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/*
 * 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.
 */
package org.antlr.v4.runtime;

/**
 * A source of tokens must provide a sequence of tokens via {@link #nextToken()}
 * and also must reveal it's source of characters; {@link CommonToken}'s text is
 * computed from a {@link CharStream}; it only store indices into the char
 * stream.
 *
 * 

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 {@link 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.

*/ public interface TokenSource { /** * Return a {@link Token} object from your input stream (usually a * {@link 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. */ public Token nextToken(); /** * Get the line number for the current position in the input stream. The * first line in the input is line 1. * * @return The line number for the current position in the input stream, or * 0 if the current token source does not track line numbers. */ public int getLine(); /** * Get the index into the current line for the current position in the input * stream. The first character on a line has position 0. * * @return The line number for the current position in the input stream, or * -1 if the current token source does not track character positions. */ public int getCharPositionInLine(); /** * Get the {@link CharStream} from which this token source is currently * providing tokens. * * @return The {@link CharStream} associated with the current position in * the input, or {@code null} if no input stream is available for the token * source. */ public CharStream getInputStream(); /** * 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 {@link IntStream#UNKNOWN_SOURCE_NAME}. */ public String getSourceName(); /** * Set the {@link TokenFactory} this token source should use for creating * {@link Token} objects from the input. * * @param factory The {@link TokenFactory} to use for creating tokens. */ public void setTokenFactory(TokenFactory factory); /** * Gets the {@link TokenFactory} this token source is currently using for * creating {@link Token} objects from the input. * * @return The {@link TokenFactory} currently used by this token source. */ public TokenFactory getTokenFactory(); }




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