[libFuzzer] Add proto definition and converter for JSON format.

TBR=metzman@chromium.org

Bug: 
Change-Id: Ibbcf61f59f6cd854344c37c6a968817b5ff2c834
Reviewed-on: https://chromium-review.googlesource.com/746990Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512880}

testing/libfuzzer/proto/BUILD.gn

+# Copyright 2017 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.
+
+import("//third_party/protobuf/proto_library.gni")
+
+copy("json_proto_copy") {
+  sources = [
+    "json.proto",
+  ]
+  outputs = [
+    "$root_gen_dir" + "/testing/libfuzzer/proto/json.proto",
+  ]
+}
+
+proto_library("json_proto") {
+  sources = [
+    "json.proto",
+  ]
+
+  # This way json.pb.h header goes into "$root_gen_dir" directory precisely,
+  # otherwise it goes into "$root_gen_dir" + "/testing/libfuzzer/proto/".
+  proto_out_dir = ""
+  deps = [
+    ":json_proto_copy",
+  ]
+}
+
+source_set("json_proto_converter") {
+  sources = [
+    "json_proto_converter.cc",
+    "json_proto_converter.h",
+  ]
+  deps = [
+    ":json_proto",
+  ]
+}

testing/libfuzzer/proto/json.proto

+// Copyright 2017 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.
+
+// The proto definition for JSON format has been written based on
+// http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
+
+syntax = "proto2";
+
+package json_proto;
+
+message JsonObject {
+  required string name = 1;
+  required JsonValue value = 2;
+}
+
+message JsonValue {
+  oneof value {
+    // Json value types:
+
+    // null: null, will be used when 'oneof' contains nothing
+
+    // object: another json object of any type
+    JsonObject object_value = 1;
+
+    // array: an array of values
+    ArrayValue array_value = 2;
+
+    // number: can be an integer, a float, an exponent
+    NumberValue number_value = 3;
+
+    // string: unicode string
+    StringValue string_value = 4;
+
+    // boolean: true or talse
+    BooleanValue boolean_value = 5;
+  }
+}
+
+message ArrayValue {
+  repeated JsonValue value = 1;
+}
+
+message NumberInteger {
+  required int64 value = 1;
+}
+
+message NumberFloat {
+  required double value = 1;
+}
+
+message NumberExponent {
+  required int32 base = 1;
+  required int32 exponent = 2;
+  required bool use_uppercase = 3;
+}
+
+message NumberExponentFrac {
+  required float base = 1;
+  required int32 exponent = 2;
+  required bool use_uppercase = 3;
+}
+
+message NumberValue {
+  required NumberInteger integer_value = 1;
+
+  // integer_value is used when oneof field below has nothing.
+  oneof value {
+    NumberFloat float_value = 2;
+    NumberExponent exponent_value = 3;
+    NumberExponentFrac exponent_frac_value = 4;
+  }
+}
+
+message StringValue {
+  required string value = 1;
+}
+
+message BooleanValue {
+  required bool value = 1;
+}

testing/libfuzzer/proto/json_proto_converter.cc

+// Copyright 2017 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.
+
+#include "testing/libfuzzer/proto/json_proto_converter.h"
+
+using namespace json_proto;
+
+void JsonProtoConverter::AppendArray(const ArrayValue& array_value) {
+  data_ << '[';
+  bool need_comma = false;
+  for (const auto& value : array_value.value()) {
+    // Trailing comma inside of an array makes JSON invalid, avoid adding that.
+    if (need_comma)
+      data_ << ',';
+    else
+      need_comma = true;
+
+    AppendValue(value);
+  }
+  data_ << ']';
+}
+
+void JsonProtoConverter::AppendNumber(const NumberValue& number_value) {
+  if (number_value.has_float_value()) {
+    data_ << number_value.float_value().value();
+  } else if (number_value.has_exponent_value()) {
+    auto value = number_value.exponent_value();
+    data_ << value.base();
+    data_ << (value.use_uppercase() ? 'E' : 'e');
+    data_ << value.exponent();
+  } else if (number_value.has_exponent_frac_value()) {
+    auto value = number_value.exponent_value();
+    data_ << value.base();
+    data_ << (value.use_uppercase() ? 'E' : 'e');
+    data_ << value.exponent();
+  } else {
+    data_ << number_value.integer_value().value();
+  }
+}
+
+void JsonProtoConverter::AppendObject(const JsonObject& json_object) {
+  data_ << '{' << '"' << json_object.name() << '"' << ':';
+  AppendValue(json_object.value());
+  data_ << '}';
+}
+
+void JsonProtoConverter::AppendValue(const JsonValue& json_value) {
+  if (json_value.has_object_value()) {
+    AppendObject(json_value.object_value());
+  } else if (json_value.has_array_value()) {
+    AppendArray(json_value.array_value());
+  } else if (json_value.has_number_value()) {
+    AppendNumber(json_value.number_value());
+  } else if (json_value.has_string_value()) {
+    data_ << '"' << json_value.string_value().value() << '"';
+  } else if (json_value.has_boolean_value()) {
+    data_ << (json_value.boolean_value().value() ? "true" : "false");
+  } else {
+    data_ << "null";
+  }
+}
+
+std::string JsonProtoConverter::Convert(const JsonObject& json_object) {
+  AppendObject(json_object);
+  return data_.str();
+}

testing/libfuzzer/proto/json_proto_converter.h

+// Copyright 2017 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 TESTING_LIBFUZZER_PROTO_JSON_PROTO_CONVERTER_H
+#define TESTING_LIBFUZZER_PROTO_JSON_PROTO_CONVERTER_H
+
+#include "testing/libfuzzer/proto/json.pb.h"
+
+#include <sstream>
+#include <string>
+
+namespace json_proto {
+
+class JsonProtoConverter {
+ public:
+  std::string Convert(const json_proto::JsonObject&);
+
+ private:
+  std::stringstream data_;
+
+  void AppendArray(const json_proto::ArrayValue&);
+  void AppendNumber(const json_proto::NumberValue&);
+  void AppendObject(const json_proto::JsonObject&);
+  void AppendValue(const json_proto::JsonValue&);
+};
+
+}  // namespace json_proto
+
+#endif  // TESTING_LIBFUZZER_PROTO_JSON_PROTO_CONVERTER_H