CommonTokenStream.cs revision 324c4644fee44b9898524c09511bd33c3f12e2df 
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
33namespace 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