jsoncpp/include/json/reader.h

// Copyright 2007-2010 Baptiste Lepilleur and The JsonCpp Authors
// Distributed under MIT license, or public domain if desired and
// recognized in your jurisdiction.
// See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE

#ifndef JSON_READER_H_INCLUDED
#define JSON_READER_H_INCLUDED

#if !defined(JSON_IS_AMALGAMATION)
#include "json_features.h"
#include "value.h"
#endif // if !defined(JSON_IS_AMALGAMATION)
#include <deque>
#include <iosfwd>
#include <istream>
#include <stack>
#include <string>

// Disable warning C4251: <data member>: <type> needs to have dll-interface to
// be used by...
#if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)
#pragma warning(push)
#pragma warning(disable : 4251)
#endif // if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)

#pragma pack(push)
#pragma pack()

namespace Json {

/** \brief Unserialize a <a HREF="http://www.json.org">JSON</a> document into a
 * Value.
 *
 * \deprecated Use CharReader and CharReaderBuilder.
 */

class JSON_API Reader {
public:
  using Char = char;
  using Location = const Char*;

  /** \brief An error tagged with where in the JSON text it was encountered.
   *
   * The offsets give the [start, limit) range of bytes within the text. Note
   * that this is bytes, not codepoints.
   */
  struct StructuredError {
    ptrdiff_t offset_start;
    ptrdiff_t offset_limit;
    String message;
  };

  /** \brief Constructs a Reader allowing all features for parsing.
   * \deprecated Use CharReader and CharReaderBuilder.
   */
  Reader();

  /** \brief Constructs a Reader allowing the specified feature set for parsing.
   * \deprecated Use CharReader and CharReaderBuilder.
   */
  Reader(const Features& features);

  /** \brief Read a Value from a <a HREF="http://www.json.org">JSON</a>
   * document.
   *
   * \param      document        UTF-8 encoded string containing the document
   *                             to read.
   * \param[out] root            Contains the root value of the document if it
   *                             was successfully parsed.
   * \param      collectComments \c true to collect comment and allow writing
   *                             them back during serialization, \c false to
   *                             discard comments.  This parameter is ignored
   *                             if Features::allowComments_ is \c false.
   * \return \c true if the document was successfully parsed, \c false if an
   * error occurred.
   */
  bool parse(const std::string& document, Value& root,
             bool collectComments = true);

  /** \brief Read a Value from a <a HREF="http://www.json.org">JSON</a>
   * document.
   *
   * \param      beginDoc        Pointer on the beginning of the UTF-8 encoded
   *                             string of the document to read.
   * \param      endDoc          Pointer on the end of the UTF-8 encoded string
   *                             of the document to read.  Must be >= beginDoc.
   * \param[out] root            Contains the root value of the document if it
   *                             was successfully parsed.
   * \param      collectComments \c true to collect comment and allow writing
   *                             them back during serialization, \c false to
   *                             discard comments.  This parameter is ignored
   *                             if Features::allowComments_ is \c false.
   * \return \c true if the document was successfully parsed, \c false if an
   * error occurred.
   */
  bool parse(const char* beginDoc, const char* endDoc, Value& root,
             bool collectComments = true);

  /// \brief Parse from input stream.
  /// \see Json::operator>>(std::istream&, Json::Value&).
  bool parse(IStream& is, Value& root, bool collectComments = true);

  /** \brief Returns a user friendly string that list errors in the parsed
   * document.
   *
   * \return Formatted error message with the list of errors with their
   * location in the parsed document. An empty string is returned if no error
   * occurred during parsing.
   * \deprecated Use getFormattedErrorMessages() instead (typo fix).
   */
  JSONCPP_DEPRECATED("Use getFormattedErrorMessages() instead.")
  String getFormatedErrorMessages() const;

  /** \brief Returns a user friendly string that list errors in the parsed
   * document.
   *
   * \return Formatted error message with the list of errors with their
   * location in the parsed document. An empty string is returned if no error
   * occurred during parsing.
   */
  String getFormattedErrorMessages() const;

  /** \brief Returns a vector of structured errors encountered while parsing.
   *
   * \return A (possibly empty) vector of StructuredError objects. Currently
   * only one error can be returned, but the caller should tolerate multiple
   * errors.  This can occur if the parser recovers from a non-fatal parse
   * error and then encounters additional errors.
   */
  std::vector<StructuredError> getStructuredErrors() const;

  /** \brief Add a semantic error message.
   *
   * \param value   JSON Value location associated with the error
   * \param message The error message.
   * \return \c true if the error was successfully added, \c false if the Value
   * offset exceeds the document size.
   */
  bool pushError(const Value& value, const String& message);

  /** \brief Add a semantic error message with extra context.
   *
   * \param value   JSON Value location associated with the error
   * \param message The error message.
   * \param extra   Additional JSON Value location to contextualize the error
   * \return \c true if the error was successfully added, \c false if either
   * Value offset exceeds the document size.
   */
  bool pushError(const Value& value, const String& message, const Value& extra);

  /** \brief Return whether there are any errors.
   *
   * \return \c true if there are no errors to report \c false if errors have
   * occurred.
   */
  bool good() const;

private:
  enum TokenType {
    tokenEndOfStream = 0,
    tokenObjectBegin,
    tokenObjectEnd,
    tokenArrayBegin,
    tokenArrayEnd,
    tokenString,
    tokenNumber,
    tokenTrue,
    tokenFalse,
    tokenNull,
    tokenArraySeparator,
    tokenMemberSeparator,
    tokenComment,
    tokenError
  };

  class Token {
  public:
    TokenType type_;
    Location start_;
    Location end_;
  };

  class ErrorInfo {
  public:
    Token token_;
    String message_;
    Location extra_;
  };

  using Errors = std::deque<ErrorInfo>;

  bool readToken(Token& token);
  bool readTokenSkippingComments(Token& token);
  void skipSpaces();
  bool match(const Char* pattern, int patternLength);
  bool readComment();
  bool readCStyleComment();
  bool readCppStyleComment();
  bool readString();
  void readNumber();
  bool readValue();
  bool readObject(Token& token);
  bool readArray(Token& token);
  bool decodeNumber(Token& token);
  bool decodeNumber(Token& token, Value& decoded);
  bool decodeString(Token& token);
  bool decodeString(Token& token, String& decoded);
  bool decodeDouble(Token& token);
  bool decodeDouble(Token& token, Value& decoded);
  bool decodeUnicodeCodePoint(Token& token, Location& current, Location end,
                              unsigned int& unicode);
  bool decodeUnicodeEscapeSequence(Token& token, Location& current,
                                   Location end, unsigned int& unicode);
  bool addError(const String& message, Token& token, Location extra = nullptr);
  bool recoverFromError(TokenType skipUntilToken);
  bool addErrorAndRecover(const String& message, Token& token,
                          TokenType skipUntilToken);
  void skipUntilSpace();
  Value& currentValue();
  Char getNextChar();
  void getLocationLineAndColumn(Location location, int& line,
                                int& column) const;
  String getLocationLineAndColumn(Location location) const;
  void addComment(Location begin, Location end, CommentPlacement placement);

  static bool containsNewLine(Location begin, Location end);
  static String normalizeEOL(Location begin, Location end);

  using Nodes = std::stack<Value*>;
  Nodes nodes_;
  Errors errors_;
  String document_;
  Location begin_{};
  Location end_{};
  Location current_{};
  Location lastValueEnd_{};
  Value* lastValue_{};
  String commentsBefore_;
  Features features_;
  bool collectComments_{};
}; // Reader

/** Interface for reading JSON from a char array.
 */
class JSON_API CharReader {
public:
  struct JSON_API StructuredError {
    ptrdiff_t offset_start;
    ptrdiff_t offset_limit;
    String message;
  };

  virtual ~CharReader() = default;
  /** \brief Read a Value from a <a HREF="http://www.json.org">JSON</a>
   * document. The document must be a UTF-8 encoded string containing the
   * document to read.
   *
   * \param      beginDoc Pointer on the beginning of the UTF-8 encoded string
   *                      of the document to read.
   * \param      endDoc   Pointer on the end of the UTF-8 encoded string of the
   *                      document to read. Must be >= beginDoc.
   * \param[out] root     Contains the root value of the document if it was
   *                      successfully parsed.
   * \param[out] errs     Formatted error messages (if not NULL) a user
   *                      friendly string that lists errors in the parsed
   *                      document.
   * \return \c true if the document was successfully parsed, \c false if an
   * error occurred.
   */
  virtual bool parse(char const* beginDoc, char const* endDoc, Value* root,
                     String* errs);

  /** \brief Returns a vector of structured errors encountered while parsing.
   * Each parse call resets the stored list of errors.
   */
  std::vector<StructuredError> getStructuredErrors() const;

  class JSON_API Factory {
  public:
    virtual ~Factory() = default;
    /** \brief Allocate a CharReader via operator new().
     * \throw std::exception if something goes wrong (e.g. invalid settings)
     */
    virtual CharReader* newCharReader() const = 0;
  }; // Factory

protected:
  class Impl {
  public:
    virtual ~Impl() = default;
    virtual bool parse(char const* beginDoc, char const* endDoc, Value* root,
                       String* errs) = 0;
    virtual std::vector<StructuredError> getStructuredErrors() const = 0;
  };

  explicit CharReader(std::unique_ptr<Impl> impl) : _impl(std::move(impl)) {}

private:
  std::unique_ptr<Impl> _impl;
}; // CharReader

/** \brief Build a CharReader implementation.
 *
 * Usage:
 *   \code
 *   using namespace Json;
 *   CharReaderBuilder builder;
 *   builder["collectComments"] = false;
 *   Value value;
 *   String errs;
 *   bool ok = parseFromStream(builder, std::cin, &value, &errs);
 *   \endcode
 */
class JSON_API CharReaderBuilder : public CharReader::Factory {
public:
  // Note: We use a Json::Value so that we can add data-members to this class
  // without a major version bump.
  /** Configuration of this builder.
   * These are case-sensitive.
   * Available settings (case-sensitive):
   * - `"collectComments": false or true`
   *   - true to collect comment and allow writing them back during
   *     serialization, false to discard comments.  This parameter is ignored
   *     if allowComments is false.
   * - `"allowComments": false or true`
   *   - true if comments are allowed.
   * - `"allowTrailingCommas": false or true`
   *   - true if trailing commas in objects and arrays are allowed.
   * - `"strictRoot": false or true`
   *   - true if root must be either an array or an object value
   * - `"allowDroppedNullPlaceholders": false or true`
   *   - true if dropped null placeholders are allowed. (See
   *     StreamWriterBuilder.)
   * - `"allowNumericKeys": false or true`
   *   - true if numeric object keys are allowed.
   * - `"allowSingleQuotes": false or true`
   *   - true if '' are allowed for strings (both keys and values)
   * - `"stackLimit": integer`
   *   - Exceeding stackLimit (recursive depth of `readValue()`) will cause an
   *     exception.
   *   - This is a security issue (seg-faults caused by deeply nested JSON), so
   *     the default is low.
   * - `"failIfExtra": false or true`
   *   - If true, `parse()` returns false when extra non-whitespace trails the
   *     JSON value in the input string.
   * - `"rejectDupKeys": false or true`
   *   - If true, `parse()` returns false when a key is duplicated within an
   *     object.
   * - `"allowSpecialFloats": false or true`
   *   - If true, special float values (NaNs and infinities) are allowed and
   *     their values are lossfree restorable.
   * - `"skipBom": false or true`
   *   - If true, if the input starts with the Unicode byte order mark (BOM),
   *     it is skipped.
   *
   * You can examine 'settings_` yourself to see the defaults. You can also
   * write and read them just like any JSON Value.
   * \sa setDefaults()
   */
  Json::Value settings_;

  CharReaderBuilder();
  ~CharReaderBuilder() override;

  CharReader* newCharReader() const override;

  /** \return true if 'settings' are legal and consistent;
   *   otherwise, indicate bad settings via 'invalid'.
   */
  bool validate(Json::Value* invalid) const;

  /** A simple way to update a specific setting.
   */
  Value& operator[](const String& key);

  /** Called by ctor, but you can use this to reset settings_.
   * \pre 'settings' != NULL (but Json::null is fine)
   * \remark Defaults:
   * \snippet src/lib_json/json_reader.cpp CharReaderBuilderDefaults
   */
  static void setDefaults(Json::Value* settings);
  /** Same as old Features::strictMode().
   * \pre 'settings' != NULL (but Json::null is fine)
   * \remark Defaults:
   * \snippet src/lib_json/json_reader.cpp CharReaderBuilderStrictMode
   */
  static void strictMode(Json::Value* settings);
  /** ECMA-404 mode.
   * \pre 'settings' != NULL (but Json::null is fine)
   * \remark Defaults:
   * \snippet src/lib_json/json_reader.cpp CharReaderBuilderECMA404Mode
   */
  static void ecma404Mode(Json::Value* settings);
};

/** Consume entire stream and use its begin/end.
 * Someday we might have a real StreamReader, but for now this
 * is convenient.
 */
bool JSON_API parseFromStream(CharReader::Factory const&, IStream&, Value* root,
                              String* errs);

/** \brief Read from 'sin' into 'root'.
 *
 * Always keep comments from the input JSON.
 *
 * This can be used to read a file into a particular sub-object.
 * For example:
 *   \code
 *   Json::Value root;
 *   cin >> root["dir"]["file"];
 *   cout << root;
 *   \endcode
 * Result:
 * \verbatim
 * {
 * "dir": {
 *    "file": {
 *    // The input stream JSON would be nested here.
 *    }
 * }
 * }
 * \endverbatim
 * \throw std::exception on parse error.
 * \see Json::operator<<()
 */
JSON_API IStream& operator>>(IStream&, Value&);

} // namespace Json

#pragma pack(pop)

#if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)
#pragma warning(pop)
#endif // if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)

#endif // JSON_READER_H_INCLUDED