Fix typo

aiorpcx/framing.py

@@ -28,6 +28,8 @@
 __all__ = ('FramerBase', 'NewlineFramer')
 
 from itertools import chain
+from collections import namedtuple
+import struct
 
 
 class FramerBase(object):
@@ -97,3 +99,56 @@ def messages(self, data):
                 self.synchronizing = True
                 raise MemoryError(f'dropping message over {self.max_size} '
                                   ' and re-synchronizing')
+
+
+BinaryMessage = namedtuple("BinaryMessage", "command payload")
+le32 = struct.Struct('<I')
+to_le32 = le32.pack
+from_le32 = le32.unpack
+
+
+class BinaryFramer(FramerBase):
+
+    def __init__(self, magic, cmd_len, checksum, checksum_len):
+        self.magic = magic
+        self.cmd_len = cmd_len
+        self.checksum = checksum
+        self.checksum_len = checksum_len
+        self.parts = []
+        self.synchronizing = False
+
+    def frame(self, messages):
+        '''Return bytes formed by framing each message in messages,
+        an iterable, and concatenating the result.
+        '''
+        return b''.join(self.frame_message(msg) for msg in messages)
+
+    def frame_message(self, message):
+        return b''.join([
+            self.magic,
+            message.command.ljust(self.cmd_len, b'\0'),
+            to_le32(len(command.payload)),
+            self.checksum(command.payload),
+            command.payload
+        ])
+
+    def messages(self, data):
+        '''A generator that yields messages for the caller to process.
+
+        Raises a MemoryError Exception if the internal buffer
+        overflows, so converting to a list before processing risks
+        message loss.
+        '''
+        assert isinstance(data, (bytes, bytearray))
+        len_offset = len(self.magic) + self.cmd_len
+        min_len = len_offset + 4 + self.checksum_len
+        parts = self.parts
+        parts.append(data)
+        parts_len = sum(len(part) for part in parts)
+        if len(parts[0]) < min_len:
+            self.parts = [b''.join(parts)]
+            if len(parts[0]) < min_len:
+                return
+        min_len += to_le32(parts[len_offset:len_offset + 4])
+        if parts_len < min_len:
+            return