TokenStream


1   package org.codehaus.groovy.syntax;
2   
3   /*
4    $Id: TokenStream.java,v 1.6 2004/03/07 12:18:54 jstrachan Exp $
5   
6    Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved.
7   
8    Redistribution and use of this software and associated documentation
9    ("Software"), with or without modification, are permitted provided
10   that the following conditions are met:
11  
12   1. Redistributions of source code must retain copyright
13      statements and notices.  Redistributions must also contain a
14      copy of this document.
15  
16   2. Redistributions in binary form must reproduce the
17      above copyright notice, this list of conditions and the
18      following disclaimer in the documentation and/or other
19      materials provided with the distribution.
20  
21   3. The name "groovy" must not be used to endorse or promote
22      products derived from this Software without prior written
23      permission of The Codehaus.  For written permission,
24      please contact info@codehaus.org.
25  
26   4. Products derived from this Software may not be called "groovy"
27      nor may "groovy" appear in their names without prior written
28      permission of The Codehaus. "groovy" is a registered
29      trademark of The Codehaus.
30  
31   5. Due credit should be given to The Codehaus -
32      http://groovy.codehaus.org/
33  
34   THIS SOFTWARE IS PROVIDED BY THE CODEHAUS AND CONTRIBUTORS
35   ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
36   NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
37   FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
38   THE CODEHAUS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
39   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
40   (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
41   SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
42   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
43   STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
44   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
45   OF THE POSSIBILITY OF SUCH DAMAGE.
46  
47   */
48  
49  
50  /**
51   *  Provides a stream of lexer tokens for use by (primarily) the parsing
52   *  systems.
53   */
54  
55  public interface TokenStream
56  {
57      // ----------------------------------------------------------------------
58      //     Interface
59      // ----------------------------------------------------------------------
60  
61      /** 
62       *  Looks-ahead to the next token.
63       *
64       *  <p>
65       *  This method is equivalent to <code>la(1)</code>.
66       *  </p>
67       *
68       *  @see #la(int)
69       *
70       *  @return The next token or null if no more tokens
71       *          available.
72       *
73       *  @throws ReadException If an error occurs attempting to lookahead
74       *          a token.
75       */
76  
77      Token la() throws ReadException, SyntaxException;
78  
79  
80      /** 
81       *  Looks-ahead to the <code>k</code><i>th</i> token.
82       *
83       *  @param k Number of token to look ahead.
84       *
85       *  @return the <code>k</code><i>th</i> token or null if no
86       *          more tokens available.
87       *
88       *  @throws ReadException If an error occurs attempting to lookahead
89       *          a token.
90       */
91  
92      Token la(int k) throws ReadException, SyntaxException;
93  
94  
95      /** 
96       *  Consumes the next token.
97       *
98       *  @param type The token type.
99       *
100      *  @return The consumed token or null if no more tokens
101      *          available.
102      *
103      *  @throws ReadException If an error occurs attempting to consume
104      *          a token.
105      */
106 
107     Token consume(int type) throws ReadException, SyntaxException;
108 
109 
110     /**
111      *  Returns a description of the source location (typically a file path).
112      */
113 
114     String   getSourceLocator();
115 
116 
117     /**
118      * Checkpoints a point in the stream that we can go back to
119      */
120 
121     void checkpoint();
122 
123 
124     /**
125      * Restores to the previous checkpoint
126      */
127 
128     void restore();
129 
130 
131     /**
132      * Returns true if the stream is out of tokens, possibly
133      * ignoring trailing whitespace.
134      */
135 
136     boolean atEnd( boolean ignoringWhitespace );
137 
138 
139 
140     /**
141      * Returns true if the stream is out of tokens.  
142      */
143 
144     boolean atEnd( );
145 
146 }
147
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