Java example source code file (NashornCallSiteDescriptor.java)

This example Java source code file (NashornCallSiteDescriptor.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

callsite_fast_scope, callsite_profile, callsite_scope, callsite_strict, callsite_trace_misses, callsite_trace_scope, callsitedescriptor, classvalue, concurrentmap, lookup, methodtype, nashorncallsitedescriptor, override, string, threading, threads

The NashornCallSiteDescriptor.java Java example source code

/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.runtime.linker;

import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.invoke.MethodType;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import jdk.internal.dynalink.CallSiteDescriptor;
import jdk.internal.dynalink.support.AbstractCallSiteDescriptor;
import jdk.internal.dynalink.support.CallSiteDescriptorFactory;

/**
 * Nashorn-specific implementation of Dynalink's {@link CallSiteDescriptor}. The reason we have our own subclass is that
 * we can have a more compact representation, as we know that we're always only using {@code "dyn:*"} operations; also
 * we're storing flags in an additional primitive field.
 */
public final class NashornCallSiteDescriptor extends AbstractCallSiteDescriptor {
    /** Flags that the call site references a scope variable (it's an identifier reference or a var declaration, not a
     * property access expression. */
    public static final int CALLSITE_SCOPE                = 0x01;
    /** Flags that the call site is in code that uses ECMAScript strict mode. */
    public static final int CALLSITE_STRICT               = 0x02;
    /** Flags that a property getter or setter call site references a scope variable that is located at a known distance
     * in the scope chain. Such getters and setters can often be linked more optimally using these assumptions. */
    public static final int CALLSITE_FAST_SCOPE    = 0x400;

    /** Flags that the call site is profiled; Contexts that have {@code "profile.callsites"} boolean property set emit
     * code where call sites have this flag set. */
    public static final int CALLSITE_PROFILE          = 0x10;
    /** Flags that the call site is traced; Contexts that have {@code "trace.callsites"} property set emit code where
     * call sites have this flag set. */
    public static final int CALLSITE_TRACE            = 0x20;
    /** Flags that the call site linkage miss (and thus, relinking) is traced; Contexts that have the keyword
     * {@code "miss"} in their {@code "trace.callsites"} property emit code where call sites have this flag set. */
    public static final int CALLSITE_TRACE_MISSES     = 0x40;
    /** Flags that entry/exit to/from the method linked at call site are traced; Contexts that have the keyword
     * {@code "enterexit"} in their {@code "trace.callsites"} property emit code where call sites have this flag
     * set. */
    public static final int CALLSITE_TRACE_ENTEREXIT  = 0x80;
    /** Flags that values passed as arguments to and returned from the method linked at call site are traced; Contexts
     * that have the keyword {@code "values"} in their {@code "trace.callsites"} property emit code where call sites
     * have this flag set. */
    public static final int CALLSITE_TRACE_VALUES    = 0x100;
    /** Ordinarily, when {@link #CALLSITE_TRACE_VALUES} is set, scope objects are not printed in the trace but instead
     * the word {@code "SCOPE"} is printed instead With this flag, scope objects are also printed. Contexts that have
     * the keyword {@code "scope"} in their {@code "trace.callsites"} property emit code where call sites have this flag
     * set. */
    public static final int CALLSITE_TRACE_SCOPE      = 0x200;

    private static final ClassValue<ConcurrentMap canonicals =
            new ClassValue<ConcurrentMap() {
        @Override
        protected ConcurrentMap<NashornCallSiteDescriptor, NashornCallSiteDescriptor> computeValue(Class type) {
            return new ConcurrentHashMap<>();
        }
    };

    private final MethodHandles.Lookup lookup;
    private final String operator;
    private final String operand;
    private final MethodType methodType;
    private final int flags;

    /**
     * Retrieves a Nashorn call site descriptor with the specified values. Since call site descriptors are immutable
     * this method is at liberty to retrieve canonicalized instances (although it is not guaranteed it will do so).
     * @param lookup the lookup describing the script
     * @param name the name at the call site, e.g. {@code "dyn:getProp|getElem|getMethod:color"}.
     * @param methodType the method type at the call site
     * @param flags Nashorn-specific call site flags
     * @return a call site descriptor with the specified values.
     */
    public static NashornCallSiteDescriptor get(final MethodHandles.Lookup lookup, final String name,
            final MethodType methodType, final int flags) {
        final String[] tokenizedName = CallSiteDescriptorFactory.tokenizeName(name);
        assert tokenizedName.length == 2 || tokenizedName.length == 3;
        assert "dyn".equals(tokenizedName[0]);
        assert tokenizedName[1] != null;
        // TODO: see if we can move mangling/unmangling into Dynalink
        return get(lookup, tokenizedName[1], tokenizedName.length == 3 ? tokenizedName[2].intern() : null,
                methodType, flags);
    }

    private static NashornCallSiteDescriptor get(final MethodHandles.Lookup lookup, final String operator, final String operand, final MethodType methodType, final int flags) {
        final NashornCallSiteDescriptor csd = new NashornCallSiteDescriptor(lookup, operator, operand, methodType, flags);
        // Many of these call site descriptors are identical (e.g. every getter for a property color will be
        // "dyn:getProp:color(Object)Object", so it makes sense canonicalizing them.
        final ConcurrentMap<NashornCallSiteDescriptor, NashornCallSiteDescriptor> classCanonicals = canonicals.get(lookup.lookupClass());
        final NashornCallSiteDescriptor canonical = classCanonicals.putIfAbsent(csd, csd);
        return canonical != null ? canonical : csd;
    }

    private NashornCallSiteDescriptor(final MethodHandles.Lookup lookup, final String operator, final String operand,
            final MethodType methodType, final int flags) {
        this.lookup = lookup;
        this.operator = operator;
        this.operand = operand;
        this.methodType = methodType;
        this.flags = flags;
    }

    @Override
    public int getNameTokenCount() {
        return operand == null ? 2 : 3;
    }

    @Override
    public String getNameToken(final int i) {
        switch(i) {
        case 0: return "dyn";
        case 1: return operator;
        case 2:
            if(operand != null) {
                return operand;
            }
            break;
        default:
            break;
        }
        throw new IndexOutOfBoundsException(String.valueOf(i));
    }

    @Override
    public Lookup getLookup() {
        return lookup;
    }

    @Override
    public boolean equals(final CallSiteDescriptor csd) {
        return super.equals(csd) && flags == getFlags(csd);
    }

    @Override
    public MethodType getMethodType() {
        return methodType;
    }

    /**
     * Returns the operator (e.g. {@code "getProp"}) in this call site descriptor's name. Equivalent to
     * {@code getNameToken(CallSiteDescriptor.OPERATOR)}. The returned operator can be composite.
     * @return the operator in this call site descriptor's name.
     */
    public String getOperator() {
        return operator;
    }

    /**
     * Returns the first operator in this call site descriptor's name. E.g. if this call site descriptor has a composite
     * operation {@code "getProp|getMethod|getElem"}, it will return {@code "getProp"}. Nashorn - being a ECMAScript
     * engine - does not distinguish between property, element, and method namespace; ECMAScript objects just have one
     * single property namespace for all these, therefore it is largely irrelevant what the composite operation is
     * structured like; if the first operation can't be satisfied, neither can the others. The first operation is
     * however sometimes used to slightly alter the semantics; for example, a distinction between {@code "getProp"} and
     * {@code "getMethod"} being the first operation can translate into whether {@code "__noSuchProperty__"} or
     * {@code "__noSuchMethod__"} will be executed in case the property is not found.
     * @return the first operator in this call site descriptor's name.
     */
    public String getFirstOperator() {
        final int delim = operator.indexOf(CallSiteDescriptor.OPERATOR_DELIMITER);
        return delim == -1 ? operator : operator.substring(0, delim);
    }

    /**
     * Returns the named operand in this descriptor's name. Equivalent to
     * {@code getNameToken(CallSiteDescriptor.NAME_OPERAND)}. E.g. for operation {@code "dyn:getProp:color"}, returns
     * {@code "color"}. For call sites without named operands (e.g. {@code "dyn:new"}) returns null.
     * @return the named operand in this descriptor's name.
     */
    public String getOperand() {
        return operand;
    }

    /**
     * Returns the Nashorn-specific flags for this call site descriptor.
     * @param desc the descriptor. It can be any kind of a call site descriptor, not necessarily a
     * {@code NashornCallSiteDescriptor}. This allows for graceful interoperability when linking Nashorn with code
     * generated outside of Nashorn.
     * @return the Nashorn-specific flags for the call site, or 0 if the passed descriptor is not a Nashorn call site
     * descriptor.
     */
    private static int getFlags(final CallSiteDescriptor desc) {
        return desc instanceof NashornCallSiteDescriptor ? ((NashornCallSiteDescriptor)desc).flags : 0;
    }

    /**
     * Returns true if this descriptor has the specified flag set, see {@code CALLSITE_*} constants in this class.
     * @param flag the tested flag
     * @return true if the flag is set, false otherwise
     */
    private boolean isFlag(final int flag) {
        return (flags & flag) != 0;
    }

    /**
     * Returns true if this descriptor has the specified flag set, see {@code CALLSITE_*} constants in this class.
     * @param desc the descriptor. It can be any kind of a call site descriptor, not necessarily a
     * {@code NashornCallSiteDescriptor}. This allows for graceful interoperability when linking Nashorn with code
     * generated outside of Nashorn.
     * @param flag the tested flag
     * @return true if the flag is set, false otherwise (it will be false if the decriptor is not a Nashorn call site
     * descriptor).
     */
    private static boolean isFlag(final CallSiteDescriptor desc, final int flag) {
        return (getFlags(desc) & flag) != 0;
    }

    /**
     * Returns true if this descriptor is a Nashorn call site descriptor and has the {@link  #CALLSITE_SCOPE} flag set.
     * @param desc the descriptor. It can be any kind of a call site descriptor, not necessarily a
     * {@code NashornCallSiteDescriptor}. This allows for graceful interoperability when linking Nashorn with code
     * generated outside of Nashorn.
     * @return true if the descriptor is a Nashorn call site descriptor, and the flag is set, false otherwise.
     */
    public static boolean isScope(final CallSiteDescriptor desc) {
        return isFlag(desc, CALLSITE_SCOPE);
    }

    /**
     * Returns true if this descriptor is a Nashorn call site descriptor and has the {@link  #CALLSITE_FAST_SCOPE} flag set.
     * @param desc the descriptor. It can be any kind of a call site descriptor, not necessarily a
     * {@code NashornCallSiteDescriptor}. This allows for graceful interoperability when linking Nashorn with code
     * generated outside of Nashorn.
     * @return true if the descriptor is a Nashorn call site descriptor, and the flag is set, false otherwise.
     */
    public static boolean isFastScope(final CallSiteDescriptor desc) {
        return isFlag(desc, CALLSITE_FAST_SCOPE);
    }

    /**
     * Returns true if this descriptor is a Nashorn call site descriptor and has the {@link  #CALLSITE_STRICT} flag set.
     * @param desc the descriptor. It can be any kind of a call site descriptor, not necessarily a
     * {@code NashornCallSiteDescriptor}. This allows for graceful interoperability when linking Nashorn with code
     * generated outside of Nashorn.
     * @return true if the descriptor is a Nashorn call site descriptor, and the flag is set, false otherwise.
     */
    public static boolean isStrict(final CallSiteDescriptor desc) {
        return isFlag(desc, CALLSITE_STRICT);
    }

    boolean isProfile() {
        return isFlag(CALLSITE_PROFILE);
    }

    boolean isTrace() {
        return isFlag(CALLSITE_TRACE);
    }

    boolean isTraceMisses() {
        return isFlag(CALLSITE_TRACE_MISSES);
    }

    boolean isTraceEnterExit() {
        return isFlag(CALLSITE_TRACE_ENTEREXIT);
    }

    boolean isTraceObjects() {
        return isFlag(CALLSITE_TRACE_VALUES);
    }

    boolean isTraceScope() {
        return isFlag(CALLSITE_TRACE_SCOPE);
    }

    @Override
    public CallSiteDescriptor changeMethodType(final MethodType newMethodType) {
        return get(getLookup(), operator, operand, newMethodType, flags);
    }
}