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_patch 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     : json_file_path_(json_file_path),
  23       allow_trailing_comma_(false) {}
  24
  25   virtual ~JSONFileValueSerializer() {}
  26
  27   // DO NOT USE except in unit tests to verify the file was written properly.
  28   // We should never serialize directly to a file since this will block the
  29   // thread. Instead, serialize to a string and write to the file you want on
  30   // the file thread.
  31   //
  32   // Attempt to serialize the data structure represented by Value into
  33   // JSON.  If the return value is true, the result will have been written
  34   // into the file whose name was passed into the constructor.
  35   virtual bool Serialize(const base::Value& root) override;
  36
  37   // Equivalent to Serialize(root) except binary values are omitted from the
  38   // output.
  39   bool SerializeAndOmitBinaryValues(const base::Value& root);
  40
  41   // Attempt to deserialize the data structure encoded in the file passed
  42   // in to the constructor into a structure of Value objects.  If the return
  43   // value is NULL, and if |error_code| is non-null, |error_code| will
  44   // contain an integer error code (either JsonFileError or JsonParseError).
  45   // If |error_message| is non-null, it will be filled in with a formatted
  46   // error message including the location of the error if appropriate.
  47   // The caller takes ownership of the returned value.
  48   virtual base::Value* Deserialize(int* error_code,
  49                                    std::string* error_message) override;
  50
  51   // This enum is designed to safely overlap with JSONReader::JsonParseError.
  52   enum JsonFileError {
  53     JSON_NO_ERROR = 0,
  54     JSON_ACCESS_DENIED = 1000,
  55     JSON_CANNOT_READ_FILE,
  56     JSON_FILE_LOCKED,
  57     JSON_NO_SUCH_FILE
  58   };
  59
  60   // File-specific error messages that can be returned.
  61   static const char* kAccessDenied;
  62   static const char* kCannotReadFile;
  63   static const char* kFileLocked;
  64   static const char* kNoSuchFile;
  65
  66   // Convert an error code into an error message.  |error_code| is assumed to
  67   // be a JsonFileError.
  68   static const char* GetErrorMessageForCode(int error_code);
  69
  70   void set_allow_trailing_comma(bool new_value) {
  71     allow_trailing_comma_ = new_value;
  72   }
  73
  74  private:
  75   bool SerializeInternal(const base::Value& root, bool omit_binary_values);
  76
  77   base::FilePath json_file_path_;
  78   bool allow_trailing_comma_;
  79
  80   // A wrapper for ReadFileToString which returns a non-zero JsonFileError if
  81   // there were file errors.
  82   int ReadFileToString(std::string* json_string);
  83
  84   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
  85 };
  86
  87 #endif  // BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
  88