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254
lib/antlr4/include/atn/PredictionContext.h
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254
lib/antlr4/include/atn/PredictionContext.h
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/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
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* Use of this file is governed by the BSD 3-clause license that
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* can be found in the LICENSE.txt file in the project root.
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*/
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#pragma once
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#include "Recognizer.h"
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#include "atn/ATN.h"
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#include "atn/ATNState.h"
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namespace antlr4 {
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namespace atn {
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struct PredictionContextHasher;
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struct PredictionContextComparer;
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class PredictionContextMergeCache;
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typedef std::unordered_set<Ref<PredictionContext>, PredictionContextHasher, PredictionContextComparer> PredictionContextCache;
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class ANTLR4CPP_PUBLIC PredictionContext {
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public:
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/// Represents $ in local context prediction, which means wildcard.
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/// *+x = *.
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static const Ref<PredictionContext> EMPTY;
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/// Represents $ in an array in full context mode, when $
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/// doesn't mean wildcard: $ + x = [$,x]. Here,
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/// $ = EMPTY_RETURN_STATE.
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// ml: originally Integer.MAX_VALUE, which would be -1 for us, but this is already used in places where
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// -1 is converted to unsigned, so we use a different value here. Any value does the job provided it doesn't
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// conflict with real return states.
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static const size_t EMPTY_RETURN_STATE = static_cast<size_t>(-10); // std::numeric_limits<size_t>::max() - 9;
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private:
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static const size_t INITIAL_HASH = 1;
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public:
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static size_t globalNodeCount;
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const size_t id;
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/// <summary>
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/// Stores the computed hash code of this <seealso cref="PredictionContext"/>. The hash
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/// code is computed in parts to match the following reference algorithm.
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///
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/// <pre>
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/// private int referenceHashCode() {
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/// int hash = <seealso cref="MurmurHash#initialize"/>(<seealso cref="#INITIAL_HASH"/>);
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///
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/// for (int i = 0; i < <seealso cref="#size()"/>; i++) {
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/// hash = <seealso cref="MurmurHash#update"/>(hash, <seealso cref="#getParent"/>(i));
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/// }
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///
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/// for (int i = 0; i < <seealso cref="#size()"/>; i++) {
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/// hash = <seealso cref="MurmurHash#update"/>(hash, <seealso cref="#getReturnState"/>(i));
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/// }
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///
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/// hash = <seealso cref="MurmurHash#finish"/>(hash, 2 * <seealso cref="#size()"/>);
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/// return hash;
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/// }
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/// </pre>
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/// </summary>
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const size_t cachedHashCode;
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protected:
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PredictionContext(size_t cachedHashCode);
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~PredictionContext();
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public:
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/// Convert a RuleContext tree to a PredictionContext graph.
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/// Return EMPTY if outerContext is empty.
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static Ref<PredictionContext> fromRuleContext(const ATN &atn, RuleContext *outerContext);
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virtual size_t size() const = 0;
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virtual Ref<PredictionContext> getParent(size_t index) const = 0;
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virtual size_t getReturnState(size_t index) const = 0;
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virtual bool operator == (const PredictionContext &o) const = 0;
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/// This means only the EMPTY (wildcard? not sure) context is in set.
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virtual bool isEmpty() const;
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virtual bool hasEmptyPath() const;
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virtual size_t hashCode() const;
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protected:
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static size_t calculateEmptyHashCode();
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static size_t calculateHashCode(Ref<PredictionContext> parent, size_t returnState);
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static size_t calculateHashCode(const std::vector<Ref<PredictionContext>> &parents,
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const std::vector<size_t> &returnStates);
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public:
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// dispatch
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static Ref<PredictionContext> merge(const Ref<PredictionContext> &a, const Ref<PredictionContext> &b,
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bool rootIsWildcard, PredictionContextMergeCache *mergeCache);
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/// <summary>
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/// Merge two <seealso cref="SingletonPredictionContext"/> instances.
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///
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/// <p/>
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///
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/// Stack tops equal, parents merge is same; return left graph.<br/>
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/// <embed src="images/SingletonMerge_SameRootSamePar.svg" type="image/svg+xml"/>
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///
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/// <p/>
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///
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/// Same stack top, parents differ; merge parents giving array node, then
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/// remainders of those graphs. A new root node is created to point to the
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/// merged parents.<br/>
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/// <embed src="images/SingletonMerge_SameRootDiffPar.svg" type="image/svg+xml"/>
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///
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/// <p/>
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///
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/// Different stack tops pointing to same parent. Make array node for the
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/// root where both element in the root point to the same (original)
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/// parent.<br/>
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/// <embed src="images/SingletonMerge_DiffRootSamePar.svg" type="image/svg+xml"/>
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///
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/// <p/>
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///
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/// Different stack tops pointing to different parents. Make array node for
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/// the root where each element points to the corresponding original
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/// parent.<br/>
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/// <embed src="images/SingletonMerge_DiffRootDiffPar.svg" type="image/svg+xml"/>
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/// </summary>
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/// <param name="a"> the first <seealso cref="SingletonPredictionContext"/> </param>
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/// <param name="b"> the second <seealso cref="SingletonPredictionContext"/> </param>
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/// <param name="rootIsWildcard"> {@code true} if this is a local-context merge,
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/// otherwise false to indicate a full-context merge </param>
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/// <param name="mergeCache"> </param>
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static Ref<PredictionContext> mergeSingletons(const Ref<SingletonPredictionContext> &a,
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const Ref<SingletonPredictionContext> &b, bool rootIsWildcard, PredictionContextMergeCache *mergeCache);
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/**
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* Handle case where at least one of {@code a} or {@code b} is
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* {@link #EMPTY}. In the following diagrams, the symbol {@code $} is used
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* to represent {@link #EMPTY}.
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*
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* <h2>Local-Context Merges</h2>
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*
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* <p>These local-context merge operations are used when {@code rootIsWildcard}
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* is true.</p>
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*
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* <p>{@link #EMPTY} is superset of any graph; return {@link #EMPTY}.<br>
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* <embed src="images/LocalMerge_EmptyRoot.svg" type="image/svg+xml"/></p>
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*
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* <p>{@link #EMPTY} and anything is {@code #EMPTY}, so merged parent is
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* {@code #EMPTY}; return left graph.<br>
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* <embed src="images/LocalMerge_EmptyParent.svg" type="image/svg+xml"/></p>
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*
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* <p>Special case of last merge if local context.<br>
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* <embed src="images/LocalMerge_DiffRoots.svg" type="image/svg+xml"/></p>
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*
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* <h2>Full-Context Merges</h2>
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*
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* <p>These full-context merge operations are used when {@code rootIsWildcard}
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* is false.</p>
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*
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* <p><embed src="images/FullMerge_EmptyRoots.svg" type="image/svg+xml"/></p>
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*
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* <p>Must keep all contexts; {@link #EMPTY} in array is a special value (and
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* null parent).<br>
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* <embed src="images/FullMerge_EmptyRoot.svg" type="image/svg+xml"/></p>
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*
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* <p><embed src="images/FullMerge_SameRoot.svg" type="image/svg+xml"/></p>
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*
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* @param a the first {@link SingletonPredictionContext}
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* @param b the second {@link SingletonPredictionContext}
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* @param rootIsWildcard {@code true} if this is a local-context merge,
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* otherwise false to indicate a full-context merge
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*/
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static Ref<PredictionContext> mergeRoot(const Ref<SingletonPredictionContext> &a,
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const Ref<SingletonPredictionContext> &b, bool rootIsWildcard);
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/**
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* Merge two {@link ArrayPredictionContext} instances.
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*
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* <p>Different tops, different parents.<br>
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* <embed src="images/ArrayMerge_DiffTopDiffPar.svg" type="image/svg+xml"/></p>
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*
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* <p>Shared top, same parents.<br>
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* <embed src="images/ArrayMerge_ShareTopSamePar.svg" type="image/svg+xml"/></p>
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*
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* <p>Shared top, different parents.<br>
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* <embed src="images/ArrayMerge_ShareTopDiffPar.svg" type="image/svg+xml"/></p>
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*
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* <p>Shared top, all shared parents.<br>
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* <embed src="images/ArrayMerge_ShareTopSharePar.svg" type="image/svg+xml"/></p>
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*
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* <p>Equal tops, merge parents and reduce top to
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* {@link SingletonPredictionContext}.<br>
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* <embed src="images/ArrayMerge_EqualTop.svg" type="image/svg+xml"/></p>
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*/
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static Ref<PredictionContext> mergeArrays(const Ref<ArrayPredictionContext> &a,
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const Ref<ArrayPredictionContext> &b, bool rootIsWildcard, PredictionContextMergeCache *mergeCache);
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protected:
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/// Make pass over all M parents; merge any equal() ones.
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/// @returns true if the list has been changed (i.e. duplicates where found).
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static bool combineCommonParents(std::vector<Ref<PredictionContext>> &parents);
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public:
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static std::string toDOTString(const Ref<PredictionContext> &context);
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static Ref<PredictionContext> getCachedContext(const Ref<PredictionContext> &context,
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PredictionContextCache &contextCache,
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std::map<Ref<PredictionContext>, Ref<PredictionContext>> &visited);
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// ter's recursive version of Sam's getAllNodes()
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static std::vector<Ref<PredictionContext>> getAllContextNodes(const Ref<PredictionContext> &context);
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static void getAllContextNodes_(const Ref<PredictionContext> &context,
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std::vector<Ref<PredictionContext>> &nodes, std::set<PredictionContext *> &visited);
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virtual std::string toString() const;
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virtual std::string toString(Recognizer *recog) const;
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std::vector<std::string> toStrings(Recognizer *recognizer, int currentState);
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std::vector<std::string> toStrings(Recognizer *recognizer, const Ref<PredictionContext> &stop, int currentState);
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};
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struct PredictionContextHasher {
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size_t operator () (const Ref<PredictionContext> &k) const {
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return k->hashCode();
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}
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};
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struct PredictionContextComparer {
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bool operator () (const Ref<PredictionContext> &lhs, const Ref<PredictionContext> &rhs) const
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{
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if (lhs == rhs) // Object identity.
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return true;
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return (lhs->hashCode() == rhs->hashCode()) && (*lhs == *rhs);
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}
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};
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class PredictionContextMergeCache {
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public:
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Ref<PredictionContext> put(Ref<PredictionContext> const& key1, Ref<PredictionContext> const& key2,
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Ref<PredictionContext> const& value);
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Ref<PredictionContext> get(Ref<PredictionContext> const& key1, Ref<PredictionContext> const& key2);
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void clear();
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std::string toString() const;
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size_t count() const;
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private:
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std::unordered_map<Ref<PredictionContext>,
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std::unordered_map<Ref<PredictionContext>, Ref<PredictionContext>, PredictionContextHasher, PredictionContextComparer>,
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PredictionContextHasher, PredictionContextComparer> _data;
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};
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} // namespace atn
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} // namespace antlr4
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