Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 842 insertions, 0 deletions

diff --git a/python/mozbuild/mozpack/mozjar.py b/python/mozbuild/mozpack/mozjar.py
new file mode 100644
index 0000000000..6500ebfcec
--- /dev/null
+++ b/python/mozbuild/mozpack/mozjar.py
@@ -0,0 +1,842 @@
+# 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/.
+
+import os
+import struct
+import zlib
+from collections import OrderedDict
+from io import BytesIO, UnsupportedOperation
+from zipfile import ZIP_DEFLATED, ZIP_STORED
+
+import six
+
+import mozpack.path as mozpath
+from mozbuild.util import ensure_bytes
+
+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,
+
+    .. code-block:: python
+
+        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": (b"I", 4), "uint16": (b"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 six.itervalues(self.STRUCT) if t not 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 six.iteritems(self.STRUCT):
+            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 name not 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 six.iteritems(self.STRUCT):
+            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(b"<" + format, data)[0], size
+
+    def serialize(self):
+        """
+        Serialize the data structure according to the data structure definition
+        from self.STRUCT.
+        """
+        serialized = struct.pack(b"<I", self.signature)
+        sizes = dict(
+            (t, name)
+            for name, t in six.iteritems(self.STRUCT)
+            if t not in JarStruct.TYPE_MAPPING
+        )
+        for name, t in six.iteritems(self.STRUCT):
+            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(b"<" + format, value)
+            else:
+                serialized += ensure_bytes(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 six.iteritems(self.STRUCT):
+            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 key not 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 six.iteritems(self._values)
+
+    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 ["compressed_size", "uncompressed_size", "crc32"]:
+            setattr(self, name, header[name])
+        self.filename = six.ensure_text(header["filename"])
+        self.compressed = header["compression"] != JAR_STORED
+        self.compress = header["compression"]
+
+    def readable(self):
+        return True
+
+    def read(self, length=-1):
+        """
+        Read some amount of uncompressed data.
+        """
+        return self.uncompressed_data.read(length)
+
+    def readinto(self, b):
+        """
+        Read bytes into a pre-allocated, writable bytes-like object `b` and return
+        the number of bytes read.
+        """
+        return self.uncompressed_data.readinto(b)
+
+    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 closed(self):
+        return self.uncompressed_data.closed
+
+    @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.compress == JAR_STORED:
+            data = data.tobytes()
+        elif self.compress == JAR_DEFLATED:
+            data = zlib.decompress(data.tobytes(), -MAX_WBITS)
+        else:
+            assert False  # Can't be another value per __init__
+        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, data=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()
+        elif file:
+            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 compression(self):
+        entries = self.entries
+        if not entries:
+            return JAR_STORED
+        return max(f["compression"] for f in six.itervalues(entries))
+
+    @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 six.moves.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 & (0o040000 << 16)):
+                continue
+            entries[six.ensure_text(entry["filename"])] = entry
+            if entry["offset"] < preload:
+                self._last_preloaded = six.ensure_text(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 six.itervalues(self.entries):
+            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, compress_level=9):
+        """
+        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. ``compress_level``
+        defines the zlib compression level. It must be a value between 0 and 9
+        and defaults to 9, the highest and slowest level of compression.
+        """
+        if fileobj:
+            self._data = fileobj
+        else:
+            self._data = open(file, "wb")
+        if compress is True:
+            compress = JAR_DEFLATED
+        self._compress = compress
+        self._compress_level = compress_level
+        self._contents = OrderedDict()
+        self._last_preloaded = None
+
+    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 six.itervalues(self._contents):
+            header = JarLocalFileHeader()
+            for name in entry.STRUCT:
+                if name in header:
+                    header[name] = entry[name]
+            entry["offset"] = offset
+            offset += len(content) + header.size
+            if six.ensure_text(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"] = six.moves.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 preload_size:
+            end["cdir_offset"] = 4
+            offset = end["cdir_size"] + end["cdir_offset"] + end.size
+            preload_size += offset
+            self._data.write(struct.pack("<I", preload_size))
+            for entry, _ in six.itervalues(self._contents):
+                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 six.itervalues(self._contents):
+            self._data.write(headers[entry].serialize())
+            if isinstance(content, memoryview):
+                self._data.write(content.tobytes())
+            else:
+                self._data.write(content)
+        # On non optimized archives, store the central directory entries.
+        if not preload_size:
+            end["cdir_offset"] = offset
+            for entry, _ in six.itervalues(self._contents):
+                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, skip_duplicates=False):
+        """
+        Add a new member to the jar archive, with the given name and the given
+        data.
+        The compress option indicates how the given data should be compressed
+        (one of JAR_STORED or JAR_DEFLATE), or compressed according
+        to the default defined when creating the JarWriter (None). True and
+        False are allowed values for backwards compatibility, mapping,
+        respectively, to JAR_DEFLATE and JAR_STORED.
+        When the data should be compressed, 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, which defaults to 0o100644 (regular file, u+rw, g+r, o+r) if
+        not specified.
+        If a duplicated member is found skip_duplicates will prevent raising
+        an exception if set to True.
+        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.
+        """
+        name = mozpath.normsep(six.ensure_text(name))
+
+        if name in self._contents and not skip_duplicates:
+            raise JarWriterError("File %s already in JarWriter" % name)
+        if compress is None:
+            compress = self._compress
+        if compress is True:
+            compress = JAR_DEFLATED
+        if compress is False:
+            compress = JAR_STORED
+        if isinstance(data, (JarFileReader, Deflater)) and data.compress == compress:
+            deflater = data
+        else:
+            deflater = Deflater(compress, compress_level=self._compress_level)
+            if isinstance(data, (six.binary_type, six.string_types)):
+                deflater.write(data)
+            elif hasattr(data, "read"):
+                try:
+                    data.seek(0)
+                except (UnsupportedOperation, AttributeError):
+                    pass
+                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 None:
+            # If no mode is given, default to u+rw, g+r, o+r.
+            mode = 0o000644
+        if not mode & 0o777000:
+            # If no file type is given, default to regular file.
+            mode |= 0o100000
+        # 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) << 16
+        if deflater.compressed:
+            entry["min_version"] = 20  # Version 2.0 supports deflated streams
+            entry["general_flag"] = 2  # Max compression
+            entry["compression"] = deflater.compress
+        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"] = six.ensure_binary(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 f not in self._contents:
+                continue
+            new_contents[f] = self._contents[f]
+            self._last_preloaded = f
+        for f in self._contents:
+            if f not 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, compress_level=9):
+        """
+        Initialize a Deflater. The compress argument determines how to
+        compress.
+        """
+        self._data = BytesIO()
+        if compress is True:
+            compress = JAR_DEFLATED
+        elif compress is False:
+            compress = JAR_STORED
+        self.compress = compress
+        if compress == JAR_DEFLATED:
+            self._deflater = zlib.compressobj(compress_level, zlib.DEFLATED, -MAX_WBITS)
+            self._deflated = BytesIO()
+        else:
+            assert compress == JAR_STORED
+            self._deflater = None
+        self.crc32 = 0
+
+    def write(self, data):
+        """
+        Append a buffer to the Deflater.
+        """
+        if isinstance(data, memoryview):
+            data = data.tobytes()
+        data = six.ensure_binary(data)
+        self._data.write(data)
+
+        if self.compress:
+            if self._deflater:
+                self._deflated.write(self._deflater.compress(data))
+            else:
+                raise JarWriterError("Can't write after flush")
+
+        self.crc32 = zlib.crc32(data, self.crc32) & 0xFFFFFFFF
+
+    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 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, 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")
+        for line in fileobj:
+            jar, path = line.strip().split(None, 1)
+            if not jar or not path:
+                continue
+            entry = self.setdefault(jar, [])
+            if path not in entry:
+                entry.append(path)