json_file_value_serializer.h

// Copyright (c) 2012 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 BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
#define BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_

#include <stddef.h>

#include <string>

#include "base/base_export.h"
#include "base/files/file_path.h"
#include "base/macros.h"
#include "base/values.h"

class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
 public:
  // |json_file_path_| is the path of a file that will be destination of the
  // serialization. The serializer will attempt to create the file at the
  // specified location.
  explicit JSONFileValueSerializer(const base::FilePath& json_file_path);

  ~JSONFileValueSerializer() override;

  // DO NOT USE except in unit tests to verify the file was written properly.
  // We should never serialize directly to a file since this will block the
  // thread. Instead, serialize to a string and write to the file you want on
  // the file thread.
  //
  // Attempt to serialize the data structure represented by Value into
  // JSON.  If the return value is true, the result will have been written
  // into the file whose name was passed into the constructor.
  bool Serialize(const base::Value& root) override;

  // Equivalent to Serialize(root) except binary values are omitted from the
  // output.
  bool SerializeAndOmitBinaryValues(const base::Value& root);

 private:
  bool SerializeInternal(const base::Value& root, bool omit_binary_values);

  const base::FilePath json_file_path_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
};

class BASE_EXPORT JSONFileValueDeserializer : public base::ValueDeserializer {
 public:
  // |json_file_path_| is the path of a file that will be source of the
  // deserialization. |options| is a bitmask of JSONParserOptions.
  explicit JSONFileValueDeserializer(const base::FilePath& json_file_path,
                                     int options = 0);

  ~JSONFileValueDeserializer() override;

  // Attempt to deserialize the data structure encoded in the file passed
  // in to the constructor into a structure of Value objects.  If the return
  // value is NULL, and if |error_code| is non-null, |error_code| will
  // contain an integer error code (either JsonFileError or JsonParseError).
  // If |error_message| is non-null, it will be filled in with a formatted
  // error message including the location of the error if appropriate.
  // The caller takes ownership of the returned value.
  std::unique_ptr<base::Value> Deserialize(int* error_code,
                                           std::string* error_message) override;

  // This enum is designed to safely overlap with JSONReader::JsonParseError.
  enum JsonFileError {
    JSON_NO_ERROR = 0,
    JSON_ACCESS_DENIED = 1000,
    JSON_CANNOT_READ_FILE,
    JSON_FILE_LOCKED,
    JSON_NO_SUCH_FILE
  };

  // File-specific error messages that can be returned.
  static const char kAccessDenied[];
  static const char kCannotReadFile[];
  static const char kFileLocked[];
  static const char kNoSuchFile[];

  // Convert an error code into an error message.  |error_code| is assumed to
  // be a JsonFileError.
  static const char* GetErrorMessageForCode(int error_code);

  // Returns the size (in bytes) of JSON string read from disk in the last
  // successful |Deserialize()| call.
  size_t get_last_read_size() const { return last_read_size_; }

 private:
  // A wrapper for ReadFileToString which returns a non-zero JsonFileError if
  // there were file errors.
  int ReadFileToString(std::string* json_string);

  const base::FilePath json_file_path_;
  const int options_;
  size_t last_read_size_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueDeserializer);
};

#endif  // BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_