| /* |
| [The "BSD license"] |
| Copyright (c) 2005-2009 Terence Parr |
| All rights reserved. |
| |
| Redistribution and use in source and binary forms, with or without |
| modification, are permitted provided that the following conditions |
| are met: |
| 1. Redistributions of source code must retain the above copyright |
| notice, this list of conditions and the following disclaimer. |
| 2. Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| 3. The name of the author may not be used to endorse or promote products |
| derived from this software without specific prior written permission. |
| |
| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package org.antlr.runtime; |
| |
| /** The most common stream of tokens where every token is buffered up |
| * and tokens are filtered for a certain channel (the parser will only |
| * see these tokens). |
| * |
| * Even though it buffers all of the tokens, this token stream pulls tokens |
| * from the tokens source on demand. In other words, until you ask for a |
| * token using consume(), LT(), etc. the stream does not pull from the lexer. |
| * |
| * The only difference between this stream and BufferedTokenStream superclass |
| * is that this stream knows how to ignore off channel tokens. There may be |
| * a performance advantage to using the superclass if you don't pass |
| * whitespace and comments etc. to the parser on a hidden channel (i.e., |
| * you set $channel instead of calling skip() in lexer rules.) |
| * |
| * @see org.antlr.runtime.UnbufferedTokenStream |
| * @see org.antlr.runtime.BufferedTokenStream |
| */ |
| public class CommonTokenStream extends BufferedTokenStream { |
| /** Skip tokens on any channel but this one; this is how we skip whitespace... */ |
| protected int channel = Token.DEFAULT_CHANNEL; |
| |
| public CommonTokenStream() { ; } |
| |
| public CommonTokenStream(TokenSource tokenSource) { |
| super(tokenSource); |
| } |
| |
| public CommonTokenStream(TokenSource tokenSource, int channel) { |
| this(tokenSource); |
| this.channel = channel; |
| } |
| |
| /** Always leave p on an on-channel token. */ |
| public void consume() { |
| if ( p == -1 ) setup(); |
| p++; |
| sync(p); |
| while ( tokens.get(p).getChannel()!=channel ) { |
| p++; |
| sync(p); |
| } |
| } |
| |
| protected Token LB(int k) { |
| if ( k==0 || (p-k)<0 ) return null; |
| |
| int i = p; |
| int n = 1; |
| // find k good tokens looking backwards |
| while ( n<=k ) { |
| // skip off-channel tokens |
| i = skipOffTokenChannelsReverse(i-1); |
| n++; |
| } |
| if ( i<0 ) return null; |
| return tokens.get(i); |
| } |
| |
| public Token LT(int k) { |
| //System.out.println("enter LT("+k+")"); |
| if ( p == -1 ) setup(); |
| if ( k == 0 ) return null; |
| if ( k < 0 ) return LB(-k); |
| int i = p; |
| int n = 1; // we know tokens[p] is a good one |
| // find k good tokens |
| while ( n<k ) { |
| // skip off-channel tokens |
| i = skipOffTokenChannels(i+1); |
| n++; |
| } |
| if ( i>range ) range = i; |
| return tokens.get(i); |
| } |
| |
| /** Given a starting index, return the index of the first on-channel |
| * token. |
| */ |
| protected int skipOffTokenChannels(int i) { |
| sync(i); |
| while ( tokens.get(i).getChannel()!=channel ) { // also stops at EOF (it's onchannel) |
| i++; |
| sync(i); |
| } |
| return i; |
| } |
| |
| protected int skipOffTokenChannelsReverse(int i) { |
| while ( i>=0 && ((Token)tokens.get(i)).getChannel()!=channel ) { |
| i--; |
| } |
| return i; |
| } |
| |
| protected void setup() { |
| p = 0; |
| sync(0); |
| int i = 0; |
| while ( tokens.get(i).getChannel()!=channel ) { |
| i++; |
| sync(i); |
| } |
| p = i; |
| } |
| |
| /** Count EOF just once. */ |
| public int getNumberOfOnChannelTokens() { |
| int n = 0; |
| fill(); |
| for (int i = 0; i < tokens.size(); i++) { |
| Token t = tokens.get(i); |
| if ( t.getChannel()==channel ) n++; |
| if ( t.getType()==Token.EOF ) break; |
| } |
| return n; |
| } |
| |
| /** Reset this token stream by setting its token source. */ |
| public void setTokenSource(TokenSource tokenSource) { |
| super.setTokenSource(tokenSource); |
| channel = Token.DEFAULT_CHANNEL; |
| } |
| } |