Move the json-related files into a separate json directory. This hopefully al...

base/json_reader.h

-// Copyright (c) 2006-2008 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.
-//
-// A JSON parser.  Converts strings of JSON into a Value object (see
-// base/values.h).
-// http://www.ietf.org/rfc/rfc4627.txt?number=4627
-//
-// Known limitations/deviations from the RFC:
-// - Only knows how to parse ints within the range of a signed 32 bit int and
-//   decimal numbers within a double.
-// - Assumes input is encoded as UTF8.  The spec says we should allow UTF-16
-//   (BE or LE) and UTF-32 (BE or LE) as well.
-// - We limit nesting to 100 levels to prevent stack overflow (this is allowed
-//   by the RFC).
-// - A Unicode FAQ ("http://unicode.org/faq/utf_bom.html") writes a data
-//   stream may start with a Unicode Byte-Order-Mark (U+FEFF), i.e. the input
-//   UTF-8 string for the JSONReader::JsonToValue() function may start with a
-//   UTF-8 BOM (0xEF, 0xBB, 0xBF).
-//   To avoid the function from mis-treating a UTF-8 BOM as an invalid
-//   character, the function skips a Unicode BOM at the beginning of the
-//   Unicode string (converted from the input UTF-8 string) before parsing it.
-//
-// TODO(tc): Add a parsing option to to relax object keys being wrapped in
-//   double quotes
-// TODO(tc): Add an option to disable comment stripping
-// TODO(aa): Consider making the constructor public and the static Read() method
-// only a convenience for the common uses with more complex configuration going
-// on the instance.
-
-#ifndef BASE_JSON_READER_H_
-#define BASE_JSON_READER_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "testing/gtest/include/gtest/gtest_prod.h"
-
-class Value;
-
-class JSONReader {
- public:
-  // A struct to hold a JS token.
-  class Token {
-   public:
-    enum Type {
-     OBJECT_BEGIN,           // {
-     OBJECT_END,             // }
-     ARRAY_BEGIN,            // [
-     ARRAY_END,              // ]
-     STRING,
-     NUMBER,
-     BOOL_TRUE,              // true
-     BOOL_FALSE,             // false
-     NULL_TOKEN,             // null
-     LIST_SEPARATOR,         // ,
-     OBJECT_PAIR_SEPARATOR,  // :
-     END_OF_INPUT,
-     INVALID_TOKEN,
-    };
-    Token(Type t, const wchar_t* b, int len)
-      : type(t), begin(b), length(len) {}
-
-    Type type;
-
-    // A pointer into JSONReader::json_pos_ that's the beginning of this token.
-    const wchar_t* begin;
-
-    // End should be one char past the end of the token.
-    int length;
-
-    // Get the character that's one past the end of this token.
-    wchar_t NextChar() {
-      return *(begin + length);
-    }
-  };
-
-  // Error messages that can be returned.
-  static const char* kBadRootElementType;
-  static const char* kInvalidEscape;
-  static const char* kSyntaxError;
-  static const char* kTrailingComma;
-  static const char* kTooMuchNesting;
-  static const char* kUnexpectedDataAfterRoot;
-  static const char* kUnsupportedEncoding;
-  static const char* kUnquotedDictionaryKey;
-
-  JSONReader();
-
-  // Reads and parses |json|, returning a Value. The caller owns the returned
-  // instance. If |json| is not a properly formed JSON string, returns NULL.
-  // If |allow_trailing_comma| is true, we will ignore trailing commas in
-  // objects and arrays even though this goes against the RFC.
-  static Value* Read(const std::string& json, bool allow_trailing_comma);
-
-  // Reads and parses |json| like Read(). |error_message_out| is optional. If
-  // specified and NULL is returned, |error_message_out| will be populated with
-  // a string describing the error. Otherwise, |error_message_out| is
-  // unmodified.
-  static Value* ReadAndReturnError(const std::string& json,
-                                   bool allow_trailing_comma,
-                                   std::string* error_message_out);
-
-  // Returns the error message if the last call to JsonToValue() failed. If the
-  // last call did not fail, returns a valid empty string.
-  std::string error_message() { return error_message_; }
-
-  // Reads and parses |json|, returning a Value. The caller owns the returned
-  // instance. If |json| is not a properly formed JSON string, returns NULL and
-  // a detailed error can be retrieved from |error_message()|.
-  // If |check_root| is true, we require that the root object be an object or
-  // array. Otherwise, it can be any valid JSON type.
-  // If |allow_trailing_comma| is true, we will ignore trailing commas in
-  // objects and arrays even though this goes against the RFC.
-  Value* JsonToValue(const std::string& json, bool check_root,
-                     bool allow_trailing_comma);
-
- private:
-  static std::string FormatErrorMessage(int line, int column,
-                                        const char* description);
-
-  DISALLOW_EVIL_CONSTRUCTORS(JSONReader);
-
-  FRIEND_TEST(JSONReaderTest, Reading);
-  FRIEND_TEST(JSONReaderTest, ErrorMessages);
-
-  // Recursively build Value.  Returns NULL if we don't have a valid JSON
-  // string.  If |is_root| is true, we verify that the root element is either
-  // an object or an array.
-  Value* BuildValue(bool is_root);
-
-  // Parses a sequence of characters into a Token::NUMBER. If the sequence of
-  // characters is not a valid number, returns a Token::INVALID_TOKEN. Note
-  // that DecodeNumber is used to actually convert from a string to an
-  // int/double.
-  Token ParseNumberToken();
-
-  // Try and convert the substring that token holds into an int or a double. If
-  // we can (ie., no overflow), return the value, else return NULL.
-  Value* DecodeNumber(const Token& token);
-
-  // Parses a sequence of characters into a Token::STRING. If the sequence of
-  // characters is not a valid string, returns a Token::INVALID_TOKEN. Note
-  // that DecodeString is used to actually decode the escaped string into an
-  // actual wstring.
-  Token ParseStringToken();
-
-  // Convert the substring into a value string.  This should always succeed
-  // (otherwise ParseStringToken would have failed).
-  Value* DecodeString(const Token& token);
-
-  // Grabs the next token in the JSON stream.  This does not increment the
-  // stream so it can be used to look ahead at the next token.
-  Token ParseToken();
-
-  // Increments |json_pos_| past leading whitespace and comments.
-  void EatWhitespaceAndComments();
-
-  // If |json_pos_| is at the start of a comment, eat it, otherwise, returns
-  // false.
-  bool EatComment();
-
-  // Checks if |json_pos_| matches str.
-  bool NextStringMatch(const std::wstring& str);
-
-  // Creates the error message that will be returned to the caller. The current
-  // line and column are determined and added into the final message.
-  void SetErrorMessage(const char* description, const wchar_t* error_pos);
-
-  // Pointer to the starting position in the input string.
-  const wchar_t* start_pos_;
-
-  // Pointer to the current position in the input string.
-  const wchar_t* json_pos_;
-
-  // Used to keep track of how many nested lists/dicts there are.
-  int stack_depth_;
-
-  // A parser flag that allows trailing commas in objects and arrays.
-  bool allow_trailing_comma_;
-
-  // Contains the error message for the last call to JsonToValue(), if any.
-  std::string error_message_;
-};
-
-#endif  // BASE_JSON_READER_H_