The Tor Browser: python/mozbuild/mozpack/mozjar.py@6474c204b198 (annotated)

python/mozbuild/mozpack/mozjar.py@6474c204b198 (annotated)

python/mozbuild/mozpack/mozjar.py

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 from io import BytesIO
 import struct
 import zlib
 import os
 from zipfile import (
     ZIP_STORED,
     ZIP_DEFLATED,
 )
 from collections import OrderedDict
 from urlparse import urlparse, ParseResult
 import mozpack.path
 JAR_STORED = ZIP_STORED
 JAR_DEFLATED = ZIP_DEFLATED
 MAX_WBITS = 15
 class JarReaderError(Exception):
     '''Error type for Jar reader errors.'''
 class JarWriterError(Exception):
     '''Error type for Jar writer errors.'''
 class JarStruct(object):
     '''
     Helper used to define ZIP archive raw data structures. Data structures
     handled by this helper all start with a magic number, defined in
     subclasses MAGIC field as a 32-bits unsigned integer, followed by data
     structured as described in subclasses STRUCT field.
     The STRUCT field contains a list of (name, type) pairs where name is a
     field name, and the type can be one of 'uint32', 'uint16' or one of the
     field names. In the latter case, the field is considered to be a string
     buffer with a length given in that field.
     For example,
         STRUCT = [
             ('version', 'uint32'),
             ('filename_size', 'uint16'),
             ('filename', 'filename_size')
         ]
     describes a structure with a 'version' 32-bits unsigned integer field,
     followed by a 'filename_size' 16-bits unsigned integer field, followed by a
     filename_size-long string buffer 'filename'.
     Fields that are used as other fields size are not stored in objects. In the
     above example, an instance of such subclass would only have two attributes:
         obj['version']
         obj['filename']
     filename_size would be obtained with len(obj['filename']).
     JarStruct subclasses instances can be either initialized from existing data
     (deserialized), or with empty fields.
     '''
     TYPE_MAPPING = {'uint32': ('I', 4), 'uint16': ('H', 2)}
     def __init__(self, data=None):
         '''
         Create an instance from the given data. Data may be omitted to create
         an instance with empty fields.
         '''
         assert self.MAGIC and isinstance(self.STRUCT, OrderedDict)
         self.size_fields = set(t for t in self.STRUCT.itervalues()
                                if not t in JarStruct.TYPE_MAPPING)
         self._values = {}
         if data:
             self._init_data(data)
         else:
             self._init_empty()
     def _init_data(self, data):
         '''
         Initialize an instance from data, following the data structure
         described in self.STRUCT. The self.MAGIC signature is expected at
         data[:4].
         '''
         assert data is not None
         self.signature, size = JarStruct.get_data('uint32', data)
         if self.signature != self.MAGIC:
             raise JarReaderError('Bad magic')
         offset = size
         # For all fields used as other fields sizes, keep track of their value
         # separately.
         sizes = dict((t, 0) for t in self.size_fields)
         for name, t in self.STRUCT.iteritems():
             if t in JarStruct.TYPE_MAPPING:
                 value, size = JarStruct.get_data(t, data[offset:])
             else:
                 size = sizes[t]
                 value = data[offset:offset + size]
                 if isinstance(value, memoryview):
                     value = value.tobytes()
             if not name in sizes:
                 self._values[name] = value
             else:
                 sizes[name] = value
             offset += size
     def _init_empty(self):
         '''
         Initialize an instance with empty fields.
         '''
         self.signature = self.MAGIC
         for name, t in self.STRUCT.iteritems():
             if name in self.size_fields:
                 continue
             self._values[name] = 0 if t in JarStruct.TYPE_MAPPING else ''
     @staticmethod
     def get_data(type, data):
         '''
         Deserialize a single field of given type (must be one of
         JarStruct.TYPE_MAPPING) at the given offset in the given data.
         '''
         assert type in JarStruct.TYPE_MAPPING
         assert data is not None
         format, size = JarStruct.TYPE_MAPPING[type]
         data = data[:size]
         if isinstance(data, memoryview):
             data = data.tobytes()
         return struct.unpack('<' + format, data)[0], size
     def serialize(self):
         '''
         Serialize the data structure according to the data structure definition
         from self.STRUCT.
         '''
         serialized = struct.pack('<I', self.signature)
         sizes = dict((t, name) for name, t in self.STRUCT.iteritems()
                      if not t in JarStruct.TYPE_MAPPING)
         for name, t in self.STRUCT.iteritems():
             if t in JarStruct.TYPE_MAPPING:
                 format, size = JarStruct.TYPE_MAPPING[t]
                 if name in sizes:
                     value = len(self[sizes[name]])
                 else:
                     value = self[name]
                 serialized += struct.pack('<' + format, value)
             else:
                 serialized += self[name]
         return serialized
     @property
     def size(self):
         '''
         Return the size of the data structure, given the current values of all
         variable length fields.
         '''
         size = JarStruct.TYPE_MAPPING['uint32'][1]
         for name, type in self.STRUCT.iteritems():
             if type in JarStruct.TYPE_MAPPING:
                 size += JarStruct.TYPE_MAPPING[type][1]
             else:
                 size += len(self[name])
         return size
     def __getitem__(self, key):
         return self._values[key]
     def __setitem__(self, key, value):
         if not key in self.STRUCT:
             raise KeyError(key)
         if key in self.size_fields:
             raise AttributeError("can't set attribute")
         self._values[key] = value
     def __contains__(self, key):
         return key in self._values
     def __iter__(self):
         return self._values.iteritems()
     def __repr__(self):
         return "<%s %s>" % (self.__class__.__name__,
                             ' '.join('%s=%s' % (n, v) for n, v in self))
 class JarCdirEnd(JarStruct):
     '''
     End of central directory record.
     '''
     MAGIC = 0x06054b50
     STRUCT = OrderedDict([
         ('disk_num', 'uint16'),
         ('cdir_disk', 'uint16'),
         ('disk_entries', 'uint16'),
         ('cdir_entries', 'uint16'),
         ('cdir_size', 'uint32'),
         ('cdir_offset', 'uint32'),
         ('comment_size', 'uint16'),
         ('comment', 'comment_size'),
     ])
 CDIR_END_SIZE = JarCdirEnd().size
 class JarCdirEntry(JarStruct):
     '''
     Central directory file header
     '''
     MAGIC = 0x02014b50
     STRUCT = OrderedDict([
         ('creator_version', 'uint16'),
         ('min_version', 'uint16'),
         ('general_flag', 'uint16'),
         ('compression', 'uint16'),
         ('lastmod_time', 'uint16'),
         ('lastmod_date', 'uint16'),
         ('crc32', 'uint32'),
         ('compressed_size', 'uint32'),
         ('uncompressed_size', 'uint32'),
         ('filename_size', 'uint16'),
         ('extrafield_size', 'uint16'),
         ('filecomment_size', 'uint16'),
         ('disknum', 'uint16'),
         ('internal_attr', 'uint16'),
         ('external_attr', 'uint32'),
         ('offset', 'uint32'),
         ('filename', 'filename_size'),
         ('extrafield', 'extrafield_size'),
         ('filecomment', 'filecomment_size'),
     ])
 class JarLocalFileHeader(JarStruct):
     '''
     Local file header
     '''
     MAGIC = 0x04034b50
     STRUCT = OrderedDict([
         ('min_version', 'uint16'),
         ('general_flag', 'uint16'),
         ('compression', 'uint16'),
         ('lastmod_time', 'uint16'),
         ('lastmod_date', 'uint16'),
         ('crc32', 'uint32'),
         ('compressed_size', 'uint32'),
         ('uncompressed_size', 'uint32'),
         ('filename_size', 'uint16'),
         ('extra_field_size', 'uint16'),
         ('filename', 'filename_size'),
         ('extra_field', 'extra_field_size'),
     ])
 class JarFileReader(object):
     '''
     File-like class for use by JarReader to give access to individual files
     within a Jar archive.
     '''
     def __init__(self, header, data):
         '''
         Initialize a JarFileReader. header is the local file header
         corresponding to the file in the jar archive, data a buffer containing
         the file data.
         '''
         assert header['compression'] in [JAR_DEFLATED, JAR_STORED]
         self._data = data
         # Copy some local file header fields.
         for name in ['filename', 'compressed_size',
                      'uncompressed_size', 'crc32']:
             setattr(self, name, header[name])
         self.compressed = header['compression'] == JAR_DEFLATED
     def read(self, length=-1):
         '''
         Read some amount of uncompressed data.
         '''
         return self.uncompressed_data.read(length)
     def readlines(self):
         '''
         Return a list containing all the lines of data in the uncompressed
         data.
         '''
         return self.read().splitlines(True)
     def __iter__(self):
         '''
         Iterator, to support the "for line in fileobj" constructs.
         '''
         return iter(self.readlines())
     def seek(self, pos, whence=os.SEEK_SET):
         '''
         Change the current position in the uncompressed data. Subsequent reads
         will start from there.
         '''
         return self.uncompressed_data.seek(pos, whence)
     def close(self):
         '''
         Free the uncompressed data buffer.
         '''
         self.uncompressed_data.close()
     @property
     def compressed_data(self):
         '''
         Return the raw compressed data.
         '''
         return self._data[:self.compressed_size]
     @property
     def uncompressed_data(self):
         '''
         Return the uncompressed data.
         '''
         if hasattr(self, '_uncompressed_data'):
             return self._uncompressed_data
         data = self.compressed_data
         if self.compressed:
             data = zlib.decompress(data.tobytes(), -MAX_WBITS)
         else:
             data = data.tobytes()
         if len(data) != self.uncompressed_size:
             raise JarReaderError('Corrupted file? %s' % self.filename)
         self._uncompressed_data = BytesIO(data)
         return self._uncompressed_data
 class JarReader(object):
     '''
     Class with methods to read Jar files. Can open standard jar files as well
     as Mozilla jar files (see further details in the JarWriter documentation).
     '''
     def __init__(self, file=None, fileobj=None):
         '''
         Opens the given file as a Jar archive. Use the given file-like object
         if one is given instead of opening the given file name.
         '''
         if fileobj:
             data = fileobj.read()
         else:
             data = open(file, 'rb').read()
         self._data = memoryview(data)
         # The End of Central Directory Record has a variable size because of
         # comments it may contain, so scan for it from the end of the file.
         offset = -CDIR_END_SIZE
         while True:
             signature = JarStruct.get_data('uint32', self._data[offset:])[0]
             if signature == JarCdirEnd.MAGIC:
                 break
             if offset == -len(self._data):
                 raise JarReaderError('Not a jar?')
             offset -= 1
         self._cdir_end = JarCdirEnd(self._data[offset:])
     def close(self):
         '''
         Free some resources associated with the Jar.
         '''
         del self._data
     @property
     def entries(self):
         '''
         Return an ordered dict of central directory entries, indexed by
         filename, in the order they appear in the Jar archive central
         directory. Directory entries are skipped.
         '''
         if hasattr(self, '_entries'):
             return self._entries
         preload = 0
         if self.is_optimized:
             preload = JarStruct.get_data('uint32', self._data)[0]
         entries = OrderedDict()
         offset = self._cdir_end['cdir_offset']
         for e in xrange(self._cdir_end['cdir_entries']):
             entry = JarCdirEntry(self._data[offset:])
             offset += entry.size
             # Creator host system. 0 is MSDOS, 3 is Unix
             host = entry['creator_version'] >> 8
             # External attributes values depend on host above. On Unix the
             # higher bits are the stat.st_mode value. On MSDOS, the lower bits
             # are the FAT attributes.
             xattr = entry['external_attr']
             # Skip directories
             if (host == 0 and xattr & 0x10) or (host == 3 and
                                                 xattr & (040000 << 16)):
                 continue
             entries[entry['filename']] = entry
             if entry['offset'] < preload:
                 self._last_preloaded = entry['filename']
         self._entries = entries
         return entries
     @property
     def is_optimized(self):
         '''
         Return whether the jar archive is optimized.
         '''
         # In optimized jars, the central directory is at the beginning of the
         # file, after a single 32-bits value, which is the length of data
         # preloaded.
         return self._cdir_end['cdir_offset'] == \
             JarStruct.TYPE_MAPPING['uint32'][1]
     @property
     def last_preloaded(self):
         '''
         Return the name of the last file that is set to be preloaded.
         See JarWriter documentation for more details on preloading.
         '''
         if hasattr(self, '_last_preloaded'):
             return self._last_preloaded
         self._last_preloaded = None
         self.entries
         return self._last_preloaded
     def _getreader(self, entry):
         '''
         Helper to create a JarFileReader corresponding to the given central
         directory entry.
         '''
         header = JarLocalFileHeader(self._data[entry['offset']:])
         for key, value in entry:
             if key in header and header[key] != value:
                 raise JarReaderError('Central directory and file header ' +
                                      'mismatch. Corrupted archive?')
         return JarFileReader(header,
                              self._data[entry['offset'] + header.size:])
     def __iter__(self):
         '''
         Iterate over all files in the Jar archive, in the form of
         JarFileReaders.
             for file in jarReader:
                 ...
         '''
         for entry in self.entries.itervalues():
             yield self._getreader(entry)
     def __getitem__(self, name):
         '''
         Get a JarFileReader for the given file name.
         '''
         return self._getreader(self.entries[name])
     def __contains__(self, name):
         '''
         Return whether the given file name appears in the Jar archive.
         '''
         return name in self.entries
 class JarWriter(object):
     '''
     Class with methods to write Jar files. Can write more-or-less standard jar
     archives as well as jar archives optimized for Gecko. See the documentation
     for the close() member function for a description of both layouts.
     '''
     def __init__(self, file=None, fileobj=None, compress=True, optimize=True):
         '''
         Initialize a Jar archive in the given file. Use the given file-like
         object if one is given instead of opening the given file name.
         The compress option determines the default behavior for storing data
         in the jar archive. The optimize options determines whether the jar
         archive should be optimized for Gecko or not.
         '''
         if fileobj:
             self._data = fileobj
         else:
             self._data = open(file, 'wb')
         self._compress = compress
         self._contents = OrderedDict()
         self._last_preloaded = None
         self._optimize = optimize
     def __enter__(self):
         '''
         Context manager __enter__ method for JarWriter.
         '''
         return self
     def __exit__(self, type, value, tb):
         '''
         Context manager __exit__ method for JarWriter.
         '''
         self.finish()
     def finish(self):
         '''
         Flush and close the Jar archive.
         Standard jar archives are laid out like the following:
             - Local file header 1
             - File data 1
             - Local file header 2
             - File data 2
             - (...)
             - Central directory entry pointing at Local file header 1
             - Central directory entry pointing at Local file header 2
             - (...)
             - End of central directory, pointing at first central directory
               entry.
         Jar archives optimized for Gecko are laid out like the following:
             - 32-bits unsigned integer giving the amount of data to preload.
             - Central directory entry pointing at Local file header 1
             - Central directory entry pointing at Local file header 2
             - (...)
             - End of central directory, pointing at first central directory
               entry.
             - Local file header 1
             - File data 1
             - Local file header 2
             - File data 2
             - (...)
             - End of central directory, pointing at first central directory
               entry.
         The duplication of the End of central directory is to accomodate some
         Zip reading tools that want an end of central directory structure to
         follow the central directory entries.
         '''
         offset = 0
         headers = {}
         preload_size = 0
         # Prepare central directory entries
         for entry, content in self._contents.itervalues():
             header = JarLocalFileHeader()
             for name in entry.STRUCT:
                 if name in header:
                     header[name] = entry[name]
             entry['offset'] = offset
             offset += len(content) + header.size
             if entry['filename'] == self._last_preloaded:
                 preload_size = offset
             headers[entry] = header
         # Prepare end of central directory
         end = JarCdirEnd()
         end['disk_entries'] = len(self._contents)
         end['cdir_entries'] = end['disk_entries']
         end['cdir_size'] = reduce(lambda x, y: x + y[0].size,
                                   self._contents.values(), 0)
         # On optimized archives, store the preloaded size and the central
         # directory entries, followed by the first end of central directory.
         if self._optimize:
             end['cdir_offset'] = 4
             offset = end['cdir_size'] + end['cdir_offset'] + end.size
             if preload_size:
                 preload_size += offset
             self._data.write(struct.pack('<I', preload_size))
             for entry, _ in self._contents.itervalues():
                 entry['offset'] += offset
                 self._data.write(entry.serialize())
             self._data.write(end.serialize())
         # Store local file entries followed by compressed data
         for entry, content in self._contents.itervalues():
             self._data.write(headers[entry].serialize())
             self._data.write(content)
         # On non optimized archives, store the central directory entries.
         if not self._optimize:
             end['cdir_offset'] = offset
             for entry, _ in self._contents.itervalues():
                 self._data.write(entry.serialize())
         # Store the end of central directory.
         self._data.write(end.serialize())
         self._data.close()
     def add(self, name, data, compress=None, mode=None):
         '''
         Add a new member to the jar archive, with the given name and the given
         data.
         The compress option indicates if the given data should be compressed
         (True), not compressed (False), or compressed according to the default
         defined when creating the JarWriter (None).
         When the data should be compressed (True or None with self.compress ==
         True), it is only really compressed if the compressed size is smaller
         than the uncompressed size.
         The mode option gives the unix permissions that should be stored
         for the jar entry.
         The given data may be a buffer, a file-like instance, a Deflater or a
         JarFileReader instance. The latter two allow to avoid uncompressing
         data to recompress it.
         '''
         if name in self._contents:
             raise JarWriterError("File %s already in JarWriter" % name)
         if compress is None:
             compress = self._compress
         if (isinstance(data, JarFileReader) and data.compressed == compress) \
                 or (isinstance(data, Deflater) and data.compress == compress):
             deflater = data
         else:
             deflater = Deflater(compress)
             if isinstance(data, basestring):
                 deflater.write(data)
             elif hasattr(data, 'read'):
                 data.seek(0)
                 deflater.write(data.read())
             else:
                 raise JarWriterError("Don't know how to handle %s" %
                                      type(data))
         # Fill a central directory entry for this new member.
         entry = JarCdirEntry()
         entry['creator_version'] = 20
         if mode is not None:
             # Set creator host system (upper byte of creator_version)
             # to 3 (Unix) so mode is honored when there is one.
             entry['creator_version'] |= 3 << 8
             entry['external_attr'] = (mode & 0xFFFF) << 16L
         if deflater.compressed:
             entry['min_version'] = 20  # Version 2.0 supports deflated streams
             entry['general_flag'] = 2  # Max compression
             entry['compression'] = JAR_DEFLATED
         else:
             entry['min_version'] = 10  # Version 1.0 for stored streams
             entry['general_flag'] = 0
             entry['compression'] = JAR_STORED
         # January 1st, 2010. See bug 592369.
         entry['lastmod_date'] = ((2010 - 1980) << 9) | (1 << 5) | 1
         entry['lastmod_time'] = 0
         entry['crc32'] = deflater.crc32
         entry['compressed_size'] = deflater.compressed_size
         entry['uncompressed_size'] = deflater.uncompressed_size
         entry['filename'] = name
         self._contents[name] = entry, deflater.compressed_data
     def preload(self, files):
         '''
         Set which members of the jar archive should be preloaded when opening
         the archive in Gecko. This reorders the members according to the order
         of given list.
         '''
         new_contents = OrderedDict()
         for f in files:
             if not f in self._contents:
                 continue
             new_contents[f] = self._contents[f]
             self._last_preloaded = f
         for f in self._contents:
             if not f in new_contents:
                 new_contents[f] = self._contents[f]
         self._contents = new_contents
 class Deflater(object):
     '''
     File-like interface to zlib compression. The data is actually not
     compressed unless the compressed form is smaller than the uncompressed
     data.
     '''
     def __init__(self, compress=True):
         '''
         Initialize a Deflater. The compress argument determines whether to
         try to compress at all.
         '''
         self._data = BytesIO()
         self.compress = compress
         if compress:
             self._deflater = zlib.compressobj(9, zlib.DEFLATED, -MAX_WBITS)
             self._deflated = BytesIO()
         else:
             self._deflater = None
     def write(self, data):
         '''
         Append a buffer to the Deflater.
         '''
         self._data.write(data)
         if self.compress:
             if self._deflater:
                 if isinstance(data, memoryview):
                     data = data.tobytes()
                 self._deflated.write(self._deflater.compress(data))
             else:
                 raise JarWriterError("Can't write after flush")
     def close(self):
         '''
         Close the Deflater.
         '''
         self._data.close()
         if self.compress:
             self._deflated.close()
     def _flush(self):
         '''
         Flush the underlying zlib compression object.
         '''
         if self.compress and self._deflater:
             self._deflated.write(self._deflater.flush())
             self._deflater = None
     @property
     def compressed(self):
         '''
         Return whether the data should be compressed.
         '''
         return self._compressed_size < self.uncompressed_size
     @property
     def _compressed_size(self):
         '''
         Return the real compressed size of the data written to the Deflater. If
         the Deflater is set not to compress, the uncompressed size is returned.
         Otherwise, the actual compressed size is returned, whether or not it is
         a win over the uncompressed size.
         '''
         if self.compress:
             self._flush()
             return self._deflated.tell()
         return self.uncompressed_size
     @property
     def compressed_size(self):
         '''
         Return the compressed size of the data written to the Deflater. If the
         Deflater is set not to compress, the uncompressed size is returned.
         Otherwise, if the data should not be compressed (the real compressed
         size is bigger than the uncompressed size), return the uncompressed
         size.
         '''
         if self.compressed:
             return self._compressed_size
         return self.uncompressed_size
     @property
     def uncompressed_size(self):
         '''
         Return the size of the data written to the Deflater.
         '''
         return self._data.tell()
     @property
     def crc32(self):
         '''
         Return the crc32 of the data written to the Deflater.
         '''
         return zlib.crc32(self._data.getvalue()) & 0xffffffff
     @property
     def compressed_data(self):
         '''
         Return the compressed data, if the data should be compressed (real
         compressed size smaller than the uncompressed size), or the
         uncompressed data otherwise.
         '''
         if self.compressed:
             return self._deflated.getvalue()
         return self._data.getvalue()
 class JarLog(dict):
     '''
     Helper to read the file Gecko generates when setting MOZ_JAR_LOG_FILE.
     The jar log is then available as a dict with the jar path as key (see
     canonicalize for more details on the key value), and the corresponding
     access log as a list value. Only the first access to a given member of
     a jar is stored.
     '''
     def __init__(self, file=None, fileobj=None):
         if not fileobj:
             fileobj = open(file, 'r')
         urlmap = {}
         for line in fileobj:
             url, path = line.strip().split(None, 1)
             if not url or not path:
                 continue
             if url not in urlmap:
                 urlmap[url] = JarLog.canonicalize(url)
             jar = urlmap[url]
             entry = self.setdefault(jar, [])
             if path not in entry:
                 entry.append(path)
     @staticmethod
     def canonicalize(url):
         '''
         The jar path is stored in a MOZ_JAR_LOG_FILE log as a url. This method
         returns a unique value corresponding to such urls.
         - file:///{path} becomes {path}
         - jar:file:///{path}!/{subpath} becomes ({path}, {subpath})
         - jar:jar:file:///{path}!/{subpath}!/{subpath2} becomes
            ({path}, {subpath}, {subpath2})
         '''
         if not isinstance(url, ParseResult):
             # Assume that if it doesn't start with jar: or file:, it's a path.
             if not url.startswith(('jar:', 'file:')):
                 url = 'file:///' + os.path.abspath(url)
             url = urlparse(url)
         assert url.scheme
         assert url.scheme in ('jar', 'file')
         if url.scheme == 'jar':
             path = JarLog.canonicalize(url.path)
             if isinstance(path, tuple):
                 return path[:-1] + tuple(path[-1].split('!/', 1))
             return tuple(path.split('!/', 1))
         if url.scheme == 'file':
             assert os.path.isabs(url.path)
             path = url.path
             # On Windows, url.path will be /drive:/path ; on Unix systems,
             # /path. As we want drive:/path instead of /drive:/path on Windows,
             # remove the leading /.
             if os.path.isabs(path[1:]):
                 path = path[1:]
             path = os.path.realpath(path)
             return mozpack.path.normsep(os.path.normcase(path))

The Tor Browser / annotate

python/mozbuild/mozpack/mozjar.py@6474c204b198 (annotated)

python/mozbuild/mozpack/mozjar.py