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#!/usr/bin/env python
#
# Copyright (c) 2008 Martin Decky
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
"""
FAT creator
"""
import sys
import os
import random
import xstruct
import array
def align_up(size, alignment):
"Return size aligned up to alignment"
if (size % alignment == 0):
return size
return (((size / alignment) + 1) * alignment)
def subtree_size(root, cluster_size, dirent_size):
"Recursive directory walk and calculate size"
size = 0
files = 2
for name in os.listdir(root):
canon = os.path.join(root, name)
if (os.path.isfile(canon)):
size += align_up(os.path.getsize(canon), cluster_size)
files += 1
if (os.path.isdir(canon)):
size += subtree_size(canon, cluster_size, dirent_size)
files += 1
return size + align_up(files * dirent_size, cluster_size)
def root_entries(root):
"Return number of root directory entries"
return len(os.listdir(root))
def write_file(path, outf, cluster_size, data_start, fat, reserved_clusters):
"Store the contents of a file"
size = os.path.getsize(path)
prev = -1
first = 0
inf = file(path, "r")
rd = 0;
while (rd < size):
empty_cluster = fat.index(0)
fat[empty_cluster] = 0xffff
if (prev != -1):
fat[prev] = empty_cluster
else:
first = empty_cluster
prev = empty_cluster
data = inf.read(cluster_size);
outf.seek(data_start + (empty_cluster - reserved_clusters) * cluster_size)
outf.write(data)
rd += len(data)
inf.close()
return first, size
def write_directory(directory, outf, cluster_size, data_start, fat, reserved_clusters, dirent_size, empty_cluster):
"Store the contents of a directory"
length = len(directory)
size = length * dirent_size
prev = -1
first = 0
i = 0
rd = 0;
while (rd < size):
if (prev != -1):
empty_cluster = fat.index(0)
fat[empty_cluster] = 0xffff
fat[prev] = empty_cluster
else:
first = empty_cluster
prev = empty_cluster
data = ''
data_len = 0
while ((i < length) and (data_len < cluster_size)):
if (i == 0):
directory[i].cluster = empty_cluster
data += directory[i].pack()
data_len += dirent_size
i += 1
outf.seek(data_start + (empty_cluster - reserved_clusters) * cluster_size)
outf.write(data)
rd += len(data)
return first, size
DIR_ENTRY = """little:
char name[8] /* file name */
char ext[3] /* file extension */
uint8_t attr /* file attributes */
padding[1] /* reserved for NT */
uint8_t ctime_fine /* create time (fine resolution) */
uint16_t ctime /* create time */
uint16_t cdate /* create date */
uint16_t adate /* access date */
padding[2] /* EA-index */
uint16_t mtime /* modification time */
uint16_t mdate /* modification date */
uint16_t cluster /* first cluster */
uint32_t size /* file size */
"""
DOT_DIR_ENTRY = """little:
uint8_t signature /* 0x2e signature */
char name[7] /* empty */
char ext[3] /* empty */
uint8_t attr /* file attributes */
padding[1] /* reserved for NT */
uint8_t ctime_fine /* create time (fine resolution) */
uint16_t ctime /* create time */
uint16_t cdate /* create date */
uint16_t adate /* access date */
padding[2] /* EA-index */
uint16_t mtime /* modification time */
uint16_t mdate /* modification date */
uint16_t cluster /* first cluster */
uint32_t size /* file size */
"""
DOTDOT_DIR_ENTRY = """little:
uint8_t signature[2] /* 0x2e signature */
char name[6] /* empty */
char ext[3] /* empty */
uint8_t attr /* file attributes */
padding[1] /* reserved for NT */
uint8_t ctime_fine /* create time (fine resolution) */
uint16_t ctime /* create time */
uint16_t cdate /* create date */
uint16_t adate /* access date */
padding[2] /* EA-index */
uint16_t mtime /* modification time */
uint16_t mdate /* modification date */
uint16_t cluster /* first cluster */
uint32_t size /* file size */
"""
def mangle_fname(name):
# FIXME: filter illegal characters
parts = name.split('.')
if (len(parts) > 0):
fname = parts[0]
else:
fname = ''
return (fname + ' ').upper()[0:8]
def mangle_ext(name):
# FIXME: filter illegal characters
parts = name.split('.')
if (len(parts) > 1):
ext = parts[1]
else:
ext = ''
return (ext + ' ').upper()[0:3]
def create_dirent(name, directory, cluster, size):
dir_entry = xstruct.create(DIR_ENTRY)
dir_entry.name = mangle_fname(name)
dir_entry.ext = mangle_ext(name)
if (directory):
dir_entry.attr = 0x30
else:
dir_entry.attr = 0x20
dir_entry.ctime_fine = 0 # FIXME
dir_entry.ctime = 0 # FIXME
dir_entry.cdate = 0 # FIXME
dir_entry.adate = 0 # FIXME
dir_entry.mtime = 0 # FIXME
dir_entry.mdate = 0 # FIXME
dir_entry.cluster = cluster
if (directory):
dir_entry.size = 0
else:
dir_entry.size = size
return dir_entry
def create_dot_dirent(empty_cluster):
dir_entry = xstruct.create(DOT_DIR_ENTRY)
dir_entry.signature = 0x2e
dir_entry.name = ' '
dir_entry.ext = ' '
dir_entry.attr = 0x10
dir_entry.ctime_fine = 0 # FIXME
dir_entry.ctime = 0 # FIXME
dir_entry.cdate = 0 # FIXME
dir_entry.adate = 0 # FIXME
dir_entry.mtime = 0 # FIXME
dir_entry.mdate = 0 # FIXME
dir_entry.cluster = empty_cluster
dir_entry.size = 0
return dir_entry
def create_dotdot_dirent(parent_cluster):
dir_entry = xstruct.create(DOTDOT_DIR_ENTRY)
dir_entry.signature = [0x2e, 0x2e]
dir_entry.name = ' '
dir_entry.ext = ' '
dir_entry.attr = 0x10
dir_entry.ctime_fine = 0 # FIXME
dir_entry.ctime = 0 # FIXME
dir_entry.cdate = 0 # FIXME
dir_entry.adate = 0 # FIXME
dir_entry.mtime = 0 # FIXME
dir_entry.mdate = 0 # FIXME
dir_entry.cluster = parent_cluster
dir_entry.size = 0
return dir_entry
def recursion(head, root, outf, cluster_size, root_start, data_start, fat, reserved_clusters, dirent_size, parent_cluster):
"Recursive directory walk"
directory = []
if (not head):
# Directory cluster preallocation
empty_cluster = fat.index(0)
fat[empty_cluster] = 0xffff
directory.append(create_dot_dirent(empty_cluster))
directory.append(create_dotdot_dirent(parent_cluster))
else:
empty_cluster = 0
for name in os.listdir(root):
canon = os.path.join(root, name)
if (os.path.isfile(canon)):
rv = write_file(canon, outf, cluster_size, data_start, fat, reserved_clusters)
directory.append(create_dirent(name, False, rv[0], rv[1]))
if (os.path.isdir(canon)):
rv = recursion(False, canon, outf, cluster_size, root_start, data_start, fat, reserved_clusters, dirent_size, empty_cluster)
directory.append(create_dirent(name, True, rv[0], rv[1]))
if (head):
outf.seek(root_start)
for dir_entry in directory:
outf.write(dir_entry.pack())
else:
return write_directory(directory, outf, cluster_size, data_start, fat, reserved_clusters, dirent_size, empty_cluster)
BOOT_SECTOR = """little:
uint8_t jmp[3] /* jump instruction */
char oem[8] /* OEM string */
uint16_t sector /* bytes per sector */
uint8_t cluster /* sectors per cluster */
uint16_t reserved /* reserved sectors */
uint8_t fats /* number of FATs */
uint16_t rootdir /* root directory entries */
uint16_t sectors /* total number of sectors */
uint8_t descriptor /* media descriptor */
uint16_t fat_sectors /* sectors per single FAT */
uint16_t track_sectors /* sectors per track */
uint16_t heads /* number of heads */
uint32_t hidden /* hidden sectors */
uint32_t sectors_big /* total number of sectors (if sectors == 0) */
/* Extended BIOS Parameter Block */
uint8_t drive /* physical drive number */
padding[1] /* reserved (current head) */
uint8_t extboot_signature /* extended boot signature */
uint32_t serial /* serial number */
char label[11] /* volume label */
char fstype[8] /* filesystem type */
padding[448] /* boot code */
uint8_t boot_signature[2] /* boot signature */
"""
EMPTY_SECTOR = """little:
padding[512] /* empty sector data */
"""
FAT_ENTRY = """little:
uint16_t next /* FAT16 entry */
"""
def usage(prname):
"Print usage syntax"
print prname + " <PATH> <IMAGE>"
def main():
if (len(sys.argv) < 3):
usage(sys.argv[0])
return
path = os.path.abspath(sys.argv[1])
if (not os.path.isdir(path)):
print "<PATH> must be a directory"
return
fat16_clusters = 4096
min_cluster_size = 1024
sector_size = 512
cluster_size = 4096
dirent_size = 32
fatent_size = 2
fat_count = 2
reserved_clusters = 2
# Make sure the filesystem is large enought for FAT16
size = subtree_size(path, cluster_size, dirent_size) + reserved_clusters * cluster_size
while (size / cluster_size < fat16_clusters):
if (cluster_size > min_cluster_size):
cluster_size /= 2
size = subtree_size(path, cluster_size, dirent_size) + reserved_clusters * cluster_size
else:
size = fat16_clusters * cluster_size + reserved_clusters * cluster_size
root_size = align_up(root_entries(path) * dirent_size, cluster_size)
fat_size = align_up(align_up(size, cluster_size) / cluster_size * fatent_size, sector_size)
sectors = (cluster_size + fat_count * fat_size + root_size + size) / sector_size
root_start = cluster_size + fat_count * fat_size
data_start = root_start + root_size
outf = file(sys.argv[2], "w")
boot_sector = xstruct.create(BOOT_SECTOR)
boot_sector.jmp = [0xEB, 0x3C, 0x90]
boot_sector.oem = "MSDOS5.0"
boot_sector.sector = sector_size
boot_sector.cluster = cluster_size / sector_size
boot_sector.reserved = cluster_size / sector_size
boot_sector.fats = fat_count
boot_sector.rootdir = root_size / dirent_size
boot_sector.sectors = (sectors if (sectors <= 65535) else 0)
boot_sector.descriptor = 0xF8
boot_sector.fat_sectors = fat_size / sector_size
boot_sector.track_sectors = 63
boot_sector.heads = 6
boot_sector.hidden = 0
boot_sector.sectors_big = (sectors if (sectors > 65535) else 0)
boot_sector.drive = 0x80
boot_sector.extboot_signature = 0x29
boot_sector.serial = random.randint(0, 0xFFFFFFFF)
boot_sector.label = "HELENOS"
boot_sector.fstype = "FAT16 "
boot_sector.boot_signature = [0x55, 0xAA]
outf.write(boot_sector.pack())
empty_sector = xstruct.create(EMPTY_SECTOR)
# Reserved sectors
for i in range(1, cluster_size / sector_size):
outf.write(empty_sector.pack())
# FAT tables
for i in range(0, fat_count):
for j in range(0, fat_size / sector_size):
outf.write(empty_sector.pack())
# Root directory
for i in range(0, root_size / sector_size):
outf.write(empty_sector.pack())
# Data
for i in range(0, size / sector_size):
outf.write(empty_sector.pack())
fat = array.array('L', [0] * (fat_size / fatent_size))
fat[0] = 0xfff8
fat[1] = 0xffff
recursion(True, path, outf, cluster_size, root_start, data_start, fat, reserved_clusters, dirent_size, 0)
# Store FAT
fat_entry = xstruct.create(FAT_ENTRY)
for i in range(0, fat_count):
outf.seek(cluster_size + i * fat_size)
for j in range(0, fat_size / fatent_size):
fat_entry.next = fat[j]
outf.write(fat_entry.pack())
outf.close()
if __name__ == '__main__':
main()