Index: base/json/json_parser.h |
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+// Copyright (c) 2012 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. |
+ |
+#ifndef BASE_JSON_JSON_PARSER_H_ |
+#define BASE_JSON_JSON_PARSER_H_ |
+#pragma once |
+ |
+#include <string> |
+ |
+#include "base/base_export.h" |
+#include "base/basictypes.h" |
+#include "base/compiler_specific.h" |
+#include "base/json/json_reader.h" |
+#include "base/string_piece.h" |
+ |
+#if !defined(OS_CHROMEOS) |
+#include "base/gtest_prod_util.h" |
+#endif |
+ |
+namespace base { |
+class Value; |
+} |
+ |
+#if defined(OS_CHROMEOS) |
+// Chromium and Chromium OS check out gtest to different places, so this is |
+// unable to compile on both if gtest_prod.h is included here. Instead, include |
+// its only contents -- this will need to be updated if the macro ever changes. |
+#define FRIEND_TEST(test_case_name, test_name)\ |
+friend class test_case_name##_##test_name##_Test |
+ |
+#define FRIEND_TEST_ALL_PREFIXES(test_case_name, test_name) \ |
+ FRIEND_TEST(test_case_name, test_name); \ |
+ FRIEND_TEST(test_case_name, DISABLED_##test_name); \ |
+ FRIEND_TEST(test_case_name, FLAKY_##test_name); \ |
+ FRIEND_TEST(test_case_name, FAILS_##test_name) |
+#endif // OS_CHROMEOS |
+ |
+namespace base { |
+namespace internal { |
+ |
+class JSONParserTest; |
+ |
+// The implementation behind the JSONReader interface. This class is not meant |
+// to be used directly; it encapsulates logic that need not be exposed publicly. |
+// |
+// This parser guarantees O(n) time through the input string. It also optimizes |
+// base::StringValue by using StringPiece where possible when returning Value |
+// objects by using "hidden roots," discussed in the implementation. |
+// |
+// Iteration happens on the byte level, with the functions CanConsume and |
+// NextChar. The conversion from byte to JSON token happens without advancing |
+// the parser in GetNextToken/ParseToken, that is tokenization operates on |
+// the current parser position without advancing. |
+// |
+// Built on top of these are a family of Consume functions that iterate |
+// internally. Invariant: on entry of a Consume function, the parser is wound |
+// to the first byte of a valid JSON token. On exit, it is on the last byte |
+// of a token, such that the next iteration of the parser will be at the byte |
+// immediately following the token, which would likely be the first byte of the |
+// next token. |
+class BASE_EXPORT_PRIVATE JSONParser { |
+ public: |
+ explicit JSONParser(int options); |
+ ~JSONParser(); |
+ |
+ // Parses the input string according to the set options and returns the |
+ // result as a Value owned by the caller. |
+ Value* Parse(const std::string& input); |
+ |
+ // Returns the error code. |
+ JSONReader::JsonParseError error_code() const; |
+ |
+ // Returns the human-friendly error message. |
+ std::string GetErrorMessage() const; |
+ |
+ private: |
+ enum Token { |
+ T_OBJECT_BEGIN, // { |
+ T_OBJECT_END, // } |
+ T_ARRAY_BEGIN, // [ |
+ T_ARRAY_END, // ] |
+ T_STRING, |
+ T_NUMBER, |
+ T_BOOL_TRUE, // true |
+ T_BOOL_FALSE, // false |
+ T_NULL, // null |
+ T_LIST_SEPARATOR, // , |
+ T_OBJECT_PAIR_SEPARATOR, // : |
+ T_END_OF_INPUT, |
+ T_INVALID_TOKEN, |
+ }; |
+ |
+ // A helper class used for parsing strings. One optimization performed is to |
+ // create base::Value with a StringPiece to avoid unnecessary std::string |
+ // copies. This is not possible if the input string needs to be decoded from |
+ // UTF-16 to UTF-8, or if an escape sequence causes characters to be skipped. |
+ // This class centralizes that logic. |
+ class StringBuilder { |
+ public: |
+ // Empty constructor. Used for creating a builder with which to Swap(). |
+ StringBuilder(); |
+ |
+ // |pos| is the beginning of an input string, excluding the |"|. |
+ explicit StringBuilder(const char* pos); |
+ |
+ ~StringBuilder(); |
+ |
+ // Swaps the contents of |other| with this. |
+ void Swap(StringBuilder* other); |
+ |
+ // Either increases the |length_| of the string or copies the character if |
+ // the StringBuilder has been converted. |c| must be in the basic ASCII |
+ // plane; all other characters need to be in UTF-8 units, appended with |
+ // AppendString below. |
+ void Append(const char& c); |
+ |
+ // Appends a string to the std::string. Must be Convert()ed to use. |
+ void AppendString(const std::string& str); |
+ |
+ // Converts the builder from its default StringPiece to a full std::string, |
+ // performing a copy. Once a builder is converted, it cannot be made a |
+ // StringPiece again. |
+ void Convert(); |
+ |
+ // Returns whether the builder can be converted to a StringPiece. |
+ bool CanBeStringPiece() const; |
+ |
+ // Returns the StringPiece representation. Returns an empty piece if it |
+ // cannot be converted. |
+ StringPiece AsStringPiece(); |
+ |
+ // Returns the builder as a std::string. |
+ const std::string& AsString(); |
+ |
+ private: |
+ // The beginning of the input string. |
+ const char* pos_; |
+ |
+ // Number of bytes in |pos_| that make up the string being built. |
+ size_t length_; |
+ |
+ // The copied string representation. NULL until Convert() is called. |
+ // Strong. scoped_ptr<T> has too much of an overhead here. |
+ std::string* string_; |
+ }; |
+ |
+ // Quick check that the stream has capacity to consume |length| more bytes. |
+ bool CanConsume(int length); |
+ |
+ // The basic way to consume a single character in the stream. Consumes one |
+ // byte of the input stream and returns a pointer to the rest of it. |
+ const char* NextChar(); |
+ |
+ // Performs the equivalent of NextChar N times. |
+ void NextNChars(int n); |
+ |
+ // Skips over whitespace and comments to find the next token in the stream. |
+ // This does not advance the parser for non-whitespace or comment chars. |
+ Token GetNextToken(); |
+ |
+ // Consumes whitespace characters and comments until the next non-that is |
+ // encountered. |
+ void EatWhitespaceAndComments(); |
+ // Helper function that consumes a comment, assuming that the parser is |
+ // currently wound to a '/'. |
+ bool EatComment(); |
+ |
+ // Calls GetNextToken() and then ParseToken(). Caller owns the result. |
+ Value* ParseNextToken(); |
+ |
+ // Takes a token that represents the start of a Value ("a structural token" |
+ // in RFC terms) and consumes it, returning the result as an object the |
+ // caller owns. |
+ Value* ParseToken(Token token); |
+ |
+ // Assuming that the parser is currently wound to '{', this parses a JSON |
+ // object into a DictionaryValue. |
+ Value* ConsumeDictionary(); |
+ |
+ // Assuming that the parser is wound to '[', this parses a JSON list into a |
+ // ListValue. |
+ Value* ConsumeList(); |
+ |
+ // Calls through ConsumeStringRaw and wraps it in a value. |
+ Value* ConsumeString(); |
+ |
+ // Assuming that the parser is wound to a double quote, this parses a string, |
+ // decoding any escape sequences and converts UTF-16 to UTF-8. Returns true on |
+ // success and Swap()s the result into |out|. Returns false on failure with |
+ // error information set. |
+ bool ConsumeStringRaw(StringBuilder* out); |
+ // Helper function for ConsumeStringRaw() that consumes the next four or 10 |
+ // bytes (parser is wound to the first character of a HEX sequence, with the |
+ // potential for consuming another \uXXXX for a surrogate). Returns true on |
+ // success and places the UTF8 code units in |dest_string|, and false on |
+ // failure. |
+ bool DecodeUTF16(std::string* dest_string); |
+ // Helper function for ConsumeStringRaw() that takes a single code point, |
+ // decodes it into UTF-8 units, and appends it to the given builder. The |
+ // point must be valid. |
+ void DecodeUTF8(const int32& point, StringBuilder* dest); |
+ |
+ // Assuming that the parser is wound to the start of a valid JSON number, |
+ // this parses and converts it to either an int or double value. |
+ Value* ConsumeNumber(); |
+ // Helper that reads characters that are ints. Returns true if a number was |
+ // read and false on error. |
+ bool ReadInt(bool allow_leading_zeros); |
+ |
+ // Consumes the literal values of |true|, |false|, and |null|, assuming the |
+ // parser is wound to the first character of any of those. |
+ Value* ConsumeLiteral(); |
+ |
+ // Compares two string buffers of a given length. |
+ static bool StringsAreEqual(const char* left, const char* right, size_t len); |
+ |
+ // Sets the error information to |code| at the current column, based on |
+ // |index_| and |index_last_line_|, with an optional positive/negative |
+ // adjustment by |column_adjust|. |
+ void ReportError(JSONReader::JsonParseError code, int column_adjust); |
+ |
+ // Given the line and column number of an error, formats one of the error |
+ // message contants from json_reader.h for human display. |
+ static std::string FormatErrorMessage(int line, int column, |
+ const std::string& description); |
+ |
+ // base::JSONParserOptions that control parsing. |
+ int options_; |
+ |
+ // Pointer to the start of the input data. |
+ const char* start_pos_; |
+ |
+ // Pointer to the current position in the input data. Equivalent to |
+ // |start_pos_ + index_|. |
+ const char* pos_; |
+ |
+ // Pointer to the last character of the input data. |
+ const char* end_pos_; |
+ |
+ // The index in the input stream to which the parser is wound. |
+ int index_; |
+ |
+ // The number of times the parser has recursed (current stack depth). |
+ int stack_depth_; |
+ |
+ // The line number that the parser is at currently. |
+ int line_number_; |
+ |
+ // The last value of |index_| on the previous line. |
+ int index_last_line_; |
+ |
+ // Error information. |
+ JSONReader::JsonParseError error_code_; |
+ int error_line_; |
+ int error_column_; |
+ |
+ friend class JSONParserTest; |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, NextChar); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeDictionary); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeList); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeString); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeLiterals); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeNumbers); |
+ FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ErrorMessages); |
+ |
+ DISALLOW_COPY_AND_ASSIGN(JSONParser); |
+}; |
+ |
+} // namespace internal |
+} // namespace base |
+ |
+#endif // BASE_JSON_JSON_PARSER_H_ |