antlr.v4.runtime.atn.PredictionContextCache source code

1 /*
2  * [The "BSD license"]
3  *  Copyright (c) 2016 Terence Parr
4  *  Copyright (c) 2016 Sam Harwell
5  *  All rights reserved.
6  *
7  *  Redistribution and use in source and binary forms, with or without
8  *  modification, are permitted provided that the following conditions
9  *  are met:
10  *
11  *  1. Redistributions of source code must retain the above copyright
12  *     notice, this list of conditions and the following disclaimer.
13  *  2. Redistributions in binary form must reproduce the above copyright
14  *     notice, this list of conditions and the following disclaimer in the
15  *     documentation and/or other materials provided with the distribution.
16  *  3. The name of the author may not be used to endorse or promote products
17  *     derived from this software without specific prior written permission.
18  *
19  *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20  *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21  *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22  *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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29  */
30 
31 module antlr.v4.runtime.atn.PredictionContextCache;
32 
33 import std.conv;
34 import antlr.v4.runtime.atn.PredictionContext;
35 
36 /**
37  * @uml
38  * Used to cache {@link PredictionContext} objects. Its used for the shared
39  * context cash associated with contexts in DFA states. This cache
40  * can be used for both lexers and parsers.
41  */
42 class PredictionContextCache
43 {
44 
45     protected PredictionContext[PredictionContext] cache;
46 
47     /**
48      * @uml
49      * Add a context to the cache and return it. If the context already exists,
50      * return that one instead and do not add a new context to the cache.
51      * Protect shared cache from unsafe thread access.
52      */
53     public PredictionContext add(PredictionContext ctx)
54     {
55 	if (ctx == PredictionContext.EMPTY)
56             return ctx;
57         if (hasKey(ctx)) {
58             // System.out.println(name+" reuses "+existing);
59             return cache[ctx];
60         }
61         cache[ctx] = ctx;
62         return ctx;
63     }
64 
65     public PredictionContext get(PredictionContext ctx)
66     {
67 	return cache[ctx];
68     }
69 
70     public int size()
71     {
72         return to!int(cache.length);
73     }
74 
75     public bool hasKey(PredictionContext predictionContext)
76     {
77         if (predictionContext in cache)
78             return true;
79         return false;
80     }
81 
82 }