utils: COMPREHENSION-TLV support
Change-Id: I8d969382b73fa152ee09c456fa4aee428fb36285
diff --git a/pySim/utils.py b/pySim/utils.py
index 3d96580..d96d05a 100644
--- a/pySim/utils.py
+++ b/pySim/utils.py
@@ -90,6 +90,50 @@
return (n + 1)//2
#########################################################################
+# poor man's COMPREHENSION-TLV decoder.
+#########################################################################
+
+def comprehensiontlv_parse_tag(binary:bytes) -> Tuple[dict, bytes]:
+ """Parse a single Tag according to ETSI TS 101 220 Section 7.1.1"""
+ if binary[0] in [0x00, 0x80, 0xff]:
+ raise ValueError("Found illegal value 0x%02x in %s" % (binary[0], binary))
+ if binary[0] == 0x7f:
+ # three-byte tag
+ tag = (binary[1] & 0x7f) << 8
+ tag |= binary[2]
+ compr = True if binary[1] & 0x80 else False
+ return ({'comprehension': compr, 'tag': tag}, binary[3:])
+ else:
+ # single byte tag
+ tag = binary[0] & 0x7f
+ compr = True if binary[0] & 0x80 else False
+ return ({'comprehension': compr, 'tag': tag}, binary[1:])
+
+def comprehensiontlv_encode_tag(tag) -> bytes:
+ """Encode a single Tag according to ETSI TS 101 220 Section 7.1.1"""
+ # permit caller to specify tag also as integer value
+ if isinstance(tag, int):
+ compr = True if tag < 0xff and tag & 0x80 else False
+ tag = {'tag': tag, 'comprehension': compr}
+ compr = tag.get('comprehension', False)
+ if tag['tag'] in [0x00, 0x80, 0xff] or tag['tag'] > 0xff:
+ # 3-byte format
+ byte3 = tag['tag'] & 0xff;
+ byte2 = (tag['tag'] >> 8) & 0x7f
+ if compr:
+ byte2 |= 0x80
+ return b'\x7f' + byte2.to_bytes(1, 'big') + byte3.to_bytes(1, 'big')
+ else:
+ # 1-byte format
+ ret = tag['tag']
+ if compr:
+ ret |= 0x80
+ return ret.to_bytes(1, 'big')
+
+# length value coding is equal to BER-TLV
+
+
+#########################################################################
# poor man's BER-TLV decoder. To be a more sophisticated OO library later
#########################################################################
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 17a9300..ed22eff 100755
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -179,6 +179,28 @@
res = utils.bertlv_parse_one(b'\x81\x01\x01');
self.assertEqual(res, ({'tag':1, 'constructed':False, 'class':2}, 1, b'\x01', b''))
+class TestComprTlv(unittest.TestCase):
+ def test_ComprTlvTagDec(self):
+ res = utils.comprehensiontlv_parse_tag(b'\x12\x23')
+ self.assertEqual(res, ({'tag': 0x12, 'comprehension': False}, b'\x23'))
+ res = utils.comprehensiontlv_parse_tag(b'\x92')
+ self.assertEqual(res, ({'tag': 0x12, 'comprehension': True}, b''))
+ res = utils.comprehensiontlv_parse_tag(b'\x7f\x12\x34')
+ self.assertEqual(res, ({'tag': 0x1234, 'comprehension': False}, b''))
+ res = utils.comprehensiontlv_parse_tag(b'\x7f\x82\x34\x56')
+ self.assertEqual(res, ({'tag': 0x234, 'comprehension': True}, b'\x56'))
+
+ def test_ComprTlvTagEnc(self):
+ res = utils.comprehensiontlv_encode_tag(0x12)
+ self.assertEqual(res, b'\x12')
+ res = utils.comprehensiontlv_encode_tag({'tag': 0x12})
+ self.assertEqual(res, b'\x12')
+ res = utils.comprehensiontlv_encode_tag({'tag': 0x12, 'comprehension':True})
+ self.assertEqual(res, b'\x92')
+ res = utils.comprehensiontlv_encode_tag(0x1234)
+ self.assertEqual(res, b'\x7f\x12\x34')
+ res = utils.comprehensiontlv_encode_tag({'tag': 0x1234, 'comprehension':True})
+ self.assertEqual(res, b'\x7f\x92\x34')
if __name__ == "__main__":
unittest.main()