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 destination of the
  18   // serialization. The serializer will attempt to create the file at the
  19   // specified location.
  20   explicit JSONFileValueSerializer(const base::FilePath& json_file_path);
  21
  22   ~JSONFileValueSerializer() override;
  23
  24   // DO NOT USE except in unit tests to verify the file was written properly.
  25   // We should never serialize directly to a file since this will block the
  26   // thread. Instead, serialize to a string and write to the file you want on
  27   // the file thread.
  28   //
  29   // Attempt to serialize the data structure represented by Value into
  30   // JSON.  If the return value is true, the result will have been written
  31   // into the file whose name was passed into the constructor.
  32   bool Serialize(const base::Value& root) override;
  33
  34   // Equivalent to Serialize(root) except binary values are omitted from the
  35   // output.
  36   bool SerializeAndOmitBinaryValues(const base::Value& root);
  37
  38  private:
  39   bool SerializeInternal(const base::Value& root, bool omit_binary_values);
  40
  41   const base::FilePath json_file_path_;
  42
  43   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
  44 };
  45
  46 class BASE_EXPORT JSONFileValueDeserializer : public base::ValueDeserializer {
  47  public:
  48   // |json_file_path_| is the path of a file that will be source of the
  49   // deserialization.
  50   explicit JSONFileValueDeserializer(const base::FilePath& json_file_path);
  51
  52   ~JSONFileValueDeserializer() override;
  53
  54   // Attempt to deserialize the data structure encoded in the file passed
  55   // in to the constructor into a structure of Value objects.  If the return
  56   // value is NULL, and if |error_code| is non-null, |error_code| will
  57   // contain an integer error code (either JsonFileError or JsonParseError).
  58   // If |error_message| is non-null, it will be filled in with a formatted
  59   // error message including the location of the error if appropriate.
  60   // The caller takes ownership of the returned value.
  61   base::Value* Deserialize(int* error_code,
  62                            std::string* error_message) override;
  63
  64   // This enum is designed to safely overlap with JSONReader::JsonParseError.
  65   enum JsonFileError {
  66     JSON_NO_ERROR = 0,
  67     JSON_ACCESS_DENIED = 1000,
  68     JSON_CANNOT_READ_FILE,
  69     JSON_FILE_LOCKED,
  70     JSON_NO_SUCH_FILE
  71   };
  72
  73   // File-specific error messages that can be returned.
  74   static const char kAccessDenied[];
  75   static const char kCannotReadFile[];
  76   static const char kFileLocked[];
  77   static const char kNoSuchFile[];
  78
  79   // Convert an error code into an error message.  |error_code| is assumed to
  80   // be a JsonFileError.
  81   static const char* GetErrorMessageForCode(int error_code);
  82
  83   void set_allow_trailing_comma(bool new_value) {
  84     allow_trailing_comma_ = new_value;
  85   }
  86
  87   // Returns the size (in bytes) of JSON string read from disk in the last
  88   // successful |Deserialize()| call.
  89   size_t get_last_read_size() const { return last_read_size_; }
  90
  91  private:
  92   // A wrapper for ReadFileToString which returns a non-zero JsonFileError if
  93   // there were file errors.
  94   int ReadFileToString(std::string* json_string);
  95
  96   const base::FilePath json_file_path_;
  97   bool allow_trailing_comma_;
  98   size_t last_read_size_;
  99
 100   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueDeserializer);
 101 };
 102
 103 #endif  // BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
 104