Lib/fontTools/ttLib/tables/_c_m_a_p.py

from __future__ import print_function, division, absolute_import
from fontTools.misc.py23 import *
from fontTools.misc.textTools import safeEval, readHex
from . import DefaultTable
import sys
import struct
import array
import operator


class table__c_m_a_p(DefaultTable.DefaultTable):
	
	def getcmap(self, platformID, platEncID):
		for subtable in self.tables:
			if (subtable.platformID == platformID and 
					subtable.platEncID == platEncID):
				return subtable
		return None # not found
	
	def decompile(self, data, ttFont):
		tableVersion, numSubTables = struct.unpack(">HH", data[:4])
		self.tableVersion = int(tableVersion)
		self.tables = tables = []
		seenOffsets = {}
		for i in range(numSubTables):
			platformID, platEncID, offset = struct.unpack(
					">HHl", data[4+i*8:4+(i+1)*8])
			platformID, platEncID = int(platformID), int(platEncID)
			format, length = struct.unpack(">HH", data[offset:offset+4])
			if format in [8,10,12,13]:
				format, reserved, length = struct.unpack(">HHL", data[offset:offset+8])
			elif format in [14]:
				format, length = struct.unpack(">HL", data[offset:offset+6])
				
			if not length:
				print("Error: cmap subtable is reported as having zero length: platformID %s, platEncID %s,  format %s offset %s. Skipping table." % (platformID, platEncID,format, offset))
				continue
			if format not in cmap_classes:
				table = cmap_format_unknown(format)
			else:
				table = cmap_classes[format](format)
			table.platformID = platformID
			table.platEncID = platEncID
			# Note that by default we decompile only the subtable header info;
			# any other data gets decompiled only when an attribute of the
			# subtable is referenced.
			table.decompileHeader(data[offset:offset+int(length)], ttFont)
			if offset in seenOffsets:
				table.cmap = tables[seenOffsets[offset]].cmap
			else:
				seenOffsets[offset] = i
			tables.append(table)
	
	def compile(self, ttFont):
		self.tables.sort()    # sort according to the spec; see CmapSubtable.__lt__()
		numSubTables = len(self.tables)
		totalOffset = 4 + 8 * numSubTables
		data = struct.pack(">HH", self.tableVersion, numSubTables)
		tableData = b""
		seen = {}  # Some tables are the same object reference. Don't compile them twice.
		done = {}  # Some tables are different objects, but compile to the same data chunk
		for table in self.tables:
			try:
				offset = seen[id(table.cmap)]
			except KeyError:
				chunk = table.compile(ttFont)
				if chunk in done:
					offset = done[chunk]
				else:
					offset = seen[id(table.cmap)] = done[chunk] = totalOffset + len(tableData)
					tableData = tableData + chunk
			data = data + struct.pack(">HHl", table.platformID, table.platEncID, offset)
		return data + tableData
	
	def toXML(self, writer, ttFont):
		writer.simpletag("tableVersion", version=self.tableVersion)
		writer.newline()
		for table in self.tables:
			table.toXML(writer, ttFont)
	
	def fromXML(self, name, attrs, content, ttFont):
		if name == "tableVersion":
			self.tableVersion = safeEval(attrs["version"])
			return
		if name[:12] != "cmap_format_":
			return
		if not hasattr(self, "tables"):
			self.tables = []
		format = safeEval(name[12:])
		if format not in cmap_classes:
			table = cmap_format_unknown(format)
		else:
			table = cmap_classes[format](format)
		table.platformID = safeEval(attrs["platformID"])
		table.platEncID = safeEval(attrs["platEncID"])
		table.fromXML(name, attrs, content, ttFont)
		self.tables.append(table)


class CmapSubtable(object):
	
	def __init__(self, format):
		self.format = format
		self.data = None
		self.ttFont = None

	def __getattr__(self, attr):
		# allow lazy decompilation of subtables.
		if attr[:2] == '__': # don't handle requests for member functions like '__lt__'
			raise AttributeError(attr)
		if self.data is None:
			raise AttributeError(attr)
		self.decompile(None, None) # use saved data.
		self.data = None # Once this table has been decompiled, make sure we don't
						# just return the original data. Also avoids recursion when
						# called with an attribute that the cmap subtable doesn't have.
		return getattr(self, attr)
	
	def decompileHeader(self, data, ttFont):
		format, length, language = struct.unpack(">HHH", data[:6])
		assert len(data) == length, "corrupt cmap table format %d (data length: %d, header length: %d)" % (format, len(data), length)
		self.format = int(format)
		self.length = int(length)
		self.language = int(language)
		self.data = data[6:]
		self.ttFont = ttFont

	def toXML(self, writer, ttFont):
		writer.begintag(self.__class__.__name__, [
				("platformID", self.platformID),
				("platEncID", self.platEncID),
				("language", self.language),
				])
		writer.newline()
		codes = sorted(self.cmap.items())
		self._writeCodes(codes, writer)
		writer.endtag(self.__class__.__name__)
		writer.newline()

	def _writeCodes(self, codes, writer):
		if (self.platformID, self.platEncID) == (3, 1) or (self.platformID, self.platEncID) == (3, 10) or self.platformID == 0:
			from fontTools.unicode import Unicode
			isUnicode = 1
		else:
			isUnicode = 0
		for code, name in codes:
			writer.simpletag("map", code=hex(code), name=name)
			if isUnicode:
				writer.comment(Unicode[code])
			writer.newline()
	
	def __lt__(self, other):
		if not isinstance(other, CmapSubtable):
			return NotImplemented

		# implemented so that list.sort() sorts according to the spec.
		selfTuple = (
			getattr(self, "platformID", None),
			getattr(self, "platEncID", None),
			getattr(self, "language", None),
			self.__dict__)
		otherTuple = (
			getattr(other, "platformID", None),
			getattr(other, "platEncID", None),
			getattr(other, "language", None),
			other.__dict__)
		return selfTuple < otherTuple


class cmap_format_0(CmapSubtable):
	
	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"
		data = self.data # decompileHeader assigns the data after the header to self.data
		assert 262 == self.length, "Format 0 cmap subtable not 262 bytes"
		glyphIdArray = array.array("B")
		glyphIdArray.fromstring(self.data)
		self.cmap = cmap = {}
		lenArray = len(glyphIdArray)
		charCodes = list(range(lenArray))
		names = map(self.ttFont.getGlyphName, glyphIdArray)
		list(map(operator.setitem, [cmap]*lenArray, charCodes, names))

	
	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HHH", 0, 262, self.language) + self.data

		charCodeList = sorted(self.cmap.items())
		charCodes = [entry[0] for entry in charCodeList]
		valueList = [entry[1] for entry in charCodeList]
		assert charCodes == list(range(256))
		valueList = map(ttFont.getGlyphID, valueList)

		glyphIdArray = array.array("B", valueList)
		data = struct.pack(">HHH", 0, 262, self.language) + glyphIdArray.tostring()
		assert len(data) == 262
		return data
	
	def fromXML(self, name, attrs, content, ttFont):
		self.language = safeEval(attrs["language"])
		if not hasattr(self, "cmap"):
			self.cmap = {}
		cmap = self.cmap
		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			if name != "map":
				continue
			cmap[safeEval(attrs["code"])] = attrs["name"]


subHeaderFormat = ">HHhH"
class SubHeader(object):
	def __init__(self):
		self.firstCode = None
		self.entryCount = None
		self.idDelta = None
		self.idRangeOffset = None
		self.glyphIndexArray = []
		
class cmap_format_2(CmapSubtable):
	
	def setIDDelta(self, subHeader):
		subHeader.idDelta = 0
		# find the minGI which is not zero.
		minGI = subHeader.glyphIndexArray[0]
		for gid in subHeader.glyphIndexArray:
			if (gid != 0) and (gid < minGI):
				minGI = gid
		# The lowest gid in glyphIndexArray, after subtracting idDelta, must be 1.
		# idDelta is a short, and must be between -32K and 32K. minGI can be between 1 and 64K.
		# We would like to pick an idDelta such that the first glyphArray GID is 1, 
		# so that we are more likely to be able to combine glypharray GID subranges.
		# This means that we have a problem when minGI is > 32K
		# Since the final gi is reconstructed from the glyphArray GID by:
		#    (short)finalGID = (gid +  idDelta) % 0x10000),
		# we can get from a glypharray GID of 1 to a final GID of 65K by subtracting 2, and casting the
		# negative number to an unsigned short. 

		if  (minGI > 1):
			if  minGI > 0x7FFF:
				subHeader.idDelta = -(0x10000 - minGI) -1
			else:
				subHeader.idDelta =  minGI -1
			idDelta = subHeader.idDelta
			for i in range(subHeader.entryCount):
				gid = subHeader.glyphIndexArray[i]
				if gid > 0: 
					subHeader.glyphIndexArray[i] = gid - idDelta 


	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"

		data = self.data # decompileHeader assigns the data after the header to self.data
		subHeaderKeys = []
		maxSubHeaderindex = 0
		# get the key array, and determine the number of subHeaders.
		allKeys = array.array("H")
		allKeys.fromstring(data[:512])
		data = data[512:]
		if sys.byteorder != "big":
			allKeys.byteswap()
		subHeaderKeys = [ key//8 for key in allKeys]
		maxSubHeaderindex = max(subHeaderKeys)
	
		#Load subHeaders
		subHeaderList = []
		pos = 0
		for i in range(maxSubHeaderindex + 1):
			subHeader = SubHeader()
			(subHeader.firstCode, subHeader.entryCount, subHeader.idDelta, \
				subHeader.idRangeOffset) = struct.unpack(subHeaderFormat, data[pos:pos + 8])
			pos += 8
			giDataPos = pos + subHeader.idRangeOffset-2
			giList = array.array("H")
			giList.fromstring(data[giDataPos:giDataPos + subHeader.entryCount*2])
			if sys.byteorder != "big":
				giList.byteswap()
			subHeader.glyphIndexArray = giList
			subHeaderList.append(subHeader)
		# How this gets processed. 
		# Charcodes may be one or two bytes.
		# The first byte of a charcode is mapped through the  subHeaderKeys, to select
		# a subHeader. For any subheader but 0, the next byte is then mapped through the
		# selected subheader. If subheader Index 0 is selected, then the byte itself is 
		# mapped through the subheader, and there is no second byte.
		# Then assume that the subsequent byte is the first byte of the next charcode,and repeat.
		# 
		# Each subheader references a range in the glyphIndexArray whose length is entryCount.
		# The range in glyphIndexArray referenced by a sunheader may overlap with the range in glyphIndexArray
		# referenced by another subheader.
		# The only subheader that will be referenced by more than one first-byte value is the subheader
		# that maps the entire range of glyphID values to glyphIndex 0, e.g notdef:
		#	 {firstChar 0, EntryCount 0,idDelta 0,idRangeOffset xx}
		# A byte being mapped though a subheader is treated as in index into a mapping of array index to font glyphIndex.
		# A subheader specifies a subrange within (0...256) by the
		# firstChar and EntryCount values. If the byte value is outside the subrange, then the glyphIndex is zero
		# (e.g. glyph not in font).
		# If the byte index is in the subrange, then an offset index is calculated as (byteIndex - firstChar).
		# The index to glyphIndex mapping is a subrange of the glyphIndexArray. You find the start of the subrange by 
		# counting idRangeOffset bytes from the idRangeOffset word. The first value in this subrange is the
		# glyphIndex for the index firstChar. The offset index should then be used in this array to get the glyphIndex.
		# Example for Logocut-Medium
		# first byte of charcode = 129; selects subheader 1.
		# subheader 1 = {firstChar 64, EntryCount 108,idDelta 42,idRangeOffset 0252}
		# second byte of charCode = 66
		# the index offset = 66-64 = 2.
		# The subrange of the glyphIndexArray starting at 0x0252 bytes from the idRangeOffset word is:
		# [glyphIndexArray index], [subrange array index] = glyphIndex
		# [256], [0]=1 	from charcode [129, 64]
		# [257], [1]=2  	from charcode [129, 65]
		# [258], [2]=3  	from charcode [129, 66]
		# [259], [3]=4  	from charcode [129, 67]
		# So, the glyphIndex = 3 from the array. Then if idDelta is not zero and the glyph ID is not zero, 
		# add it to the glyphID to get the final glyphIndex
		# value. In this case the final glyph index = 3+ 42 -> 45 for the final glyphIndex. Whew!
		
		self.data = b""
		self.cmap = cmap = {}
		notdefGI = 0
		for firstByte in range(256):
			subHeadindex = subHeaderKeys[firstByte]
			subHeader = subHeaderList[subHeadindex]
			if subHeadindex == 0:
				if (firstByte < subHeader.firstCode) or (firstByte >= subHeader.firstCode + subHeader.entryCount):
					continue # gi is notdef.
				else:
					charCode = firstByte
					offsetIndex = firstByte - subHeader.firstCode
					gi = subHeader.glyphIndexArray[offsetIndex]
					if gi != 0:
						gi = (gi + subHeader.idDelta) % 0x10000
					else:
						continue # gi is notdef.
				cmap[charCode] = gi
			else:
				if subHeader.entryCount:
					charCodeOffset = firstByte * 256 + subHeader.firstCode
					for offsetIndex in range(subHeader.entryCount):
						charCode = charCodeOffset + offsetIndex
						gi = subHeader.glyphIndexArray[offsetIndex]
						if gi != 0:
							gi = (gi + subHeader.idDelta) % 0x10000
						else:
							continue
						cmap[charCode] = gi
				# If not subHeader.entryCount, then all char codes with this first byte are
				# mapped to .notdef. We can skip this subtable, and leave the glyphs un-encoded, which is the 
				# same as mapping it to .notdef.
		# cmap values are GID's.
		glyphOrder = self.ttFont.getGlyphOrder()
		gids = list(cmap.values())
		charCodes = list(cmap.keys())
		lenCmap = len(gids)
		try:
			names = list(map(operator.getitem, [glyphOrder]*lenCmap, gids ))
		except IndexError:
			getGlyphName = self.ttFont.getGlyphName
			names = list(map(getGlyphName, gids ))
		list(map(operator.setitem, [cmap]*lenCmap, charCodes, names))
	
		
	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HHH", self.format, self.length, self.language) + self.data
		kEmptyTwoCharCodeRange = -1
		notdefGI = 0

		items = sorted(self.cmap.items())
		charCodes = [item[0] for item in items]
		names = [item[1] for item in items]
		nameMap = ttFont.getReverseGlyphMap()
		lenCharCodes = len(charCodes) 
		try:
			gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
		except KeyError:
			nameMap = ttFont.getReverseGlyphMap(rebuild=True)
			try:
				gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
			except KeyError:
				# allow virtual GIDs in format 2 tables
				gids = []
				for name in names:
					try:
						gid = nameMap[name]
					except KeyError:
						try:
							if (name[:3] == 'gid'):
								gid = eval(name[3:])
							else:
								gid = ttFont.getGlyphID(name)
						except:
							raise KeyError(name)

					gids.append(gid)

		# Process the (char code to gid) item list  in char code order.
		# By definition, all one byte char codes map to subheader 0. 
		# For all the two byte char codes, we assume that the first byte maps maps to the empty subhead (with an entry count of 0, 
		# which defines all char codes in its range to map to notdef) unless proven otherwise.
		# Note that since the char code items are processed in char code order, all the char codes with the
		# same first byte are in sequential order.

		subHeaderKeys = [ kEmptyTwoCharCodeRange for x in  range(256)] # list of indices into subHeaderList.
		subHeaderList = []

		# We force this subheader entry 0  to exist in the subHeaderList in the case where some one comes up
		# with a cmap where all the one byte char codes map to notdef,
		# with the result that the subhead 0 would not get created just by processing the item list.
		charCode = charCodes[0]
		if charCode > 255:
			subHeader = SubHeader()
			subHeader.firstCode = 0
			subHeader.entryCount = 0
			subHeader.idDelta = 0
			subHeader.idRangeOffset = 0
			subHeaderList.append(subHeader)
			
		
		lastFirstByte = -1
		items = zip(charCodes, gids)
		for charCode, gid in items:
			if gid == 0:
				continue
			firstbyte = charCode >> 8
			secondByte = charCode & 0x00FF

			if firstbyte != lastFirstByte: # Need to update the current subhead, and start a new one.
				if lastFirstByte > -1:
					# fix GI's and iDelta of current subheader.
					self.setIDDelta(subHeader)

					# If it was sunheader 0 for one-byte charCodes, then we need to set the subHeaderKeys value to zero
					# for the indices matching the char codes.
					if lastFirstByte == 0:
						for index in range(subHeader.entryCount):
							charCode = subHeader.firstCode + index
							subHeaderKeys[charCode] = 0

					assert (subHeader.entryCount == len(subHeader.glyphIndexArray)), "Error - subhead entry count does not match len of glyphID subrange."
				# init new subheader
				subHeader = SubHeader()
				subHeader.firstCode = secondByte
				subHeader.entryCount = 1
				subHeader.glyphIndexArray.append(gid)
				subHeaderList.append(subHeader)
				subHeaderKeys[firstbyte] = len(subHeaderList) -1
				lastFirstByte = firstbyte
			else:
				# need to fill in with notdefs all the code points between the last charCode and the current charCode.
				codeDiff = secondByte - (subHeader.firstCode + subHeader.entryCount)
				for i in range(codeDiff):
					subHeader.glyphIndexArray.append(notdefGI)
				subHeader.glyphIndexArray.append(gid)
				subHeader.entryCount = subHeader.entryCount + codeDiff + 1
					
		# fix GI's and iDelta of last subheader that we we added to the subheader array.
		self.setIDDelta(subHeader)

		# Now we add a final subheader for the subHeaderKeys which maps to empty two byte charcode ranges.
		subHeader = SubHeader()
		subHeader.firstCode = 0
		subHeader.entryCount = 0
		subHeader.idDelta = 0
		subHeader.idRangeOffset = 2
		subHeaderList.append(subHeader)
		emptySubheadIndex = len(subHeaderList) - 1
		for index in range(256):
			if subHeaderKeys[index] == kEmptyTwoCharCodeRange:
				subHeaderKeys[index] = emptySubheadIndex
		# Since this is the last subheader, the GlyphIndex Array starts two bytes after the start of the
		# idRangeOffset word of this subHeader. We can safely point to the first entry in the GlyphIndexArray,
		# since the first subrange of the GlyphIndexArray is for subHeader 0, which always starts with 
		# charcode 0 and GID 0.
		
		idRangeOffset = (len(subHeaderList)-1)*8  + 2 # offset to beginning of glyphIDArray from first subheader idRangeOffset.
		subheadRangeLen = len(subHeaderList) -1 # skip last special empty-set subheader; we've already hardocodes its idRangeOffset to 2.
		for index in range(subheadRangeLen): 
			subHeader = subHeaderList[index]
			subHeader.idRangeOffset = 0
			for j  in range(index):
				prevSubhead = subHeaderList[j]
				if prevSubhead.glyphIndexArray == subHeader.glyphIndexArray: # use the glyphIndexArray subarray
					subHeader.idRangeOffset = prevSubhead.idRangeOffset - (index-j)*8
					subHeader.glyphIndexArray = []
					break
			if subHeader.idRangeOffset == 0: # didn't find one. 
				subHeader.idRangeOffset = idRangeOffset
				idRangeOffset = (idRangeOffset - 8) + subHeader.entryCount*2 # one less subheader, one more subArray.
			else:
				idRangeOffset = idRangeOffset - 8  # one less subheader

		# Now we can write out the data!
		length = 6 + 512 + 8*len(subHeaderList) # header, 256 subHeaderKeys, and subheader array.
		for subhead in 	subHeaderList[:-1]:
			length = length + len(subhead.glyphIndexArray)*2  # We can't use subhead.entryCount, as some of the subhead may share subArrays.
		dataList = [struct.pack(">HHH", 2, length, self.language)]
		for index in subHeaderKeys:
			dataList.append(struct.pack(">H", index*8))
		for subhead in 	subHeaderList:
			dataList.append(struct.pack(subHeaderFormat, subhead.firstCode, subhead.entryCount, subhead.idDelta, subhead.idRangeOffset))
		for subhead in 	subHeaderList[:-1]:
			for gi in subhead.glyphIndexArray:
				dataList.append(struct.pack(">H", gi))
		data = bytesjoin(dataList)
		assert (len(data) == length), "Error: cmap format 2 is not same length as calculated! actual: " + str(len(data))+ " calc : " + str(length)
		return data


	def fromXML(self, name, attrs, content, ttFont):
		self.language = safeEval(attrs["language"])
		if not hasattr(self, "cmap"):
			self.cmap = {}
		cmap = self.cmap

		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			if name != "map":
				continue
			cmap[safeEval(attrs["code"])] = attrs["name"]


cmap_format_4_format = ">7H"

#uint16  endCode[segCount]          # Ending character code for each segment, last = 0xFFFF.
#uint16  reservedPad                # This value should be zero
#uint16  startCode[segCount]        # Starting character code for each segment
#uint16  idDelta[segCount]          # Delta for all character codes in segment
#uint16  idRangeOffset[segCount]    # Offset in bytes to glyph indexArray, or 0
#uint16  glyphIndexArray[variable]  # Glyph index array

def splitRange(startCode, endCode, cmap):
	# Try to split a range of character codes into subranges with consecutive
	# glyph IDs in such a way that the cmap4 subtable can be stored "most"
	# efficiently. I can't prove I've got the optimal solution, but it seems
	# to do well with the fonts I tested: none became bigger, many became smaller.
	if startCode == endCode:
		return [], [endCode]
	
	lastID = cmap[startCode]
	lastCode = startCode
	inOrder = None
	orderedBegin = None
	subRanges = []
	
	# Gather subranges in which the glyph IDs are consecutive.
	for code in range(startCode + 1, endCode + 1):
		glyphID = cmap[code]
		
		if glyphID - 1 == lastID:
			if inOrder is None or not inOrder:
				inOrder = 1
				orderedBegin = lastCode
		else:
			if inOrder:
				inOrder = 0
				subRanges.append((orderedBegin, lastCode))
				orderedBegin = None
				
		lastID = glyphID
		lastCode = code
	
	if inOrder:
		subRanges.append((orderedBegin, lastCode))
	assert lastCode == endCode
	
	# Now filter out those new subranges that would only make the data bigger.
	# A new segment cost 8 bytes, not using a new segment costs 2 bytes per
	# character.
	newRanges = []
	for b, e in subRanges:
		if b == startCode and e == endCode:
			break  # the whole range, we're fine
		if b == startCode or e == endCode:
			threshold = 4  # split costs one more segment
		else:
			threshold = 8  # split costs two more segments
		if (e - b + 1) > threshold:
			newRanges.append((b, e))
	subRanges = newRanges
	
	if not subRanges:
		return [], [endCode]
	
	if subRanges[0][0] != startCode:
		subRanges.insert(0, (startCode, subRanges[0][0] - 1))
	if subRanges[-1][1] != endCode:
		subRanges.append((subRanges[-1][1] + 1, endCode))
	
	# Fill the "holes" in the segments list -- those are the segments in which
	# the glyph IDs are _not_ consecutive.
	i = 1
	while i < len(subRanges):
		if subRanges[i-1][1] + 1 != subRanges[i][0]:
			subRanges.insert(i, (subRanges[i-1][1] + 1, subRanges[i][0] - 1))
			i = i + 1
		i = i + 1
	
	# Transform the ranges into startCode/endCode lists.
	start = []
	end = []
	for b, e in subRanges:
		start.append(b)
		end.append(e)
	start.pop(0)
	
	assert len(start) + 1 == len(end)
	return start, end


class cmap_format_4(CmapSubtable):
	
	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(self.data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"

		data = self.data # decompileHeader assigns the data after the header to self.data
		(segCountX2, searchRange, entrySelector, rangeShift) = \
					struct.unpack(">4H", data[:8])
		data = data[8:]
		segCount = segCountX2 // 2
		
		allCodes = array.array("H")
		allCodes.fromstring(data)
		self.data = data = None

		if sys.byteorder != "big":
			allCodes.byteswap()
		
		# divide the data
		endCode = allCodes[:segCount]
		allCodes = allCodes[segCount+1:]  # the +1 is skipping the reservedPad field
		startCode = allCodes[:segCount]
		allCodes = allCodes[segCount:]
		idDelta = allCodes[:segCount]
		allCodes = allCodes[segCount:]
		idRangeOffset = allCodes[:segCount]
		glyphIndexArray = allCodes[segCount:]
		lenGIArray = len(glyphIndexArray)

		# build 2-byte character mapping
		charCodes = []
		gids = []
		for i in range(len(startCode) - 1):	# don't do 0xffff!
			rangeCharCodes = list(range(startCode[i], endCode[i] + 1))
			charCodes = charCodes + rangeCharCodes
			for charCode in rangeCharCodes:
				rangeOffset = idRangeOffset[i]
				if rangeOffset == 0:
					glyphID = charCode + idDelta[i]
				else:
					# *someone* needs to get killed.
					index = idRangeOffset[i] // 2 + (charCode - startCode[i]) + i - len(idRangeOffset)
					assert (index < lenGIArray), "In format 4 cmap, range (%d), the calculated index (%d) into the glyph index array  is not less than the length of the array (%d) !" % (i, index, lenGIArray)
					if glyphIndexArray[index] != 0:  # if not missing glyph
						glyphID = glyphIndexArray[index] + idDelta[i]
					else:
						glyphID = 0  # missing glyph
				gids.append(glyphID % 0x10000)

		self.cmap = cmap = {}
		lenCmap = len(gids)
		glyphOrder = self.ttFont.getGlyphOrder()
		try:
			names = list(map(operator.getitem, [glyphOrder]*lenCmap, gids ))
		except IndexError:
			getGlyphName = self.ttFont.getGlyphName
			names = list(map(getGlyphName, gids ))
		list(map(operator.setitem, [cmap]*lenCmap, charCodes, names))
		


	def setIDDelta(self, idDelta):
		# The lowest gid in glyphIndexArray, after subtracting idDelta, must be 1.
		# idDelta is a short, and must be between -32K and 32K
		# startCode can be between 0 and 64K-1, and the first glyph index can be between 1 and 64K-1
		# This means that we have a problem because we can need to assign to idDelta values
		# between -(64K-2) and 64K -1.
		# Since the final gi is reconstructed from the glyphArray GID by:
		#    (short)finalGID = (gid +  idDelta) % 0x10000),
		# we can get from a startCode of 0 to a final GID of 64 -1K by subtracting 1, and casting the
		# negative number to an unsigned short.
		# Similarly , we can get from a startCode of 64K-1 to a final GID of 1 by adding 2, because of
		# the modulo arithmetic.

		if idDelta > 0x7FFF:
			idDelta = idDelta - 0x10000
		elif idDelta <  -0x7FFF:
			idDelta = idDelta + 0x10000

		return idDelta


	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HHH", self.format, self.length, self.language) + self.data

		from fontTools.ttLib.sfnt import maxPowerOfTwo
		
		charCodes = list(self.cmap.keys())
		lenCharCodes = len(charCodes)
		if lenCharCodes == 0:
			startCode = [0xffff]
			endCode = [0xffff]
		else:
			charCodes.sort()
			names = list(map(operator.getitem, [self.cmap]*lenCharCodes, charCodes))
			nameMap = ttFont.getReverseGlyphMap()
			try:
				gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
			except KeyError:
				nameMap = ttFont.getReverseGlyphMap(rebuild=True)
				try:
					gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
				except KeyError:
					# allow virtual GIDs in format 4 tables
					gids = []
					for name in names:
						try:
							gid = nameMap[name]
						except KeyError:
							try:
								if (name[:3] == 'gid'):
									gid = eval(name[3:])
								else:
									gid = ttFont.getGlyphID(name)
							except:
								raise KeyError(name)
	
						gids.append(gid)
			cmap = {}  # code:glyphID mapping
			list(map(operator.setitem, [cmap]*len(charCodes), charCodes, gids))
		
			# Build startCode and endCode lists.
			# Split the char codes in ranges of consecutive char codes, then split
			# each range in more ranges of consecutive/not consecutive glyph IDs.
			# See splitRange().
			lastCode = charCodes[0]
			endCode = []
			startCode = [lastCode]
			for charCode in charCodes[1:]:  # skip the first code, it's the first start code
				if charCode == lastCode + 1:
					lastCode = charCode
					continue
				start, end = splitRange(startCode[-1], lastCode, cmap)
				startCode.extend(start)
				endCode.extend(end)
				startCode.append(charCode)
				lastCode = charCode
			endCode.append(lastCode)
			startCode.append(0xffff)
			endCode.append(0xffff)
		
		# build up rest of cruft
		idDelta = []
		idRangeOffset = []
		glyphIndexArray = []
		for i in range(len(endCode)-1):  # skip the closing codes (0xffff)
			indices = []
			for charCode in range(startCode[i], endCode[i] + 1):
				indices.append(cmap[charCode])
			if  (indices == list(range(indices[0], indices[0] + len(indices)))):
				idDeltaTemp = self.setIDDelta(indices[0] - startCode[i])
				idDelta.append( idDeltaTemp)
				idRangeOffset.append(0)
			else:
				# someone *definitely* needs to get killed.
				idDelta.append(0)
				idRangeOffset.append(2 * (len(endCode) + len(glyphIndexArray) - i))
				glyphIndexArray.extend(indices)
		idDelta.append(1)  # 0xffff + 1 == (tadaa!) 0. So this end code maps to .notdef
		idRangeOffset.append(0)
		
		# Insane. 
		segCount = len(endCode)
		segCountX2 = segCount * 2
		maxExponent = maxPowerOfTwo(segCount)
		searchRange = 2 * (2 ** maxExponent)
		entrySelector = maxExponent
		rangeShift = 2 * segCount - searchRange
		
		charCodeArray = array.array("H", endCode + [0] + startCode)
		idDeltaeArray = array.array("h", idDelta)
		restArray = array.array("H", idRangeOffset + glyphIndexArray)
		if sys.byteorder != "big":
			charCodeArray.byteswap()
			idDeltaeArray.byteswap()
			restArray.byteswap()
		data = charCodeArray.tostring() + idDeltaeArray.tostring() + restArray.tostring()

		length = struct.calcsize(cmap_format_4_format) + len(data)
		header = struct.pack(cmap_format_4_format, self.format, length, self.language, 
				segCountX2, searchRange, entrySelector, rangeShift)
		return header + data
	
	def fromXML(self, name, attrs, content, ttFont):
		self.language = safeEval(attrs["language"])
		if not hasattr(self, "cmap"):
			self.cmap = {}
		cmap = self.cmap

		for element in content:
			if not isinstance(element, tuple):
				continue
			nameMap, attrsMap, dummyContent = element
			if nameMap != "map":
				assert 0, "Unrecognized keyword in cmap subtable"
			cmap[safeEval(attrsMap["code"])] = attrsMap["name"]


class cmap_format_6(CmapSubtable):
	
	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"

		data = self.data # decompileHeader assigns the data after the header to self.data
		firstCode, entryCount = struct.unpack(">HH", data[:4])
		firstCode = int(firstCode)
		data = data[4:]
		#assert len(data) == 2 * entryCount  # XXX not true in Apple's Helvetica!!!
		glyphIndexArray = array.array("H")
		glyphIndexArray.fromstring(data[:2 * int(entryCount)])
		if sys.byteorder != "big":
			glyphIndexArray.byteswap()
		self.data = data = None

		self.cmap = cmap = {}

		lenArray = len(glyphIndexArray)
		charCodes = list(range(firstCode, firstCode + lenArray))
		glyphOrder = self.ttFont.getGlyphOrder()
		try:
			names = list(map(operator.getitem, [glyphOrder]*lenArray, glyphIndexArray ))
		except IndexError:
			getGlyphName = self.ttFont.getGlyphName
			names = list(map(getGlyphName, glyphIndexArray ))
		list(map(operator.setitem, [cmap]*lenArray, charCodes, names))
	
	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HHH", self.format, self.length, self.language) + self.data
		cmap = self.cmap
		codes = list(cmap.keys())
		if codes: # yes, there are empty cmap tables.
			codes = list(range(codes[0], codes[-1] + 1))
			firstCode = codes[0]
			valueList = [cmap.get(code, ".notdef") for code in codes]
			valueList = map(ttFont.getGlyphID, valueList)
			glyphIndexArray = array.array("H", valueList)
			if sys.byteorder != "big":
				glyphIndexArray.byteswap()
			data = glyphIndexArray.tostring()
		else:
			data = b""
			firstCode = 0
		header = struct.pack(">HHHHH", 
				6, len(data) + 10, self.language, firstCode, len(codes))
		return header + data
	
	def fromXML(self, name, attrs, content, ttFont):
		self.language = safeEval(attrs["language"])
		if not hasattr(self, "cmap"):
			self.cmap = {}
		cmap = self.cmap

		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			if name != "map":
				continue
			cmap[safeEval(attrs["code"])] = attrs["name"]


class cmap_format_12_or_13(CmapSubtable):
	
	def __init__(self, format):
		self.format = format
		self.reserved = 0
		self.data = None
		self.ttFont = None

	def decompileHeader(self, data, ttFont):
		format, reserved, length, language, nGroups = struct.unpack(">HHLLL", data[:16])
		assert len(data) == (16 + nGroups*12) == (length), "corrupt cmap table format %d (data length: %d, header length: %d)" % (format, len(data), length)
		self.format = format
		self.reserved = reserved
		self.length = length
		self.language = language
		self.nGroups = nGroups
		self.data = data[16:]
		self.ttFont = ttFont

	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"

		data = self.data # decompileHeader assigns the data after the header to self.data
		charCodes = []
		gids = []
		pos = 0
		for i in range(self.nGroups):
			startCharCode, endCharCode, glyphID = struct.unpack(">LLL",data[pos:pos+12] )
			pos += 12
			lenGroup = 1 + endCharCode - startCharCode
			charCodes += list(range(startCharCode, endCharCode +1))
			gids += self._computeGIDs(glyphID, lenGroup)
		self.data = data = None
		self.cmap = cmap = {}
		lenCmap = len(gids)
		glyphOrder = self.ttFont.getGlyphOrder()
		try:
			names = list(map(operator.getitem, [glyphOrder]*lenCmap, gids ))
		except IndexError:
			getGlyphName = self.ttFont.getGlyphName
			names = list(map(getGlyphName, gids ))
		list(map(operator.setitem, [cmap]*lenCmap, charCodes, names))
	
	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HHLLL", self.format, self.reserved, self.length, self.language, self.nGroups) + self.data
		charCodes = list(self.cmap.keys())
		lenCharCodes = len(charCodes) 
		names = list(self.cmap.values())
		nameMap = ttFont.getReverseGlyphMap()
		try:
			gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
		except KeyError:
			nameMap = ttFont.getReverseGlyphMap(rebuild=True)
			try:
				gids = list(map(operator.getitem, [nameMap]*lenCharCodes, names))
			except KeyError:
				# allow virtual GIDs in format 12 tables
				gids = []
				for name in names:
					try:
						gid = nameMap[name]
					except KeyError:
						try:
							if (name[:3] == 'gid'):
								gid = eval(name[3:])
							else:
								gid = ttFont.getGlyphID(name)
						except:
							raise KeyError(name)

					gids.append(gid)
		
		cmap = {}  # code:glyphID mapping
		list(map(operator.setitem, [cmap]*len(charCodes), charCodes, gids))

		charCodes.sort()
		index = 0
		startCharCode = charCodes[0]
		startGlyphID = cmap[startCharCode]
		lastGlyphID = startGlyphID - self._format_step
		lastCharCode = startCharCode - 1
		nGroups = 0
		dataList =  []
		maxIndex = len(charCodes)
		for index in range(maxIndex):
			charCode = charCodes[index]
			glyphID = cmap[charCode]
			if not self._IsInSameRun(glyphID, lastGlyphID, charCode, lastCharCode):
				dataList.append(struct.pack(">LLL", startCharCode, lastCharCode, startGlyphID))
				startCharCode = charCode
				startGlyphID = glyphID
				nGroups = nGroups + 1
			lastGlyphID = glyphID
			lastCharCode = charCode
		dataList.append(struct.pack(">LLL", startCharCode, lastCharCode, startGlyphID))
		nGroups = nGroups + 1
		data = bytesjoin(dataList)
		lengthSubtable = len(data) +16
		assert len(data) == (nGroups*12) == (lengthSubtable-16) 
		return struct.pack(">HHLLL", self.format, self.reserved , lengthSubtable, self.language, nGroups) + data
	
	def toXML(self, writer, ttFont):
		writer.begintag(self.__class__.__name__, [
				("platformID", self.platformID),
				("platEncID", self.platEncID),
				("format", self.format),
				("reserved", self.reserved),
				("length", self.length),
				("language", self.language),
				("nGroups", self.nGroups),
				])
		writer.newline()
		codes = sorted(self.cmap.items())
		self._writeCodes(codes, writer)
		writer.endtag(self.__class__.__name__)
		writer.newline()
	
	def fromXML(self, name, attrs, content, ttFont):
		self.format = safeEval(attrs["format"])
		self.reserved = safeEval(attrs["reserved"])
		self.length = safeEval(attrs["length"])
		self.language = safeEval(attrs["language"])
		self.nGroups = safeEval(attrs["nGroups"])
		if not hasattr(self, "cmap"):
			self.cmap = {}
		cmap = self.cmap

		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			if name != "map":
				continue
			cmap[safeEval(attrs["code"])] = attrs["name"]


class cmap_format_12(cmap_format_12_or_13):
	def __init__(self, format):
		cmap_format_12_or_13.__init__(self, format)
		self._format_step = 1

	def _computeGIDs(self, startingGlyph, numberOfGlyphs):
		return list(range(startingGlyph, startingGlyph + numberOfGlyphs))

	def _IsInSameRun(self, glyphID, lastGlyphID, charCode, lastCharCode):
		return (glyphID == 1 + lastGlyphID) and (charCode == 1 + lastCharCode)


class cmap_format_13(cmap_format_12_or_13):
	def __init__(self, format):
		cmap_format_12_or_13.__init__(self, format)
		self._format_step = 0

	def _computeGIDs(self, startingGlyph, numberOfGlyphs):
		return [startingGlyph] * numberOfGlyphs

	def _IsInSameRun(self, glyphID, lastGlyphID, charCode, lastCharCode):
		return (glyphID == lastGlyphID) and (charCode == 1 + lastCharCode)


def  cvtToUVS(threeByteString):
	data = b"\0" + threeByteString
	val, = struct.unpack(">L", data)
	return val

def  cvtFromUVS(val):
	assert 0 <= val < 0x1000000
	fourByteString = struct.pack(">L", val)
	return fourByteString[1:]


class cmap_format_14(CmapSubtable):

	def decompileHeader(self, data, ttFont):
		format, length, numVarSelectorRecords = struct.unpack(">HLL", data[:10])
		self.data = data[10:]
		self.length = length
		self.numVarSelectorRecords = numVarSelectorRecords
		self.ttFont = ttFont
		self.language = 0xFF # has no language.

	def decompile(self, data, ttFont):
		if data is not None and ttFont is not None and ttFont.lazy:
			self.decompileHeader(data, ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"
		data = self.data
		
		self.cmap = {} # so that clients that expect this to exist in a cmap table won't fail.
		uvsDict = {}
		recOffset = 0
		for n in range(self.numVarSelectorRecords):
			uvs, defOVSOffset, nonDefUVSOffset =  struct.unpack(">3sLL", data[recOffset:recOffset +11])		
			recOffset += 11
			varUVS = cvtToUVS(uvs)
			if defOVSOffset:
				startOffset = defOVSOffset  - 10
				numValues, = struct.unpack(">L", data[startOffset:startOffset+4])
				startOffset +=4
				for r in range(numValues):
					uv, addtlCnt = struct.unpack(">3sB", data[startOffset:startOffset+4])
					startOffset += 4
					firstBaseUV = cvtToUVS(uv)
					cnt = addtlCnt+1
					baseUVList = list(range(firstBaseUV, firstBaseUV+cnt))
					glyphList = [None]*cnt
					localUVList = zip(baseUVList, glyphList)
					try:
						uvsDict[varUVS].extend(localUVList)
					except KeyError:
						uvsDict[varUVS] = list(localUVList)
				
			if nonDefUVSOffset:
				startOffset = nonDefUVSOffset  - 10
				numRecs, = struct.unpack(">L", data[startOffset:startOffset+4])
				startOffset +=4
				localUVList = []
				for r in range(numRecs):
					uv, gid = struct.unpack(">3sH", data[startOffset:startOffset+5])
					startOffset += 5
					uv = cvtToUVS(uv)
					glyphName = self.ttFont.getGlyphName(gid)
					localUVList.append( [uv, glyphName] )
				try:
					uvsDict[varUVS].extend(localUVList)
				except KeyError:
					uvsDict[varUVS] = localUVList
					
		self.uvsDict = uvsDict
							
	def toXML(self, writer, ttFont):
		writer.begintag(self.__class__.__name__, [
				("platformID", self.platformID),
				("platEncID", self.platEncID),
				("format", self.format),
				("length", self.length),
				("numVarSelectorRecords", self.numVarSelectorRecords),
				])
		writer.newline()
		uvsDict = self.uvsDict
		uvsList = sorted(uvsDict.keys())
		for uvs in uvsList:
			uvList = uvsDict[uvs]
			uvList.sort(key=lambda item: (item[1] is not None, item[0], item[1]))
			for uv, gname in uvList:
				if gname is None:
					gname = "None"
				# I use the arg rather than th keyword syntax in order to preserve the attribute order.
				writer.simpletag("map", [ ("uvs",hex(uvs)), ("uv",hex(uv)), ("name", gname)]  )
				writer.newline()
		writer.endtag(self.__class__.__name__)
		writer.newline()

	def fromXML(self, name, attrs, content, ttFont):
		self.format = safeEval(attrs["format"])
		self.length = safeEval(attrs["length"])
		self.numVarSelectorRecords = safeEval(attrs["numVarSelectorRecords"])
		self.language = 0xFF # provide a value so that  CmapSubtable.__lt__() won't fail
		if not hasattr(self, "cmap"):
			self.cmap = {} # so that clients that expect this to exist in a cmap table won't fail.
		if not hasattr(self, "uvsDict"):
			self.uvsDict  = {}
			uvsDict = self.uvsDict 

		for element in content:
			if not isinstance(element, tuple):
				continue
			name, attrs, content = element
			if name != "map":
				continue
			uvs = safeEval(attrs["uvs"])
			uv = safeEval(attrs["uv"])
			gname = attrs["name"]
			if gname == "None":
				gname = None
			try:
				uvsDict[uvs].append( [uv, gname])
			except KeyError:
				uvsDict[uvs] = [ [uv, gname] ]
			

	def compile(self, ttFont):
		if self.data:
			return struct.pack(">HLL", self.format, self.length , self.numVarSelectorRecords) + self.data

		uvsDict = self.uvsDict
		uvsList = sorted(uvsDict.keys())
		self.numVarSelectorRecords = len(uvsList)
		offset = 10 + self.numVarSelectorRecords*11 # current value is end of VarSelectorRecords block.
		data = []
		varSelectorRecords =[]
		for uvs in uvsList:
			entryList = uvsDict[uvs]

			defList = [entry for entry in entryList if entry[1] is None]
			if defList:
				defList = [entry[0] for entry in defList]
				defOVSOffset = offset
				defList.sort()

				lastUV = defList[0]
				cnt = -1
				defRecs = []
				for defEntry in defList:
					cnt +=1
					if (lastUV+cnt) != defEntry:
						rec = struct.pack(">3sB", cvtFromUVS(lastUV), cnt-1)
						lastUV = defEntry
						defRecs.append(rec)
						cnt = 0
					
				rec = struct.pack(">3sB", cvtFromUVS(lastUV), cnt)
				defRecs.append(rec)

				numDefRecs = len(defRecs)
				data.append(struct.pack(">L", numDefRecs))
				data.extend(defRecs)
				offset += 4 + numDefRecs*4
			else:
				defOVSOffset = 0

			ndefList = [entry for entry in entryList if entry[1] is not None]
			if ndefList:
				nonDefUVSOffset = offset
				ndefList.sort()
				numNonDefRecs = len(ndefList)
				data.append(struct.pack(">L", numNonDefRecs))
				offset += 4 + numNonDefRecs*5

				for uv, gname in ndefList:
					gid = ttFont.getGlyphID(gname)
					ndrec = struct.pack(">3sH", cvtFromUVS(uv), gid)
					data.append(ndrec)
			else:
				nonDefUVSOffset = 0
				
			vrec = struct.pack(">3sLL", cvtFromUVS(uvs), defOVSOffset, nonDefUVSOffset)
			varSelectorRecords.append(vrec)
				
		data = bytesjoin(varSelectorRecords) + bytesjoin(data)
		self.length = 10 + len(data)
		headerdata = struct.pack(">HLL", self.format, self.length , self.numVarSelectorRecords)
		self.data = headerdata + data
	
		return self.data
		
		
class cmap_format_unknown(CmapSubtable):
	
	def toXML(self, writer, ttFont):
		cmapName = self.__class__.__name__[:12] + str(self.format)
		writer.begintag(cmapName, [
				("platformID", self.platformID),
				("platEncID", self.platEncID),
				])
		writer.newline()
		writer.dumphex(self.data)
		writer.endtag(cmapName)
		writer.newline()
	
	def fromXML(self, name, attrs, content, ttFont):
		self.data = readHex(content)
		self.cmap = {}
	
	def decompileHeader(self, data, ttFont):
		self.language = 0  # dummy value
		self.data = data
	
	def decompile(self, data, ttFont):
		# we usually get here indirectly from the subtable __getattr__ function, in which case both args must be None.
		# If not, someone is calling  the subtable decompile() directly, and must provide both args.
		if data is not None and ttFont is not None:
			self.decompileHeader(data[offset:offset+int(length)], ttFont)
		else:
			assert (data is None and ttFont is None), "Need both data and ttFont arguments"

	def compile(self, ttFont):
		if self.data:
			return self.data
		else:
			return None

cmap_classes = {
		0: cmap_format_0,
		2: cmap_format_2,
		4: cmap_format_4,
		6: cmap_format_6,
		12: cmap_format_12,
		13: cmap_format_13,
		14: cmap_format_14,
		}