DecisionEventInfo.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 "antlr4-common.h"

namespace antlr4 {
namespace atn {

  /// <summary>
  /// This is the base class for gathering detailed information about prediction
  /// events which occur during parsing.
  ///
  /// Note that we could record the parser call stack at the time this event
  /// occurred but in the presence of left recursive rules, the stack is kind of
  /// meaningless. It's better to look at the individual configurations for their
  /// individual stacks. Of course that is a <seealso cref="PredictionContext"/> object
  /// not a parse tree node and so it does not have information about the extent
  /// (start...stop) of the various subtrees. Examining the stack tops of all
  /// configurations provide the return states for the rule invocations.
  /// From there you can get the enclosing rule.
  ///
  /// @since 4.3
  /// </summary>
  class ANTLR4CPP_PUBLIC DecisionEventInfo {
  public:
    /// <summary>
    /// The invoked decision number which this event is related to.
    /// </summary>
    /// <seealso cref= ATN#decisionToState </seealso>
    const size_t decision;

    /// <summary>
    /// The configuration set containing additional information relevant to the
    /// prediction state when the current event occurred, or {@code null} if no
    /// additional information is relevant or available.
    /// </summary>
    const ATNConfigSet *configs;

    /// <summary>
    /// The input token stream which is being parsed.
    /// </summary>
    const TokenStream *input;

    /// <summary>
    /// The token index in the input stream at which the current prediction was
    /// originally invoked.
    /// </summary>
    const size_t startIndex;

    /// <summary>
    /// The token index in the input stream at which the current event occurred.
    /// </summary>
    const size_t stopIndex;

    /// <summary>
    /// {@code true} if the current event occurred during LL prediction;
    /// otherwise, {@code false} if the input occurred during SLL prediction.
    /// </summary>
    const bool fullCtx;

    DecisionEventInfo(size_t decision, ATNConfigSet *configs, TokenStream *input, size_t startIndex,
                      size_t stopIndex, bool fullCtx);
  };

} // namespace atn
} // namespace antlr4