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      1 /*
      2  * [The "BSD licence"]
      3  * Copyright (c) 2005-2008 Terence Parr
      4  * All rights reserved.
      5  *
      6  * Conversion to C#:
      7  * Copyright (c) 2009 Sam Harwell
      8  * All rights reserved.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 namespace Antlr.Runtime {
     34     using Antlr.Runtime.Misc;
     35     using CLSCompliant = System.CLSCompliantAttribute;
     36     using NotSupportedException = System.NotSupportedException;
     37     using IndexOutOfRangeException = System.IndexOutOfRangeException;
     38 
     39     /** A token stream that pulls tokens from the code source on-demand and
     40      *  without tracking a complete buffer of the tokens. This stream buffers
     41      *  the minimum number of tokens possible.  It's the same as
     42      *  OnDemandTokenStream except that OnDemandTokenStream buffers all tokens.
     43      *
     44      *  You can't use this stream if you pass whitespace or other off-channel
     45      *  tokens to the parser. The stream can't ignore off-channel tokens.
     46      *
     47      *  You can only look backwards 1 token: LT(-1).
     48      *
     49      *  Use this when you need to read from a socket or other infinite stream.
     50      *
     51      *  @see BufferedTokenStream
     52      *  @see CommonTokenStream
     53      */
     54     public class UnbufferedTokenStream : LookaheadStream<IToken>, ITokenStream {
     55         [CLSCompliant(false)]
     56         protected ITokenSource tokenSource;
     57         protected int tokenIndex; // simple counter to set token index in tokens
     58 
     59         /** Skip tokens on any channel but this one; this is how we skip whitespace... */
     60         protected int channel = TokenChannels.Default;
     61 
     62         public UnbufferedTokenStream(ITokenSource tokenSource) {
     63             this.tokenSource = tokenSource;
     64         }
     65 
     66         public ITokenSource TokenSource {
     67             get {
     68                 return this.tokenSource;
     69             }
     70         }
     71 
     72         public string SourceName {
     73             get {
     74                 return TokenSource.SourceName;
     75             }
     76         }
     77 
     78         public override IToken NextElement() {
     79             IToken t = this.tokenSource.NextToken();
     80             t.TokenIndex = this.tokenIndex++;
     81             return t;
     82         }
     83 
     84         public override bool IsEndOfFile(IToken o) {
     85             return o.Type == CharStreamConstants.EndOfFile;
     86         }
     87 
     88         public IToken Get(int i) {
     89             throw new NotSupportedException("Absolute token indexes are meaningless in an unbuffered stream");
     90         }
     91 
     92         public int LA(int i) {
     93             return LT(i).Type;
     94         }
     95 
     96         public string ToString(int start, int stop) {
     97             return "n/a";
     98         }
     99 
    100         public string ToString(IToken start, IToken stop) {
    101             return "n/a";
    102         }
    103     }
    104 }
    105