# Source code for fontTools.ttLib.sfnt

    """ttLib/sfnt.py -- low-level module to deal with the sfnt file format.

    Defines two public classes:

    - SFNTReader
    - SFNTWriter

    (Normally you don't have to use these classes explicitly; they are
    used automatically by ttLib.TTFont.)

    The reading and writing of sfnt files is separated in two distinct
    classes, since whenever the number of tables changes or whenever
    a table's length changes you need to rewrite the whole file anyway.
    """

    from io import BytesIO
    from types import SimpleNamespace
    from fontTools.misc.textTools import Tag
    from fontTools.misc import sstruct
    from fontTools.ttLib import TTLibError, TTLibFileIsCollectionError
    import struct
    from collections import OrderedDict
    import logging

    log = logging.getLogger(__name__)

    class SFNTReader(object):
        def __new__(cls, *args, **kwargs):
            """Return an instance of the SFNTReader sub-class which is compatible
            with the input file type.
            """
            if args and cls is SFNTReader:
                infile = args[0]
                infile.seek(0)
                sfntVersion = Tag(infile.read(4))
                infile.seek(0)
                if sfntVersion == "wOF2":
                    # return new WOFF2Reader object
                    from fontTools.ttLib.woff2 import WOFF2Reader

                    return object.__new__(WOFF2Reader)
            # return default object
            return object.__new__(cls)

        def __init__(self, file, checkChecksums=0, fontNumber=-1):
            self.file = file
            self.checkChecksums = checkChecksums

            self.flavor = None
            self.flavorData = None
            self.DirectoryEntry = SFNTDirectoryEntry
            self.file.seek(0)
            self.sfntVersion = self.file.read(4)
            self.file.seek(0)
            if self.sfntVersion == b"ttcf":
                header = readTTCHeader(self.file)
                numFonts = header.numFonts
                if not 0 <= fontNumber < numFonts:
                    raise TTLibFileIsCollectionError(
                        "specify a font number between 0 and %d (inclusive)"
                        % (numFonts - 1)
                    )
                self.numFonts = numFonts
                self.file.seek(header.offsetTable[fontNumber])
                data = self.file.read(sfntDirectorySize)
                if len(data) != sfntDirectorySize:
                    raise TTLibError("Not a Font Collection (not enough data)")
                sstruct.unpack(sfntDirectoryFormat, data, self)
            elif self.sfntVersion == b"wOFF":
                self.flavor = "woff"
                self.DirectoryEntry = WOFFDirectoryEntry
                data = self.file.read(woffDirectorySize)
                if len(data) != woffDirectorySize:
                    raise TTLibError("Not a WOFF font (not enough data)")
                sstruct.unpack(woffDirectoryFormat, data, self)
            else:
                data = self.file.read(sfntDirectorySize)
                if len(data) != sfntDirectorySize:
                    raise TTLibError("Not a TrueType or OpenType font (not enough data)")
                sstruct.unpack(sfntDirectoryFormat, data, self)
            self.sfntVersion = Tag(self.sfntVersion)

            if self.sfntVersion not in ("\x00\x01\x00\x00", "OTTO", "true"):
                raise TTLibError("Not a TrueType or OpenType font (bad sfntVersion)")
            tables = {}
            for i in range(self.numTables):
                entry = self.DirectoryEntry()
                entry.fromFile(self.file)
                tag = Tag(entry.tag)
                tables[tag] = entry
            self.tables = OrderedDict(sorted(tables.items(), key=lambda i: i[1].offset))

            # Load flavor data if any
            if self.flavor == "woff":
                self.flavorData = WOFFFlavorData(self)

        def has_key(self, tag):
            return tag in self.tables

        __contains__ = has_key

        def keys(self):
            return self.tables.keys()

        def __getitem__(self, tag):
            """Fetch the raw table data."""
            entry = self.tables[Tag(tag)]
            data = entry.loadData(self.file)
            if self.checkChecksums:
                if tag == "head":
                    # Beh: we have to special-case the 'head' table.
                    checksum = calcChecksum(data[:8] + b"\0\0\0\0" + data[12:])
                else:
                    checksum = calcChecksum(data)
                if self.checkChecksums > 1:
                    # Be obnoxious, and barf when it's wrong
                    assert checksum == entry.checkSum, "bad checksum for '%s' table" % tag
                elif checksum != entry.checkSum:
                    # Be friendly, and just log a warning.
                    log.warning("bad checksum for '%s' table", tag)
            return data

        def __delitem__(self, tag):
            del self.tables[Tag(tag)]

        def close(self):
            self.file.close()

        # We define custom __getstate__ and __setstate__ to make SFNTReader pickle-able
        # and deepcopy-able. When a TTFont is loaded as lazy=True, SFNTReader holds a
        # reference to an external file object which is not pickleable. So in __getstate__
        # we store the file name and current position, and in __setstate__ we reopen the
        # same named file after unpickling.

        def __getstate__(self):
            if isinstance(self.file, BytesIO):
                # BytesIO is already pickleable, return the state unmodified
                return self.__dict__

            # remove unpickleable file attribute, and only store its name and pos
            state = self.__dict__.copy()
            del state["file"]
            state["_filename"] = self.file.name
            state["_filepos"] = self.file.tell()
            return state

        def __setstate__(self, state):
            if "file" not in state:
                self.file = open(state.pop("_filename"), "rb")
                self.file.seek(state.pop("_filepos"))
            self.__dict__.update(state)

    # default compression level for WOFF 1.0 tables and metadata
    ZLIB_COMPRESSION_LEVEL = 6

    # if set to True, use zopfli instead of zlib for compressing WOFF 1.0.
    # The Python bindings are available at https://pypi.python.org/pypi/zopfli
    USE_ZOPFLI = False

    # mapping between zlib's compression levels and zopfli's 'numiterations'.
    # Use lower values for files over several MB in size or it will be too slow
    ZOPFLI_LEVELS = {
        # 0: 0,  # can't do 0 iterations...
        1: 1,
        2: 3,
        3: 5,
        4: 8,
        5: 10,
        6: 15,
        7: 25,
        8: 50,
        9: 100,
    }

    def compress(data, level=ZLIB_COMPRESSION_LEVEL):
        """Compress 'data' to Zlib format. If 'USE_ZOPFLI' variable is True,
        zopfli is used instead of the zlib module.
        The compression 'level' must be between 0 and 9. 1 gives best speed,
        9 gives best compression (0 gives no compression at all).
        The default value is a compromise between speed and compression (6).
        """
        if not (0 <= level <= 9):
            raise ValueError("Bad compression level: %s" % level)
        if not USE_ZOPFLI or level == 0:
            from zlib import compress

            return compress(data, level)
        else:
            from zopfli.zlib import compress

            return compress(data, numiterations=ZOPFLI_LEVELS[level])

    class SFNTWriter(object):
        def __new__(cls, *args, **kwargs):
            """Return an instance of the SFNTWriter sub-class which is compatible
            with the specified 'flavor'.
            """
            flavor = None
            if kwargs and "flavor" in kwargs:
                flavor = kwargs["flavor"]
            elif args and len(args) > 3:
                flavor = args[3]
            if cls is SFNTWriter:
                if flavor == "woff2":
                    # return new WOFF2Writer object
                    from fontTools.ttLib.woff2 import WOFF2Writer

                    return object.__new__(WOFF2Writer)
            # return default object
            return object.__new__(cls)

        def __init__(
            self,
            file,
            numTables,
            sfntVersion="\000\001\000\000",
            flavor=None,
            flavorData=None,
        ):
            self.file = file
            self.numTables = numTables
            self.sfntVersion = Tag(sfntVersion)
            self.flavor = flavor
            self.flavorData = flavorData

            if self.flavor == "woff":
                self.directoryFormat = woffDirectoryFormat
                self.directorySize = woffDirectorySize
                self.DirectoryEntry = WOFFDirectoryEntry

                self.signature = "wOFF"

                # to calculate WOFF checksum adjustment, we also need the original SFNT offsets
                self.origNextTableOffset = (
                    sfntDirectorySize + numTables * sfntDirectoryEntrySize
                )
            else:
                assert not self.flavor, "Unknown flavor '%s'" % self.flavor
                self.directoryFormat = sfntDirectoryFormat
                self.directorySize = sfntDirectorySize
                self.DirectoryEntry = SFNTDirectoryEntry

                from fontTools.ttLib import getSearchRange

                self.searchRange, self.entrySelector, self.rangeShift = getSearchRange(
                    numTables, 16
                )

            self.directoryOffset = self.file.tell()
            self.nextTableOffset = (
                self.directoryOffset
                + self.directorySize
                + numTables * self.DirectoryEntry.formatSize
            )
            # clear out directory area
            self.file.seek(self.nextTableOffset)
            # make sure we're actually where we want to be. (old cStringIO bug)
            self.file.write(b"\0" * (self.nextTableOffset - self.file.tell()))
            self.tables = OrderedDict()

        def setEntry(self, tag, entry):
            if tag in self.tables:
                raise TTLibError("cannot rewrite '%s' table" % tag)

            self.tables[tag] = entry

        def __setitem__(self, tag, data):
            """Write raw table data to disk."""
            if tag in self.tables:
                raise TTLibError("cannot rewrite '%s' table" % tag)

            entry = self.DirectoryEntry()
            entry.tag = tag
            entry.offset = self.nextTableOffset
            if tag == "head":
                entry.checkSum = calcChecksum(data[:8] + b"\0\0\0\0" + data[12:])
                self.headTable = data
                entry.uncompressed = True
            else:
                entry.checkSum = calcChecksum(data)
            entry.saveData(self.file, data)

            if self.flavor == "woff":
                entry.origOffset = self.origNextTableOffset
                self.origNextTableOffset += (entry.origLength + 3) & ~3

            self.nextTableOffset = self.nextTableOffset + ((entry.length + 3) & ~3)
            # Add NUL bytes to pad the table data to a 4-byte boundary.
            # Don't depend on f.seek() as we need to add the padding even if no
            # subsequent write follows (seek is lazy), ie. after the final table
            # in the font.
            self.file.write(b"\0" * (self.nextTableOffset - self.file.tell()))
            assert self.nextTableOffset == self.file.tell()

            self.setEntry(tag, entry)

        def __getitem__(self, tag):
            return self.tables[tag]

        def close(self):
            """All tables must have been written to disk. Now write the
            directory.
            """
            tables = sorted(self.tables.items())
            if len(tables) != self.numTables:
                raise TTLibError(
                    "wrong number of tables; expected %d, found %d"
                    % (self.numTables, len(tables))
                )

            if self.flavor == "woff":
                self.signature = b"wOFF"
                self.reserved = 0

                self.totalSfntSize = 12
                self.totalSfntSize += 16 * len(tables)
                for tag, entry in tables:
                    self.totalSfntSize += (entry.origLength + 3) & ~3

                data = self.flavorData if self.flavorData else WOFFFlavorData()
                if data.majorVersion is not None and data.minorVersion is not None:
                    self.majorVersion = data.majorVersion
                    self.minorVersion = data.minorVersion
                else:
                    if hasattr(self, "headTable"):
                        self.majorVersion, self.minorVersion = struct.unpack(
                            ">HH", self.headTable[4:8]
                        )
                    else:
                        self.majorVersion = self.minorVersion = 0
                if data.metaData:
                    self.metaOrigLength = len(data.metaData)
                    self.file.seek(0, 2)
                    self.metaOffset = self.file.tell()
                    compressedMetaData = compress(data.metaData)
                    self.metaLength = len(compressedMetaData)
                    self.file.write(compressedMetaData)
                else:
                    self.metaOffset = self.metaLength = self.metaOrigLength = 0
                if data.privData:
                    self.file.seek(0, 2)
                    off = self.file.tell()
                    paddedOff = (off + 3) & ~3
                    self.file.write(b"\0" * (paddedOff - off))
                    self.privOffset = self.file.tell()
                    self.privLength = len(data.privData)
                    self.file.write(data.privData)
                else:
                    self.privOffset = self.privLength = 0

                self.file.seek(0, 2)
                self.length = self.file.tell()

            else:
                assert not self.flavor, "Unknown flavor '%s'" % self.flavor
                pass

            directory = sstruct.pack(self.directoryFormat, self)

            self.file.seek(self.directoryOffset + self.directorySize)
            seenHead = 0
            for tag, entry in tables:
                if tag == "head":
                    seenHead = 1
                directory = directory + entry.toString()
            if seenHead:
                self.writeMasterChecksum(directory)
            self.file.seek(self.directoryOffset)
            self.file.write(directory)

        def _calcMasterChecksum(self, directory):
            # calculate checkSumAdjustment
            tags = list(self.tables.keys())
            checksums = []
            for i in range(len(tags)):
                checksums.append(self.tables[tags[i]].checkSum)

            if self.DirectoryEntry != SFNTDirectoryEntry:
                # Create a SFNT directory for checksum calculation purposes
                from fontTools.ttLib import getSearchRange

                self.searchRange, self.entrySelector, self.rangeShift = getSearchRange(
                    self.numTables, 16
                )
                directory = sstruct.pack(sfntDirectoryFormat, self)
                tables = sorted(self.tables.items())
                for tag, entry in tables:
                    sfntEntry = SFNTDirectoryEntry()
                    sfntEntry.tag = entry.tag
                    sfntEntry.checkSum = entry.checkSum
                    sfntEntry.offset = entry.origOffset
                    sfntEntry.length = entry.origLength
                    directory = directory + sfntEntry.toString()

            directory_end = sfntDirectorySize + len(self.tables) * sfntDirectoryEntrySize
            assert directory_end == len(directory)

            checksums.append(calcChecksum(directory))
            checksum = sum(checksums) & 0xFFFFFFFF
            # BiboAfba!
            checksumadjustment = (0xB1B0AFBA - checksum) & 0xFFFFFFFF
            return checksumadjustment

        def writeMasterChecksum(self, directory):
            checksumadjustment = self._calcMasterChecksum(directory)
            # write the checksum to the file
            self.file.seek(self.tables["head"].offset + 8)
            self.file.write(struct.pack(">L", checksumadjustment))

        def reordersTables(self):
            return False

    # -- sfnt directory helpers and cruft

    ttcHeaderFormat = """
    		> # big endian
    		TTCTag:                  4s # "ttcf"
    		Version:                 L  # 0x00010000 or 0x00020000
    		numFonts:                L  # number of fonts
    		# OffsetTable[numFonts]: L  # array with offsets from beginning of file
    		# ulDsigTag:             L  # version 2.0 only
    		# ulDsigLength:          L  # version 2.0 only
    		# ulDsigOffset:          L  # version 2.0 only
    """

    ttcHeaderSize = sstruct.calcsize(ttcHeaderFormat)

    sfntDirectoryFormat = """
    		> # big endian
    		sfntVersion:    4s
    		numTables:      H    # number of tables
    		searchRange:    H    # (max2 <= numTables)*16
    		entrySelector:  H    # log2(max2 <= numTables)
    		rangeShift:     H    # numTables*16-searchRange
    """

    sfntDirectorySize = sstruct.calcsize(sfntDirectoryFormat)

    sfntDirectoryEntryFormat = """
    		> # big endian
    		tag:            4s
    		checkSum:       L
    		offset:         L
    		length:         L
    """

    sfntDirectoryEntrySize = sstruct.calcsize(sfntDirectoryEntryFormat)

    woffDirectoryFormat = """
    		> # big endian
    		signature:      4s   # "wOFF"
    		sfntVersion:    4s
    		length:         L    # total woff file size
    		numTables:      H    # number of tables
    		reserved:       H    # set to 0
    		totalSfntSize:  L    # uncompressed size
    		majorVersion:   H    # major version of WOFF file
    		minorVersion:   H    # minor version of WOFF file
    		metaOffset:     L    # offset to metadata block
    		metaLength:     L    # length of compressed metadata
    		metaOrigLength: L    # length of uncompressed metadata
    		privOffset:     L    # offset to private data block
    		privLength:     L    # length of private data block
    """

    woffDirectorySize = sstruct.calcsize(woffDirectoryFormat)

    woffDirectoryEntryFormat = """
    		> # big endian
    		tag:            4s
    		offset:         L
    		length:         L    # compressed length
    		origLength:     L    # original length
    		checkSum:       L    # original checksum
    """

    woffDirectoryEntrySize = sstruct.calcsize(woffDirectoryEntryFormat)

    class DirectoryEntry(object):
        def __init__(self):
            self.uncompressed = False  # if True, always embed entry raw

        def fromFile(self, file):
            sstruct.unpack(self.format, file.read(self.formatSize), self)

        def fromString(self, str):
            sstruct.unpack(self.format, str, self)

        def toString(self):
            return sstruct.pack(self.format, self)

        def __repr__(self):
            if hasattr(self, "tag"):
                return "<%s '%s' at %x>" % (self.__class__.__name__, self.tag, id(self))
            else:
                return "<%s at %x>" % (self.__class__.__name__, id(self))

        def loadData(self, file):
            file.seek(self.offset)
            data = file.read(self.length)
            assert len(data) == self.length
            if hasattr(self.__class__, "decodeData"):
                data = self.decodeData(data)
            return data

        def saveData(self, file, data):
            if hasattr(self.__class__, "encodeData"):
                data = self.encodeData(data)
            self.length = len(data)
            file.seek(self.offset)
            file.write(data)

        def decodeData(self, rawData):
            return rawData

        def encodeData(self, data):
            return data

    class SFNTDirectoryEntry(DirectoryEntry):
        format = sfntDirectoryEntryFormat
        formatSize = sfntDirectoryEntrySize

    class WOFFDirectoryEntry(DirectoryEntry):
        format = woffDirectoryEntryFormat
        formatSize = woffDirectoryEntrySize

        def __init__(self):
            super(WOFFDirectoryEntry, self).__init__()
            # With fonttools<=3.1.2, the only way to set a different zlib
            # compression level for WOFF directory entries was to set the class
            # attribute 'zlibCompressionLevel'. This is now replaced by a globally
            # defined `ZLIB_COMPRESSION_LEVEL`, which is also applied when
            # compressing the metadata. For backward compatibility, we still
            # use the class attribute if it was already set.
            if not hasattr(WOFFDirectoryEntry, "zlibCompressionLevel"):
                self.zlibCompressionLevel = ZLIB_COMPRESSION_LEVEL

        def decodeData(self, rawData):
            import zlib

            if self.length == self.origLength:
                data = rawData
            else:
                assert self.length < self.origLength
                data = zlib.decompress(rawData)
                assert len(data) == self.origLength
            return data

        def encodeData(self, data):
            self.origLength = len(data)
            if not self.uncompressed:
                compressedData = compress(data, self.zlibCompressionLevel)
            if self.uncompressed or len(compressedData) >= self.origLength:
                # Encode uncompressed
                rawData = data
                self.length = self.origLength
            else:
                rawData = compressedData
                self.length = len(rawData)
            return rawData

    class WOFFFlavorData:
        Flavor = "woff"

        def __init__(self, reader=None):
            self.majorVersion = None
            self.minorVersion = None
            self.metaData = None
            self.privData = None
            if reader:
                self.majorVersion = reader.majorVersion
                self.minorVersion = reader.minorVersion
                if reader.metaLength:
                    reader.file.seek(reader.metaOffset)
                    rawData = reader.file.read(reader.metaLength)
                    assert len(rawData) == reader.metaLength
                    data = self._decompress(rawData)
                    assert len(data) == reader.metaOrigLength
                    self.metaData = data
                if reader.privLength:
                    reader.file.seek(reader.privOffset)
                    data = reader.file.read(reader.privLength)
                    assert len(data) == reader.privLength
                    self.privData = data

        def _decompress(self, rawData):
            import zlib

            return zlib.decompress(rawData)

    def calcChecksum(data):
        """Calculate the checksum for an arbitrary block of data.

        If the data length is not a multiple of four, it assumes
        it is to be padded with null byte.

                >>> print(calcChecksum(b"abcd"))
                1633837924
                >>> print(calcChecksum(b"abcdxyz"))
                3655064932
        """
        remainder = len(data) % 4
        if remainder:
            data += b"\0" * (4 - remainder)
        value = 0
        blockSize = 4096
        assert blockSize % 4 == 0
        for i in range(0, len(data), blockSize):
            block = data[i : i + blockSize]
            longs = struct.unpack(">%dL" % (len(block) // 4), block)
            value = (value + sum(longs)) & 0xFFFFFFFF
        return value

    def readTTCHeader(file):
        file.seek(0)
        data = file.read(ttcHeaderSize)
        if len(data) != ttcHeaderSize:
            raise TTLibError("Not a Font Collection (not enough data)")
        self = SimpleNamespace()
        sstruct.unpack(ttcHeaderFormat, data, self)
        if self.TTCTag != "ttcf":
            raise TTLibError("Not a Font Collection")
        assert self.Version == 0x00010000 or self.Version == 0x00020000, (
            "unrecognized TTC version 0x%08x" % self.Version
        )
        self.offsetTable = struct.unpack(
            ">%dL" % self.numFonts, file.read(self.numFonts * 4)
        )
        if self.Version == 0x00020000:
            pass  # ignoring version 2.0 signatures
        return self

    def writeTTCHeader(file, numFonts):
        self = SimpleNamespace()
        self.TTCTag = "ttcf"
        self.Version = 0x00010000
        self.numFonts = numFonts
        file.seek(0)
        file.write(sstruct.pack(ttcHeaderFormat, self))
        offset = file.tell()
        file.write(struct.pack(">%dL" % self.numFonts, *([0] * self.numFonts)))
        return offset

    if __name__ == "__main__":
        import sys
        import doctest

        sys.exit(doctest.testmod().failed)