Move varint and delim read/write to toplevel

To `libp2p.utils`.

libp2p/utils.py

@@ -0,0 +1,78 @@
+import asyncio
+import struct
+from typing import Tuple
+
+from libp2p.typing import StreamReader
+
+
+TIMEOUT = 10
+
+
+def encode_uvarint(number: int) -> bytes:
+    """Pack `number` into varint bytes"""
+    buf = b""
+    while True:
+        towrite = number & 0x7F
+        number >>= 7
+        if number:
+            buf += bytes((towrite | 0x80,))
+        else:
+            buf += bytes((towrite,))
+            break
+    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:
+            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
+
+
+def encode_varint_prefixed(msg_bytes: bytes) -> bytes:
+    varint_len = encode_uvarint(len(msg_bytes))
+    return varint_len + msg_bytes
+
+
+async def read_varint_prefixed_bytes(
+    reader: StreamReader, timeout: int = TIMEOUT
+) -> bytes:
+    len_msg = await decode_uvarint_from_stream(reader, timeout)
+    return await reader.read(len_msg)
+
+
+# Delimited read/write
+
+
+def encode_delim(msg_str: str) -> bytes:
+    delimited_msg = msg_str + "\n"
+    return encode_varint_prefixed(delimited_msg.encode())
+
+
+async def read_delim(reader: StreamReader, timeout: int = TIMEOUT) -> str:
+    msg_bytes = await read_varint_prefixed_bytes(reader, timeout)
+    return msg_bytes.decode().rstrip()