TreePatternLexer.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.Tree {
34    using StringBuilder = System.Text.StringBuilder;
35
36    public class TreePatternLexer {
37        public const int EOF = -1;
38        public const int BEGIN = 1;
39        public const int END = 2;
40        public const int ID = 3;
41        public const int ARG = 4;
42        public const int PERCENT = 5;
43        public const int COLON = 6;
44        public const int DOT = 7;
45
46        /** <summary>The tree pattern to lex like "(A B C)"</summary> */
47        protected string pattern;
48
49        /** <summary>Index into input string</summary> */
50        protected int p = -1;
51
52        /** <summary>Current char</summary> */
53        protected int c;
54
55        /** <summary>How long is the pattern in char?</summary> */
56        protected int n;
57
58        /** <summary>Set when token type is ID or ARG (name mimics Java's StreamTokenizer)</summary> */
59        public StringBuilder sval = new StringBuilder();
60
61        public bool error = false;
62
63        public TreePatternLexer(string pattern) {
64            this.pattern = pattern;
65            this.n = pattern.Length;
66            Consume();
67        }
68
69        public virtual int NextToken() {
70            sval.Length = 0; // reset, but reuse buffer
71            while (c != EOF) {
72                if (c == ' ' || c == '\n' || c == '\r' || c == '\t') {
73                    Consume();
74                    continue;
75                }
76                if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_') {
77                    sval.Append((char)c);
78                    Consume();
79                    while ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
80                            (c >= '0' && c <= '9') || c == '_') {
81                        sval.Append((char)c);
82                        Consume();
83                    }
84                    return ID;
85                }
86                if (c == '(') {
87                    Consume();
88                    return BEGIN;
89                }
90                if (c == ')') {
91                    Consume();
92                    return END;
93                }
94                if (c == '%') {
95                    Consume();
96                    return PERCENT;
97                }
98                if (c == ':') {
99                    Consume();
100                    return COLON;
101                }
102                if (c == '.') {
103                    Consume();
104                    return DOT;
105                }
106                if (c == '[') { // grab [x] as a string, returning x
107                    Consume();
108                    while (c != ']') {
109                        if (c == '\\') {
110                            Consume();
111                            if (c != ']') {
112                                sval.Append('\\');
113                            }
114                            sval.Append((char)c);
115                        } else {
116                            sval.Append((char)c);
117                        }
118                        Consume();
119                    }
120                    Consume();
121                    return ARG;
122                }
123                Consume();
124                error = true;
125                return EOF;
126            }
127            return EOF;
128        }
129
130        protected virtual void Consume() {
131            p++;
132            if (p >= n) {
133                c = EOF;
134            } else {
135                c = pattern[p];
136            }
137        }
138    }
139}
140