Java Double Number From toDoublePow2(long m, int n)

Description

Returns the closest double representation of the specified long number multiplied by a power of two.

License

Open Source License

Parameter

Parameter	Description
m	the <code>long</code> multiplier. (must be non-negative)
n	the power of two exponent.

Return

m * 2n.

Declaration

private static double toDoublePow2(long m, int n) 

Method Source Code

//package com.java2s;

public class Main {
    /**/*from w  w  w . j a v  a2  s. c om*/
     * Returns the closest <code>double</code> representation of the
     * specified <code>long</code> number multiplied by a power of two.
     *
     * @param m the <code>long</code> multiplier. (must be non-negative)
     * @param n the power of two exponent.
     * @return <code>m * 2<sup>n</sup></code>.
     */
    private static double toDoublePow2(long m, int n) {
        assert m >= 0;
        if (m == 0)
            return 0.0;
        int bitLength = Long.SIZE - Long.numberOfLeadingZeros(m);
        int shift = bitLength - 53;
        long exp = 1023L + 52 + n + shift; // Use long to avoid overflow.
        if (exp >= 0x7FF)
            return Double.POSITIVE_INFINITY;
        if (exp <= 0) { // Degenerated number (subnormal, assume 0 for bit 52)
            if (exp <= -54)
                return 0.0;
            return toDoublePow2(m, n + 54) / 18014398509481984L; // 2^54 Exact.
        }
        // Normal number.
        long bits = (shift > 0) ? (m >> shift) + ((m >> (shift - 1)) & 1) : // Rounding.
                m << -shift;
        if (((bits >> 52) != 1) && (++exp >= 0x7FF))
            return Double.POSITIVE_INFINITY;
        bits &= 0x000fffffffffffffL; // Clears MSB (bit 52)
        bits |= exp << 52;
        return Double.longBitsToDouble(bits);
    }
}

Related

1. toDoubleByObject(Object obj)
2. toDoubleDigit(int number)
3. toDoubleMatrix(Number[][] matrix)
4. toDoubleObject(Object obj)
5. toDoublePow10(long m, int n)
6. toDoublePrecision(long fixedPrecisionOrdinate)
7. toDoublePrimitiveArray(final Double[] wrappedArray)
8. toDoubleQuotes(String str)
9. toDoubles(byte[] bytes)