base/json/json_value_serializer.h

   1 // Copyright (c) 2011 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_VALUE_SERIALIZER_H_
   6 #define BASE_JSON_JSON_VALUE_SERIALIZER_H_
   7 #pragma once
   8
   9 #include <string>
  10
  11 #include "base/base_export.h"
  12 #include "base/basictypes.h"
  13 #include "base/file_path.h"
  14 #include "base/values.h"
  15
  16 class BASE_EXPORT JSONStringValueSerializer : public base::ValueSerializer {
  17  public:
  18   // json_string is the string that will be source of the deserialization
  19   // or the destination of the serialization.  The caller of the constructor
  20   // retains ownership of the string.
  21   explicit JSONStringValueSerializer(std::string* json_string)
  22       : json_string_(json_string),
  23         initialized_with_const_string_(false),
  24         pretty_print_(false),
  25         allow_trailing_comma_(false) {
  26   }
  27
  28   // This version allows initialization with a const string reference for
  29   // deserialization only.
  30   explicit JSONStringValueSerializer(const std::string& json_string)
  31       : json_string_(&const_cast<std::string&>(json_string)),
  32         initialized_with_const_string_(true),
  33         pretty_print_(false),
  34         allow_trailing_comma_(false) {
  35   }
  36
  37   virtual ~JSONStringValueSerializer();
  38
  39   // Attempt to serialize the data structure represented by Value into
  40   // JSON.  If the return value is true, the result will have been written
  41   // into the string passed into the constructor.
  42   virtual bool Serialize(const Value& root) OVERRIDE;
  43
  44   // Equivalent to Serialize(root) except binary values are omitted from the
  45   // output.
  46   bool SerializeAndOmitBinaryValues(const Value& root);
  47
  48   // Attempt to deserialize the data structure encoded in the string passed
  49   // in to the constructor into a structure of Value objects.  If the return
  50   // value is NULL, and if |error_code| is non-null, |error_code| will
  51   // contain an integer error code (either JsonFileError or JsonParseError).
  52   // If |error_message| is non-null, it will be filled in with a formatted
  53   // error message including the location of the error if appropriate.
  54   // The caller takes ownership of the returned value.
  55   virtual Value* Deserialize(int* error_code,
  56                              std::string* error_message) OVERRIDE;
  57
  58   void set_pretty_print(bool new_value) { pretty_print_ = new_value; }
  59   bool pretty_print() { return pretty_print_; }
  60
  61   void set_allow_trailing_comma(bool new_value) {
  62     allow_trailing_comma_ = new_value;
  63   }
  64
  65  private:
  66   bool SerializeInternal(const Value& root, bool omit_binary_values);
  67
  68   std::string* json_string_;
  69   bool initialized_with_const_string_;
  70   bool pretty_print_;  // If true, serialization will span multiple lines.
  71   // If true, deserialization will allow trailing commas.
  72   bool allow_trailing_comma_;
  73
  74   DISALLOW_COPY_AND_ASSIGN(JSONStringValueSerializer);
  75 };
  76
  77 class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
  78  public:
  79   // json_file_patch is the path of a file that will be source of the
  80   // deserialization or the destination of the serialization.
  81   // When deserializing, the file should exist, but when serializing, the
  82   // serializer will attempt to create the file at the specified location.
  83   explicit JSONFileValueSerializer(const FilePath& json_file_path)
  84     : json_file_path_(json_file_path),
  85       allow_trailing_comma_(false) {}
  86
  87   virtual ~JSONFileValueSerializer() {}
  88
  89   // DO NOT USE except in unit tests to verify the file was written properly.
  90   // We should never serialize directly to a file since this will block the
  91   // thread. Instead, serialize to a string and write to the file you want on
  92   // the file thread.
  93   //
  94   // Attempt to serialize the data structure represented by Value into
  95   // JSON.  If the return value is true, the result will have been written
  96   // into the file whose name was passed into the constructor.
  97   virtual bool Serialize(const Value& root) OVERRIDE;
  98
  99   // Equivalent to Serialize(root) except binary values are omitted from the
 100   // output.
 101   bool SerializeAndOmitBinaryValues(const Value& root);
 102
 103   // Attempt to deserialize the data structure encoded in the file passed
 104   // in to the constructor into a structure of Value objects.  If the return
 105   // value is NULL, and if |error_code| is non-null, |error_code| will
 106   // contain an integer error code (either JsonFileError or JsonParseError).
 107   // If |error_message| is non-null, it will be filled in with a formatted
 108   // error message including the location of the error if appropriate.
 109   // The caller takes ownership of the returned value.
 110   virtual Value* Deserialize(int* error_code,
 111                              std::string* error_message) OVERRIDE;
 112
 113   // This enum is designed to safely overlap with JSONReader::JsonParseError.
 114   enum JsonFileError {
 115     JSON_NO_ERROR = 0,
 116     JSON_ACCESS_DENIED = 1000,
 117     JSON_CANNOT_READ_FILE,
 118     JSON_FILE_LOCKED,
 119     JSON_NO_SUCH_FILE
 120   };
 121
 122   // File-specific error messages that can be returned.
 123   static const char* kAccessDenied;
 124   static const char* kCannotReadFile;
 125   static const char* kFileLocked;
 126   static const char* kNoSuchFile;
 127
 128   // Convert an error code into an error message.  |error_code| is assumed to
 129   // be a JsonFileError.
 130   static const char* GetErrorMessageForCode(int error_code);
 131
 132   void set_allow_trailing_comma(bool new_value) {
 133     allow_trailing_comma_ = new_value;
 134   }
 135
 136  private:
 137   bool SerializeInternal(const Value& root, bool omit_binary_values);
 138
 139   FilePath json_file_path_;
 140   bool allow_trailing_comma_;
 141
 142   // A wrapper for file_util::ReadFileToString which returns a non-zero
 143   // JsonFileError if there were file errors.
 144   int ReadFileToString(std::string* json_string);
 145
 146   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
 147 };
 148
 149 #endif  // BASE_JSON_JSON_VALUE_SERIALIZER_H_