SLEvalRootNode.java

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package com.oracle.truffle.sl.nodes;

import java.util.Map;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.TruffleLanguage.ContextReference;
import com.oracle.truffle.api.frame.FrameDescriptor;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.source.SourceSection;
import com.oracle.truffle.sl.SLLanguage;
import com.oracle.truffle.sl.runtime.SLContext;
import com.oracle.truffle.sl.runtime.SLNull;

/**
 * In addition to {@link SLRootNode}, this class performs two additional tasks:
 *
 * <ul>
 * <li>Lazily registration of functions on first execution. This fulfills the semantics of
 * "evaluating" source code in SL.</li>
 * <li>Conversion of arguments to types understood by SL. The SL source code can be evaluated from a
 * different language, i.e., the caller can be a node from a different language that uses types not
 * understood by SL.</li>
 * </ul>
 */
public final class SLEvalRootNode extends SLRootNode {

    private final Map<String, SLRootNode> functions;
    @CompilationFinal private boolean registered;

    private final ContextReference<SLContext> reference;

    public SLEvalRootNode(SLLanguage language, FrameDescriptor frameDescriptor, SLExpressionNode bodyNode, SourceSection sourceSection, String name, Map<String, SLRootNode> functions) {
        super(language, frameDescriptor, bodyNode, sourceSection, name);
        this.functions = functions;
        this.reference = language.getContextReference();
    }

    @Override
    public Object execute(VirtualFrame frame) {
        /* Lazy registrations of functions on first execution. */
        if (!registered) {
            /* Function registration is a slow-path operation that must not be compiled. */
            CompilerDirectives.transferToInterpreterAndInvalidate();
            reference.get().getFunctionRegistry().register(functions);
            registered = true;
        }

        if (getBodyNode() == null) {
            /* The source code did not have a "main" function, so nothing to execute. */
            return SLNull.SINGLETON;
        }

        /* Conversion of arguments to types understood by SL. */
        Object[] arguments = frame.getArguments();
        for (int i = 0; i < arguments.length; i++) {
            arguments[i] = SLContext.fromForeignValue(arguments[i]);
        }

        /* Now we can execute the body of the "main" function. */
        return super.execute(frame);
    }
}