python: implement decoding of protobuf packed repeated fields

also add typing
fixes #426

python/src/trezorlib/protobuf.py

@@ -14,57 +14,89 @@
 # You should have received a copy of the License along with this library.
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
-'''
-Extremely minimal streaming codec for a subset of protobuf.  Supports uint32,
-bytes, string, embedded message and repeated fields.
+"""
+Extremely minimal streaming codec for a subset of protobuf.
+Supports uint32, bytes, string, embedded message and repeated fields.
 
-For de-sererializing (loading) protobuf types, object with `Reader`
-interface is required:
-
->>> class Reader:
->>>     def readinto(self, buffer):
->>>         """
->>>         Reads `len(buffer)` bytes into `buffer`, or raises `EOFError`.
->>>         """
-
-For serializing (dumping) protobuf types, object with `Writer` interface is
-required:
-
->>> class Writer:
->>>     def write(self, buffer):
->>>         """
->>>         Writes all bytes from `buffer`, or raises `EOFError`.
->>>         """
-'''
+For de-serializing (loading) protobuf types, object with `Reader` interface is required.
+For serializing (dumping) protobuf types, object with `Writer` interface is required.
+"""
 
 import logging
 from io import BytesIO
-from typing import Any, Optional
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+)
+
+from typing_extensions import Protocol
+
+FieldType = Union[
+    "EnumType",
+    Type["MessageType"],
+    Type["UVarintType"],
+    Type["SVarintType"],
+    Type["BoolType"],
+    Type["UnicodeType"],
+    Type["BytesType"],
+]
+FieldInfo = Tuple[str, FieldType, int]
+MT = TypeVar("MT", bound="MessageType")
+
+
+class Reader(Protocol):
+    def readinto(self, buffer: bytearray) -> int:
+        """
+        Reads exactly `len(buffer)` bytes into `buffer`. Returns number of bytes read,
+        or 0 if it cannot read that much.
+        """
+
+
+class Writer(Protocol):
+    def write(self, buffer: bytes) -> int:
+        """
+        Writes all bytes from `buffer`, or raises `EOFError`
+        """
+
 
 _UVARINT_BUFFER = bytearray(1)
 
 LOG = logging.getLogger(__name__)
 
 
-def load_uvarint(reader):
+def load_uvarint(reader: Reader) -> int:
     buffer = _UVARINT_BUFFER
     result = 0
     shift = 0
     byte = 0x80
+    bytes_read = 0
     while byte & 0x80:
         if reader.readinto(buffer) == 0:
-            raise EOFError
+            if bytes_read > 0:
+                raise IOError("Interrupted UVarint")
+            else:
+                raise EOFError
+        bytes_read += 1
         byte = buffer[0]
         result += (byte & 0x7F) << shift
         shift += 7
     return result
 
 
-def dump_uvarint(writer, n):
+def dump_uvarint(writer: Writer, n: int) -> None:
     if n < 0:
         raise ValueError("Cannot dump signed value, convert it to unsigned first.")
     buffer = _UVARINT_BUFFER
-    shifted = True
+    shifted = 1
     while shifted:
         shifted = n >> 7
         buffer[0] = (n & 0x7F) | (0x80 if shifted else 0x00)
@@ -92,14 +124,14 @@ def dump_uvarint(writer, n):
 # So we have to branch on whether the number is negative.
 
 
-def sint_to_uint(sint):
+def sint_to_uint(sint: int) -> int:
     res = sint << 1
     if sint < 0:
         res = ~res
     return res
 
 
-def uint_to_sint(uint):
+def uint_to_sint(uint: int) -> int:
     sign = uint & 1
     res = uint >> 1
     if sign:
@@ -122,7 +154,7 @@ class BoolType:
 class EnumType:
     WIRE_TYPE = 0
 
-    def __init__(self, enum_name, enum_values):
+    def __init__(self, enum_name: str, enum_values: Iterable[int]) -> None:
         self.enum_name = enum_name
         self.enum_values = enum_values
 
@@ -170,18 +202,18 @@ class MessageType:
     WIRE_TYPE = 2
 
     @classmethod
-    def get_fields(cls):
+    def get_fields(cls) -> Dict[int, FieldInfo]:
         return {}
 
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any) -> None:
         for kw in kwargs:
             setattr(self, kw, kwargs[kw])
         self._fill_missing()
 
-    def __eq__(self, rhs):
+    def __eq__(self, rhs: Any) -> bool:
         return self.__class__ is rhs.__class__ and self.__dict__ == rhs.__dict__
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         d = {}
         for key, value in self.__dict__.items():
             if value is None or value == []:
@@ -189,16 +221,16 @@ class MessageType:
             d[key] = value
         return "<%s: %s>" % (self.__class__.__name__, d)
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[str]:
         return iter(self.keys())
 
-    def keys(self):
+    def keys(self) -> Iterator[str]:
         return (name for name, _, _ in self.get_fields().values())
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: str) -> Any:
         return getattr(self, key)
 
-    def _fill_missing(self):
+    def _fill_missing(self) -> None:
         # fill missing fields
         for fname, ftype, fflags in self.get_fields().values():
             if not hasattr(self, fname):
@@ -207,20 +239,20 @@ class MessageType:
                 else:
                     setattr(self, fname, None)
 
-    def ByteSize(self):
+    def ByteSize(self) -> int:
         data = BytesIO()
         dump_message(data, self)
         return len(data.getvalue())
 
 
 class LimitedReader:
-    def __init__(self, reader, limit):
+    def __init__(self, reader: Reader, limit: int) -> None:
         self.reader = reader
         self.limit = limit
 
-    def readinto(self, buf):
+    def readinto(self, buf: bytearray) -> int:
         if self.limit < len(buf):
-            raise EOFError
+            return 0
         else:
             nread = self.reader.readinto(buf)
             self.limit -= nread
@@ -228,10 +260,10 @@ class LimitedReader:
 
 
 class CountingWriter:
-    def __init__(self):
+    def __init__(self) -> None:
         self.size = 0
 
-    def write(self, buf):
+    def write(self, buf: bytes) -> int:
         nwritten = len(buf)
         self.size += nwritten
         return nwritten
@@ -240,7 +272,51 @@ class CountingWriter:
 FLAG_REPEATED = 1
 
 
-def load_message(reader, msg_type):
+def decode_packed_array_field(ftype: FieldType, reader: Reader) -> List[Any]:
+    length = load_uvarint(reader)
+    packed_reader = LimitedReader(reader, length)
+    values = []
+    try:
+        while True:
+            values.append(decode_varint_field(ftype, packed_reader))
+    except EOFError:
+        pass
+    return values
+
+
+def decode_varint_field(ftype: FieldType, reader: Reader) -> Union[int, bool]:
+    value = load_uvarint(reader)
+    if ftype is UVarintType:
+        return value
+    elif ftype is SVarintType:
+        return uint_to_sint(value)
+    elif ftype is BoolType:
+        return bool(value)
+    elif isinstance(ftype, EnumType):
+        return ftype.validate(value)
+    else:
+        raise TypeError  # not a varint field or unknown type
+
+
+def decode_length_delimited_field(
+    ftype: FieldType, reader: Reader
+) -> Union[bytes, str, MessageType]:
+    value = load_uvarint(reader)
+    if ftype is BytesType:
+        buf = bytearray(value)
+        reader.readinto(buf)
+        return bytes(buf)
+    elif ftype is UnicodeType:
+        buf = bytearray(value)
+        reader.readinto(buf)
+        return buf.decode()
+    elif isinstance(ftype, type) and issubclass(ftype, MessageType):
+        return load_message(LimitedReader(reader, value), ftype)
+    else:
+        raise TypeError  # field type is unknown
+
+
+def load_message(reader: Reader, msg_type: Type[MT]) -> MT:
     fields = msg_type.get_fields()
     msg = msg_type()
 
@@ -266,42 +342,38 @@ def load_message(reader, msg_type):
             continue
 
         fname, ftype, fflags = field
-        if wtype != ftype.WIRE_TYPE:
+
+        if wtype == 2 and ftype.WIRE_TYPE == 0 and fflags & FLAG_REPEATED:
+            # packed array
+            fvalues = decode_packed_array_field(ftype, reader)
+
+        elif wtype != ftype.WIRE_TYPE:
             raise TypeError  # parsed wire type differs from the schema
 
-        ivalue = load_uvarint(reader)
-
-        if ftype is UVarintType:
-            fvalue = ivalue
-        elif ftype is SVarintType:
-            fvalue = uint_to_sint(ivalue)
-        elif ftype is BoolType:
-            fvalue = bool(ivalue)
-        elif isinstance(ftype, EnumType):
-            fvalue = ftype.validate(ivalue)
-        elif ftype is BytesType:
-            buf = bytearray(ivalue)
-            reader.readinto(buf)
-            fvalue = bytes(buf)
-        elif ftype is UnicodeType:
-            buf = bytearray(ivalue)
-            reader.readinto(buf)
-            fvalue = buf.decode()
-        elif issubclass(ftype, MessageType):
-            fvalue = load_message(LimitedReader(reader, ivalue), ftype)
+        elif wtype == 2:
+            fvalues = [decode_length_delimited_field(ftype, reader)]
+
+        elif wtype == 0:
+            fvalues = [decode_varint_field(ftype, reader)]
+
         else:
-            raise TypeError  # field type is unknown
+            raise TypeError  # unknown wire type
 
         if fflags & FLAG_REPEATED:
             pvalue = getattr(msg, fname)
-            pvalue.append(fvalue)
+            pvalue.extend(fvalues)
             fvalue = pvalue
+        elif len(fvalues) != 1:
+            raise ValueError("Unexpected multiple values in non-repeating field")
+        else:
+            fvalue = fvalues[0]
+
         setattr(msg, fname, fvalue)
 
     return msg
 
 
-def dump_message(writer, msg):
+def dump_message(writer: Writer, msg: MessageType) -> None:
     repvalue = [0]
     mtype = msg.__class__
     fields = mtype.get_fields()
@@ -362,7 +434,7 @@ def format_message(
     truncate_after: Optional[int] = 256,
     truncate_to: Optional[int] = 64,
 ) -> str:
-    def mostly_printable(bytes):
+    def mostly_printable(bytes: bytes) -> bool:
         if not bytes:
             return True
         printable = sum(1 for byte in bytes if 0x20 <= byte <= 0x7E)
@@ -377,13 +449,14 @@ def format_message(
     def pformat(name: str, value: Any, indent: int) -> str:
         level = sep * indent
         leadin = sep * (indent + 1)
+        ftype = get_type(name)
 
         if isinstance(value, MessageType):
             return format_message(value, indent, sep)
 
         if isinstance(value, list):
             # short list of simple values
-            if not value or not isinstance(value[0], MessageType):
+            if not value or isinstance(value, (UVarintType, SVarintType, BoolType)):
                 return repr(value)
 
             # long list, one line per entry
@@ -412,10 +485,8 @@ def format_message(
                 output = "0x" + value.hex()
             return "{} bytes {}{}".format(length, output, suffix)
 
-        if isinstance(value, int):
-            ftype = get_type(name)
-            if isinstance(ftype, EnumType):
-                return "{} ({})".format(ftype.to_str(value), value)
+        if isinstance(value, int) and isinstance(ftype, EnumType):
+            return "{} ({})".format(ftype.to_str(value), value)
 
         return repr(value)
 
@@ -426,7 +497,7 @@ def format_message(
     )
 
 
-def value_to_proto(ftype, value):
+def value_to_proto(ftype: FieldType, value: Any) -> Any:
     if isinstance(ftype, type) and issubclass(ftype, MessageType):
         raise TypeError("value_to_proto only converts simple values")
 
@@ -454,7 +525,7 @@ def value_to_proto(ftype, value):
             raise TypeError("can't convert {} value to bytes".format(type(value)))
 
 
-def dict_to_proto(message_type, d):
+def dict_to_proto(message_type: Type[MT], d: Dict[str, Any]) -> MT:
     params = {}
     for fname, ftype, fflags in message_type.get_fields().values():
         repeated = fflags & FLAG_REPEATED
@@ -466,7 +537,7 @@ def dict_to_proto(message_type, d):
             value = [value]
 
         if isinstance(ftype, type) and issubclass(ftype, MessageType):
-            function = dict_to_proto
+            function = dict_to_proto  # type: Callable[[Any, Any], Any]
         else:
             function = value_to_proto
 
@@ -479,8 +550,8 @@ def dict_to_proto(message_type, d):
     return message_type(**params)
 
 
-def to_dict(msg, hexlify_bytes=True):
-    def convert_value(value):
+def to_dict(msg: MessageType, hexlify_bytes: bool = True) -> Dict[str, Any]:
+    def convert_value(value: Any) -> Any:
         if hexlify_bytes and isinstance(value, bytes):
             return value.hex()
         elif isinstance(value, MessageType):