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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) 2008-2009 Sam Harwell, Pixel Mine, Inc.
      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 System.Collections.Generic;
     35 
     36     using InvalidOperationException = System.InvalidOperationException;
     37     using StringBuilder = System.Text.StringBuilder;
     38 
     39     /** <summary>
     40      *  The most common stream of tokens is one where every token is buffered up
     41      *  and tokens are prefiltered for a certain channel (the parser will only
     42      *  see these tokens and cannot change the filter channel number during the
     43      *  parse).
     44      *  </summary>
     45      *
     46      *  <remarks>TODO: how to access the full token stream?  How to track all tokens matched per rule?</remarks>
     47      */
     48     [System.Serializable]
     49     public class CommonTokenStream : BufferedTokenStream {
     50         /** Skip tokens on any channel but this one; this is how we skip whitespace... */
     51         private int _channel;
     52 
     53         public CommonTokenStream() {
     54         }
     55 
     56         public CommonTokenStream(ITokenSource tokenSource)
     57             : this(tokenSource, TokenChannels.Default) {
     58         }
     59 
     60         public CommonTokenStream(ITokenSource tokenSource, int channel)
     61             : base(tokenSource) {
     62             this._channel = channel;
     63         }
     64 
     65         public int Channel {
     66             get {
     67                 return _channel;
     68             }
     69         }
     70 
     71         /** Reset this token stream by setting its token source. */
     72         public override ITokenSource TokenSource {
     73             get {
     74                 return base.TokenSource;
     75             }
     76             set {
     77                 base.TokenSource = value;
     78                 _channel = TokenChannels.Default;
     79             }
     80         }
     81 
     82         /** Always leave p on an on-channel token. */
     83         public override void Consume() {
     84             if (_p == -1)
     85                 Setup();
     86             _p++;
     87             Sync(_p);
     88             while (_tokens[_p].Channel != _channel) {
     89                 _p++;
     90                 Sync(_p);
     91             }
     92         }
     93 
     94         protected override IToken LB(int k) {
     95             if (k == 0 || (_p - k) < 0)
     96                 return null;
     97 
     98             int i = _p;
     99             int n = 1;
    100             // find k good tokens looking backwards
    101             while (n <= k) {
    102                 // skip off-channel tokens
    103                 i = SkipOffTokenChannelsReverse(i - 1);
    104                 n++;
    105             }
    106             if (i < 0)
    107                 return null;
    108             return _tokens[i];
    109         }
    110 
    111         public override IToken LT(int k) {
    112             if (_p == -1)
    113                 Setup();
    114             if (k == 0)
    115                 return null;
    116             if (k < 0)
    117                 return LB(-k);
    118             int i = _p;
    119             int n = 1; // we know tokens[p] is a good one
    120             // find k good tokens
    121             while (n < k) {
    122                 // skip off-channel tokens
    123                 i = SkipOffTokenChannels(i + 1);
    124                 n++;
    125             }
    126 
    127             if (i > Range)
    128                 Range = i;
    129 
    130             return _tokens[i];
    131         }
    132 
    133         /** Given a starting index, return the index of the first on-channel
    134          *  token.
    135          */
    136         protected virtual int SkipOffTokenChannels(int i) {
    137             Sync(i);
    138             while (_tokens[i].Channel != _channel) {
    139                 // also stops at EOF (it's on channel)
    140                 i++;
    141                 Sync(i);
    142             }
    143             return i;
    144         }
    145 
    146         protected virtual int SkipOffTokenChannelsReverse(int i) {
    147             while (i >= 0 && ((IToken)_tokens[i]).Channel != _channel) {
    148                 i--;
    149             }
    150 
    151             return i;
    152         }
    153 
    154         protected override void Setup() {
    155             _p = 0;
    156             Sync(0);
    157             int i = 0;
    158             while (_tokens[i].Channel != _channel) {
    159                 i++;
    160                 Sync(i);
    161             }
    162             _p = i;
    163         }
    164     }
    165 }
    166