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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()