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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript.optimizer;

import org.mozilla.javascript.ArrowFunction;
import org.mozilla.javascript.Callable;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.ContextFactory;
import org.mozilla.javascript.ES6Generator;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.JavaScriptException;
import org.mozilla.javascript.NativeFunction;
import org.mozilla.javascript.NativeGenerator;
import org.mozilla.javascript.NativeIterator;
import org.mozilla.javascript.Script;
import org.mozilla.javascript.ScriptRuntime;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.ScriptableObject;
import org.mozilla.javascript.Undefined;

public final class OptRuntime extends ScriptRuntime {
    public static final Double oneObj = Double.valueOf(1.0);
    public static final Double minusOneObj = Double.valueOf(-1.0);

    /** Implement ....() call shrinking optimizer code. */
    public static Object call0(Callable fun, Scriptable thisObj, Context cx, Scriptable scope) {
        return fun.call(cx, scope, thisObj, ScriptRuntime.emptyArgs);
    }

    /** Implement ....(arg) call shrinking optimizer code. */
    public static Object call1(
            Callable fun, Scriptable thisObj, Object arg0, Context cx, Scriptable scope) {
        return fun.call(cx, scope, thisObj, new Object[] {arg0});
    }

    /** Implement ....(arg0, arg1) call shrinking optimizer code. */
    public static Object call2(
            Callable fun,
            Scriptable thisObj,
            Object arg0,
            Object arg1,
            Context cx,
            Scriptable scope) {
        return fun.call(cx, scope, thisObj, new Object[] {arg0, arg1});
    }

    /** Implement ....(arg0, arg1, ...) call shrinking optimizer code. */
    public static Object callN(
            Callable fun, Scriptable thisObj, Object[] args, Context cx, Scriptable scope) {
        return fun.call(cx, scope, thisObj, args);
    }

    /** Implement name(args) call shrinking optimizer code. */
    public static Object callName(Object[] args, String name, Context cx, Scriptable scope) {
        Callable f = getNameFunctionAndThis(name, cx, scope);
        Scriptable thisObj = lastStoredScriptable(cx);
        return f.call(cx, scope, thisObj, args);
    }

    /** Implement name() call shrinking optimizer code. */
    public static Object callName0(String name, Context cx, Scriptable scope) {
        Callable f = getNameFunctionAndThis(name, cx, scope);
        Scriptable thisObj = lastStoredScriptable(cx);
        return f.call(cx, scope, thisObj, ScriptRuntime.emptyArgs);
    }

    /** Implement x.property() call shrinking optimizer code. */
    public static Object callProp0(Object value, String property, Context cx, Scriptable scope) {
        Callable f = getPropFunctionAndThis(value, property, cx, scope);
        Scriptable thisObj = lastStoredScriptable(cx);
        return f.call(cx, scope, thisObj, ScriptRuntime.emptyArgs);
    }

    public static Object add(Object val1, double val2, Context cx) {
        if (val1 instanceof Double) {
            return ((Double) val1) + val2;
        }
        if (val1 instanceof Integer) {
            return ((Integer) val1) + val2;
        }
        return ScriptRuntime.add(val1, val2, cx);
    }

    public static Object add(double val1, Object val2, Context cx) {
        if (val2 instanceof Double) {
            return val1 + ((Double) val2);
        }
        if (val2 instanceof Integer) {
            return val1 + ((Integer) val2);
        }
        return ScriptRuntime.add(val1, val2, cx);
    }

    /** @deprecated Use {@link #elemIncrDecr(Object, double, Context, Scriptable, int)} instead */
    @Deprecated
    public static Object elemIncrDecr(Object obj, double index, Context cx, int incrDecrMask) {
        return elemIncrDecr(obj, index, cx, getTopCallScope(cx), incrDecrMask);
    }

    public static Object elemIncrDecr(
            Object obj, double index, Context cx, Scriptable scope, int incrDecrMask) {
        return ScriptRuntime.elemIncrDecr(obj, Double.valueOf(index), cx, scope, incrDecrMask);
    }

    public static Object[] padStart(Object[] currentArgs, int count) {
        Object[] result = new Object[currentArgs.length + count];
        System.arraycopy(currentArgs, 0, result, count, currentArgs.length);
        return result;
    }

    public static void initFunction(
            NativeFunction fn, int functionType, Scriptable scope, Context cx) {
        ScriptRuntime.initFunction(cx, scope, fn, functionType, false);
    }

    public static Function bindThis(
            NativeFunction fn, Context cx, Scriptable scope, Scriptable thisObj) {
        return new ArrowFunction(cx, scope, fn, thisObj);
    }

    public static Object callSpecial(
            Context cx,
            Callable fun,
            Scriptable thisObj,
            Object[] args,
            Scriptable scope,
            Scriptable callerThis,
            int callType,
            String fileName,
            int lineNumber) {
        return ScriptRuntime.callSpecial(
                cx, fun, thisObj, args, scope, callerThis, callType, fileName, lineNumber);
    }

    public static Object newObjectSpecial(
            Context cx,
            Object fun,
            Object[] args,
            Scriptable scope,
            Scriptable callerThis,
            int callType) {
        return ScriptRuntime.newSpecial(cx, fun, args, scope, callType);
    }

    public static Double wrapDouble(double num) {
        if (num == 0.0) {
            if (1 / num > 0) {
                // +0.0
                return zeroObj;
            }
        } else if (num == 1.0) {
            return oneObj;
        } else if (num == -1.0) {
            return minusOneObj;
        } else if (Double.isNaN(num)) {
            return NaNobj;
        }
        return Double.valueOf(num);
    }

    static String encodeIntArray(int[] array) {
        // XXX: this extremely inefficient for small integers
        if (array == null) {
            return null;
        }
        int n = array.length;
        char[] buffer = new char[1 + n * 2];
        buffer[0] = 1;
        for (int i = 0; i != n; ++i) {
            int value = array[i];
            int shift = 1 + i * 2;
            buffer[shift] = (char) (value >>> 16);
            buffer[shift + 1] = (char) value;
        }
        return new String(buffer);
    }

    private static int[] decodeIntArray(String str, int arraySize) {
        // XXX: this extremely inefficient for small integers
        if (arraySize == 0) {
            if (str != null) throw new IllegalArgumentException();
            return null;
        }
        if (str.length() != 1 + arraySize * 2 && str.charAt(0) != 1) {
            throw new IllegalArgumentException();
        }
        int[] array = new int[arraySize];
        for (int i = 0; i != arraySize; ++i) {
            int shift = 1 + i * 2;
            array[i] = (str.charAt(shift) << 16) | str.charAt(shift + 1);
        }
        return array;
    }

    public static Scriptable newArrayLiteral(
            Object[] objects, String encodedInts, int skipCount, Context cx, Scriptable scope) {
        int[] skipIndexces = decodeIntArray(encodedInts, skipCount);
        return newArrayLiteral(objects, skipIndexces, cx, scope);
    }

    public static void main(final Script script, final String[] args) {
        ContextFactory.getGlobal()
                .call(
                        cx -> {
                            ScriptableObject global = getGlobal(cx);

                            // get the command line arguments and define "arguments"
                            // array in the top-level object
                            Object[] argsCopy = new Object[args.length];
                            System.arraycopy(args, 0, argsCopy, 0, args.length);
                            Scriptable argsObj = cx.newArray(global, argsCopy);
                            global.defineProperty("arguments", argsObj, ScriptableObject.DONTENUM);
                            script.exec(cx, global);
                            return null;
                        });
    }

    public static void throwStopIteration(Object scope, Object genState) {
        Object value = getGeneratorReturnValue(genState);
        Object si =
                (value == Undefined.instance)
                        ? NativeIterator.getStopIterationObject((Scriptable) scope)
                        : new NativeIterator.StopIteration(value);
        throw new JavaScriptException(si, "", 0);
    }

    public static Scriptable createNativeGenerator(
            NativeFunction funObj,
            Scriptable scope,
            Scriptable thisObj,
            int maxLocals,
            int maxStack) {
        GeneratorState gs = new GeneratorState(thisObj, maxLocals, maxStack);
        if (Context.getCurrentContext().getLanguageVersion() >= Context.VERSION_ES6) {
            return new ES6Generator(scope, funObj, gs);
        } else {
            return new NativeGenerator(scope, funObj, gs);
        }
    }

    public static Object[] getGeneratorStackState(Object obj) {
        GeneratorState rgs = (GeneratorState) obj;
        if (rgs.stackState == null) rgs.stackState = new Object[rgs.maxStack];
        return rgs.stackState;
    }

    public static Object[] getGeneratorLocalsState(Object obj) {
        GeneratorState rgs = (GeneratorState) obj;
        if (rgs.localsState == null) rgs.localsState = new Object[rgs.maxLocals];
        return rgs.localsState;
    }

    public static void setGeneratorReturnValue(Object obj, Object val) {
        GeneratorState rgs = (GeneratorState) obj;
        rgs.returnValue = val;
    }

    public static Object getGeneratorReturnValue(Object obj) {
        GeneratorState rgs = (GeneratorState) obj;
        return (rgs.returnValue == null ? Undefined.instance : rgs.returnValue);
    }

    public static class GeneratorState {
        static final String CLASS_NAME =
                "org/mozilla/javascript/optimizer/OptRuntime$GeneratorState";

        @SuppressWarnings("unused")
        public int resumptionPoint;

        static final String resumptionPoint_NAME = "resumptionPoint";
        static final String resumptionPoint_TYPE = "I";

        @SuppressWarnings("unused")
        public Scriptable thisObj;

        static final String thisObj_NAME = "thisObj";
        static final String thisObj_TYPE = "Lorg/mozilla/javascript/Scriptable;";

        Object[] stackState;
        Object[] localsState;
        int maxLocals;
        int maxStack;
        Object returnValue;

        GeneratorState(Scriptable thisObj, int maxLocals, int maxStack) {
            this.thisObj = thisObj;
            this.maxLocals = maxLocals;
            this.maxStack = maxStack;
        }
    }
}