nativemath.java

這是一個javascript 的 interpreter是了解 web browser的好材料

/* -*- Mode: java; tab-width: 4; indent-tabs-mode: 1; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Norris Boyd
 *   Igor Bukanov
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.javascript;

/**
 * This class implements the Math native object.
 * See ECMA 15.8.
 * @author Norris Boyd
 */

final class NativeMath extends IdScriptableObject
{
    static final long serialVersionUID = -8838847185801131569L;

    private static final Object MATH_TAG = new Object();

    static void init(Scriptable scope, boolean sealed)
    {
        NativeMath obj = new NativeMath();
        obj.activatePrototypeMap(MAX_ID);
        obj.setPrototype(getObjectPrototype(scope));
        obj.setParentScope(scope);
        if (sealed) { obj.sealObject(); }
        ScriptableObject.defineProperty(scope, "Math", obj,
                                        ScriptableObject.DONTENUM);
    }

    private NativeMath()
    {
    }

    public String getClassName() { return "Math"; }

    protected void initPrototypeId(int id)
    {
        if (id <= LAST_METHOD_ID) {
            String name;
            int arity;
            switch (id) {
              case Id_toSource: arity = 0; name = "toSource"; break;
              case Id_abs:      arity = 1; name = "abs";      break;
              case Id_acos:     arity = 1; name = "acos";     break;
              case Id_asin:     arity = 1; name = "asin";     break;
              case Id_atan:     arity = 1; name = "atan";     break;
              case Id_atan2:    arity = 2; name = "atan2";    break;
              case Id_ceil:     arity = 1; name = "ceil";     break;
              case Id_cos:      arity = 1; name = "cos";      break;
              case Id_exp:      arity = 1; name = "exp";      break;
              case Id_floor:    arity = 1; name = "floor";    break;
              case Id_log:      arity = 1; name = "log";      break;
              case Id_max:      arity = 2; name = "max";      break;
              case Id_min:      arity = 2; name = "min";      break;
              case Id_pow:      arity = 2; name = "pow";      break;
              case Id_random:   arity = 0; name = "random";   break;
              case Id_round:    arity = 1; name = "round";    break;
              case Id_sin:      arity = 1; name = "sin";      break;
              case Id_sqrt:     arity = 1; name = "sqrt";     break;
              case Id_tan:      arity = 1; name = "tan";      break;
              default: throw new IllegalStateException(String.valueOf(id));
            }
            initPrototypeMethod(MATH_TAG, id, name, arity);
        } else {
            String name;
            double x;
            switch (id) {
              case Id_E:       x = Math.E;             name = "E";       break;
              case Id_PI:      x = Math.PI;            name = "PI";      break;
              case Id_LN10:    x = 2.302585092994046;  name = "LN10";    break;
              case Id_LN2:     x = 0.6931471805599453; name = "LN2";     break;
              case Id_LOG2E:   x = 1.4426950408889634; name = "LOG2E";   break;
              case Id_LOG10E:  x = 0.4342944819032518; name = "LOG10E";  break;
              case Id_SQRT1_2: x = 0.7071067811865476; name = "SQRT1_2"; break;
              case Id_SQRT2:   x = 1.4142135623730951; name = "SQRT2";   break;
              default: throw new IllegalStateException(String.valueOf(id));
            }
            initPrototypeValue(id, name, ScriptRuntime.wrapNumber(x),
                               DONTENUM | READONLY | PERMANENT);
        }
    }

    public Object execIdCall(IdFunctionObject f, Context cx, Scriptable scope,
                             Scriptable thisObj, Object[] args)
    {
        if (!f.hasTag(MATH_TAG)) {
            return super.execIdCall(f, cx, scope, thisObj, args);
        }
        double x;
        int methodId = f.methodId();
        switch (methodId) {
            case Id_toSource:
                return "Math";

            case Id_abs:
                x = ScriptRuntime.toNumber(args, 0);
                // abs(-0.0) should be 0.0, but -0.0 < 0.0 == false
                x = (x == 0.0) ? 0.0 : (x < 0.0) ? -x : x;
                break;

            case Id_acos:
            case Id_asin:
                x = ScriptRuntime.toNumber(args, 0);
                if (x == x && -1.0 <= x && x <= 1.0) {
                    x = (methodId == Id_acos) ? Math.acos(x) : Math.asin(x);
                } else {
                    x = Double.NaN;
                }
                break;

            case Id_atan:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.atan(x);
                break;

            case Id_atan2:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.atan2(x, ScriptRuntime.toNumber(args, 1));
                break;

            case Id_ceil:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.ceil(x);
                break;

            case Id_cos:
                x = ScriptRuntime.toNumber(args, 0);
                x = (x == Double.POSITIVE_INFINITY
                     || x == Double.NEGATIVE_INFINITY)
                    ? Double.NaN : Math.cos(x);
                break;

            case Id_exp:
                x = ScriptRuntime.toNumber(args, 0);
                x = (x == Double.POSITIVE_INFINITY) ? x
                    : (x == Double.NEGATIVE_INFINITY) ? 0.0
                    : Math.exp(x);
                break;

            case Id_floor:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.floor(x);
                break;

            case Id_log:
                x = ScriptRuntime.toNumber(args, 0);
                // Java's log(<0) = -Infinity; we need NaN
                x = (x < 0) ? Double.NaN : Math.log(x);
                break;

            case Id_max:
            case Id_min:
                x = (methodId == Id_max)
                    ? Double.NEGATIVE_INFINITY : Double.POSITIVE_INFINITY;
                for (int i = 0; i != args.length; ++i) {
                    double d = ScriptRuntime.toNumber(args[i]);
                    if (d != d) {
                        x = d; // NaN
                        break;
                    }
                    if (methodId == Id_max) {
                        // if (x < d) x = d; does not work due to -0.0 >= +0.0
                        x = Math.max(x, d);
                    } else {
                        x = Math.min(x, d);