cpp/third_party/antlr4-cpp-runtime-4/runtime/src/TokenSource.h

/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

#pragma once

#include "TokenFactory.h"

namespace antlr4 {

  /// <summary>
  /// A source of tokens must provide a sequence of tokens via <seealso cref="#nextToken()"/>
  /// and also must reveal it's source of characters; <seealso cref="CommonToken"/>'s text is
  /// computed from a <seealso cref="CharStream"/>; it only store indices into the char
  /// stream.
  /// <p/>
  /// Errors from the lexer are never passed to the parser. Either you want to keep
  /// going or you do not upon token recognition error. If you do not want to
  /// continue lexing then you do not want to continue parsing. Just throw an
  /// exception not under <seealso cref="RecognitionException"/> and Java will naturally toss
  /// you all the way out of the recognizers. If you want to continue lexing then
  /// you should not throw an exception to the parser--it has already requested a
  /// token. Keep lexing until you get a valid one. Just report errors and keep
  /// going, looking for a valid token.
  /// </summary>
  class ANTLR4CPP_PUBLIC TokenSource {
  public:
    virtual ~TokenSource();

    /// Return a <seealso cref="Token"/> object from your input stream (usually a
    /// <seealso cref="CharStream"/>). Do not fail/return upon lexing error; keep chewing
    /// on the characters until you get a good one; errors are not passed through
    /// to the parser.
    virtual std::unique_ptr<Token> nextToken() = 0;

    /// <summary>
    /// Get the line number for the current position in the input stream. The
    /// first line in the input is line 1.
    /// </summary>
    /// <returns> The line number for the current position in the input stream, or
    /// 0 if the current token source does not track line numbers. </returns>
    virtual size_t getLine() const = 0;

    /// <summary>
    /// Get the index into the current line for the current position in the input
    /// stream. The first character on a line has position 0.
    /// </summary>
    /// <returns> The line number for the current position in the input stream, or
    /// (sze_t)-1 if the current token source does not track character positions. </returns>
    virtual size_t getCharPositionInLine() = 0;

    /// <summary>
    /// Get the <seealso cref="CharStream"/> from which this token source is currently
    /// providing tokens.
    /// </summary>
    /// <returns> The <seealso cref="CharStream"/> associated with the current position in
    /// the input, or {@code null} if no input stream is available for the token
    /// source. </returns>
    virtual CharStream* getInputStream() = 0;

    /// <summary>
    /// Gets the name of the underlying input source. This method returns a
    /// non-null, non-empty string. If such a name is not known, this method
    /// returns <seealso cref="IntStream#UNKNOWN_SOURCE_NAME"/>.
    /// </summary>
    virtual std::string getSourceName() = 0;

    /// <summary>
    /// Set the <seealso cref="TokenFactory"/> this token source should use for creating
    /// <seealso cref="Token"/> objects from the input.
    /// </summary>
    /// <param name="factory"> The <seealso cref="TokenFactory"/> to use for creating tokens. </param>
    template<typename T1>
    void setTokenFactory(TokenFactory<T1> * /*factory*/) {}

    /// <summary>
    /// Gets the <seealso cref="TokenFactory"/> this token source is currently using for
    /// creating <seealso cref="Token"/> objects from the input.
    /// </summary>
    /// <returns> The <seealso cref="TokenFactory"/> currently used by this token source. </returns>
    virtual TokenFactory<CommonToken>* getTokenFactory() = 0;
  };

} // namespace antlr4