digitlist.java

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/*
 * @(#)DigitList.java	1.13 98/01/12
 *
 * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - All Rights Reserved
 *
 * Portions copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
 *
 *   The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 *   Taligent is a registered trademark of Taligent, Inc.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 *
 */

package java.text;

/**
 * Digit List. Private to DecimalFormat.
 * Handles the transcoding
 * between numeric values and strings of characters.  Only handles
 * non-negative numbers.  The division of labor between DigitList and
 * DecimalFormat is that DigitList handles the radix 10 representation
 * issues; DecimalFormat handles the locale-specific issues such as
 * positive/negative, grouping, decimal point, currency, and so on.
 *
 * A DigitList is really a representation of a floating point value.
 * It may be an integer value; we assume that a double has sufficient
 * precision to represent all digits of a long.
 *
 * The DigitList representation consists of a string of characters,
 * which are the digits radix 10, from '0' to '9'.  It also has a radix
 * 10 exponent associated with it.  The value represented by a DigitList
 * object can be computed by mulitplying the fraction f, where 0 <= f < 1,
 * derived by placing all the digits of the list to the right of the
 * decimal point, by 10^exponent.
 *
 * @see  Locale
 * @see  Format
 * @see  NumberFormat
 * @see  DecimalFormat
 * @see  ChoiceFormat
 * @see  MessageFormat
 * @version      1.13 01/12/98
 * @author       Mark Davis, Alan Liu
 */
final class DigitList implements Cloneable {
    /**
     * The maximum number of significant digits in an IEEE 754 double, that
     * is, in a Java double.  This must not be increased, or garbage digits
     * will be generated, and should not be decreased, or accuracy will be lost.
     */
    public static final int MAX_COUNT = 19; // == Long.toString(Long.MAX_VALUE).length()
    public static final int DBL_DIG = 17;

    /**
     * These data members are intentionally public and can be set directly.
     *
     * The value represented is given by placing the decimal point before
     * digits[decimalAt].  If decimalAt is < 0, then leading zeros between
     * the decimal point and the first nonzero digit are implied.  If decimalAt
     * is > count, then trailing zeros between the digits[count-1] and the
     * decimal point are implied.
     *
     * Equivalently, the represented value is given by f * 10^decimalAt.  Here
     * f is a value 0.1 <= f < 1 arrived at by placing the digits in Digits to
     * the right of the decimal.
     *
     * DigitList is normalized, so if it is non-zero, figits[0] is non-zero.  We
     * don't allow denormalized numbers because our exponent is effectively of
     * unlimited magnitude.  The count value contains the number of significant
     * digits present in digits[].
     *
     * Zero is represented by any DigitList with count == 0 or with each digits[i]
     * for all i <= count == '0'.
     */
    public int decimalAt = 0;
    public int count = 0;
    public byte[] digits = new byte[MAX_COUNT];

    /**
     * Return true if the represented number is zero.
     */
    boolean isZero()
    {
        for (int i=0; i<count; ++i) if (digits[i] != '0') return false;
        return true;
    }

    /**
     * Clears out the digits.
     * Use before appending them.
     * Typically, you set a series of digits with append, then at the point
     * you hit the decimal point, you set myDigitList.decimalAt = myDigitList.count;
     * then go on appending digits.
     */
    public void clear () {
        decimalAt = 0;
        count = 0;
    }
    /**
     * Appends digits to the list. Ignores all digits over MAX_COUNT,
     * since they are not significant for either longs or doubles.
     */
    public void append (int digit) {
        if (count < MAX_COUNT)
            digits[count++] = (byte) digit;
    }
    /**
     * Utility routine to get the value of the digit list
     * If (count == 0) this throws a NumberFormatException, which
     * mimics Long.parseLong().
     */
    public final double getDouble() {
        if (count == 0) return 0.0;
        StringBuffer temp = new StringBuffer(count);
        temp.append('.');
        for (int i = 0; i < count; ++i) temp.append((char)(digits[i]));
        temp.append('E');
        temp.append(Integer.toString(decimalAt));
        return Double.valueOf(temp.toString()).doubleValue();
        // long value = Long.parseLong(temp.toString());
        // return (value * Math.pow(10, decimalAt - count));
    }

    /**
     * Utility routine to get the value of the digit list.
     * If (count == 0) this returns 0, unlike Long.parseLong().
     */
    public final long getLong() {
        // for now, simple implementation; later, do proper IEEE native stuff

        if (count == 0) return 0;

        // We have to check for this, because this is the one NEGATIVE value
        // we represent.  If we tried to just pass the digits off to parseLong,
        // we'd get a parse failure.
        if (isLongMIN_VALUE()) return Long.MIN_VALUE;

        StringBuffer temp = new StringBuffer(count);
        for (int i = 0; i < decimalAt; ++i)
        {
            temp.append((i < count) ? (char)(digits[i]) : '0');
        }
        return Long.parseLong(temp.toString());
    }

    /**
     * Return true if the number represented by this object can fit into
     * a long.
     */
    boolean fitsIntoLong(boolean isPositive)
    {
        // Figure out if the result will fit in a long.  We have to
        // first look for nonzero digits after the decimal point;
        // then check the size.  If the digit count is 18 or less, then
        // the value can definitely be represented as a long.  If it is 19
        // then it may be too large.

        // Trim trailing zeros.  This does not change the represented value.
        while (count > 0 && digits[count - 1] == (byte)'0') --count;

        if (count == 0) return true;

        if (decimalAt < count || decimalAt > MAX_COUNT) return false;

        if (decimalAt < MAX_COUNT) return true;

        // At this point we have decimalAt == count, and count == MAX_COUNT.
        // The number will overflow if it is larger than 9223372036854775807
        // or smaller than -9223372036854775808.
        for (int i=0; i<count; ++i)
        {
            byte dig = digits[i], max = LONG_MIN_REP[i];
            if (dig > max) return false;
            if (dig < max) return true;
        }

        // At this point the first count digits match.  If decimalAt is less
        // than count, then the remaining digits are zero, and we return true.
        if (count < decimalAt) return true;

        // Now we have a representation of Long.MIN_VALUE, without the leading
        // negative sign.  If this represents a positive value, then it does
        // not fit; otherwise it fits.
        return !isPositive;
    }

    private static final boolean DEBUG = false;

    /**
     * Set the digit list to a representation of the given double value.
     * This method supports fixed-point notation.
     * @param source Value to be converted; must not be Inf, -Inf, Nan,
     * or a value <= 0.
     * @param maximumFractionDigits The most fractional digits which should
     * be converted.
     */
    public final void set(double source, int maximumFractionDigits)
    {
        set(source, maximumFractionDigits, true);
    }

    /**
     * Set the digit list to a representation of the given double value.
     * This method supports both fixed-point and exponential notation.
     * @param source Value to be converted; must not be Inf, -Inf, Nan,
     * or a value <= 0.
     * @param maximumDigits The most fractional or total digits which should
     * be converted.
     * @param fixedPoint If true, then maximumDigits is the maximum
     * fractional digits to be converted.  If false, total digits.
     */
    final void set(double source, int maximumDigits, boolean fixedPoint)
    {
        // Generate a representation of the form DDDDD, DDDDD.DDDDD, or
        // DDDDDE+/-DDDDD.
        String rep = Double.toString(source);

        decimalAt = -1;
        count = 0;
        int exponent = 0;
        // Number of zeros between decimal point and first non-zero digit after
        // decimal point, for numbers < 1.
        int leadingZerosAfterDecimal = 0;
        boolean nonZeroDigitSeen = false;
        for (int i=0; i < rep.length(); ++i)
        {
            char c = rep.charAt(i);
            if (c == '.')
            {
            decimalAt = count;
            }
            else if (c == 'e' || c == 'E')
            {
            exponent = Integer.valueOf(rep.substring(i+1)).intValue();
            break;
            }
            else if (count < MAX_COUNT)
            {
            if (!nonZeroDigitSeen)
            {
                nonZeroDigitSeen = (c != '0');
                if (!nonZeroDigitSeen && decimalAt != -1) ++leadingZerosAfterDecimal;
            }

            if (nonZeroDigitSeen) digits[count++] = (byte)c;
            }
        }
        if (decimalAt == -1) decimalAt = count;
        decimalAt += exponent - leadingZerosAfterDecimal;

        if (fixedPoint)
        {