base/json/json_file_value_serializer.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
   6 #define BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
   7
   8 #include <string>
   9
  10 #include "base/base_export.h"
  11 #include "base/basictypes.h"
  12 #include "base/files/file_path.h"
  13 #include "base/values.h"
  14
  15 class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
  16  public:
  17   // |json_file_path_| is the path of a file that will be source of the
  18   // deserialization or the destination of the serialization.
  19   // When deserializing, the file should exist, but when serializing, the
  20   // serializer will attempt to create the file at the specified location.
  21   explicit JSONFileValueSerializer(const base::FilePath& json_file_path);
  22
  23   ~JSONFileValueSerializer() override;
  24
  25   // DO NOT USE except in unit tests to verify the file was written properly.
  26   // We should never serialize directly to a file since this will block the
  27   // thread. Instead, serialize to a string and write to the file you want on
  28   // the file thread.
  29   //
  30   // Attempt to serialize the data structure represented by Value into
  31   // JSON.  If the return value is true, the result will have been written
  32   // into the file whose name was passed into the constructor.
  33   bool Serialize(const base::Value& root) override;
  34
  35   // Equivalent to Serialize(root) except binary values are omitted from the
  36   // output.
  37   bool SerializeAndOmitBinaryValues(const base::Value& root);
  38
  39   // Attempt to deserialize the data structure encoded in the file passed
  40   // in to the constructor into a structure of Value objects.  If the return
  41   // value is NULL, and if |error_code| is non-null, |error_code| will
  42   // contain an integer error code (either JsonFileError or JsonParseError).
  43   // If |error_message| is non-null, it will be filled in with a formatted
  44   // error message including the location of the error if appropriate.
  45   // The caller takes ownership of the returned value.
  46   base::Value* Deserialize(int* error_code,
  47                            std::string* error_message) override;
  48
  49   // This enum is designed to safely overlap with JSONReader::JsonParseError.
  50   enum JsonFileError {
  51     JSON_NO_ERROR = 0,
  52     JSON_ACCESS_DENIED = 1000,
  53     JSON_CANNOT_READ_FILE,
  54     JSON_FILE_LOCKED,
  55     JSON_NO_SUCH_FILE
  56   };
  57
  58   // File-specific error messages that can be returned.
  59   static const char kAccessDenied[];
  60   static const char kCannotReadFile[];
  61   static const char kFileLocked[];
  62   static const char kNoSuchFile[];
  63
  64   // Convert an error code into an error message.  |error_code| is assumed to
  65   // be a JsonFileError.
  66   static const char* GetErrorMessageForCode(int error_code);
  67
  68   void set_allow_trailing_comma(bool new_value) {
  69     allow_trailing_comma_ = new_value;
  70   }
  71
  72   // Returns the syze (in bytes) of JSON string read from disk in the last
  73   // successful |Deserialize()| call.
  74   size_t get_last_read_size() const { return last_read_size_; }
  75
  76  private:
  77   bool SerializeInternal(const base::Value& root, bool omit_binary_values);
  78
  79   const base::FilePath json_file_path_;
  80   bool allow_trailing_comma_;
  81   size_t last_read_size_;
  82
  83   // A wrapper for ReadFileToString which returns a non-zero JsonFileError if
  84   // there were file errors.
  85   int ReadFileToString(std::string* json_string);
  86
  87   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
  88 };
  89
  90 #endif  // BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
  91