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. Its used for the shared
14  * context cash associated with contexts in DFA states. This cache
15  * can be used for both lexers and parsers.
16  */
17 class PredictionContextCache
18 {
19 
20     protected PredictionContext[PredictionContext] cache;
21 
22     /**
23      * Add a context to the cache and return it. If the context already exists,
24      * return that one instead and do not add a new context to the cache.
25      * Protect shared cache from unsafe thread access.
26      */
27     public PredictionContext add(PredictionContext ctx)
28     {
29 	if (ctx == PredictionContext.EMPTY)
30             return ctx;
31         if (hasKey(ctx)) {
32             // System.out.println(name+" reuses "+existing);
33             return cache[ctx];
34         }
35         cache[ctx] = ctx;
36         return ctx;
37     }
38 
39     public PredictionContext get(PredictionContext ctx)
40     {
41 	return cache[ctx];
42     }
43 
44     public size_t size()
45     {
46         return cache.length;
47     }
48 
49     public bool hasKey(PredictionContext predictionContext)
50     {
51         if (predictionContext in cache)
52             return true;
53         return false;
54     }
55 
56 }