be/src/kudu/util/jsonreader.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.
#ifndef KUDU_UTIL_JSONREADER_H_
#define KUDU_UTIL_JSONREADER_H_

#include <cstdint>
#include <string>
#include <vector>

#include <rapidjson/document.h>

#include "kudu/gutil/macros.h"
#include "kudu/util/status.h"

namespace kudu {

// Wraps the JSON parsing functionality of rapidjson::Document.
//
// Unlike JsonWriter, this class does not hide rapidjson internals from
// clients. That's because there's just no easy way to implement object and
// array parsing otherwise. At most, this class aspires to be a simpler
// error-handling wrapper for reading and parsing.
class JsonReader {
 public:
  explicit JsonReader(std::string text);
  ~JsonReader();

  Status Init();

  // Extractor methods.
  //
  // If 'field' is not NULL, will look for a field with that name in the
  // given object, returning Status::NotFound if it cannot be found. If
  // 'field' is NULL, will try to convert 'object' directly into the
  // desire type.

  Status ExtractBool(const rapidjson::Value* object,
                     const char* field,
                     bool* result) const;

  Status ExtractInt32(const rapidjson::Value* object,
                      const char* field,
                      int32_t* result) const;

  Status ExtractInt64(const rapidjson::Value* object,
                      const char* field,
                      int64_t* result) const;

  Status ExtractString(const rapidjson::Value* object,
                       const char* field,
                       std::string* result) const;

  // 'result' is only valid for as long as JsonReader is alive.
  Status ExtractObject(const rapidjson::Value* object,
                       const char* field,
                       const rapidjson::Value** result) const;

  // 'result' is only valid for as long as JsonReader is alive.
  Status ExtractObjectArray(const rapidjson::Value* object,
                            const char* field,
                            std::vector<const rapidjson::Value*>* result) const;

  const rapidjson::Value* root() const { return &document_; }

 private:
  Status ExtractField(const rapidjson::Value* object,
                      const char* field,
                      const rapidjson::Value** result) const;

  std::string text_;
  rapidjson::Document document_;

  DISALLOW_COPY_AND_ASSIGN(JsonReader);
};

} // namespace kudu

#endif // KUDU_UTIL_JSONREADER_H_