Fix #259: Use the unsigned LEB128 impl from py-wasm

Reference: https://github.com/ethereum/py-wasm/blob/master/wasm/parsers/leb128.py

libp2p/exceptions.py

@@ -6,3 +6,7 @@ class ValidationError(BaseLibp2pError):
     """
     Raised when something does not pass a validation check.
     """
+
+
+class ParseError(BaseLibp2pError):
+    pass

libp2p/stream_muxer/mplex/mplex.py

@@ -6,7 +6,11 @@ from libp2p.peer.id import ID
 from libp2p.security.secure_conn_interface import ISecureConn
 from libp2p.stream_muxer.abc import IMuxedConn, IMuxedStream
 from libp2p.typing import TProtocol
-from libp2p.utils import decode_uvarint_from_stream, encode_uvarint
+from libp2p.utils import (
+    decode_uvarint_from_stream,
+    encode_uvarint,
+    read_varint_prefixed_bytes,
+)
 
 from .constants import HeaderTags
 from .exceptions import StreamNotFound
@@ -119,11 +123,11 @@ class Mplex(IMuxedConn):
         :return: a new ``MplexStream``
         """
         stream_id = self._get_next_stream_id()
-        name = str(stream_id).encode()
+        name = str(stream_id)
         stream = MplexStream(name, stream_id, True, self)
         self.buffers[stream_id] = asyncio.Queue()
         # Default stream name is the `stream_id`
-        await self.send_message(HeaderTags.NewStream, name, stream_id)
+        await self.send_message(HeaderTags.NewStream, name.encode(), stream_id)
         return stream
 
     async def accept_stream(self, name: str) -> None:
@@ -180,7 +184,7 @@ class Mplex(IMuxedConn):
                 # TODO: Handle more tags, and refactor `HeaderTags`
                 if flag == HeaderTags.NewStream.value:
                     # new stream detected on connection
-                    await self.accept_stream(message)
+                    await self.accept_stream(message.decode())
                 elif flag in (
                     HeaderTags.MessageInitiator.value,
                     HeaderTags.MessageReceiver.value,
@@ -199,14 +203,14 @@ class Mplex(IMuxedConn):
         # FIXME: No timeout is used in Go implementation.
         # Timeout is set to a relatively small value to alleviate wait time to exit
         #  loop in handle_incoming
-        timeout = 0.1
+        header = await decode_uvarint_from_stream(self.secured_conn)
+        # TODO: Handle the case of EOF and other exceptions?
         try:
-            header = await decode_uvarint_from_stream(self.secured_conn, timeout)
-            length = await decode_uvarint_from_stream(self.secured_conn, timeout)
             message = await asyncio.wait_for(
-                self.secured_conn.read(length), timeout=timeout
+                read_varint_prefixed_bytes(self.secured_conn), timeout=5
             )
         except asyncio.TimeoutError:
+            # TODO: Investigate what we should do if time is out.
             return None, None, None
 
         flag = header & 0x07

libp2p/utils.py

@@ -1,9 +1,20 @@
-import asyncio
-import struct
-from typing import Tuple
+import itertools
+import math
 
+from libp2p.exceptions import ParseError
 from libp2p.typing import StreamReader
 
+# Unsigned LEB128(varint codec)
+# Reference: https://github.com/ethereum/py-wasm/blob/master/wasm/parsers/leb128.py
+
+LOW_MASK = 2 ** 7 - 1
+HIGH_MASK = 2 ** 7
+
+
+# The maximum shift width for a 64 bit integer.  We shouldn't have to decode
+# integers larger than this.
+SHIFT_64_BIT_MAX = int(math.ceil(64 / 7)) * 7
+
 
 def encode_uvarint(number: int) -> bytes:
     """Pack `number` into varint bytes"""
@@ -19,35 +30,29 @@ def encode_uvarint(number: int) -> bytes:
     return buf
 
 
-def decode_uvarint(buff: bytes, index: int) -> Tuple[int, int]:
-    shift = 0
-    result = 0
-    while True:
-        i = buff[index]
-        result |= (i & 0x7F) << shift
-        shift += 7
-        if not i & 0x80:
+async def decode_uvarint_from_stream(reader: StreamReader) -> int:
+    """
+    https://en.wikipedia.org/wiki/LEB128
+    """
+    res = 0
+    for shift in itertools.count(0, 7):
+        if shift > SHIFT_64_BIT_MAX:
+            raise ParseError("TODO: better exception msg: Integer is too large...")
+
+        byte = await reader.read(1)
+
+        try:
+            value = byte[0]
+        except IndexError:
+            raise ParseError(
+                "Unexpected end of stream while parsing LEB128 encoded integer"
+            )
+
+        res += (value & LOW_MASK) << shift
+
+        if not value & HIGH_MASK:
             break
-        index += 1
-
-    return result, index + 1
-
-
-async def decode_uvarint_from_stream(reader: StreamReader, timeout: float) -> int:
-    shift = 0
-    result = 0
-    while True:
-        byte = await asyncio.wait_for(reader.read(1), timeout=timeout)
-        i = struct.unpack(">H", b"\x00" + byte)[0]
-        result |= (i & 0x7F) << shift
-        shift += 7
-        if not i & 0x80:
-            break
-
-    return result
-
-
-# Varint-prefixed read/write
+    return res
 
 
 def encode_varint_prefixed(msg_bytes: bytes) -> bytes:
@@ -56,7 +61,7 @@ def encode_varint_prefixed(msg_bytes: bytes) -> bytes:
 
 
 async def read_varint_prefixed_bytes(reader: StreamReader) -> bytes:
-    len_msg = await decode_uvarint_from_stream(reader, None)
+    len_msg = await decode_uvarint_from_stream(reader)
     data = await reader.read(len_msg)
     if len(data) != len_msg:
         raise ValueError(