sao: add decoder helpers, hash checks

titles/sao/handlers/helpers.py

@@ -0,0 +1,50 @@
+from typing import Tuple
+import struct
+import logging
+
+BIGINT_OFF = 16
+LONG_OFF = 8
+INT_OFF = 4
+SHORT_OFF = 2
+BYTE_OFF = 1
+
+def decode_num(data: bytes, offset: int, size: int) -> int:
+    try:
+        return int.from_bytes(data[offset:offset + size], 'big')
+    except:
+        logging.getLogger('sao').error(f"Failed to parse {data[offset:offset + size]} as BE number of width {size}")
+        return 0
+
+def decode_byte(data: bytes, offset: int) -> int:
+    return decode_num(data, offset, BYTE_OFF)
+
+def decode_short(data: bytes, offset: int) -> int:
+    return decode_num(data, offset, SHORT_OFF)
+
+def decode_int(data: bytes, offset: int) -> int:
+    return decode_num(data, offset, INT_OFF)
+
+def decode_long(data: bytes, offset: int) -> int:
+    return decode_num(data, offset, LONG_OFF)
+
+def decode_bigint(data: bytes, offset: int) -> int:
+    return decode_num(data, offset, BIGINT_OFF)
+
+def decode_str(data: bytes, offset: int) -> Tuple[str, int]:
+    try:
+        str_len = decode_int(data, offset)
+        num_bytes_decoded = INT_OFF + str_len
+        str_out = data[offset + INT_OFF:offset + num_bytes_decoded].decode("utf-16-le", errors="replace")
+        return (str_out, num_bytes_decoded)
+    except:
+        logging.getLogger('sao').error(f"Failed to parse {data[offset:]} as string!")
+        return ("", 0)
+
+def encode_str(s: str) -> bytes:
+    try:
+        str_bytes = s.encode("utf-16-le", errors="replace")
+        str_len_bytes = struct.pack("!I", len(str_bytes))
+        return str_len_bytes + str_bytes
+    except:
+        logging.getLogger('sao').error(f"Failed to encode {s} as bytes!")
+        return b""