Initial commit

parser.py

@@ -0,0 +1,98 @@
+''' Parse OSC packet into dict '''
+
+# set True to enable log messages
+DEBUG = True
+
+import struct
+import traceback
+
+def _parse_str(body: bytearray) -> (str, int):
+    ''' Parse OSC string '''
+    try:
+        result = ''
+        for b in body:
+            if b == 0:
+                break
+            result += chr(b)
+        else:
+            return None
+        l = ((len(result) // 4) + 1) * 4
+        if l > len(body):
+            return None
+        return (result, l)
+    except:
+        if DEBUG: traceback.print_exc()
+        return None
+
+def _parse_int(body: bytearray) -> (int, int):
+    ''' Parse OSC int '''
+    try:
+        return (struct.unpack('>i', body[0:4])[0], 4)
+    except:
+        if DEBUG: traceback.print_exc()
+        return None
+
+def _parse_float(body: bytearray) -> (float, int):
+    ''' Parse OSC float '''
+    try:
+        return (struct.unpack('>f', body[0:4])[0], 4)
+    except:
+        if DEBUG: traceback.print_exc()
+        return None
+
+def parse(body: bytearray) -> dict | None:
+    ''' Parse OSC datagram into dict. '''
+    # too short
+    if len(body) < 8:
+        if DEBUG: print('[OSC PARSER] Body is shorter than 8 bytes')
+        return None
+    # does not start with slash
+    if body[0] != ord('/'):
+        if DEBUG: print('[OSC PARSER] First byte of packet is not forward slash')
+        return None
+    # get the address
+    addr = _parse_str(body)
+    if not addr:
+        if DEBUG: print('[OSC PARSER] Failed to parse address (OSC-string)')
+        return None
+    # edit body
+    body = body[addr[1]:]
+    # get the type tag
+    type_tag = _parse_str(body)
+    if not type_tag:
+        if DEBUG: print('[OSC PARSER] Failed to parse type tag (OSC-string)')
+        return None
+    # edit body
+    body = body[type_tag[1]:]
+    # type is invalid
+    if type_tag[0][0] != ',':
+        if DEBUG: print('[OSC PARSER] The first symbol of type tag must be comma')
+        return None
+    # arguments
+    args = []
+    # type parsers
+    type_parsers = {
+        'i': _parse_int,
+        'f': _parse_float,
+        's': _parse_str
+    }
+    # parse the arguments
+    for arg_type in type_tag[0][1:]:
+        # parse body if parser exists
+        if arg_type not in type_parsers:
+            if DEBUG: print('[OSC PARSER] Argument of type \'%s\' can\'t be parsed by this library' % arg_type)
+            return None
+        parse_result = type_parsers[arg_type](body)
+        # failed to parse
+        if parse_result is None:
+            if DEBUG: print('[OSC PARSER] Failed to parse an argument of type \'%s\'' % arg_type)
+            return None
+        # success
+        args.append(parse_result[0])
+        body = body[parse_result[1]:]
+    # result
+    return {
+        'addr': addr[0],
+        'type_tag': type_tag[0],
+        'args': args
+    }