annotate pytouhou/formats/pbg3.py @ 490:1b532e7dd521

Decrease PBG3 loading time by improving lzss and bitstream integration.
author Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
date Fri, 04 Oct 2013 14:28:49 +0200
parents 70e2ed71b09c
children 6b76c9ba3975
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1 # -*- encoding: utf-8 -*-
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2 ##
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3 ## Copyright (C) 2011 Thibaut Girka <thib@sitedethib.com>
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4 ##
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5 ## This program is free software; you can redistribute it and/or modify
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6 ## it under the terms of the GNU General Public License as published
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7 ## by the Free Software Foundation; version 3 only.
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8 ##
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9 ## This program is distributed in the hope that it will be useful,
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10 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 ## GNU General Public License for more details.
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13 ##
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14
204
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15 """PBG3 archive files handling.
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16
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17 This module provides classes for handling the PBG3 file format.
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18 The PBG3 format is the archive format used by Touhou: EoSD.
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19
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20 PBG3 files are merely a bitstream composed of a header,
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21 a file table, and LZSS-compressed files.
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22 """
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23
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24 from collections import namedtuple
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25
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26 from pytouhou.utils.bitstream import BitStream
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27 from pytouhou.utils import lzss
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28
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29 from pytouhou.utils.helpers import get_logger
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30
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31 from pytouhou.formats import WrongFormatError
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32
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33 logger = get_logger(__name__)
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34
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35
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36 class PBG3BitStream(BitStream):
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37 """Helper class to handle strings and integers in PBG3 bitstreams."""
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38
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39 def read_int(self):
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40 """Read an integer from the bitstream.
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41
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42 Integers have variable sizes. They begin with a two-bit value indicating
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43 the number of (non-aligned) bytes to read.
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44 """
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45
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46 size = self.read(2)
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47 return self.read((size + 1) * 8)
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48
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49
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50 def read_string(self, maxsize):
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51 """Read a string from the bitstream.
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52
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53 Strings are stored as standard NULL-termianted sequences of bytes.
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54 The only catch is that they are not byte-aligned.
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55 """
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56
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57 string = []
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58 for i in range(maxsize):
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59 byte = self.read(8)
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60 if byte == 0:
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61 break
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62 string.append(byte)
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63 return ''.join(chr(byte) for byte in string)
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64
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65
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66
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67 PBG3Entry = namedtuple('PBG3Entry', 'unknown1 unknown2 checksum offset size')
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68
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69
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70
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71 class PBG3(object):
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72 """Handle PBG3 archive files.
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73
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74 PBG3 is a file archive format used in Touhou 6: EoSD.
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75 This class provides a representation of such files, as well as functions to
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76 read and extract files from a PBG3 archive.
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77
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78 Instance variables:
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79 entries -- list of PBG3Entry objects describing files present in the archive
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80 bitstream -- PBG3BitStream object
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81 """
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82
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83 def __init__(self, entries=None, bitstream=None):
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84 self.entries = entries or {}
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85 self.bitstream = bitstream #TODO
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86
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87
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88 def __enter__(self):
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89 return self
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91
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92 def __exit__(self, type, value, traceback):
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93 return self.bitstream.__exit__(type, value, traceback)
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94
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95
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96 @classmethod
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97 def read(cls, file):
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98 """Read a PBG3 file.
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99
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100 Raise an exception if the file is invalid.
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101 Return a PBG3 instance otherwise.
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102 """
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103
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104 magic = file.read(4)
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105 if magic != b'PBG3':
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106 raise WrongFormatError(magic)
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107
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108 bitstream = PBG3BitStream(file)
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109 entries = {}
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110
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111 nb_entries = bitstream.read_int()
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112 offset = bitstream.read_int()
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113 bitstream.seek(offset)
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114 for i in range(nb_entries):
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115 unknown1 = bitstream.read_int()
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116 unknown2 = bitstream.read_int()
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117 checksum = bitstream.read_int() # Checksum of *compressed data*
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118 offset = bitstream.read_int()
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119 size = bitstream.read_int()
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120 name = bitstream.read_string(255).decode('ascii')
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121 entries[name] = PBG3Entry(unknown1, unknown2, checksum, offset, size)
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122
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123 return PBG3(entries, bitstream)
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124
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125
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126 def list_files(self):
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127 """List files present in the archive."""
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128 return self.entries.keys()
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129
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130
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131 def extract(self, filename, check=False):
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132 """Extract a given file.
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133
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134 If “filename” is in the archive, extract it and return its contents.
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135 Otherwise, raise an exception.
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136
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137 By default, the checksum of the file won't be verified,
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138 you can however force the verification using the “check” argument.
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139 """
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140
0
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141 unkwn1, unkwn2, checksum, offset, size = self.entries[filename]
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142 self.bitstream.seek(offset)
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143 data = lzss.decompress(self.bitstream, size)
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144 if check:
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145 # Verify the checksum
0
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146 compressed_size = self.bitstream.io.tell() - offset
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147 self.bitstream.seek(offset)
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148 value = 0
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149 for c in self.bitstream.io.read(compressed_size):
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150 value += ord(c)
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151 value &= 0xFFFFFFFF
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152 if value != checksum:
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3da4de9decd0 Use logging module
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153 logger.warn('corrupted data!')
0
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154 return data
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155