ecma/Expressions/11.7.2.js

/* The contents of this file are subject to the Netscape 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/NPL/
 *
 * 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 Mozilla Communicator client code, released March
 * 31, 1998.
 *
 * The Initial Developer of the Original Code is Netscape Communications
 * Corporation. Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s):
 *
 */
/**
    File Name:          11.7.2.js
    ECMA Section:       11.7.2  The signed right shift operator ( >> )
    Description:
    Performs a sign-filling bitwise right shift operation on the left argument
    by the amount specified by the right argument.

    The production ShiftExpression : ShiftExpression >> AdditiveExpression is
    evaluated as follows:

    1.  Evaluate ShiftExpression.
    2.  Call GetValue(Result(1)).
    3.  Evaluate AdditiveExpression.
    4.  Call GetValue(Result(3)).
    5.  Call ToInt32(Result(2)).
    6.  Call ToUint32(Result(4)).
    7.  Mask out all but the least significant 5 bits of Result(6), that is,
        compute Result(6) & 0x1F.
    8.  Perform sign-extending right shift of Result(5) by Result(7) bits. The
        most significant bit is propagated. The result is a signed 32 bit
        integer.
    9.  Return Result(8).

    Author:             christine (at) netscape.com
    Date:               12 november 1997
*/
    var SECTION = "11.7.2";
    var VERSION = "ECMA_1";
    startTest();
    var testcases = getTestCases();

    writeHeaderToLog( SECTION + "  The signed right shift operator ( >> )");
    test();

function test() {
    for ( tc=0; tc < testcases.length; tc++ ) {
        testcases[tc].passed = writeTestCaseResult(
                            testcases[tc].expect,
                            testcases[tc].actual,
                            testcases[tc].description +" = "+
                            testcases[tc].actual );

        testcases[tc].reason += ( testcases[tc].passed ) ? "" : "wrong value ";
    }
    stopTest();
    return ( testcases );
}
function getTestCases() {
    var array = new Array();
    var item = 0;
    var power = 0;
    var addexp = 0;

    for ( power = 0; power <= 32; power++ ) {
        shiftexp = Math.pow( 2, power );

        for ( addexp = 0; addexp <= 32; addexp++ ) {
            array[item++] = new TestCase( SECTION,
                                    shiftexp + " >> " + addexp,
                                    SignedRightShift( shiftexp, addexp ),
                                    shiftexp >> addexp );
        }
    }

    for ( power = 0; power <= 32; power++ ) {
        shiftexp = -Math.pow( 2, power );

        for ( addexp = 0; addexp <= 32; addexp++ ) {
            array[item++] = new TestCase( SECTION,
                                    shiftexp + " >> " + addexp,
                                    SignedRightShift( shiftexp, addexp ),
                                    shiftexp >> addexp );
        }
    }

    return ( array );
}

function ToInteger( n ) {
    n = Number( n );
    var sign = ( n < 0 ) ? -1 : 1;

    if ( n != n ) {
        return 0;
    }
    if ( Math.abs( n ) == 0 || Math.abs( n ) == Number.POSITIVE_INFINITY ) {
        return n;
    }
    return ( sign * Math.floor(Math.abs(n)) );
}
function ToInt32( n ) {
    n = Number( n );
    var sign = ( n < 0 ) ? -1 : 1;

    if ( Math.abs( n ) == 0 || Math.abs( n ) == Number.POSITIVE_INFINITY) {
        return 0;
    }

    n = (sign * Math.floor( Math.abs(n) )) % Math.pow(2,32);
    n = ( n >= Math.pow(2,31) ) ? n - Math.pow(2,32) : n;

    return ( n );
}
function ToUint32( n ) {
    n = Number( n );
    var sign = ( n < 0 ) ? -1 : 1;

    if ( Math.abs( n ) == 0 || Math.abs( n ) == Number.POSITIVE_INFINITY) {
        return 0;
    }
    n = sign * Math.floor( Math.abs(n) )

    n = n % Math.pow(2,32);

    if ( n < 0 ){
        n += Math.pow(2,32);
    }

    return ( n );
}
function ToUint16( n ) {
    var sign = ( n < 0 ) ? -1 : 1;

    if ( Math.abs( n ) == 0 || Math.abs( n ) == Number.POSITIVE_INFINITY) {
        return 0;
    }

    n = ( sign * Math.floor( Math.abs(n) ) ) % Math.pow(2,16);

    if (n <0) {
        n += Math.pow(2,16);
    }

    return ( n );
}
function Mask( b, n ) {
    b = ToUint32BitString( b );
    b = b.substring( b.length - n );
    b = ToUint32Decimal( b );
    return ( b );
}
function ToUint32BitString( n ) {
    var b = "";
    for ( p = 31; p >=0; p-- ) {
        if ( n >= Math.pow(2,p) ) {
            b += "1";
            n -= Math.pow(2,p);
        } else {
            b += "0";
        }
    }
    return b;
}
function ToInt32BitString( n ) {
    var b = "";
    var sign = ( n < 0 ) ? -1 : 1;

    b += ( sign == 1 ) ? "0" : "1";

    for ( p = 30; p >=0; p-- ) {
        if ( (sign == 1 ) ? sign * n >= Math.pow(2,p) : sign * n > Math.pow(2,p) ) {
            b += ( sign == 1 ) ? "1" : "0";
            n -= sign * Math.pow( 2, p );
        } else {
            b += ( sign == 1 ) ? "0" : "1";
        }
    }

    return b;
}
function ToInt32Decimal( bin ) {
    var r = 0;
    var sign;

    if ( Number(bin.charAt(0)) == 0 ) {
        sign = 1;
        r = 0;
    } else {
        sign = -1;
        r = -(Math.pow(2,31));
    }

    for ( var j = 0; j < 31; j++ ) {
        r += Math.pow( 2, j ) * Number(bin.charAt(31-j));
    }

    return r;
}
function ToUint32Decimal( bin ) {
    var r = 0;

    for ( l = bin.length; l < 32; l++ ) {
        bin = "0" + bin;
    }

    for ( j = 0; j < 31; j++ ) {
        r += Math.pow( 2, j ) * Number(bin.charAt(31-j));
    }

    return r;
}
function SignedRightShift( s, a ) {
    s = ToInt32( s );
    a = ToUint32( a );
    a = Mask( a, 5 );
    return ( SignedRShift( s, a ) );
}
function SignedRShift( s, a ) {
    s = ToInt32BitString( s );

    var firstbit = s.substring(0,1);

    s = s.substring( 1, s.length );

    for ( var z = 0; z < a; z++ ) {
        s = firstbit + s;
    }

    s = s.substring( 0, s.length - a);

    s = firstbit +s;


    return ToInt32(ToInt32Decimal(s));
}