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// Copyright (c) 2013, Webit Team. All Rights Reserved.
package webit.script.util;

/**
 *
 * @author zqq90
 */
public class NumberUtil {

    private final static ThreadLocal charsBufLocal = new ThreadLocal();
    public final static int SIZE = 20;

    public static char[] get() {
        char[] buf;
        if ((buf = charsBufLocal.get()) != null) {
            return buf;
        } else {
            charsBufLocal.set(buf = new char[SIZE]);
            return buf;
        }
    }

    public static int getChars(long i, int index, char[] buf) {
        long q;
        int r;
        int charPos = index;
        char sign = 0;

        if (i < 0) {
            sign = '-';
            i = -i;
        }

        // Get 2 digits/iteration using longs until quotient fits into an int
        while (i > Integer.MAX_VALUE) {
            q = i / 100;
            // really: r = i - (q * 100);
            r = (int) (i - ((q << 6) + (q << 5) + (q << 2)));
            i = q;
            buf[--charPos] = DigitOnes[r];
            buf[--charPos] = DigitTens[r];
        }

        // Get 2 digits/iteration using ints
        int q2;
        int i2 = (int) i;
        while (i2 >= 65536) {
            q2 = i2 / 100;
            // really: r = i2 - (q * 100);
            r = i2 - ((q2 << 6) + (q2 << 5) + (q2 << 2));
            i2 = q2;
            buf[--charPos] = DigitOnes[r];
            buf[--charPos] = DigitTens[r];
        }

        // Fall thru to fast mode for smaller numbers
        // assert(i2 <= 65536, i2);
        for (;;) {
            q2 = (i2 * 52429) >>> (16 + 3);
            r = i2 - ((q2 << 3) + (q2 << 1)); // r = i2-(q2*10) ...
            buf[--charPos] = digits[r];
            i2 = q2;
            if (i2 == 0) {
                break;
            }
        }
        if (sign != 0) {
            buf[--charPos] = sign;
        }
        return charPos;
    }

    public static int getChars(int i, int index, char[] buf) {
        int q, r;
        int charPos = index;
        char sign = 0;

        if (i < 0) {
            sign = '-';
            i = -i;
        }

        // Generate two digits per iteration
        while (i >= 65536) {
            q = i / 100;
            // really: r = i - (q * 100);
            r = i - ((q << 6) + (q << 5) + (q << 2));
            i = q;
            buf[--charPos] = DigitOnes[r];
            buf[--charPos] = DigitTens[r];
        }

        // Fall thru to fast mode for smaller numbers
        // assert(i <= 65536, i);
        for (;;) {
            q = (i * 52429) >>> (16 + 3);
            r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
            buf[--charPos] = digits[r];
            i = q;
            if (i == 0) {
                break;
            }
        }
        if (sign != 0) {
            buf[--charPos] = sign;
        }
        return charPos;
    }
//    public static int getChars(byte b, int index, char[] buf) {
//        int i = b;
//        int q, r;
//        int charPos = index;
//        char sign = 0;
//
//        if (i < 0) {
//            sign = '-';
//            i = -i;
//        }
//
//        // Fall thru to fast mode for smaller numbers
//        // assert(i <= 65536, i);
//        for (;;) {
//            q = (i * 52429) >>> (16 + 3);
//            r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
//            buf[--charPos] = digits[r];
//            i = q;
//            if (i == 0) {
//                break;
//            }
//        }
//        if (sign != 0) {
//            buf[--charPos] = sign;
//        }
//        return charPos;
//    }
    /**
     * All possible chars for representing a number as a String
     */
    final static char[] digits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
    final static char[] DigitTens = {
        '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
        '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
        '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
        '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
        '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
        '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
        '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
        '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
        '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
        '9', '9', '9', '9', '9', '9', '9', '9', '9', '9'};
    final static char[] DigitOnes = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
}