1 /*
   2  * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /*
  27  * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
  28  * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
  29  *
  30  *   The original version of this source code and documentation is copyrighted
  31  * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
  32  * materials are provided under terms of a License Agreement between Taligent
  33  * and Sun. This technology is protected by multiple US and International
  34  * patents. This notice and attribution to Taligent may not be removed.
  35  *   Taligent is a registered trademark of Taligent, Inc.
  36  *
  37  */
  38 
  39 package java.text;
  40 
  41 import java.math.BigDecimal;
  42 import java.math.BigInteger;
  43 import java.math.RoundingMode;
  44 
  45 /**
  46  * Digit List. Private to DecimalFormat.
  47  * Handles the transcoding
  48  * between numeric values and strings of characters.  Only handles
  49  * non-negative numbers.  The division of labor between DigitList and
  50  * DecimalFormat is that DigitList handles the radix 10 representation
  51  * issues; DecimalFormat handles the locale-specific issues such as
  52  * positive/negative, grouping, decimal point, currency, and so on.
  53  *
  54  * A DigitList is really a representation of a floating point value.
  55  * It may be an integer value; we assume that a double has sufficient
  56  * precision to represent all digits of a long.
  57  *
  58  * The DigitList representation consists of a string of characters,
  59  * which are the digits radix 10, from '0' to '9'.  It also has a radix
  60  * 10 exponent associated with it.  The value represented by a DigitList
  61  * object can be computed by mulitplying the fraction f, where 0 <= f < 1,
  62  * derived by placing all the digits of the list to the right of the
  63  * decimal point, by 10^exponent.
  64  *
  65  * @see  java.util.Locale
  66  * @see  Format
  67  * @see  NumberFormat
  68  * @see  DecimalFormat
  69  * @see  ChoiceFormat
  70  * @see  MessageFormat
  71  * @author       Mark Davis, Alan Liu
  72  */
  73 final class DigitList implements Cloneable {
  74     /**
  75      * The maximum number of significant digits in an IEEE 754 double, that
  76      * is, in a Java double.  This must not be increased, or garbage digits
  77      * will be generated, and should not be decreased, or accuracy will be lost.
  78      */
  79     public static final int MAX_COUNT = 19; // == Long.toString(Long.MAX_VALUE).length()
  80 
  81     /**
  82      * These data members are intentionally public and can be set directly.
  83      *
  84      * The value represented is given by placing the decimal point before
  85      * digits[decimalAt].  If decimalAt is < 0, then leading zeros between
  86      * the decimal point and the first nonzero digit are implied.  If decimalAt
  87      * is > count, then trailing zeros between the digits[count-1] and the
  88      * decimal point are implied.
  89      *
  90      * Equivalently, the represented value is given by f * 10^decimalAt.  Here
  91      * f is a value 0.1 <= f < 1 arrived at by placing the digits in Digits to
  92      * the right of the decimal.
  93      *
  94      * DigitList is normalized, so if it is non-zero, figits[0] is non-zero.  We
  95      * don't allow denormalized numbers because our exponent is effectively of
  96      * unlimited magnitude.  The count value contains the number of significant
  97      * digits present in digits[].
  98      *
  99      * Zero is represented by any DigitList with count == 0 or with each digits[i]
 100      * for all i <= count == '0'.
 101      */
 102     public int decimalAt = 0;
 103     public int count = 0;
 104     public char[] digits = new char[MAX_COUNT];
 105 
 106     private char[] data;
 107     private RoundingMode roundingMode = RoundingMode.HALF_EVEN;
 108     private boolean isNegative = false;
 109 
 110     /**
 111      * Return true if the represented number is zero.
 112      */
 113     boolean isZero() {
 114         for (int i=0; i < count; ++i) {
 115             if (digits[i] != '0') {
 116                 return false;
 117             }
 118         }
 119         return true;
 120     }
 121 
 122     /**
 123      * Set the rounding mode
 124      */
 125     void setRoundingMode(RoundingMode r) {
 126         roundingMode = r;
 127     }
 128 
 129     /**
 130      * Clears out the digits.
 131      * Use before appending them.
 132      * Typically, you set a series of digits with append, then at the point
 133      * you hit the decimal point, you set myDigitList.decimalAt = myDigitList.count;
 134      * then go on appending digits.
 135      */
 136     public void clear () {
 137         decimalAt = 0;
 138         count = 0;
 139     }
 140 
 141     /**
 142      * Appends a digit to the list, extending the list when necessary.
 143      */
 144     public void append(char digit) {
 145         if (count == digits.length) {
 146             char[] data = new char[count + 100];
 147             System.arraycopy(digits, 0, data, 0, count);
 148             digits = data;
 149         }
 150         digits[count++] = digit;
 151     }
 152 
 153     /**
 154      * Utility routine to get the value of the digit list
 155      * If (count == 0) this throws a NumberFormatException, which
 156      * mimics Long.parseLong().
 157      */
 158     public final double getDouble() {
 159         if (count == 0) {
 160             return 0.0;
 161         }
 162 
 163         StringBuffer temp = getStringBuffer();
 164         temp.append('.');
 165         temp.append(digits, 0, count);
 166         temp.append('E');
 167         temp.append(decimalAt);
 168         return Double.parseDouble(temp.toString());
 169     }
 170 
 171     /**
 172      * Utility routine to get the value of the digit list.
 173      * If (count == 0) this returns 0, unlike Long.parseLong().
 174      */
 175     public final long getLong() {
 176         // for now, simple implementation; later, do proper IEEE native stuff
 177 
 178         if (count == 0) {
 179             return 0;
 180         }
 181 
 182         // We have to check for this, because this is the one NEGATIVE value
 183         // we represent.  If we tried to just pass the digits off to parseLong,
 184         // we'd get a parse failure.
 185         if (isLongMIN_VALUE()) {
 186             return Long.MIN_VALUE;
 187         }
 188 
 189         StringBuffer temp = getStringBuffer();
 190         temp.append(digits, 0, count);
 191         for (int i = count; i < decimalAt; ++i) {
 192             temp.append('0');
 193         }
 194         return Long.parseLong(temp.toString());
 195     }
 196 
 197     public final BigDecimal getBigDecimal() {
 198         if (count == 0) {
 199             if (decimalAt == 0) {
 200                 return BigDecimal.ZERO;
 201             } else {
 202                 return new BigDecimal("0E" + decimalAt);
 203             }
 204         }
 205 
 206        if (decimalAt == count) {
 207            return new BigDecimal(digits, 0, count);
 208        } else {
 209            return new BigDecimal(digits, 0, count).scaleByPowerOfTen(decimalAt - count);
 210        }
 211     }
 212 
 213     /**
 214      * Return true if the number represented by this object can fit into
 215      * a long.
 216      * @param isPositive true if this number should be regarded as positive
 217      * @param ignoreNegativeZero true if -0 should be regarded as identical to
 218      * +0; otherwise they are considered distinct
 219      * @return true if this number fits into a Java long
 220      */
 221     boolean fitsIntoLong(boolean isPositive, boolean ignoreNegativeZero) {
 222         // Figure out if the result will fit in a long.  We have to
 223         // first look for nonzero digits after the decimal point;
 224         // then check the size.  If the digit count is 18 or less, then
 225         // the value can definitely be represented as a long.  If it is 19
 226         // then it may be too large.
 227 
 228         // Trim trailing zeros.  This does not change the represented value.
 229         while (count > 0 && digits[count - 1] == '0') {
 230             --count;
 231         }
 232 
 233         if (count == 0) {
 234             // Positive zero fits into a long, but negative zero can only
 235             // be represented as a double. - bug 4162852
 236             return isPositive || ignoreNegativeZero;
 237         }
 238 
 239         if (decimalAt < count || decimalAt > MAX_COUNT) {
 240             return false;
 241         }
 242 
 243         if (decimalAt < MAX_COUNT) return true;
 244 
 245         // At this point we have decimalAt == count, and count == MAX_COUNT.
 246         // The number will overflow if it is larger than 9223372036854775807
 247         // or smaller than -9223372036854775808.
 248         for (int i=0; i<count; ++i) {
 249             char dig = digits[i], max = LONG_MIN_REP[i];
 250             if (dig > max) return false;
 251             if (dig < max) return true;
 252         }
 253 
 254         // At this point the first count digits match.  If decimalAt is less
 255         // than count, then the remaining digits are zero, and we return true.
 256         if (count < decimalAt) return true;
 257 
 258         // Now we have a representation of Long.MIN_VALUE, without the leading
 259         // negative sign.  If this represents a positive value, then it does
 260         // not fit; otherwise it fits.
 261         return !isPositive;
 262     }
 263 
 264     /**
 265      * Set the digit list to a representation of the given double value.
 266      * This method supports fixed-point notation.
 267      * @param isNegative Boolean value indicating whether the number is negative.
 268      * @param source Value to be converted; must not be Inf, -Inf, Nan,
 269      * or a value <= 0.
 270      * @param maximumFractionDigits The most fractional digits which should
 271      * be converted.
 272      */
 273     public final void set(boolean isNegative, double source, int maximumFractionDigits) {
 274         set(isNegative, source, maximumFractionDigits, true);
 275     }
 276 
 277     /**
 278      * Set the digit list to a representation of the given double value.
 279      * This method supports both fixed-point and exponential notation.
 280      * @param isNegative Boolean value indicating whether the number is negative.
 281      * @param source Value to be converted; must not be Inf, -Inf, Nan,
 282      * or a value <= 0.
 283      * @param maximumDigits The most fractional or total digits which should
 284      * be converted.
 285      * @param fixedPoint If true, then maximumDigits is the maximum
 286      * fractional digits to be converted.  If false, total digits.
 287      */
 288     final void set(boolean isNegative, double source, int maximumDigits, boolean fixedPoint) {
 289         set(isNegative, Double.toString(source), maximumDigits, fixedPoint);
 290     }
 291 
 292     /**
 293      * Generate a representation of the form DDDDD, DDDDD.DDDDD, or
 294      * DDDDDE+/-DDDDD.
 295      */
 296     final void set(boolean isNegative, String s, int maximumDigits, boolean fixedPoint) {
 297         this.isNegative = isNegative;
 298         int len = s.length();
 299         char[] source = getDataChars(len);
 300         s.getChars(0, len, source, 0);
 301 
 302         decimalAt = -1;
 303         count = 0;
 304         int exponent = 0;
 305         // Number of zeros between decimal point and first non-zero digit after
 306         // decimal point, for numbers < 1.
 307         int leadingZerosAfterDecimal = 0;
 308         boolean nonZeroDigitSeen = false;
 309 
 310         for (int i = 0; i < len; ) {
 311             char c = source[i++];
 312             if (c == '.') {
 313                 decimalAt = count;
 314             } else if (c == 'e' || c == 'E') {
 315                 exponent = parseInt(source, i, len);
 316                 break;
 317             } else {
 318                 if (!nonZeroDigitSeen) {
 319                     nonZeroDigitSeen = (c != '0');
 320                     if (!nonZeroDigitSeen && decimalAt != -1)
 321                         ++leadingZerosAfterDecimal;
 322                 }
 323                 if (nonZeroDigitSeen) {
 324                     digits[count++] = c;
 325                 }
 326             }
 327         }
 328         if (decimalAt == -1) {
 329             decimalAt = count;
 330         }
 331         if (nonZeroDigitSeen) {
 332             decimalAt += exponent - leadingZerosAfterDecimal;
 333         }
 334 
 335         if (fixedPoint) {
 336             // The negative of the exponent represents the number of leading
 337             // zeros between the decimal and the first non-zero digit, for
 338             // a value < 0.1 (e.g., for 0.00123, -decimalAt == 2).  If this
 339             // is more than the maximum fraction digits, then we have an underflow
 340             // for the printed representation.
 341             if (-decimalAt > maximumDigits) {
 342                 // Handle an underflow to zero when we round something like
 343                 // 0.0009 to 2 fractional digits.
 344                 count = 0;
 345                 return;
 346             } else if (-decimalAt == maximumDigits) {
 347                 // If we round 0.0009 to 3 fractional digits, then we have to
 348                 // create a new one digit in the least significant location.
 349                 if (shouldRoundUp(0)) {
 350                     count = 1;
 351                     ++decimalAt;
 352                     digits[0] = '1';
 353                 } else {
 354                     count = 0;
 355                 }
 356                 return;
 357             }
 358             // else fall through
 359         }
 360 
 361         // Eliminate trailing zeros.
 362         while (count > 1 && digits[count - 1] == '0') {
 363             --count;
 364         }
 365 
 366         // Eliminate digits beyond maximum digits to be displayed.
 367         // Round up if appropriate.
 368         round(fixedPoint ? (maximumDigits + decimalAt) : maximumDigits);
 369     }
 370 
 371     /**
 372      * Round the representation to the given number of digits.
 373      * @param maximumDigits The maximum number of digits to be shown.
 374      * Upon return, count will be less than or equal to maximumDigits.
 375      */
 376     private final void round(int maximumDigits) {
 377         // Eliminate digits beyond maximum digits to be displayed.
 378         // Round up if appropriate.
 379         if (maximumDigits >= 0 && maximumDigits < count) {
 380             if (shouldRoundUp(maximumDigits)) {
 381                 // Rounding up involved incrementing digits from LSD to MSD.
 382                 // In most cases this is simple, but in a worst case situation
 383                 // (9999..99) we have to adjust the decimalAt value.
 384                 for (;;) {
 385                     --maximumDigits;
 386                     if (maximumDigits < 0) {
 387                         // We have all 9's, so we increment to a single digit
 388                         // of one and adjust the exponent.
 389                         digits[0] = '1';
 390                         ++decimalAt;
 391                         maximumDigits = 0; // Adjust the count
 392                         break;
 393                     }
 394 
 395                     ++digits[maximumDigits];
 396                     if (digits[maximumDigits] <= '9') break;
 397                     // digits[maximumDigits] = '0'; // Unnecessary since we'll truncate this
 398                 }
 399                 ++maximumDigits; // Increment for use as count
 400             }
 401             count = maximumDigits;
 402 
 403             // Eliminate trailing zeros.
 404             while (count > 1 && digits[count-1] == '0') {
 405                 --count;
 406             }
 407         }
 408     }
 409 
 410 
 411     /**
 412      * Return true if truncating the representation to the given number
 413      * of digits will result in an increment to the last digit.  This
 414      * method implements the rounding modes defined in the
 415      * java.math.RoundingMode class.
 416      * [bnf]
 417      * @param maximumDigits the number of digits to keep, from 0 to
 418      * <code>count-1</code>.  If 0, then all digits are rounded away, and
 419      * this method returns true if a one should be generated (e.g., formatting
 420      * 0.09 with "#.#").
 421      * @exception ArithmeticException if rounding is needed with rounding
 422      *            mode being set to RoundingMode.UNNECESSARY
 423      * @return true if digit <code>maximumDigits-1</code> should be
 424      * incremented
 425      */
 426     private boolean shouldRoundUp(int maximumDigits) {
 427         if (maximumDigits < count) {
 428             switch(roundingMode) {
 429             case UP:
 430                 for (int i=maximumDigits; i<count; ++i) {
 431                     if (digits[i] != '0') {
 432                         return true;
 433                     }
 434                 }
 435                 break;
 436             case DOWN:
 437                 break;
 438             case CEILING:
 439                 for (int i=maximumDigits; i<count; ++i) {
 440                     if (digits[i] != '0') {
 441                         return !isNegative;
 442                     }
 443                 }
 444                 break;
 445             case FLOOR:
 446                 for (int i=maximumDigits; i<count; ++i) {
 447                     if (digits[i] != '0') {
 448                         return isNegative;
 449                     }
 450                 }
 451                 break;
 452             case HALF_UP:
 453                 if (digits[maximumDigits] >= '5') {
 454                     return true;
 455                 }
 456                 break;
 457             case HALF_DOWN:
 458                 if (digits[maximumDigits] > '5') {
 459                     return true;
 460                 } else if (digits[maximumDigits] == '5' ) {
 461                     for (int i=maximumDigits+1; i<count; ++i) {
 462                         if (digits[i] != '0') {
 463                             return true;
 464                         }
 465                     }
 466                 }
 467                 break;
 468             case HALF_EVEN:
 469                 // Implement IEEE half-even rounding
 470                 if (digits[maximumDigits] > '5') {
 471                     return true;
 472                 } else if (digits[maximumDigits] == '5' ) {
 473                     for (int i=maximumDigits+1; i<count; ++i) {
 474                         if (digits[i] != '0') {
 475                             return true;
 476                         }
 477                     }
 478                     return maximumDigits > 0 && (digits[maximumDigits-1] % 2 != 0);
 479                 }
 480                 break;
 481             case UNNECESSARY:
 482                 for (int i=maximumDigits; i<count; ++i) {
 483                     if (digits[i] != '0') {
 484                         throw new ArithmeticException(
 485                             "Rounding needed with the rounding mode being set to RoundingMode.UNNECESSARY");
 486                     }
 487                 }
 488                 break;
 489             default:
 490                 assert false;
 491             }
 492         }
 493         return false;
 494     }
 495 
 496     /**
 497      * Utility routine to set the value of the digit list from a long
 498      */
 499     public final void set(boolean isNegative, long source) {
 500         set(isNegative, source, 0);
 501     }
 502 
 503     /**
 504      * Set the digit list to a representation of the given long value.
 505      * @param isNegative Boolean value indicating whether the number is negative.
 506      * @param source Value to be converted; must be >= 0 or ==
 507      * Long.MIN_VALUE.
 508      * @param maximumDigits The most digits which should be converted.
 509      * If maximumDigits is lower than the number of significant digits
 510      * in source, the representation will be rounded.  Ignored if <= 0.
 511      */
 512     public final void set(boolean isNegative, long source, int maximumDigits) {
 513         this.isNegative = isNegative;
 514 
 515         // This method does not expect a negative number. However,
 516         // "source" can be a Long.MIN_VALUE (-9223372036854775808),
 517         // if the number being formatted is a Long.MIN_VALUE.  In that
 518         // case, it will be formatted as -Long.MIN_VALUE, a number
 519         // which is outside the legal range of a long, but which can
 520         // be represented by DigitList.
 521         if (source <= 0) {
 522             if (source == Long.MIN_VALUE) {
 523                 decimalAt = count = MAX_COUNT;
 524                 System.arraycopy(LONG_MIN_REP, 0, digits, 0, count);
 525             } else {
 526                 decimalAt = count = 0; // Values <= 0 format as zero
 527             }
 528         } else {
 529             // Rewritten to improve performance.  I used to call
 530             // Long.toString(), which was about 4x slower than this code.
 531             int left = MAX_COUNT;
 532             int right;
 533             while (source > 0) {
 534                 digits[--left] = (char)('0' + (source % 10));
 535                 source /= 10;
 536             }
 537             decimalAt = MAX_COUNT - left;
 538             // Don't copy trailing zeros.  We are guaranteed that there is at
 539             // least one non-zero digit, so we don't have to check lower bounds.
 540             for (right = MAX_COUNT - 1; digits[right] == '0'; --right)
 541                 ;
 542             count = right - left + 1;
 543             System.arraycopy(digits, left, digits, 0, count);
 544         }
 545         if (maximumDigits > 0) round(maximumDigits);
 546     }
 547 
 548     /**
 549      * Set the digit list to a representation of the given BigDecimal value.
 550      * This method supports both fixed-point and exponential notation.
 551      * @param isNegative Boolean value indicating whether the number is negative.
 552      * @param source Value to be converted; must not be a value <= 0.
 553      * @param maximumDigits The most fractional or total digits which should
 554      * be converted.
 555      * @param fixedPoint If true, then maximumDigits is the maximum
 556      * fractional digits to be converted.  If false, total digits.
 557      */
 558     final void set(boolean isNegative, BigDecimal source, int maximumDigits, boolean fixedPoint) {
 559         String s = source.toString();
 560         extendDigits(s.length());
 561 
 562         set(isNegative, s, maximumDigits, fixedPoint);
 563     }
 564 
 565     /**
 566      * Set the digit list to a representation of the given BigInteger value.
 567      * @param isNegative Boolean value indicating whether the number is negative.
 568      * @param source Value to be converted; must be >= 0.
 569      * @param maximumDigits The most digits which should be converted.
 570      * If maximumDigits is lower than the number of significant digits
 571      * in source, the representation will be rounded.  Ignored if <= 0.
 572      */
 573     final void set(boolean isNegative, BigInteger source, int maximumDigits) {
 574         this.isNegative = isNegative;
 575         String s = source.toString();
 576         int len = s.length();
 577         extendDigits(len);
 578         s.getChars(0, len, digits, 0);
 579 
 580         decimalAt = len;
 581         int right;
 582         for (right = len - 1; right >= 0 && digits[right] == '0'; --right)
 583             ;
 584         count = right + 1;
 585 
 586         if (maximumDigits > 0) {
 587             round(maximumDigits);
 588         }
 589     }
 590 
 591     /**
 592      * equality test between two digit lists.
 593      */
 594     public boolean equals(Object obj) {
 595         if (this == obj)                      // quick check
 596             return true;
 597         if (!(obj instanceof DigitList))         // (1) same object?
 598             return false;
 599         DigitList other = (DigitList) obj;
 600         if (count != other.count ||
 601         decimalAt != other.decimalAt)
 602             return false;
 603         for (int i = 0; i < count; i++)
 604             if (digits[i] != other.digits[i])
 605                 return false;
 606         return true;
 607     }
 608 
 609     /**
 610      * Generates the hash code for the digit list.
 611      */
 612     public int hashCode() {
 613         int hashcode = decimalAt;
 614 
 615         for (int i = 0; i < count; i++) {
 616             hashcode = hashcode * 37 + digits[i];
 617         }
 618 
 619         return hashcode;
 620     }
 621 
 622     /**
 623      * Creates a copy of this object.
 624      * @return a clone of this instance.
 625      */
 626     public Object clone() {
 627         try {
 628             DigitList other = (DigitList) super.clone();
 629             char[] newDigits = new char[digits.length];
 630             System.arraycopy(digits, 0, newDigits, 0, digits.length);
 631             other.digits = newDigits;
 632             other.tempBuffer = null;
 633             return other;
 634         } catch (CloneNotSupportedException e) {
 635             throw new InternalError(e);
 636         }
 637     }
 638 
 639     /**
 640      * Returns true if this DigitList represents Long.MIN_VALUE;
 641      * false, otherwise.  This is required so that getLong() works.
 642      */
 643     private boolean isLongMIN_VALUE() {
 644         if (decimalAt != count || count != MAX_COUNT) {
 645             return false;
 646         }
 647 
 648         for (int i = 0; i < count; ++i) {
 649             if (digits[i] != LONG_MIN_REP[i]) return false;
 650         }
 651 
 652         return true;
 653     }
 654 
 655     private static final int parseInt(char[] str, int offset, int strLen) {
 656         char c;
 657         boolean positive = true;
 658         if ((c = str[offset]) == '-') {
 659             positive = false;
 660             offset++;
 661         } else if (c == '+') {
 662             offset++;
 663         }
 664 
 665         int value = 0;
 666         while (offset < strLen) {
 667             c = str[offset++];
 668             if (c >= '0' && c <= '9') {
 669                 value = value * 10 + (c - '0');
 670             } else {
 671                 break;
 672             }
 673         }
 674         return positive ? value : -value;
 675     }
 676 
 677     // The digit part of -9223372036854775808L
 678     private static final char[] LONG_MIN_REP = "9223372036854775808".toCharArray();
 679 
 680     public String toString() {
 681         if (isZero()) {
 682             return "0";
 683         }
 684         StringBuffer buf = getStringBuffer();
 685         buf.append("0.");
 686         buf.append(digits, 0, count);
 687         buf.append("x10^");
 688         buf.append(decimalAt);
 689         return buf.toString();
 690     }
 691 
 692     private StringBuffer tempBuffer;
 693 
 694     private StringBuffer getStringBuffer() {
 695         if (tempBuffer == null) {
 696             tempBuffer = new StringBuffer(MAX_COUNT);
 697         } else {
 698             tempBuffer.setLength(0);
 699         }
 700         return tempBuffer;
 701     }
 702 
 703     private void extendDigits(int len) {
 704         if (len > digits.length) {
 705             digits = new char[len];
 706         }
 707     }
 708 
 709     private final char[] getDataChars(int length) {
 710         if (data == null || data.length < length) {
 711             data = new char[length];
 712         }
 713         return data;
 714     }
 715 }