mojo: Add deserialization to python structs.

mojo/public/python/mojo/bindings/descriptor.py

Index: mojo/public/python/mojo/bindings/descriptor.py
diff --git a/mojo/public/python/mojo/bindings/descriptor.py b/mojo/public/python/mojo/bindings/descriptor.py
index 06d636b7db6631d4d2d0fe41ab2aa68d17846469..42fb3a4da98888e34818b950cea0bf79abe828e2 100644
--- a/mojo/public/python/mojo/bindings/descriptor.py
+++ b/mojo/public/python/mojo/bindings/descriptor.py
@@ -7,6 +7,7 @@ The descriptors used to define generated elements of the mojo python bindings.
 """
 
 import array
+import itertools
 import struct
 
 # pylint: disable=F0401
@@ -55,7 +56,7 @@ class SerializableType(Type):
 
   def Serialize(self, value, data_offset, data, handle_offset):
     """
-    Serialize an value of this type.
+    Serialize a value of this type.
 
     Args:
       value: the value to serialize.
@@ -69,6 +70,21 @@ class SerializableType(Type):
     """
     raise NotImplementedError()
 
+  def Deserialize(self, value, data, handles):
+    """
+    Deserialize a value of this type.
+
+    Args:
+      value: the base value for this type. This is always a numeric type, and
+             corresponds to the first element in the tuple returned by
+             Serialize.
+      data: the bytearray to retrieve additional data from.
+      handles: the array of handles contained in the message to deserialize.
+
+    Returns the deserialized value.
+    """
+    raise NotImplementedError()
+
 
 class BooleanType(Type):
   """Type object for booleans"""
@@ -88,6 +104,9 @@ class NumericType(SerializableType):
   def Serialize(self, value, data_offset, data, handle_offset):
     return (value, [])
 
+  def Deserialize(self, value, data, handles):
+    return value
+
 
 class IntegerType(NumericType):
   """Type object for integer types."""
@@ -135,15 +154,28 @@ class PointerType(SerializableType):
   def Serialize(self, value, data_offset, data, handle_offset):
     if value is None and not self.nullable:
       raise serialization.SerializationException(
-          "Trying to serialize null for non nullable type.")
+          'Trying to serialize null for non nullable type.')
     if value is None:
       return (0, [])
     return self.SerializePointer(value, data_offset, data, handle_offset)
 
+  def Deserialize(self, value, data, handles):
+    if value == 0:
+      if not self.nullable:
+        raise serialization.DeserializationException(
+            'Trying to deserialize null for non nullable type.')
+      return None
+    pointed_data = data[value:]
+    (size, nb_elements) = serialization.HEADER_STRUCT.unpack_from(pointed_data)
+    return self.DeserializePointer(size, nb_elements, pointed_data, handles)
+
   def SerializePointer(self, value, data_offset, data, handle_offset):
     """Serialize the not null value."""
     raise NotImplementedError()
 
+  def DeserializePointer(self, size, nb_elements, data, handles):
+    raise NotImplementedError()
+
 
 class StringType(PointerType):
   """
@@ -170,6 +202,11 @@ class StringType(PointerType):
     return self._array_type.SerializeArray(
         string_array, data_offset, data, handle_offset)
 
+  def DeserializePointer(self, size, nb_elements, data, handles):
+    string_array = self._array_type.DeserializeArray(
+        size, nb_elements, data, handles)
+    return unicode(string_array.tostring(), 'utf8')
+
 
 class HandleType(SerializableType):
   """Type object for handles."""
@@ -188,11 +225,20 @@ class HandleType(SerializableType):
   def Serialize(self, value, data_offset, data, handle_offset):
     if not value.IsValid() and not self.nullable:
       raise serialization.SerializationException(
-          "Trying to serialize null for non nullable type.")
+          'Trying to serialize null for non nullable type.')
     if not value.IsValid():
       return (-1, [])
     return (handle_offset, [value])
 
+  def Deserialize(self, value, data, handles):
+    if value == -1:
+      if not self.nullable:
+        raise serialization.DeserializationException(
+            'Trying to deserialize null for non nullable type.')
+      return mojo.system.Handle()
+    # TODO(qsr) validate handle order
+    return handles[value]
+
 
 class BaseArrayType(PointerType):
   """Abstract Type object for arrays."""
@@ -203,13 +249,22 @@ class BaseArrayType(PointerType):
 
   def SerializePointer(self, value, data_offset, data, handle_offset):
     if self.length != 0 and len(value) != self.length:
-      raise serialization.SerializationException("Incorrect array size")
+      raise serialization.SerializationException('Incorrect array size')
     return self.SerializeArray(value, data_offset, data, handle_offset)
 
   def SerializeArray(self, value, data_offset, data, handle_offset):
     """Serialize the not null array."""
     raise NotImplementedError()
 
+  def DeserializePointer(self, size, nb_elements, data, handles):
+    if self.length != 0 and size != self.length:
+      raise serialization.DeserializationException('Incorrect array size')
+    return self.DeserializeArray(size, nb_elements, data, handles)
+
+  def DeserializeArray(self, size, nb_elements, data, handles):
+    raise NotImplementedError()
+
+
 class BooleanArrayType(BaseArrayType):
 
   def __init__(self, nullable=False, length=0):
@@ -224,8 +279,17 @@ class BooleanArrayType(BaseArrayType):
   def SerializeArray(self, value, data_offset, data, handle_offset):
     groups = [value[i:i+8] for i in range(0, len(value), 8)]
     converted = array.array('B', [_ConvertBooleansToByte(x) for x in groups])
-    return self._array_type.SerializeArray(
-        converted, data_offset, data, handle_offset)
+    return _SerializeNativeArray(converted, data_offset, data, len(value))
+
+  def DeserializeArray(self, size, nb_elements, data, handles):
+    converted = self._array_type.DeserializeArray(
+        size, nb_elements, data, handles)
+    elements = list(itertools.islice(
+        itertools.chain.from_iterable(
+            [_ConvertByteToBooleans(x, 8) for x in converted]),
+        0,
+        nb_elements))
+    return elements
 
 
 class GenericArrayType(BaseArrayType):
@@ -245,12 +309,11 @@ class GenericArrayType(BaseArrayType):
     size = (serialization.HEADER_STRUCT.size +
             self.sub_type.GetByteSize() * len(value))
     data_end = len(data)
-    position = len(data) - data_offset
+    position = len(data) + serialization.HEADER_STRUCT.size
     data.extend(bytearray(size +
                           serialization.NeededPaddingForAlignment(size)))
     returned_handles = []
     to_pack = []
-    position = position + 2
     for item in value:
       (new_data, new_handles) = self.sub_type.Serialize(
           item,
@@ -261,12 +324,23 @@ class GenericArrayType(BaseArrayType):
       returned_handles.extend(new_handles)
       position = position + self.sub_type.GetByteSize()
     serialization.HEADER_STRUCT.pack_into(data, data_end, size, len(value))
-    struct.pack_into("%d%s" % (len(value), self.sub_type.GetTypeCode()),
+    struct.pack_into('%d%s' % (len(value), self.sub_type.GetTypeCode()),
                      data,
                      data_end + serialization.HEADER_STRUCT.size,
                      *to_pack)
     return (data_offset, returned_handles)
 
+  def DeserializeArray(self, size, nb_elements, data, handles):
+    values = struct.unpack_from(
+        '%d%s' % (nb_elements, self.sub_type.GetTypeCode()),
+        data[serialization.HEADER_STRUCT.size:])
+    result = []
+    position = serialization.HEADER_STRUCT.size
+    for value in values:
+      result.append(self.sub_type.Deserialize(value, data[position:], handles))
+      position += self.sub_type.GetByteSize()
+    return result
+
 
 class NativeArrayType(BaseArrayType):
   """Type object for arrays of native types."""
@@ -284,15 +358,12 @@ class NativeArrayType(BaseArrayType):
     return array.array(self.array_typecode, value)
 
   def SerializeArray(self, value, data_offset, data, handle_offset):
-    data_size = len(data)
-    data.extend(bytearray(serialization.HEADER_STRUCT.size))
-    data.extend(value.tostring())
-    data_length = len(data) - data_size
-    data.extend(bytearray(
-        serialization.NeededPaddingForAlignment(data_length)))
-    serialization.HEADER_STRUCT.pack_into(
-        data, data_size, data_length, len(value))
-    return (data_offset, [])
+    return _SerializeNativeArray(value, data_offset, data, len(value))
+
+  def DeserializeArray(self, size, nb_elements, data, handles):
+    result = array.array(self.array_typecode)
+    result.fromstring(data[serialization.HEADER_STRUCT.size:size].tobytes())
+    return result
 
 
 class StructType(PointerType):
@@ -318,6 +389,9 @@ class StructType(PointerType):
     data.extend(new_data)
     return (data_offset, new_handles)
 
+  def DeserializePointer(self, size, nb_elements, data, handles):
+    return self.struct_type.Deserialize(data, handles)
+
 
 class NoneType(SerializableType):
   """Placeholder type, used temporarily until all mojo types are handled."""
@@ -331,6 +405,9 @@ class NoneType(SerializableType):
   def Serialize(self, value, data_offset, data, handle_offset):
     return (0, [])
 
+  def Deserialize(self, value, data, handles):
+    return None
+
 
 TYPE_NONE = NoneType()
 
@@ -392,6 +469,9 @@ class FieldGroup(object):
   def Serialize(self, obj, data_offset, data, handle_offset):
     raise NotImplementedError()
 
+  def Deserialize(self, value, data, handles):
+    raise NotImplementedError()
+
 
 class SingleFieldGroup(FieldGroup, FieldDescriptor):
   """A FieldGroup that contains a single FieldDescriptor."""
@@ -414,6 +494,10 @@ class SingleFieldGroup(FieldGroup, FieldDescriptor):
     value = getattr(obj, self.name)
     return self.field_type.Serialize(value, data_offset, data, handle_offset)
 
+  def Deserialize(self, value, data, handles):
+    entity = self.field_type.Deserialize(value, data, handles)
+    return { self.name: entity }
+
 
 class BooleanGroup(FieldGroup):
   """A FieldGroup to pack booleans."""
@@ -422,7 +506,7 @@ class BooleanGroup(FieldGroup):
     self.version = min([descriptor.field_number  for descriptor in descriptors])
 
   def GetTypeCode(self):
-    return "B"
+    return 'B'
 
   def GetByteSize(self):
     return 1
@@ -435,7 +519,33 @@ class BooleanGroup(FieldGroup):
         [getattr(obj, field.name) for field in self.GetDescriptors()])
     return (value, [])
 
+  def Deserialize(self, value, data, handles):
+    values =  itertools.izip_longest([x.name for x in self.descriptors],
+                                      _ConvertByteToBooleans(value),
+                                     fillvalue=False)
+    return dict(values)
+
+
+def _SerializeNativeArray(value, data_offset, data, length):
+  data_size = len(data)
+  data.extend(bytearray(serialization.HEADER_STRUCT.size))
+  data.extend(value.tostring())
+  data_length = len(data) - data_size
+  data.extend(bytearray(serialization.NeededPaddingForAlignment(data_length)))
+  serialization.HEADER_STRUCT.pack_into(data, data_size, data_length, length)
+  return (data_offset, [])
+
 
 def _ConvertBooleansToByte(booleans):
   """Pack a list of booleans into an integer."""
   return reduce(lambda x, y: x * 2 + y, reversed(booleans), 0)
+
+
+def _ConvertByteToBooleans(value, min_size=0):
+  "Unpack an integer into a list of booleans."""
+  res = []
+  while value:
+    res.append(bool(value&1))
+    value = value / 2
+  res.extend([False] * (min_size - len(res)))
+  return res