Add Decred transaction to and from bytes.

basicswap/util/integer.py

@@ -5,13 +5,18 @@
 # file LICENSE or http://www.opensource.org/licenses/mit-license.php.
 
 
-def decode_varint(b: bytes) -> int:
-    i = 0
-    shift = 0
-    for c in b:
-        i += (c & 0x7F) << shift
-        shift += 7
-    return i
+def decode_varint(b: bytes, offset: int = 0) -> (int, int):
+    i: int = 0
+    num_bytes: int = 0
+    while True:
+        c = b[offset + num_bytes]
+        i += (c & 0x7F) << (num_bytes * 7)
+        num_bytes += 1
+        if not c & 0x80:
+            break
+        if num_bytes > 8:
+            raise ValueError('Too many bytes')
+    return i, num_bytes
 
 
 def encode_varint(i: int) -> bytes: