Encode major version as a uint8 in detached timestamps

Backwards compatible because we only use major version 1.

There's no way we'd ever need more than 256 major versions. So no reason
to use a more complex encoding.

Author: petertodd

opentimestamps/core/serialize.py

@@ -155,6 +155,9 @@ def write_varuint(self, value):
                     break
                 value >>= 7
 
+    def write_uint8(self, value):
+        self.fd.write(bytes([value]))
+
     def write_bytes(self, value):
         self.fd.write(value)
 
@@ -199,6 +202,9 @@ def read_varuint(self):
 
         return value
 
+    def read_uint8(self):
+        return self.fd_read(1)[0]
+
     def read_bytes(self, expected_length=None):
         if expected_length is None:
             expected_length = self.read_varuint(None)

opentimestamps/core/timestamp.py

@@ -316,7 +316,7 @@ def from_fd(cls, file_hash_op, fd):
     def serialize(self, ctx):
         ctx.write_bytes(self.HEADER_MAGIC)
 
-        ctx.write_varuint(self.MAJOR_VERSION)
+        ctx.write_uint8(self.MAJOR_VERSION)
 
         self.file_hash_op.serialize(ctx)
         assert self.file_hash_op.DIGEST_LENGTH == len(self.timestamp.msg)
@@ -328,7 +328,7 @@ def serialize(self, ctx):
     def deserialize(cls, ctx):
         ctx.assert_magic(cls.HEADER_MAGIC)
 
-        major = ctx.read_varuint() # FIXME: max-int limit
+        major = ctx.read_uint8()
         if major != cls.MAJOR_VERSION:
             raise opentimestamps.core.serialize.UnsupportedMajorVersion("Version %d detached timestamp files are not supported" % major)