# Source code for fontTools.ttLib.tables.D_S_I_G_

    from fontTools.misc.textTools import bytesjoin, strjoin, tobytes, tostr, safeEval
    from fontTools.misc import sstruct
    from . import DefaultTable
    import base64

    DSIG_HeaderFormat = """
    	> # big endian
    	ulVersion:      L
    	usNumSigs:      H
    	usFlag:         H
    """
    # followed by an array of usNumSigs DSIG_Signature records
    DSIG_SignatureFormat = """
    	> # big endian
    	ulFormat:       L
    	ulLength:       L # length includes DSIG_SignatureBlock header
    	ulOffset:       L
    """
    # followed by an array of usNumSigs DSIG_SignatureBlock records,
    # each followed immediately by the pkcs7 bytes
    DSIG_SignatureBlockFormat = """
    	> # big endian
    	usReserved1:    H
    	usReserved2:    H
    	cbSignature:    l # length of following raw pkcs7 data
    """

    #
    # NOTE
    # the DSIG table format allows for SignatureBlocks residing
    # anywhere in the table and possibly in a different order as
    # listed in the array after the first table header
    #
    # this implementation does not keep track of any gaps and/or data
    # before or after the actual signature blocks while decompiling,
    # and puts them in the same physical order as listed in the header
    # on compilation with no padding whatsoever.
    #

    class table_D_S_I_G_(DefaultTable.DefaultTable):

    	def decompile(self, data, ttFont):
    		dummy, newData = sstruct.unpack2(DSIG_HeaderFormat, data, self)
    		assert self.ulVersion == 1, "DSIG ulVersion must be 1"
    		assert self.usFlag & ~1 == 0, "DSIG usFlag must be 0x1 or 0x0"
    		self.signatureRecords = sigrecs = []
    		for n in range(self.usNumSigs):
    			sigrec, newData = sstruct.unpack2(DSIG_SignatureFormat, newData, SignatureRecord())
    			assert sigrec.ulFormat == 1, "DSIG signature record #%d ulFormat must be 1" % n
    			sigrecs.append(sigrec)
    		for sigrec in sigrecs:
    			dummy, newData = sstruct.unpack2(DSIG_SignatureBlockFormat, data[sigrec.ulOffset:], sigrec)
    			assert sigrec.usReserved1 == 0, "DSIG signature record #%d usReserverd1 must be 0" % n
    			assert sigrec.usReserved2 == 0, "DSIG signature record #%d usReserverd2 must be 0" % n
    			sigrec.pkcs7 = newData[:sigrec.cbSignature]

    	def compile(self, ttFont):
    		packed = sstruct.pack(DSIG_HeaderFormat, self)
    		headers = [packed]
    		offset = len(packed) + self.usNumSigs * sstruct.calcsize(DSIG_SignatureFormat)
    		data = []
    		for sigrec in self.signatureRecords:
    			# first pack signature block
    			sigrec.cbSignature = len(sigrec.pkcs7)
    			packed = sstruct.pack(DSIG_SignatureBlockFormat, sigrec) + sigrec.pkcs7
    			data.append(packed)
    			# update redundant length field
    			sigrec.ulLength = len(packed)
    			# update running table offset
    			sigrec.ulOffset = offset
    			headers.append(sstruct.pack(DSIG_SignatureFormat, sigrec))
    			offset += sigrec.ulLength
    		if offset % 2:
    			# Pad to even bytes
    			data.append(b'\0')
    		return bytesjoin(headers+data)

    	def toXML(self, xmlWriter, ttFont):
    		xmlWriter.comment("note that the Digital Signature will be invalid after recompilation!")
    		xmlWriter.newline()
    		xmlWriter.simpletag("tableHeader", version=self.ulVersion, numSigs=self.usNumSigs, flag="0x%X" % self.usFlag)
    		for sigrec in self.signatureRecords:
    			xmlWriter.newline()
    			sigrec.toXML(xmlWriter, ttFont)
    		xmlWriter.newline()

    	def fromXML(self, name, attrs, content, ttFont):
    		if name == "tableHeader":
    			self.signatureRecords = []
    			self.ulVersion = safeEval(attrs["version"])
    			self.usNumSigs = safeEval(attrs["numSigs"])
    			self.usFlag = safeEval(attrs["flag"])
    			return
    		if name == "SignatureRecord":
    			sigrec = SignatureRecord()
    			sigrec.fromXML(name, attrs, content, ttFont)
    			self.signatureRecords.append(sigrec)

    pem_spam = lambda l, spam = {
    	"-----BEGIN PKCS7-----": True, "-----END PKCS7-----": True, "": True
    }: not spam.get(l.strip())

    def b64encode(b):
    	s = base64.b64encode(b)
    	# Line-break at 76 chars.
    	items = []
    	while s:
    		items.append(tostr(s[:76]))
    		items.append('\n')
    		s = s[76:]
    	return strjoin(items)

    class SignatureRecord(object):
    	def __repr__(self):
    		return "<%s: %s>" % (self.__class__.__name__, self.__dict__)

    	def toXML(self, writer, ttFont):
    		writer.begintag(self.__class__.__name__, format=self.ulFormat)
    		writer.newline()
    		writer.write_noindent("-----BEGIN PKCS7-----\n")
    		writer.write_noindent(b64encode(self.pkcs7))
    		writer.write_noindent("-----END PKCS7-----\n")
    		writer.endtag(self.__class__.__name__)

    	def fromXML(self, name, attrs, content, ttFont):
    		self.ulFormat = safeEval(attrs["format"])
    		self.usReserved1 = safeEval(attrs.get("reserved1", "0"))
    		self.usReserved2 = safeEval(attrs.get("reserved2", "0"))
    		self.pkcs7 = base64.b64decode(tobytes(strjoin(filter(pem_spam, content))))