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:
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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.
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17  *     derived from this software without specific prior written permission.
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19  *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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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 // Class PredictionContextCache
37 /**
38  * @uml
39  * Used to cache {@link PredictionContext} objects. Its used for the shared
40  * context cash associated with contexts in DFA states. This cache
41  * can be used for both lexers and parsers.
42  */
43 class PredictionContextCache
44 {
45 
46     protected PredictionContext[PredictionContext] cache;
47 
48     /**
49      * @uml
50      * Add a context to the cache and return it. If the context already exists,
51      * return that one instead and do not add a new context to the cache.
52      * Protect shared cache from unsafe thread access.
53      */
54     public PredictionContext add(PredictionContext ctx)
55     {
56 	if (ctx == PredictionContext.EMPTY)
57             return ctx;
58         if (hasKey(ctx)) {
59             // System.out.println(name+" reuses "+existing);
60             return cache[ctx];
61         }
62         cache[ctx] = ctx;
63         return ctx;
64     }
65 
66     public PredictionContext get(PredictionContext ctx)
67     {
68 	return cache[ctx];
69     }
70 
71     public int size()
72     {
73         return to!int(cache.length);
74     }
75 
76     public bool hasKey(PredictionContext predictionContext)
77     {
78         if (predictionContext in cache)
79             return true;
80         return false;
81     }
82 
83 }