added fontTools.misc.eexec and a MacOS/PPC shared lib (eexecOp) that provides the C implementation.

git-svn-id: svn://svn.code.sf.net/p/fonttools/code/trunk@56 4cde692c-a291-49d1-8350-778aa11640f8

Lib/fontTools/misc/eexec.py

@@ -0,0 +1,70 @@
+"""fontTools.misc.eexec.py -- Module implementing the eexec and 
+charstring encryption algorithm as used by PostScript Type 1 fonts.
+"""
+
+# Warning: Although a Python implementation is provided here, 
+# all four public functions get overridden by the *much* faster 
+# C extension module eexecOp, if available.
+
+import string
+
+error = "eexec.error"
+
+
+def _decryptChar(cipher, R):
+	cipher = ord(cipher)
+	plain = ( (cipher ^ (R>>8)) ) & 0xFF
+	R = ( (cipher + R) * 52845L + 22719L ) & 0xFFFF
+	return chr(plain), R
+
+def _encryptChar(plain, R):
+	plain = ord(plain)
+	cipher = ( (plain ^ (R>>8)) ) & 0xFF
+	R = ( (cipher + R) * 52845L + 22719L ) & 0xFFFF
+	return chr(cipher), R
+
+
+def decrypt(cipherstring, R):
+	# I could probably speed this up by inlining _decryptChar,
+	# but... we've got eexecOp, so who cares ;-)
+	plainList = []
+	for cipher in cipherstring:
+		plain, R = _decryptChar(cipher, R)
+		plainList.append(plain)
+	plainstring = string.join(plainList, '')
+	return plainstring, int(R)
+
+def encrypt(plainstring, R):
+	cipherList = []
+	for plain in plainstring:
+		cipher, R = _encryptChar(plain, R)
+		cipherList.append(cipher)
+	cipherstring = string.join(cipherList, '')
+	return cipherstring, int(R)
+
+
+def hexString(s):
+	xxx
+
+def deHexString(h):
+	xxx
+
+
+def _test():
+	import eexecOp
+	testStr = "\0\0asdadads asds"
+	print decrypt, decrypt(testStr, 12321)
+	print eexecOp.decrypt, eexecOp.decrypt(testStr, 12321)
+	print encrypt, encrypt(testStr, 12321)
+	print eexecOp.encrypt, eexecOp.encrypt(testStr, 12321)
+
+
+if __name__ == "__main__":
+	_test()
+
+
+try:
+	from eexecOp import *
+except ImportError:
+	pass # Use the slow Python versions
+