Change in osmocom-bb[master]: trx_toolkit/codec.py: implement check() API for Envelope

[fixeria]

fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmocom-bb/+/23136 )


Change subject: trx_toolkit/codec.py: implement check() API for Envelope
......................................................................

trx_toolkit/codec.py: implement check() API for Envelope

Change-Id: I8258504493cf85c401677866fe8474de2e49786b
Related: OS#4006, SYS#4895
---
M src/target/trx_toolkit/codec.py
M src/target/trx_toolkit/test_codec.py
2 files changed, 28 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/36/23136/1

diff --git a/src/target/trx_toolkit/codec.py b/src/target/trx_toolkit/codec.py
index e3cd600..cc3b5ed 100644
--- a/src/target/trx_toolkit/codec.py
+++ b/src/target/trx_toolkit/codec.py
@@ -271,6 +271,15 @@
 	def __delitem__(self, key: str) -> None:
 		del self.content[key]
 
+	def check(self) -> None:
+		''' Check the content before encoding and after decoding.
+		    Raise exceptions (e.g. ValueError) if something is wrong.
+
+		    Do not assert for every possible error (e.g. a negative value
+		    for a Uint field) if an exception will be thrown by the field's
+		    to_bytes() method anyway.  Only additional constraints here.
+		'''
+
 	def from_bytes(self, data: bytes, offset: int = 0) -> int:
 		self.content = { } # forget the old content
 		try: # Fields throw exceptions
@@ -282,6 +291,7 @@
 		if self.check_len and len(data) != offset:
 			raise DecodeError(self, 'Unhandled tail octets: %s'
 						% data[offset:].hex())
+		self.check() # Check the content after decoding (raises exceptions)
 		return offset
 
 	def to_bytes(self) -> bytes:
@@ -291,4 +301,5 @@
 			except Exception as e:
 				# Add contextual info
 				raise EncodeError(self, f) from e
+		self.check() # Check the content before encoding (raises exceptions)
 		return b''.join([proc(f) for f in self.STRUCT])
diff --git a/src/target/trx_toolkit/test_codec.py b/src/target/trx_toolkit/test_codec.py
index 0499f3a..287be92 100644
--- a/src/target/trx_toolkit/test_codec.py
+++ b/src/target/trx_toolkit/test_codec.py
@@ -419,6 +419,10 @@
 		self.STRUCT[-1].get_pres_dec = lambda v, _: bool(v['flag'])
 		self.STRUCT[-1].get_pres_enc = lambda v: bool(v['flag'])
 
+	def check(self) -> None:
+		if not self['ver'] in (0, 1, 2):
+			raise ValueError('Unknown version %d' % self['ver'])
+
 class Envelope(unittest.TestCase):
 	def test_rest_octets(self):
 		pdu = TestPDU(check_len=False)
@@ -467,5 +471,18 @@
 		pdu.from_bytes(b'\x28\x00\x00\x01\xf0\xbe\xed')
 		self.assertEqual(pdu.content, content)
 
+	def test_to_bytes_check(self):
+		pdu = TestPDU()
+
+		pdu.content = { 'ver' : 8, 'flag' : 1, 'data' : b'', 'tail' : b'\xde\xbe' }
+		with self.assertRaises(ValueError):
+			pdu.to_bytes()
+
+	def test_from_bytes_check(self):
+		pdu = TestPDU()
+
+		with self.assertRaises(ValueError):
+			pdu.from_bytes(b'\xf0\x00\x00\x00')
+
 if __name__ == '__main__':
 	unittest.main()

-- 
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Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-Change-Id: I8258504493cf85c401677866fe8474de2e49786b
Gerrit-Change-Number: 23136
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-MessageType: newchange
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