antlr.v4.runtime.atn.ATNSimulator source code

1 /*
2  * Copyright (c) 2012-2017 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.ATNSimulator;
8 
9 import std.uuid;
10 import antlr.v4.runtime.UnsupportedOperationException;
11 import antlr.v4.runtime.atn.ATN;
12 import antlr.v4.runtime.atn.ATNDeserializer;
13 import antlr.v4.runtime.atn.InterfaceATNSimulator;
14 import antlr.v4.runtime.dfa.DFAState;
15 import antlr.v4.runtime.atn.PredictionContextCache;
16 import antlr.v4.runtime.atn.PredictionContext;
17 
18 // Class ATNSimulator
19 /**
20  * TODO add class description
21  */
22 abstract class ATNSimulator : InterfaceATNSimulator
23 {
24 
25     public static int SERIALIZED_VERSION;
26 
27     /**
28      * @uml
29      * This is the current serialized UUID.
30      * deprecated Use {@link ATNDeserializer#checkCondition(boolean)} instead.
31      */
32     public static UUID SERIALIZED_UUID;
33 
34     /**
35      * @uml
36      * Must distinguish between missing edge and edge we know leads nowhere
37      */
38     public static DFAState ERROR;
39 
40     public ATN atn;
41 
42     /**
43      * The context cache maps all PredictionContext objects that are equals()
44      * to a single cached copy. This cache is shared across all contexts
45      * in all ATNConfigs in all DFA states.  We rebuild each ATNConfigSet
46      * to use only cached nodes/graphs in addDFAState(). We don't want to
47      * fill this during closure() since there are lots of contexts that
48      * pop up but are not used ever again. It also greatly slows down closure().
49      *
50      * <p>This cache makes a huge difference in memory and a little bit in speed.
51      * For the Java grammar on java.*, it dropped the memory requirements
52      * at the end from 25M to 16M. We don't store any of the full context
53      * graphs in the DFA because they are limited to local context only,
54      * but apparently there's a lot of repetition there as well. We optimize
55      * the config contexts before storing the config set in the DFA states
56      * by literally rebuilding them with cached subgraphs only.</p>
57      *
58      * <p>I tried a cache for use during closure operations, that was
59      * whacked after each adaptivePredict(). It cost a little bit
60      * more time I think and doesn't save on the overall footprint
61      * so it's not worth the complexity.</p>
62      */
63     public PredictionContextCache sharedContextCache;
64 
65     public static this()
66     {
67         SERIALIZED_VERSION = ATNDeserializer.SERIALIZED_VERSION;
68         SERIALIZED_UUID = ATNDeserializer.SERIALIZED_UUID;
69     }
70 
71     public this(ATN atn, PredictionContextCache sharedContextCache)
72     {
73         this.atn = atn;
74         this.sharedContextCache = sharedContextCache;
75     }
76 
77     abstract public void reset();
78 
79     /**
80      * @uml
81      * Clear the DFA cache used by the current instance. Since the DFA cache may
82      * be shared by multiple ATN simulators, this method may affect the
83      * performance (but not accuracy) of other parsers which are being used
84      * concurrently.
85      *
86      *  @throws UnsupportedOperationException if the current instance does not
87      * support clearing the DFA.
88      */
89     public void clearDFA()
90     {
91         throw new UnsupportedOperationException("This ATN simulator does not support clearing the DFA.");
92     }
93 
94     public PredictionContextCache getSharedContextCache()
95     {
96         return sharedContextCache;
97     }
98 
99     public PredictionContext getCachedContext(PredictionContext context)
100     {
101         if (sharedContextCache is null)
102             return context;
103         PredictionContext[PredictionContext] visited;
104         return PredictionContext.getCachedContext(context,
105                                                   sharedContextCache,
106                                                   visited);
107     }
108 
109     /**
110      * @uml
111      * deprecated Use {@link ATNDeserializer#deserialize} instead.
112      */
113     public ATN deserialize(wstring data)
114     {
115         return new ATNDeserializer().deserialize(data);
116     }
117 
118 }