebug_num (first_cluster)
		//kdebug ("+")
		//kdebug_num (cluster)
		//kdebug (":")
		while cluster--:
			first_cluster = fat[first_cluster]
			//kdebug ("->")
			//kdebug_num (first_cluster)
			if first_cluster == ~0:
				//kdebug ("sector beyond end of file requested\n")
				return ~0
		//kdebug ("\n")
		return first_cluster
	struct File:
		Fat *fat
		unsigned size
		unsigned first_cluster
		char name[11]
		bool archive, readonly, system, hidden, directory, volume
		unsigned create_second, create_minute_hour, create_date, access_date, time, date
		unsigned checksum
		void load_cluster (unsigned idx, unsigned offset_in_cluster, Iris::Page p = page, unsigned offset = 0):
			unsigned cluster = fat->fat_lookup (first_cluster, idx >> fat->cluster_size_bits)
			//kdebug ("loading cluster ")
			//kdebug_num (idx)
			//kdebug ("+")
			//kdebug_num (offset_in_cluster)
			//kdebug ("@")
			//kdebug_num (cluster)
			//kdebug (" from file\n")
			if cluster == ~0:
				kdebug ("invalid cluster requested from file\n")
				return
			read_block (((fat->header_sectors + (Iris::Num (cluster).value () << fat->sectors_per_cluster_bits)) << fat->sector_size_bits) + offset_in_cluster, p, fat->cluster_size_bits < PAGE_BITS ? 1 << fat->cluster_size_bits : PAGE_SIZE, offset)
	char *load_dir_entry (unsigned dir, unsigned idx):
		unsigned sector = idx >> (sector_size_bits - 5)
		unsigned num = (idx << 5) & ~BLOCK_MASK
		Iris::Num hwsector
		if dir == ROOT_CLUSTER:
			if sector < root_sectors:
				hwsector = header_sectors - root_sectors + sector
			else:
				return NULL
		else:
			unsigned entry = fat_lookup (dir, sector)
			if entry == ~0:
				return NULL
			hwsector = header_sectors + (Iris::Num (entry).value () << sectors_per_cluster_bits)
		read_block (hwsector.value () << sector_size_bits)
		return &data[num]
	char *find_idx (unsigned dir, unsigned *idx, unsigned *count = NULL):
		unsigned todo = *idx + 1
		char *e
		if count:
			*count = 0
		for *idx = 0; todo; ++*idx:
			e = load_dir_entry (dir, *idx)
			if !e:
				return NULL
			if (e[0xb] & 0xff) == 0xf:
				// This is part of a long filename.
				continue
			if (e[0] & 0xff) == 0xe5:
				// This is a deleted file.
				continue
			if !e[0]:
				// This is a free entry.
				continue
			if count:
				++*count
			--todo
		--*idx
		return e
	unsigned get_dir_size (unsigned dir):
		unsigned num = 0 - 2
		unsigned ret
		find_idx (dir, &num, &ret)
		return ret
	bool get_dir_entry (unsigned dir, unsigned idx, File *f):
		char *e = load_dir_entry (dir, idx)
		if !e:
			kdebug ("unable to load dir entry\n")
			return false
		f->fat = this
		//kdebug ("loading dir entry for ")
		for unsigned i = 0; i < 11; ++i:
			f->name[i] = e[i]
			//kdebug_char (f->name[i])
		//kdebug ("\n")
		f->readonly = e[0xb] & 0x1
		f->system = e[0xb] & 0x2
		f->hidden = e[0xb] & 0x4
		f->volume = e[0xb] & 0x8
		f->directory = e[0xb] & 0x10
		f->archive = e[0xb] & 0x20
		f->create_second = read_num (e + 0xd, 1)
		f->create_minute_hour = read_num (e + 0xe, 2)
		f->create_date = read_num (e + 0x10, 2)
		f->access_date = read_num (e + 0x12, 2)
		f->time = read_num (e + 0x16, 1)
		f->date = read_num (e + 0x18, 1)
		f->size = read_num (e + 0x1c, 4)
		f->first_cluster = (read_num (e + 0x14, 2) << 16 | read_num (e + 0x1a, 2)) - 2
		f->checksum = 0
		for unsigned i = 0; i < 11; ++i:
			f->checksum = ((((f->checksum & 1) << 7) | ((f->checksum & 0xfe) >> 1)) + f->name[i]) & 0xff
		//kdebug ("loaded dir entry, first cluster = ")
		//kdebug_num (f->first_cluster)
		//kdebug ("\n")
		return true
	struct LFN:
		unsigned ordinal
		unsigned name[13]
		unsigned checksum
	bool load_lfn (unsigned dir, unsigned idx, unsigned t, unsigned checksum, LFN *lfn):
		if t >= idx:
			return false
		char *e = load_dir_entry (dir, idx - t - 1)
		if (e[0xb] & 0xff) != 0xf:
			return false
		lfn->ordinal = read_num (e + 0x00, 1)
		for unsigned i = 0; i < 5; ++i:
			lfn->name[i] = read_num (e + 0x01 + 2 * i, 2)
		lfn->checksum = read_num (e + 0xd, 1)
		for unsigned i = 0; i < 6; ++i:
			lfn->name[i + 5] = read_num (e + 0xe + 2 * i, 2)
		for unsigned i = 0; i < 2; ++i:
			lfn->name[i + 11] = read_num (e + 0x1c + 2 * i, 2)
		return true
	unsigned parse_shortname (File const &f, char *name):
		if f.name[0] == ' ':
			Iris::panic (0, "fat name starts with space")
		unsigned len = 8
		while f.name[len - 1] == ' ':
			--len
		char *ptr = name
		for unsigned i = 0; i < len; ++i:
			*ptr++ = f.name[i]
		if f.name[8] == ' ':
			return len
		*ptr++ = '.'
		len = 3
		while f.name[8 + len - 1] == ' ':
			--len
		for unsigned i = 0; i < len; ++i:
			*ptr++ = f.name[8 + i]
		return ptr - name
	unsigned get_name_size (unsigned dir, unsigned idx, File const &f):
		LFN lfn
		unsigned num = 0
		if !load_lfn (dir, idx, 0, f.checksum, &lfn):
			// Not a long filename.
			char n[12]
			return parse_shortname (f, n)
		unsigned ordinal = 0
		while true:
			if !load_lfn (dir, idx, num, f.checksum, &lfn):
				Iris::panic (0, "error parsing long filename")
			if (lfn.ordinal & 0x3f) != ++ordinal:
				Iris::panic (lfn.ordinal, "error in sequence for long filename")
			if lfn.ordinal & 0x40:
				break
			++num
		unsigned i
		for i = 0; i < 13; ++i:
			if !lfn.name[i]:
				break
		return num * 13 + i

// Capability encoding.
// 0:ROOT_CLUSTER = non fat-32 root directory.
// 0:cluster = other directory.
// cluster:index = file index from directory at cluster.
// cluster|0x80000000:index = filename for file with index from directory at cluster.

Iris::Num start ():
	init_alloc ()
	current_block = ~0
	dev = Iris::my_parent.get_capability <Iris::WString> ()
	if dev.get_align_bits () > SECTOR_BITS:
		kdebug ("fat device doesn't support 512 byte access")
		return 1
	device_size = dev.get_size ()
	data = (char *)0x15000; //alloc_space (1)
	page = Iris::my_memory.create_page ()
	page.set_flags (Iris::Page::PAYING)
	Iris::my_memory.map (page, (unsigned)data)

	Fat fat

	fat.reset ()
	fat.print_br ()

	Iris::Cap root
	if fat.root_cluster:
		root = Iris::my_receiver.create_capability (Iris::Num (fat.root_cluster, 0))
	else:
		root = Iris::my_receiver.create_capability (Iris::Num (ROOT_CLUSTER, 0))

	Iris::my_parent.provide_capability <Iris::Directory> (root.copy ())
	Iris::free_cap (root)

	while true:
		Iris::wait ()
		unsigned dir = Iris::recv.protected_data.h
		if dir & 0x80000000:
			dir &= ~0x80000000
			// File name.
			unsigned idx = Iris::recv.protected_data.l
			Iris::Cap reply = Iris::get_reply ()
			unsigned num = Iris::recv.data[1].l
			unsigned size = Iris::recv.data[0].h >> 16
			unsigned cmd = Iris::recv.data[0].l
			Fat::File f
			if !fat.find_idx (dir, &idx):
				Iris::panic (Iris::recv.protected_data.l, "invalid index")
			if !fat.get_dir_entry (dir, idx, &f):
				Iris::panic (Iris::recv.protected_data.l, "invalid dir entry requested for filename")
			switch cmd:
				case Iris::String::GET_SIZE:
					//kdebug ("filename size requested\n")
					reply.invoke (fat.get_name_size (dir, idx, f))
					break
				case Iris::String::GET_CHARS:
					//kdebug ("filename chars requested\n")
					//kdebug ("flags: ")
					//kdebug_char (f.readonly ? 'R' : 'r')
					//kdebug_char (f.system ? 'S' : 's')
					//kdebug_char (f.hidden ? 'H' : 'h')
					//kdebug_char (f.volume ? 'V' : 'v')
					//kdebug_char (f.directory ? 'D' : 'd')
					//kdebug_char (f.archive ? 'A' : 'a')
					//kdebug_char ('\n')

					/**/union { unsigned u[4]; char c[16]; } u
					for unsigned k = 0; k < 4; ++k:
						u.u[k] = 0
					Fat::LFN lfn
					if !fat.load_lfn (dir, idx, 0, f.checksum, &lfn):
						// Not a long filename.
						char n[12]
						unsigned len = fat.parse_shortname (f, n)
						//kdebug ("short filename: ")
						for unsigned k = 0; k + num < len; ++k:
							u.c[k] = n[k + num]
							//kdebug_char (u.c[k])
						//kdebug ("\n")
					else:
						// Very inefficient, but it works: reload everything for every character.
						//kdebug ("filename: ")
						for unsigned c = 0; c < 16; ++c:
							if !fat.load_lfn (dir, idx, (num + c) / 13, f.checksum, &lfn):
								// Filename isn't this long: keep the rest at 0.
								break
							u.c[c] = lfn.name[(num + c) % 13]
							if u.c[c] == 0:
								break
							//kdebug_char (u.c[c])
						//kdebug ("\n")
					reply.invoke (Iris::Num (u.u[0], u.u[1]), Iris::Num (u.u[2], u.u[3]))
					break
				case Iris::String::GET_ALIGN_BITS:
					//kdebug ("filename align requested\n")
					reply.invoke (0)
					break
				case Iris::String::GET_BLOCK:
				default:
					Iris::panic (Iris::recv.data[0].l, "invalid request for fat filename")
			Iris::free_cap (reply)
		else if dir:
			// If it *has* a directory, it *is* a file.
			unsigned idx = Iris::recv.protected_data.l
			Iris::Cap reply = Iris::get_reply ()
			Iris::Cap arg = Iris::get_arg ()
			Iris::Num num = Iris::recv.data[1]
			unsigned size = Iris::recv.data[0].h >> 16
			unsigned offset = Iris::recv.data[0].h & 0xffff
			unsigned cmd = Iris::recv.data[0].l
			Fat::File f
			fat.get_dir_entry (dir, idx, &f)
			switch cmd:
				case Iris::String::GET_SIZE:
					//kdebug ("file size requested\n")
					reply.invoke (f.size)
					break
				case Iris::String::GET_CHARS:
					//kdebug ("file chars requested\n")
					unsigned mask = (1 << fat.cluster_size_bits) - 1
					f.load_cluster (num.l & ~mask, num.l & mask)
					unsigned n = num.l & mask & ~0xf
					unsigned *dat = (unsigned *)(data + n)
					reply.invoke (Iris::Num (dat[0], dat[1]), Iris::Num (dat[2], dat[3]))
					break
				case Iris::String::GET_ALIGN_BITS:
					//kdebug ("file align requested\n")
					reply.invoke (fat.cluster_size_bits <= PAGE_BITS ? fat.cluster_size_bits : PAGE_BITS)
					break
				case Iris::String::GET_BLOCK:
					//kdebug ("file block requested\n")
					unsigned mask = (1 << fat.cluster_size_bits) - 1
					//kdebug ("mask = ")
					//kdebug_num (mask)
					//kdebug ("\n")
					if offset > PAGE_SIZE:
						//kdebug ("invalid offset requested\n")
						break
					if size + offset > PAGE_SIZE:
						Iris::panic (size, "invalid size requested")
						size = PAGE_SIZE - offset
					for unsigned i = 0; i < size; i += 1 << fat.cluster_size_bits:
						f.load_cluster ((num.l & ~mask) + i, num.l & mask, arg, i + offset)
					reply.invoke ()
					break
				case Iris::WString::TRUNCATE:
				case Iris::WString::SET_CHARS:
				case Iris::WString::SET_BLOCK:
					Iris::panic (Iris::recv.data[0].l, "writing to files not supported yet")
				default:
					Iris::panic (Iris::recv.data[0].l, "invalid request for fat file")
			Iris::free_cap (reply)
			Iris::free_cap (arg)
		else:
			// Directory.
			switch Iris::recv.data[0].l:
				case Iris::Directory::GET_SIZE:
					//kdebug ("dir size requested\n")
					Iris::Cap reply = Iris::get_reply ()
					reply.invoke (fat.get_dir_size (Iris::recv.protected_data.l))
					Iris::free_cap (reply)
					break
				case Iris::Directory::GET_NAME:
					//kdebug ("dir name requested\n")
					Iris::Cap reply = Iris::get_reply ()
					Iris::Cap ret = Iris::my_receiver.create_capability (Iris::Num (Iris::recv.data[1].l, Iris::recv.protected_data.l | 0x80000000))
					reply.invoke (0, 0, ret.copy ())
					Iris::free_cap (reply)
					Iris::free_cap (ret)
					break
				case Iris::Directory::GET_FILE_RO:
					//kdebug ("dir file requested\n")
					Iris::Cap reply = Iris::get_reply ()
					dir = Iris::recv.protected_data.l
					unsigned idx = Iris::recv.data[1].l
					unsigned oldidx = idx
					if !fat.find_idx (dir, &idx):
						kdebug_num (oldidx)
						kdebug ("\n")
						Iris::panic (1, "file not found")
					Fat::File f
					fat.get_dir_entry (dir, idx, &f)
					Iris::Cap ret
					if f.directory:
						//kdebug ("dir provided: ")
						//kdebug_num (f.first_cluster)
						//kdebug ("\n")
						ret = Iris::my_receiver.create_capability (Iris::Num (f.first_cluster, 0))
					else:
						ret = Iris::my_receiver.create_capability (Iris::Num (idx, dir))
					reply.invoke (0, 0, ret.copy ())
					Iris::free_cap (reply)
					Iris::free_cap (ret)
					break
				case Iris::Directory::GET_FILE_INFO:
					//kdebug ("dir file info requested\n")
					Iris::Cap reply = Iris::get_reply ()
					dir = Iris::recv.protected_data.l
					unsigned idx = Iris::recv.data[1].l
					unsigned oldidx = idx
					if !fat.find_idx (dir, &idx):
						kdebug_num (oldidx)
						kdebug ("\n")
						Iris::panic (2, "file not found")
					unsigned type = Iris::recv.data[0].h
					Fat::File f
					fat.get_dir_entry (dir, idx, &f)
					reply.invoke (f.directory ? 1 : 0)
					Iris::free_cap (reply)
					break
				case Iris::Directory::LOCK_RO:
				case Iris::Directory::UNLOCK_RO:
					//kdebug ("dir lock or unlock requested\n")
					Iris::recv.reply.invoke ()
					break
				default:
					//kdebug ("invalid dir operation requested\n")
					Iris::recv.reply.invoke ()
					break