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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.
*/
#pragma once
#include "BufferedTokenStream.h"
namespace antlr4 {
/**
* This class extends {@link BufferedTokenStream} with functionality to filter
* token streams to tokens on a particular channel (tokens where
* {@link Token#getChannel} returns a particular value).
*
* <p>
* This token stream provides access to all tokens by index or when calling
* methods like {@link #getText}. The channel filtering is only used for code
* accessing tokens via the lookahead methods {@link #LA}, {@link #LT}, and
* {@link #LB}.</p>
*
* <p>
* By default, tokens are placed on the default channel
* ({@link Token#DEFAULT_CHANNEL}), but may be reassigned by using the
* {@code ->channel(HIDDEN)} lexer command, or by using an embedded action to
* call {@link Lexer#setChannel}.
* </p>
*
* <p>
* Note: lexer rules which use the {@code ->skip} lexer command or call
* {@link Lexer#skip} do not produce tokens at all, so input text matched by
* such a rule will not be available as part of the token stream, regardless of
* channel.</p>
*/
class ANTLR4CPP_PUBLIC CommonTokenStream : public BufferedTokenStream {
public:
/**
* Constructs a new {@link CommonTokenStream} using the specified token
* source and the default token channel ({@link Token#DEFAULT_CHANNEL}).
*
* @param tokenSource The token source.
*/
CommonTokenStream(TokenSource *tokenSource);
/**
* Constructs a new {@link CommonTokenStream} using the specified token
* source and filtering tokens to the specified channel. Only tokens whose
* {@link Token#getChannel} matches {@code channel} or have the
* {@link Token#getType} equal to {@link Token#EOF} will be returned by the
* token stream lookahead methods.
*
* @param tokenSource The token source.
* @param channel The channel to use for filtering tokens.
*/
CommonTokenStream(TokenSource *tokenSource, size_t channel);
virtual Token* LT(ssize_t k) override;
/// Count EOF just once.
virtual int getNumberOfOnChannelTokens();
protected:
/**
* Specifies the channel to use for filtering tokens.
*
* <p>
* The default value is {@link Token#DEFAULT_CHANNEL}, which matches the
* default channel assigned to tokens created by the lexer.</p>
*/
size_t channel;
virtual ssize_t adjustSeekIndex(size_t i) override;
virtual Token* LB(size_t k) override;
};
} // namespace antlr4
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