antlr.v4.runtime.atn.PredictionContextCache source code

1 /*
2  * Copyright (c) 2012-2019 The ANTLR Project. All rights reserved.
3  * Use of this file is governed by the BSD 3-clause license that
4  * can be found in the LICENSE.txt file in the project root.
5  */
6 
7 module antlr.v4.runtime.atn.PredictionContextCache;
8 
9 import std.conv;
10 import antlr.v4.runtime.atn.PredictionContext;
11 
12 /**
13  * Used to cache {@link PredictionContext} objects.
14  *
15  * Its used for the shared
16  * context objects associated with contexts in DFA states. This cache
17  * can be used for both lexers and parsers.
18  */
19 class PredictionContextCache
20 {
21 
22     protected PredictionContext[PredictionContext] cache;
23 
24     /**
25      * Add a context to the cache and return it.
26      *
27      * If the context already exists,
28      * return that one instead and do not add a new context to the cache.
29      * Protect shared cache from unsafe thread access.
30      */
31     public PredictionContext add(PredictionContext predictionContext)
32     {
33 	if (predictionContext == PredictionContext.EMPTY)
34             return predictionContext;
35         if (hasKey(predictionContext)) {
36             // System.out.println(name+" reuses "+existing);
37             return cache[predictionContext];
38         }
39         cache[predictionContext] = predictionContext;
40         return predictionContext;
41     }
42 
43     /**
44      * Get the predictionContext from cache.
45      */
46     public PredictionContext get(PredictionContext predictionContext)
47     {
48 	return cache[predictionContext];
49     }
50 
51     /**
52      * Contains the cache the predictionContext?
53      */
54     public bool hasKey(PredictionContext predictionContext)
55     {
56         return (predictionContext in cache) !is null;
57     }
58 
59     /**
60      * Size of current cache.
61      */
62     public size_t size()
63     {
64         return cache.length;
65     }
66 
67 }