mojom: Add associative arrays to the mojom language.

mojo/public/cpp/bindings/lib/map_data_internal.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_DATA_INTERNAL_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_DATA_INTERNAL_H_
+
+#include "mojo/public/cpp/bindings/lib/array_internal.h"
+#include "mojo/public/cpp/bindings/lib/validate_params.h"
+#include "mojo/public/cpp/bindings/lib/validation_errors.h"
+
+namespace mojo {
+namespace internal {
+
+template <typename MapKey>
+struct MapDataKeyValidateParams {
+ public:
+  typedef NoValidateParams ElementValidateParams;
+  static const uint32_t expected_num_elements = 0;
+  static const bool element_is_nullable = false;
+};
+
+template <>
+struct MapDataKeyValidateParams<mojo::internal::Array_Data<char>*> {

[yzshen1, 2014/10/08 21:58:32]

Please add a comment saying that this is for non-nullable string.

+ public:
+  typedef ArrayValidateParams<0, false, NoValidateParams> ElementValidateParams;
+  static const uint32_t expected_num_elements = 0;
+  static const bool element_is_nullable = false;
+};
+
+// Map serializes into a struct which has two arrays as struct fields, the keys
+// and the values.
+template <typename First, typename Second>

[yzshen1, 2014/10/08 21:58:32]

nit: calling them Key and Value may be more consistent with other classes.

+class Map_Data {
+ public:
+  static Map_Data* New(mojo::internal::Buffer* buf) {
+    return new (buf->Allocate(sizeof(Map_Data))) Map_Data();
+  }
+
+  template <typename ValueParams>
+  static bool Validate(const void* data,
+                       mojo::internal::BoundsChecker* bounds_checker) {
+    if (!data)
+      return true;
+
+    if (!ValidateStructHeader(data, sizeof(Map_Data), 2, bounds_checker))
+      return false;
+
+    const Map_Data* MOJO_ALLOW_UNUSED object =

[yzshen1, 2014/10/08 21:58:32]

no need to have MOJO_ALLOW_UNUSED. (we have this in the generic struct case is
because we may not need to validate any fields for some structs.)

+        static_cast<const Map_Data*>(data);
+    if (!mojo::internal::ValidateEncodedPointer(&object->first.offset)) {

[yzshen1, 2014/10/08 21:58:32]

we are already in mojo::internal (here and elsewhere)

+      ReportValidationError(mojo::internal::VALIDATION_ERROR_ILLEGAL_POINTER);
+      return false;
+    }
+    if (!object->first.offset) {
+      ReportValidationError(
+          mojo::internal::VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
+          "null key array in map struct");
+      return false;
+    }
+    if (!internal::Array_Data<First>::template Validate<

[yzshen1, 2014/10/08 21:58:32]

We are already in internal:: (here and elsewhere)

+            MapDataKeyValidateParams<First>>(
+            mojo::internal::DecodePointerRaw(&object->first.offset),

[yzshen1, 2014/10/08 21:58:32]

indent 4 more spaces?

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

This patch was run through git cl-format.

+            bounds_checker)) {
+      return false;
+    }
+
+    if (!mojo::internal::ValidateEncodedPointer(&object->second.offset)) {
+      ReportValidationError(mojo::internal::VALIDATION_ERROR_ILLEGAL_POINTER);
+      return false;
+    }
+    if (!object->second.offset) {
+      ReportValidationError(
+          mojo::internal::VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
+          "null value array in map struct");
+      return false;
+    }
+    if (!internal::Array_Data<Second>::template Validate<ValueParams>(
+            mojo::internal::DecodePointerRaw(&object->second.offset),
+            bounds_checker)) {
+      return false;
+    }
+
+    const ArrayHeader* first_header = static_cast<const ArrayHeader*>(
+        mojo::internal::DecodePointerRaw(&object->first.offset));
+    const ArrayHeader* second_header = static_cast<const ArrayHeader*>(
+        mojo::internal::DecodePointerRaw(&object->second.offset));
+    if (first_header->num_elements != second_header->num_elements) {
+      ReportValidationError(
+          mojo::internal::VALIDATION_ERROR_DIFFERENT_SIZED_ARRAYS_IN_MAP);
+      return false;
+    }
+
+    return true;
+  }
+
+  mojo::internal::StructHeader header_;
+
+  mojo::internal::ArrayPointer<First> first;
+  mojo::internal::ArrayPointer<Second> second;
+
+  void EncodePointersAndHandles(std::vector<mojo::Handle>* handles) {
+    mojo::internal::Encode(&first, handles);
+    mojo::internal::Encode(&second, handles);
+  }
+
+  void DecodePointersAndHandles(std::vector<mojo::Handle>* handles) {
+    mojo::internal::Decode(&first, handles);
+    mojo::internal::Decode(&second, handles);
+  }
+
+ private:
+  Map_Data() {
+    header_.num_bytes = sizeof(*this);
+    header_.num_fields = 2;
+  }
+  ~Map_Data() = delete;

[yzshen1, 2014/10/08 21:58:32]

This makes sense. And I think we should do the same for other struct data and
array data. - right?

+};
+

[yzshen1, 2014/10/08 21:58:32]

maybe we can static_assert the size (of some Map_Data<> specialization) here.

+}  // namespace internal
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MAP_DATA_INTERNAL_H_