mojom: Add associative arrays to the mojom language.

mojo/public/cpp/bindings/lib/map_serialization.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_SERIALIZATION_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_SERIALIZATION_H_
+
+#include "mojo/public/cpp/bindings/lib/array_internal.h"
+#include "mojo/public/cpp/bindings/lib/map_data_internal.h"
+#include "mojo/public/cpp/bindings/lib/map_internal.h"
+#include "mojo/public/cpp/bindings/lib/string_serialization.h"
+#include "mojo/public/cpp/bindings/map.h"
+
+namespace mojo {
+
+template <typename Key, typename Value>
+inline size_t GetSerializedSize_(const Map<Key, Value>& input);
+
+template <typename ValidateParams, typename E, typename F>
+inline void SerializeArray_(Array<E> input,
+                            internal::Buffer* buf,
+                            internal::Array_Data<F>** output);
+
+namespace internal {
+
+template <typename MapType,
+          typename DataType,
+          bool kValueIsMoveOnlyType = IsMoveOnlyType<MapType>::value>
+struct MapSerializer;
+
+template <typename MapType, typename DataType>
+struct MapSerializer<MapType, DataType, false> {
+  static size_t GetHeaderSize() { return sizeof(Array_Data<DataType>); }

[yzshen1, 2014/10/08 21:58:33]

- Comments about the methods of MapSerializer would be helpful.
- I think GetHeaderSize() may be not necessary, because array header should
always be sizeof(ArrayHeader). Otherwise we are in bigger trouble.

+  static size_t GetBaseArraySize(size_t count) {
+    return Align(count * sizeof(DataType));
+  }
+  static size_t GetItemSize(const MapType& item) { return 0; }
+};
+
+template <>
+struct MapSerializer<bool, bool, false> {
+  static size_t GetHeaderSize() { return sizeof(Array_Data<bool>); }
+  static size_t GetBaseArraySize(size_t count) {
+    return Align((count + 7) / 8);
+  }
+  static size_t GetItemSize(bool item) { return 0; }
+};
+
+template <typename H>
+struct MapSerializer<ScopedHandleBase<H>, H, true> {
+  static size_t GetHeaderSize() { return sizeof(Array_Data<H>); }
+  static size_t GetBaseArraySize(size_t count) {
+    return Align(count * sizeof(H));
+  }
+  static size_t GetItemSize(const H& item) { return 0; }
+};
+
+template <typename S>
+struct MapSerializer<S, typename S::Data_*, true> {
+  static size_t GetHeaderSize() {
+    return sizeof(Array_Data<typename S::Data_*>);
+  }
+  static size_t GetBaseArraySize(size_t count) {
+    return count * sizeof(internal::StructPointer<typename S::Data_>);
+  }
+  static size_t GetItemSize(const S& item) { return GetSerializedSize_(item); }
+};
+
+template <>
+struct MapSerializer<String, String_Data*, false> {
+  static size_t GetHeaderSize() { return sizeof(Array_Data<String_Data*>); }
+  static size_t GetBaseArraySize(size_t count) {
+    return count * sizeof(internal::StringPointer);
+  }
+  static size_t GetItemSize(const String& item) {
+    return GetSerializedSize_(item);
+  }
+};
+
+template <typename MapKey,
+          typename MapValue,
+          typename DataKey,
+          typename DataValue>
+struct SizeAccumulator {
+  SizeAccumulator(size_t* data_size) : size(data_size) {}
+  size_t* size;
+
+  void operator()(const MapKey& key, const MapValue& value) {
+    *size += internal::MapSerializer<MapKey, DataKey>::GetItemSize(key);
+    *size += internal::MapSerializer<MapValue, DataValue>::GetItemSize(value);
+  }
+};
+
+template <typename MapKey>
+struct MapKeyValidateParams {

[yzshen1, 2014/10/08 21:58:33]

I think you have defined these types in map_data_internal.h

[Elliot Glaysher, 2014/10/08 23:40:49]

The ones in map_data_internal.h are different then these with different names.
However, with some further changes to how SerializeMap_ worked, I was able to
get rid of these.

+ public:
+  typedef NoValidateParams ElementValidateParams;
+  static const uint32_t expected_num_elements = 0;
+  static const bool element_is_nullable = false;
+};
+
+template <>
+struct MapKeyValidateParams<String> {
+ public:
+  typedef ArrayValidateParams<0, false, NoValidateParams> ElementValidateParams;
+  static const uint32_t expected_num_elements = 0;
+  static const bool element_is_nullable = false;
+};
+
+}  // namespace internal
+
+// TODO(erg): This can't go away yet. We still need to calculate out the size
+// of a struct header, and two arrays.
+template <typename MapKey, typename MapValue>
+inline size_t GetSerializedSize_(const Map<MapKey, MapValue>& input) {
+  if (!input)
+    return 0;
+  typedef typename internal::WrapperTraits<MapKey>::DataType DataKey;
+  typedef typename internal::WrapperTraits<MapValue>::DataType DataValue;
+
+  size_t count = input.size();
+  size_t struct_overhead = sizeof(mojo::internal::Map_Data<DataKey, DataValue>);
+  size_t key_base_size =
+      internal::MapSerializer<MapKey, DataKey>::GetHeaderSize() +
+      internal::MapSerializer<MapKey, DataKey>::GetBaseArraySize(count);
+  size_t value_base_size =
+      internal::MapSerializer<MapValue, DataValue>::GetHeaderSize() +
+      internal::MapSerializer<MapValue, DataValue>::GetBaseArraySize(count);
+
+  size_t key_data_size = 0;
+  size_t value_data_size = 0;
+  for (auto it = input.begin(); it != input.end(); ++it) {
+    key_data_size +=
+        internal::MapSerializer<MapKey, DataKey>::GetItemSize(it.GetKey());
+    value_data_size +=
+        internal::MapSerializer<MapValue, DataValue>::GetItemSize(
+            it.GetValue());
+  }
+
+  return struct_overhead + key_base_size + key_data_size +
+         // SOME SORT OF ALIGNMENT GOES HERE?

[yzshen1, 2014/10/08 21:58:33]

I think you have considered all alignment properly.

+         value_base_size + value_data_size;
+}
+
+// We don't need a KeyValidateParams, because we konw exactly what params are
+// needed. (Keys are primitive types or non-nullable strings.)
+template <typename ValueValidateParams,
+          typename KeyWrapperType,

[yzshen1, 2014/10/08 21:58:33]

nit: it might be better to use consistent names for template parameters, I think
you use MapKey, MapValue, DataKey, DataValue, etc. in other methods.

+          typename ValueWrapperType,
+          typename KeySerializationType,
+          typename ValueSerializationType>
+inline void SerializeMap_(
+    Map<KeyWrapperType, ValueWrapperType> input,
+    internal::Buffer* buf,
+    internal::Map_Data<KeySerializationType, ValueSerializationType>** output) {
+  if (input) {
+    internal::Map_Data<KeySerializationType, ValueSerializationType>* result =
+        internal::Map_Data<KeySerializationType, ValueSerializationType>::New(
+            buf);
+    if (result) {
+      Array<KeyWrapperType> keys;
+      Array<ValueWrapperType> values;
+      input.DecomposeMapTo(&keys, &values);
+      SerializeArray_<internal::MapKeyValidateParams<KeyWrapperType>>(
+          keys.Pass(), buf, &result->first.ptr);
+      SerializeArray_<ValueValidateParams>(
+          values.Pass(), buf, &result->second.ptr);
+    }
+    *output = result;
+  } else {
+    *output = nullptr;
+  }
+}
+
+template <typename KeyWrapperType,
+          typename ValueWrapperType,
+          typename KeySerializationType,
+          typename ValueSerializationType>
+inline void Deserialize_(
+    internal::Map_Data<KeySerializationType, ValueSerializationType>* input,
+    Map<KeyWrapperType, ValueWrapperType>* output) {
+  if (input) {
+    Array<KeyWrapperType> keys;
+    Array<ValueWrapperType> values;
+
+    Deserialize_(input->first.ptr, &keys);
+    Deserialize_(input->second.ptr, &values);
+
+    *output = Map<KeyWrapperType, ValueWrapperType>(keys.Pass(), values.Pass());
+  } else {
+    output->reset();
+  }
+}
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_SERIALIZATION_H_