// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.text;

import com.google.common.annotations.Beta;

/**
 * Utility class to format a double into a String.
 * <p>
 * This is intended as a lower-cost replacement for the standard
 * String.valueOf(double) since that method will cause lock
 * contention if it's used too often.
 * <p>
 * Note that this implementation won't always produce the same results
 * as java.lang.* formatting.
 * <p>
 * Also, this implementation is very poorly tested at the moment, so
 * it should be used carefully, only in cases where you know the input
 * will be well-defined and you don't need full precision.
 *
 * @author arnej27959
 */

@Beta
public final class DoubleFormatter {

    private static void tooSmall(StringBuilder target, long mantissa, int exponent) {
        double carry = 0;
        int prExp = 0;
        while (exponent < 0) {
            while (mantissa < (1L << 53)) {
                carry *= 10.0;
                mantissa *= 10;
                ++prExp;
            }
            carry *= 0.5;
            carry += 0.5*(mantissa & 1);
            mantissa >>= 1;
            ++exponent;
        }
        while (mantissa < (1L << 53)) {
            carry *= 10.0;
            mantissa *= 10;
            ++prExp;
        }
        mantissa += (long)(carry+0.5);

        int[] befor = { 0, 0, 0, 0, 0,   0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0,   0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0,   0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0,   0, 0, 0, 0, 0,
                        0, 0, 0, 0, 0,   0, 0, 0, 0, 0 };
        int b = 0;
        for (int i = 0; mantissa > 0; i++) {
            befor[i] = (int)(mantissa % 10);
            mantissa /= 10;
            ++b;
        }
        --b;
        target.append((char)('0'+befor[b]));
        target.append('.');
        if (b == 0) {
            target.append('0');
        } else {
            for (int i = b; i-- > 0; ) {
                target.append((char)('0'+befor[i]));
            }
        }
        prExp -= b;
        target.append("E-");
        target.append(String.valueOf(prExp));
    }

    public static StringBuilder fmt(StringBuilder target, double v) {
        append(target, v);
        return target;
    }

    public static String stringValue(double v) {
        return fmt(new StringBuilder(), v).toString();
    }


    //Hardcode some byte arrays to make them quickly available
    public static final char[] INFINITY = {'I','n','f','i','n','i','t','y'};
    public static final char[] NaN = {'N','a','N'};
    public static final char[][] ZEROS = {
        {},
        {'0'},
        {'0','0'},
        {'0','0','0'},
        {'0','0','0','0'},
        {'0','0','0','0','0'},
        {'0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
    };

    private static final char[] charForDigit = {
        '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h',
        'i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'
    };

    //And required double related constants.  
    private static final long  DoubleSignMask = 0x8000000000000000L;
    private static final long  DoubleExpMask  = 0x7ff0000000000000L;
    private static final long  DoubleFractMask= ~(DoubleSignMask|DoubleExpMask);
    private static final int  DoubleExpShift = 52;
    private static final int  DoubleExpBias = 1023;

    private static final double[] d_tenthPowers = {
        1e-323D, 1e-322D, 1e-321D, 1e-320D, 1e-319D, 1e-318D, 1e-317D, 1e-316D, 1e-315D, 1e-314D, 
        1e-313D, 1e-312D, 1e-311D, 1e-310D, 1e-309D, 1e-308D, 1e-307D, 1e-306D, 1e-305D, 1e-304D, 
        1e-303D, 1e-302D, 1e-301D, 1e-300D, 1e-299D, 1e-298D, 1e-297D, 1e-296D, 1e-295D, 1e-294D, 
        1e-293D, 1e-292D, 1e-291D, 1e-290D, 1e-289D, 1e-288D, 1e-287D, 1e-286D, 1e-285D, 1e-284D, 
        1e-283D, 1e-282D, 1e-281D, 1e-280D, 1e-279D, 1e-278D, 1e-277D, 1e-276D, 1e-275D, 1e-274D, 
        1e-273D, 1e-272D, 1e-271D, 1e-270D, 1e-269D, 1e-268D, 1e-267D, 1e-266D, 1e-265D, 1e-264D, 
        1e-263D, 1e-262D, 1e-261D, 1e-260D, 1e-259D, 1e-258D, 1e-257D, 1e-256D, 1e-255D, 1e-254D, 
        1e-253D, 1e-252D, 1e-251D, 1e-250D, 1e-249D, 1e-248D, 1e-247D, 1e-246D, 1e-245D, 1e-244D, 
        1e-243D, 1e-242D, 1e-241D, 1e-240D, 1e-239D, 1e-238D, 1e-237D, 1e-236D, 1e-235D, 1e-234D, 
        1e-233D, 1e-232D, 1e-231D, 1e-230D, 1e-229D, 1e-228D, 1e-227D, 1e-226D, 1e-225D, 1e-224D, 
        1e-223D, 1e-222D, 1e-221D, 1e-220D, 1e-219D, 1e-218D, 1e-217D, 1e-216D, 1e-215D, 1e-214D, 
        1e-213D, 1e-212D, 1e-211D, 1e-210D, 1e-209D, 1e-208D, 1e-207D, 1e-206D, 1e-205D, 1e-204D, 
        1e-203D, 1e-202D, 1e-201D, 1e-200D, 1e-199D, 1e-198D, 1e-197D, 1e-196D, 1e-195D, 1e-194D, 
        1e-193D, 1e-192D, 1e-191D, 1e-190D, 1e-189D, 1e-188D, 1e-187D, 1e-186D, 1e-185D, 1e-184D, 
        1e-183D, 1e-182D, 1e-181D, 1e-180D, 1e-179D, 1e-178D, 1e-177D, 1e-176D, 1e-175D, 1e-174D, 
        1e-173D, 1e-172D, 1e-171D, 1e-170D, 1e-169D, 1e-168D, 1e-167D, 1e-166D, 1e-165D, 1e-164D, 
        1e-163D, 1e-162D, 1e-161D, 1e-160D, 1e-159D, 1e-158D, 1e-157D, 1e-156D, 1e-155D, 1e-154D, 
        1e-153D, 1e-152D, 1e-151D, 1e-150D, 1e-149D, 1e-148D, 1e-147D, 1e-146D, 1e-145D, 1e-144D, 
        1e-143D, 1e-142D, 1e-141D, 1e-140D, 1e-139D, 1e-138D, 1e-137D, 1e-136D, 1e-135D, 1e-134D, 
        1e-133D, 1e-132D, 1e-131D, 1e-130D, 1e-129D, 1e-128D, 1e-127D, 1e-126D, 1e-125D, 1e-124D, 
        1e-123D, 1e-122D, 1e-121D, 1e-120D, 1e-119D, 1e-118D, 1e-117D, 1e-116D, 1e-115D, 1e-114D, 
        1e-113D, 1e-112D, 1e-111D, 1e-110D, 1e-109D, 1e-108D, 1e-107D, 1e-106D, 1e-105D, 1e-104D, 
        1e-103D, 1e-102D, 1e-101D, 1e-100D, 1e-99D, 1e-98D, 1e-97D, 1e-96D, 1e-95D, 1e-94D, 
        1e-93D, 1e-92D, 1e-91D, 1e-90D, 1e-89D, 1e-88D, 1e-87D, 1e-86D, 1e-85D, 1e-84D, 
        1e-83D, 1e-82D, 1e-81D, 1e-80D, 1e-79D, 1e-78D, 1e-77D, 1e-76D, 1e-75D, 1e-74D, 
        1e-73D, 1e-72D, 1e-71D, 1e-70D, 1e-69D, 1e-68D, 1e-67D, 1e-66D, 1e-65D, 1e-64D, 
        1e-63D, 1e-62D, 1e-61D, 1e-60D, 1e-59D, 1e-58D, 1e-57D, 1e-56D, 1e-55D, 1e-54D, 
        1e-53D, 1e-52D, 1e-51D, 1e-50D, 1e-49D, 1e-48D, 1e-47D, 1e-46D, 1e-45D, 1e-44D, 
        1e-43D, 1e-42D, 1e-41D, 1e-40D, 1e-39D, 1e-38D, 1e-37D, 1e-36D, 1e-35D, 1e-34D, 
        1e-33D, 1e-32D, 1e-31D, 1e-30D, 1e-29D, 1e-28D, 1e-27D, 1e-26D, 1e-25D, 1e-24D, 
        1e-23D, 1e-22D, 1e-21D, 1e-20D, 1e-19D, 1e-18D, 1e-17D, 1e-16D, 1e-15D, 1e-14D, 
        1e-13D, 1e-12D, 1e-11D, 1e-10D, 1e-9D, 1e-8D, 1e-7D, 1e-6D, 1e-5D, 1e-4D, 
        1e-3D, 1e-2D, 1e-1D, 1e0D, 1e1D, 1e2D, 1e3D, 1e4D, 
        1e5D, 1e6D, 1e7D, 1e8D, 1e9D, 1e10D, 1e11D, 1e12D, 1e13D, 1e14D, 
        1e15D, 1e16D, 1e17D, 1e18D, 1e19D, 1e20D, 1e21D, 1e22D, 1e23D, 1e24D, 
        1e25D, 1e26D, 1e27D, 1e28D, 1e29D, 1e30D, 1e31D, 1e32D, 1e33D, 1e34D, 
        1e35D, 1e36D, 1e37D, 1e38D, 1e39D, 1e40D, 1e41D, 1e42D, 1e43D, 1e44D, 
        1e45D, 1e46D, 1e47D, 1e48D, 1e49D, 1e50D, 1e51D, 1e52D, 1e53D, 1e54D, 
        1e55D, 1e56D, 1e57D, 1e58D, 1e59D, 1e60D, 1e61D, 1e62D, 1e63D, 1e64D, 
        1e65D, 1e66D, 1e67D, 1e68D, 1e69D, 1e70D, 1e71D, 1e72D, 1e73D, 1e74D, 
        1e75D, 1e76D, 1e77D, 1e78D, 1e79D, 1e80D, 1e81D, 1e82D, 1e83D, 1e84D, 
        1e85D, 1e86D, 1e87D, 1e88D, 1e89D, 1e90D, 1e91D, 1e92D, 1e93D, 1e94D, 
        1e95D, 1e96D, 1e97D, 1e98D, 1e99D, 1e100D, 1e101D, 1e102D, 1e103D, 1e104D, 
        1e105D, 1e106D, 1e107D, 1e108D, 1e109D, 1e110D, 1e111D, 1e112D, 1e113D, 1e114D, 
        1e115D, 1e116D, 1e117D, 1e118D, 1e119D, 1e120D, 1e121D, 1e122D, 1e123D, 1e124D, 
        1e125D, 1e126D, 1e127D, 1e128D, 1e129D, 1e130D, 1e131D, 1e132D, 1e133D, 1e134D, 
        1e135D, 1e136D, 1e137D, 1e138D, 1e139D, 1e140D, 1e141D, 1e142D, 1e143D, 1e144D, 
        1e145D, 1e146D, 1e147D, 1e148D, 1e149D, 1e150D, 1e151D, 1e152D, 1e153D, 1e154D, 
        1e155D, 1e156D, 1e157D, 1e158D, 1e159D, 1e160D, 1e161D, 1e162D, 1e163D, 1e164D, 
        1e165D, 1e166D, 1e167D, 1e168D, 1e169D, 1e170D, 1e171D, 1e172D, 1e173D, 1e174D, 
        1e175D, 1e176D, 1e177D, 1e178D, 1e179D, 1e180D, 1e181D, 1e182D, 1e183D, 1e184D, 
        1e185D, 1e186D, 1e187D, 1e188D, 1e189D, 1e190D, 1e191D, 1e192D, 1e193D, 1e194D, 
        1e195D, 1e196D, 1e197D, 1e198D, 1e199D, 1e200D, 1e201D, 1e202D, 1e203D, 1e204D, 
        1e205D, 1e206D, 1e207D, 1e208D, 1e209D, 1e210D, 1e211D, 1e212D, 1e213D, 1e214D, 
        1e215D, 1e216D, 1e217D, 1e218D, 1e219D, 1e220D, 1e221D, 1e222D, 1e223D, 1e224D, 
        1e225D, 1e226D, 1e227D, 1e228D, 1e229D, 1e230D, 1e231D, 1e232D, 1e233D, 1e234D, 
        1e235D, 1e236D, 1e237D, 1e238D, 1e239D, 1e240D, 1e241D, 1e242D, 1e243D, 1e244D, 
        1e245D, 1e246D, 1e247D, 1e248D, 1e249D, 1e250D, 1e251D, 1e252D, 1e253D, 1e254D, 
        1e255D, 1e256D, 1e257D, 1e258D, 1e259D, 1e260D, 1e261D, 1e262D, 1e263D, 1e264D, 
        1e265D, 1e266D, 1e267D, 1e268D, 1e269D, 1e270D, 1e271D, 1e272D, 1e273D, 1e274D, 
        1e275D, 1e276D, 1e277D, 1e278D, 1e279D, 1e280D, 1e281D, 1e282D, 1e283D, 1e284D, 
        1e285D, 1e286D, 1e287D, 1e288D, 1e289D, 1e290D, 1e291D, 1e292D, 1e293D, 1e294D, 
        1e295D, 1e296D, 1e297D, 1e298D, 1e299D, 1e300D, 1e301D, 1e302D, 1e303D, 1e304D, 
        1e305D, 1e306D, 1e307D, 1e308D
    };


    /**
     * Assumes i is positive. Returns the magnitude of i in base 10.
     */
    private static long tenthPower(long i)
    {
        if (i < 10L) return 1;
        else if (i < 100L) return 10L;
        else if (i < 1000L) return 100L;
        else if (i < 10000L) return 1000L;
        else if (i < 100000L) return 10000L;
        else if (i < 1000000L) return 100000L;
        else if (i < 10000000L) return 1000000L;
        else if (i < 100000000L) return 10000000L;
        else if (i < 1000000000L) return 100000000L;
        else if (i < 10000000000L) return 1000000000L;
        else if (i < 100000000000L) return 10000000000L;
        else if (i < 1000000000000L) return 100000000000L;
        else if (i < 10000000000000L) return 1000000000000L;
        else if (i < 100000000000000L) return 10000000000000L;
        else if (i < 1000000000000000L) return 100000000000000L;
        else if (i < 10000000000000000L) return 1000000000000000L;
        else if (i < 100000000000000000L) return 10000000000000000L;
        else if (i < 1000000000000000000L) return 100000000000000000L;
        else return  1000000000000000000L;
    }


    private static int magnitude(double d)
    {
        //It works. What else can I say.
        long doubleToLongBits = Double.doubleToLongBits(d);
        int magnitude = 
            (int) ((((doubleToLongBits & DoubleExpMask) >> DoubleExpShift) - DoubleExpBias) * 0.301029995663981);

        if (magnitude < -323)
            magnitude = -323;
        else if (magnitude > 308)
            magnitude = 308;

        if (d >= d_tenthPowers[magnitude+323])
        {
            while(magnitude < 309 && d >= d_tenthPowers[magnitude+323])
                magnitude++;
            magnitude--;
            return magnitude;
        }
        else
        {
            while(magnitude > -324 && d < d_tenthPowers[magnitude+323])
                magnitude--;
            return magnitude;
        }
    }

    static long[] l_tenthPowers = {
        1,
        10L,
        100L,
        1000L,
        10000L,
        100000L,
        1000000L,
        10000000L,
        100000000L,
        1000000000L,
        10000000000L,
        100000000000L,
        1000000000000L,
        10000000000000L,
        100000000000000L,
        1000000000000000L,
        10000000000000000L,
        100000000000000000L,
        1000000000000000000L,
    };

    public static long getNthDigit(long l, int n)
    {
        return (l/(tenthPower(l)/l_tenthPowers[n-1]))%10;
    }




    public static void append(StringBuilder s, double d)
    {
        if (d == Double.NEGATIVE_INFINITY)
            s.append(NEGATIVE_INFINITY);
        else if (d == Double.POSITIVE_INFINITY)
            s.append(POSITIVE_INFINITY);
        else if (d != d)
            s.append(NaN);
        else if (d == 0.0)
        {
            if ( (Double.doubleToLongBits(d) & DoubleSignMask) != 0)
                s.append('-');
            s.append(DOUBLE_ZERO);
        }
        else
        {
            if (d < 0)
            {
                s.append('-');
                d = -d;
            }

            if (d >= 0.001 && d < 0.01)
            {
                long i = (long) (d * 1E20);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                s.append(DOUBLE_ZERO2);
                appendFractDigits(s, i,-1);
            }
            else if (d >= 0.01 && d < 0.1)
            {
                long i = (long) (d * 1E19);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                s.append(DOUBLE_ZERO);
                appendFractDigits(s, i,-1);
            }
            else if (d >= 0.1 && d < 1)
            {
                long i = (long) (d * 1E18);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                s.append(DOUBLE_ZERO0);
                appendFractDigits(s, i,-1);
            }
            else if (d >= 1 && d < 10)
            {
                long i = (long) (d * 1E17);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,1);
            }
            else if (d >= 10 && d < 100)
            {
                long i = (long) (d * 1E16);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,2);
            }
            else if (d >= 100 && d < 1000)
            {
                long i = (long) (d * 1E15);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,3);
            }
            else if (d >= 1000 && d < 10000)
            {
                long i = (long) (d * 1E14);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,4);
            }
            else if (d >= 10000 && d < 100000)
            {
                long i = (long) (d * 1E13);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,5);
            }
            else if (d >= 100000 && d < 1000000)
            {
                long i = (long) (d * 1E12);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,6);
            }
            else if (d >= 1000000 && d < 10000000)
            {
                long i = (long) (d * 1E11);
                i = i%100 >= 50 ? (i/100) + 1 : i/100;
                appendFractDigits(s, i,7);
            }
            else
            {
                int magnitude = magnitude(d);
                long i;
                if (magnitude < -280) {
                    long valueBits = Double.doubleToRawLongBits(d);
                    long mantissa = valueBits & 0x000fffffffffffffL;
                    int exponent = (int)((valueBits >> 52) & 0x7ff);
                    if (exponent == 0) {
                        tooSmall(s, mantissa, -1074);
                    } else {
                        mantissa |= 0x0010000000000000L;
                        exponent -= 1075;
                        tooSmall(s, mantissa, exponent);
                    }
                } else {
                    i = (long) (d / d_tenthPowers[magnitude + 323 - 17]);
                    i = i%100 >= 50 ? (i/100) + 1 : i/100;
                    appendFractDigits(s, i, 1);
                    s.append('E');
                    append(s, magnitude);
                }
            }
        }
    }
    public static void append(StringBuilder s, int i)
    {
        if (i < 0)
        {
            if (i == Integer.MIN_VALUE)
            {
                //cannot make this positive due to integer overflow
                s.append("-2147483648");
            }
            s.append('-');
            i = -i;
        }
        int mag;
        int c;
        if (i < 10)
        {
            //one digit
            s.append(charForDigit[i]);
        }
        else if (i < 100)
        {
            //two digits
            s.append(charForDigit[i/10]);
            s.append(charForDigit[i%10]);
        }
        else if (i < 1000)
        {
            //three digits
            s.append(charForDigit[i/100]);
            s.append(charForDigit[(c=i%100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 10000)
        {
            //four digits
            s.append(charForDigit[i/1000]);
            s.append(charForDigit[(c=i%1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 100000)
        {
            //five digits
            s.append(charForDigit[i/10000]);
            s.append(charForDigit[(c=i%10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 1000000)
        {
            //six digits
            s.append(charForDigit[i/100000]);
            s.append(charForDigit[(c=i%100000)/10000]);
            s.append(charForDigit[(c%=10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 10000000)
        {
            //seven digits
            s.append(charForDigit[i/1000000]);
            s.append(charForDigit[(c=i%1000000)/100000]);
            s.append(charForDigit[(c%=100000)/10000]);
            s.append(charForDigit[(c%=10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 100000000)
        {
            //eight digits
            s.append(charForDigit[i/10000000]);
            s.append(charForDigit[(c=i%10000000)/1000000]);
            s.append(charForDigit[(c%=1000000)/100000]);
            s.append(charForDigit[(c%=100000)/10000]);
            s.append(charForDigit[(c%=10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else if (i < 1000000000)
        {
            //nine digits
            s.append(charForDigit[i/100000000]);
            s.append(charForDigit[(c=i%100000000)/10000000]);
            s.append(charForDigit[(c%=10000000)/1000000]);
            s.append(charForDigit[(c%=1000000)/100000]);
            s.append(charForDigit[(c%=100000)/10000]);
            s.append(charForDigit[(c%=10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
        else
        {
            //ten digits
            s.append(charForDigit[i/1000000000]);
            s.append(charForDigit[(c=i%1000000000)/100000000]);
            s.append(charForDigit[(c%=100000000)/10000000]);
            s.append(charForDigit[(c%=10000000)/1000000]);
            s.append(charForDigit[(c%=1000000)/100000]);
            s.append(charForDigit[(c%=100000)/10000]);
            s.append(charForDigit[(c%=10000)/1000]);
            s.append(charForDigit[(c%=1000)/100]);
            s.append(charForDigit[(c%=100)/10]);
            s.append(charForDigit[c%10]);
        }
    }
    private static void appendFractDigits(StringBuilder s, long i, int decimalOffset)
    {
        long mag = tenthPower(i);
        long c;
        while ( i > 0 )
        {
            c = i/mag;
            s.append(charForDigit[(int) c]);
            decimalOffset--;
            if (decimalOffset == 0)
                s.append('.');
            c *= mag;
            if ( c <= i)
                i -= c;
            mag = mag/10;
        }
        if (i != 0)
            s.append(charForDigit[(int) i]);
        else if (decimalOffset > 0)
        {
            s.append(ZEROS[decimalOffset]);
            decimalOffset = 1;
        }

        decimalOffset--;
        if (decimalOffset == 0)
            s.append(DOT_ZERO);
        else if (decimalOffset == -1)
            s.append('0');
    }

    public static final char[] NEGATIVE_INFINITY = {'-','I','n','f','i','n','i','t','y'};
    public static final char[] POSITIVE_INFINITY = {'I','n','f','i','n','i','t','y'};
    public static final char[] DOUBLE_ZERO = {'0','.','0'};
    public static final char[] DOUBLE_ZERO2 = {'0','.','0','0'};
    public static final char[] DOUBLE_ZERO0 = {'0','.'};
    public static final char[] DOT_ZERO = {'.','0'};

}