--- /dev/null
+/* 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 "CharStream.h"
+#include "atn/LexerAction.h"
+
+namespace antlr4 {
+namespace atn {
+
+ /// Represents an executor for a sequence of lexer actions which traversed during
+ /// the matching operation of a lexer rule (token).
+ ///
+ /// <para>The executor tracks position information for position-dependent lexer actions
+ /// efficiently, ensuring that actions appearing only at the end of the rule do
+ /// not cause bloating of the <seealso cref="DFA"/> created for the lexer.</para>
+ class ANTLR4CPP_PUBLIC LexerActionExecutor : public std::enable_shared_from_this<LexerActionExecutor> {
+ public:
+ /// <summary>
+ /// Constructs an executor for a sequence of <seealso cref="LexerAction"/> actions. </summary>
+ /// <param name="lexerActions"> The lexer actions to execute. </param>
+ LexerActionExecutor(const std::vector<Ref<LexerAction>> &lexerActions);
+ virtual ~LexerActionExecutor();
+
+ /// <summary>
+ /// Creates a <seealso cref="LexerActionExecutor"/> which executes the actions for
+ /// the input {@code lexerActionExecutor} followed by a specified
+ /// {@code lexerAction}.
+ /// </summary>
+ /// <param name="lexerActionExecutor"> The executor for actions already traversed by
+ /// the lexer while matching a token within a particular
+ /// <seealso cref="LexerATNConfig"/>. If this is {@code null}, the method behaves as
+ /// though it were an empty executor. </param>
+ /// <param name="lexerAction"> The lexer action to execute after the actions
+ /// specified in {@code lexerActionExecutor}.
+ /// </param>
+ /// <returns> A <seealso cref="LexerActionExecutor"/> for executing the combine actions
+ /// of {@code lexerActionExecutor} and {@code lexerAction}. </returns>
+ static Ref<LexerActionExecutor> append(Ref<LexerActionExecutor> const& lexerActionExecutor,
+ Ref<LexerAction> const& lexerAction);
+
+ /// <summary>
+ /// Creates a <seealso cref="LexerActionExecutor"/> which encodes the current offset
+ /// for position-dependent lexer actions.
+ ///
+ /// <para>Normally, when the executor encounters lexer actions where
+ /// <seealso cref="LexerAction#isPositionDependent"/> returns {@code true}, it calls
+ /// <seealso cref="IntStream#seek"/> on the input <seealso cref="CharStream"/> to set the input
+ /// position to the <em>end</em> of the current token. This behavior provides
+ /// for efficient DFA representation of lexer actions which appear at the end
+ /// of a lexer rule, even when the lexer rule matches a variable number of
+ /// characters.</para>
+ ///
+ /// <para>Prior to traversing a match transition in the ATN, the current offset
+ /// from the token start index is assigned to all position-dependent lexer
+ /// actions which have not already been assigned a fixed offset. By storing
+ /// the offsets relative to the token start index, the DFA representation of
+ /// lexer actions which appear in the middle of tokens remains efficient due
+ /// to sharing among tokens of the same length, regardless of their absolute
+ /// position in the input stream.</para>
+ ///
+ /// <para>If the current executor already has offsets assigned to all
+ /// position-dependent lexer actions, the method returns {@code this}.</para>
+ /// </summary>
+ /// <param name="offset"> The current offset to assign to all position-dependent
+ /// lexer actions which do not already have offsets assigned.
+ /// </param>
+ /// <returns> A <seealso cref="LexerActionExecutor"/> which stores input stream offsets
+ /// for all position-dependent lexer actions. </returns>
+ virtual Ref<LexerActionExecutor> fixOffsetBeforeMatch(int offset);
+
+ /// <summary>
+ /// Gets the lexer actions to be executed by this executor. </summary>
+ /// <returns> The lexer actions to be executed by this executor. </returns>
+ virtual std::vector<Ref<LexerAction>> getLexerActions() const;
+
+ /// <summary>
+ /// Execute the actions encapsulated by this executor within the context of a
+ /// particular <seealso cref="Lexer"/>.
+ ///
+ /// <para>This method calls <seealso cref="IntStream#seek"/> to set the position of the
+ /// {@code input} <seealso cref="CharStream"/> prior to calling
+ /// <seealso cref="LexerAction#execute"/> on a position-dependent action. Before the
+ /// method returns, the input position will be restored to the same position
+ /// it was in when the method was invoked.</para>
+ /// </summary>
+ /// <param name="lexer"> The lexer instance. </param>
+ /// <param name="input"> The input stream which is the source for the current token.
+ /// When this method is called, the current <seealso cref="IntStream#index"/> for
+ /// {@code input} should be the start of the following token, i.e. 1
+ /// character past the end of the current token. </param>
+ /// <param name="startIndex"> The token start index. This value may be passed to
+ /// <seealso cref="IntStream#seek"/> to set the {@code input} position to the beginning
+ /// of the token. </param>
+ virtual void execute(Lexer *lexer, CharStream *input, size_t startIndex);
+
+ virtual size_t hashCode() const;
+ virtual bool operator == (const LexerActionExecutor &obj) const;
+ virtual bool operator != (const LexerActionExecutor &obj) const;
+
+ private:
+ const std::vector<Ref<LexerAction>> _lexerActions;
+
+ /// Caches the result of <seealso cref="#hashCode"/> since the hash code is an element
+ /// of the performance-critical <seealso cref="LexerATNConfig#hashCode"/> operation.
+ const size_t _hashCode;
+
+ size_t generateHashCode() const;
+ };
+
+} // namespace atn
+} // namespace antlr4
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