xref: /external/fonttools/Lib/fontTools/ttLib/sfnt.py

"""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 to number of tables changes or whenever
a table's length chages you need to rewrite the whole file anyway.
"""

from io import BytesIO
from types import SimpleNamespace
from fontTools.misc.py23 import Tag
from fontTools.misc import sstruct
from fontTools.ttLib import TTLibError
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 TTLibError("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('\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.
	Optionally takes a 'start' argument, which allows you to
	calculate a checksum in chunks by feeding it a previous
	result.

	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)