/// <summary>
/// Execute the actions encapsulated by this executor within the context of a
/// particular
/// <see cref="Antlr4.Runtime.Lexer">Antlr4.Runtime.Lexer</see>
/// .
/// <p>This method calls
/// <see cref="Antlr4.Runtime.IIntStream.Seek(int)">Antlr4.Runtime.IIntStream.Seek(int)</see>
/// to set the position of the
/// <code>input</code>
///
/// <see cref="Antlr4.Runtime.ICharStream">Antlr4.Runtime.ICharStream</see>
/// prior to calling
/// <see cref="ILexerAction.Execute(Antlr4.Runtime.Lexer)">ILexerAction.Execute(Antlr4.Runtime.Lexer)</see>
/// 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.</p>
/// </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
/// <see cref="Antlr4.Runtime.IIntStream.Index()">Antlr4.Runtime.IIntStream.Index()</see>
/// for
/// <code>input</code>
/// 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
/// <see cref="Antlr4.Runtime.IIntStream.Seek(int)">Antlr4.Runtime.IIntStream.Seek(int)</see>
/// to set the
/// <code>input</code>
/// position to the beginning
/// of the token.
/// </param>
public virtual void Execute(Lexer lexer, ICharStream input, int startIndex)
{
bool requiresSeek = false;
int stopIndex = input.Index;
try
{
foreach (ILexerAction lexerAction in lexerActions)
{
ILexerAction action = lexerAction;
if (action is LexerIndexedCustomAction)
{
int offset = ((LexerIndexedCustomAction)action).GetOffset();
input.Seek(startIndex + offset);
action = ((LexerIndexedCustomAction)action).GetAction();
requiresSeek = (startIndex + offset) != stopIndex;
}
else
{
if (action.IsPositionDependent())
{
input.Seek(stopIndex);
requiresSeek = false;
}
}
action.Execute(lexer);
}
}
finally
{
if (requiresSeek)
{
input.Seek(stopIndex);
}
}
}
