Add plugins (#27)

plugins/wasm-cpp/common/json_util.h

@@ -0,0 +1,120 @@
+/* Copyright 2020 Istio Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "common/nlohmann_json.hpp"
+
+/**
+ * Utilities for working with JSON without exceptions.
+ */
+namespace Wasm {
+namespace Common {
+
+using JsonObject = ::nlohmann::json;
+
+enum JsonParserResultDetail {
+  UNKNOWN,
+  OK,
+  OUT_OF_RANGE,
+  TYPE_ERROR,
+  INVALID_VALUE,
+};
+
+std::optional<JsonObject> JsonParse(std::string_view str);
+
+template <typename T>
+std::pair<std::optional<T>, JsonParserResultDetail> JsonValueAs(
+    const JsonObject&) {
+  static_assert(true, "Unsupported Type");
+}
+
+template <>
+std::pair<std::optional<std::string_view>, JsonParserResultDetail>
+JsonValueAs<std::string_view>(const JsonObject& j);
+
+template <>
+std::pair<std::optional<std::string>, JsonParserResultDetail>
+JsonValueAs<std::string>(const JsonObject& j);
+
+template <>
+std::pair<std::optional<int64_t>, JsonParserResultDetail> JsonValueAs<int64_t>(
+    const JsonObject& j);
+
+template <>
+std::pair<std::optional<uint64_t>, JsonParserResultDetail>
+JsonValueAs<uint64_t>(const JsonObject& j);
+
+template <>
+std::pair<std::optional<bool>, JsonParserResultDetail> JsonValueAs<bool>(
+    const JsonObject& j);
+
+template <>
+std::pair<std::optional<JsonObject>, JsonParserResultDetail>
+JsonValueAs<JsonObject>(const JsonObject& j);
+
+template <>
+std::pair<std::optional<std::vector<std::string_view>>, JsonParserResultDetail>
+JsonValueAs<std::vector<std::string_view>>(const JsonObject& j);
+
+template <class T>
+class JsonGetField {
+ public:
+  JsonGetField(const JsonObject& j, std::string_view field);
+  const JsonParserResultDetail& detail() { return detail_; }
+  T value() { return object_; }
+  T value_or(T v) {
+    if (detail_ != JsonParserResultDetail::OK)
+      return v;
+    else
+      return object_;
+  };
+
+ private:
+  JsonParserResultDetail detail_;
+  T object_;
+};
+
+template <class T>
+JsonGetField<T>::JsonGetField(const JsonObject& j, std::string_view field) {
+  auto it = j.find(field);
+  if (it == j.end()) {
+    detail_ = JsonParserResultDetail::OUT_OF_RANGE;
+    return;
+  }
+  auto value = JsonValueAs<T>(it.value());
+  detail_ = value.second;
+  if (value.first.has_value()) {
+    object_ = value.first.value();
+  }
+}
+
+// Iterate over an optional array field.
+// Returns false if set and not an array, or any of the visitor calls returns
+// false.
+bool JsonArrayIterate(
+    const JsonObject& j, std::string_view field,
+    const std::function<bool(const JsonObject& elt)>& visitor);
+
+// Iterate over an optional object field key set.
+// Returns false if set and not an object, or any of the visitor calls returns
+// false.
+bool JsonObjectIterate(const JsonObject& j, std::string_view field,
+                       const std::function<bool(std::string key)>& visitor);
+bool JsonObjectIterate(const JsonObject& j,
+                       const std::function<bool(std::string key)>& visitor);
+
+}  // namespace Common
+}  // namespace Wasm