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package com.oracle.truffle.api.nodes;

import static com.oracle.truffle.api.nodes.NodeAccessor.ENGINE;
import static com.oracle.truffle.api.nodes.NodeAccessor.LANGUAGE;

import java.util.concurrent.locks.Lock;

import com.oracle.truffle.api.CompilerAsserts;
import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.TruffleLanguage;
import com.oracle.truffle.api.TruffleLanguage.ContextReference;
import com.oracle.truffle.api.TruffleLanguage.InlineParsingRequest;
import com.oracle.truffle.api.TruffleLanguage.LanguageReference;
import com.oracle.truffle.api.frame.VirtualFrame;

Represents an executable node in a Truffle AST. The executable node represents an AST fragment that can be executed using a frame instance created by the framework. 
See Also:
TruffleLanguage.parse(InlineParsingRequest)
Since:
0.31/**
 * Represents an executable node in a Truffle AST. The executable node represents an AST fragment
 * that can be {@link #execute(VirtualFrame) executed} using a {@link VirtualFrame frame} instance
 * created by the framework.
 *
 * @see TruffleLanguage#parse(com.oracle.truffle.api.TruffleLanguage.InlineParsingRequest)
 * @since 0.31
 */
public abstract class ExecutableNode extends Node {

    /*
     * Either instance of TruffleLanguage, PolyglotEngineImpl or null.
     */
    @CompilationFinal private Object engineRef;
    @CompilationFinal ReferenceCache referenceCache;

    
Creates new executable node with a given language instance. The language instance is obtainable while TruffleLanguage.parse(InlineParsingRequest) is executed. 
Params:
language – the language this executable node is associated with
Since:
0.31/**
     * Creates new executable node with a given language instance. The language instance is
     * obtainable while {@link TruffleLanguage#parse(InlineParsingRequest)} is executed.
     *
     * @param language the language this executable node is associated with
     * @since 0.31
     */
    protected ExecutableNode(TruffleLanguage<?> language) {
        CompilerAsserts.neverPartOfCompilation();
        if (language != null) {
            this.engineRef = language;
        } else {
            this.engineRef = ENGINE.getCurrentPolyglotEngine();
        }
        /*
         * This can no longer happen for normal languages. It could only happen for language
         * instances that were created directly without service provider. This case is rare enough,
         * to not be worth a check for every root node.
         */
        assert language == null || getLanguageInfo() != null : "Truffle language instance is not initialized.";
    }

    final TruffleLanguage<?> getLanguage() {
        if (engineRef instanceof TruffleLanguage<?>) {
            return (TruffleLanguage<?>) engineRef;
        } else {
            return null;
        }
    }

    final void applyEngineRef(ExecutableNode node) {
        this.engineRef = node.engineRef;
    }

    final Object getEngine() {
        Object ref = engineRef;
        if (ref instanceof TruffleLanguage<?>) {
            return ENGINE.getPolyglotEngine(LANGUAGE.getPolyglotLanguageInstance((TruffleLanguage<?>) ref));
        } else {
            return ref;
        }
    }

    
Execute this fragment at the place where it was parsed.
Params:
frame – the actual frame valid at the parsed location
Returns:
the result of the execution, must be an interop type (i.e. either implementing
        TruffleObject or be a primitive value), or null.
Since:
0.31/**
     * Execute this fragment at the place where it was parsed.
     *
     * @param frame the actual frame valid at the parsed location
     * @return the result of the execution, must be an interop type (i.e. either implementing
     *         TruffleObject or be a primitive value), or <code>null</code>.
     * @since 0.31
     */
    public abstract Object execute(VirtualFrame frame);

    
Returns public information about the language. The language can be assumed equal if the instances of the language info instance are the same. To access internal details of the language within the language implementation use Node.lookupLanguageReference(Class<TruffleLanguage>). 
Since:
0.31/**
     * Returns public information about the language. The language can be assumed equal if the
     * instances of the language info instance are the same. To access internal details of the
     * language within the language implementation use {@link #lookupLanguageReference(Class)}.
     *
     * @since 0.31
     */
    public final LanguageInfo getLanguageInfo() {
        TruffleLanguage<?> language = getLanguage();
        if (language != null) {
            return LANGUAGE.getLanguageInfo(language);
        } else {
            return null;
        }
    }

    
Returns the language instance associated with this executable node. The language instance is intended for internal use in languages and is only accessible if the concrete type of the language is known. Public information about the language can be accessed using getLanguageInfo(). The language is null if the executable node is not associated with a language. This method is guaranteed to return a PE constant if the root node is also a PE constant. 
See Also:
getLanguageInfo()
Since:
0.31/**
     * Returns the language instance associated with this executable node. The language instance is
     * intended for internal use in languages and is only accessible if the concrete type of the
     * language is known. Public information about the language can be accessed using
     * {@link #getLanguageInfo()}. The language is <code>null</code> if the executable node is not
     * associated with a language. This method is guaranteed to return a
     * {@link CompilerDirectives#isPartialEvaluationConstant(Object) PE constant} if the root node
     * is also a PE constant.
     *
     * @see #getLanguageInfo()
     * @since 0.31
     */
    @SuppressWarnings({"rawtypes", "unchecked"})
    public final <C extends TruffleLanguage> C getLanguage(Class<C> languageClass) {
        TruffleLanguage<?> language = getLanguage();
        if (language == null) {
            return null;
        }
        if (language.getClass() != languageClass) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            throw new ClassCastException(String.format("Illegal language class specified. Expected '%s'.", language.getClass().getName()));
        }
        return (C) language;
    }

    static final class ReferenceCache {

        final Class<?> languageClass;
        final LanguageReference<?> languageReference;
        final ContextReference<?> contextReference;
        final ReferenceCache next;

        @SuppressWarnings("unchecked")
        ReferenceCache(ExecutableNode executableNode, @SuppressWarnings("rawtypes") Class<? extends TruffleLanguage> languageClass, ReferenceCache next) {
            this.languageClass = languageClass;
            if (languageClass != null) {
                Object engine = executableNode.getEngine();
                TruffleLanguage<?> language = executableNode.getLanguage();
                this.languageReference = ENGINE.lookupLanguageReference(engine, language, languageClass);
                this.contextReference = ENGINE.lookupContextReference(engine, language, languageClass);
            } else {
                this.languageReference = null;
                this.contextReference = null;
            }
            this.next = next;
        }

    }

    @ExplodeLoop
    @SuppressWarnings("rawtypes")
    final ReferenceCache lookupReferenceCache(Class<? extends TruffleLanguage> languageClass) {
        do {
            ReferenceCache current = this.referenceCache;
            if (current == GENERIC) {
                return null;
            }
            while (current != null) {
                if ((current.languageClass == languageClass)) {
                    return current;
                }
                current = current.next;
            }
            CompilerDirectives.transferToInterpreterAndInvalidate();
            specializeReferenceCache(languageClass);
        } while (true);
    }

    private static final ReferenceCache GENERIC = new ReferenceCache(null, null, null);

    @SuppressWarnings("rawtypes")
    private void specializeReferenceCache(Class<? extends TruffleLanguage> languageClass) {
        Lock lock = getLock();
        lock.lock();
        try {
            ReferenceCache current = this.referenceCache;
            if (current == null) {
                this.referenceCache = new ReferenceCache(this, languageClass, null);
            } else {
                if (getEngine() == null) {
                    this.referenceCache = GENERIC;
                } else {
                    int count = 0;
                    ReferenceCache original = current;
                    do {
                        count++;
                        current = current.next;
                    } while (current != null);
                    if (count >= 5) {
                        this.referenceCache = GENERIC;
                    } else {
                        this.referenceCache = new ReferenceCache(this, languageClass, original);
                    }
                }
            }
        } finally {
            lock.unlock();
        }
    }

}