DigitList


1   /*
2    * @(#)DigitList.java   1.30 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   /*
9    * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
10   * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
11   *
12   *   The original version of this source code and documentation is copyrighted
13   * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
14   * materials are provided under terms of a License Agreement between Taligent
15   * and Sun. This technology is protected by multiple US and International
16   * patents. This notice and attribution to Taligent may not be removed.
17   *   Taligent is a registered trademark of Taligent, Inc.
18   *
19   */
20  
21  package java.text;
22  
23  import java.math.BigDecimal  ;
24  import java.math.BigInteger  ;
25  
26  /**
27   * Digit List. Private to DecimalFormat.
28   * Handles the transcoding
29   * between numeric values and strings of characters.  Only handles
30   * non-negative numbers.  The division of labor between DigitList and
31   * DecimalFormat is that DigitList handles the radix 10 representation
32   * issues; DecimalFormat handles the locale-specific issues such as
33   * positive/negative, grouping, decimal point, currency, and so on.
34   *
35   * A DigitList is really a representation of a floating point value.
36   * It may be an integer value; we assume that a double has sufficient
37   * precision to represent all digits of a long.
38   *
39   * The DigitList representation consists of a string of characters,
40   * which are the digits radix 10, from '0' to '9'.  It also has a radix
41   * 10 exponent associated with it.  The value represented by a DigitList
42   * object can be computed by mulitplying the fraction f, where 0 <= f < 1,
43   * derived by placing all the digits of the list to the right of the
44   * decimal point, by 10^exponent.
45   *
46   * @see  Locale
47   * @see  Format
48   * @see  NumberFormat
49   * @see  DecimalFormat
50   * @see  ChoiceFormat
51   * @see  MessageFormat
52   * @version      1.30 12/19/03
53   * @author       Mark Davis, Alan Liu
54   */
55  final class DigitList implements Cloneable   {
56      /**
57       * The maximum number of significant digits in an IEEE 754 double, that
58       * is, in a Java double.  This must not be increased, or garbage digits
59       * will be generated, and should not be decreased, or accuracy will be lost.
60       */
61      public static final int MAX_COUNT = 19; // == Long.toString(Long.MAX_VALUE).length()
62  
63      /**
64       * These data members are intentionally public and can be set directly.
65       *
66       * The value represented is given by placing the decimal point before
67       * digits[decimalAt].  If decimalAt is < 0, then leading zeros between
68       * the decimal point and the first nonzero digit are implied.  If decimalAt
69       * is > count, then trailing zeros between the digits[count-1] and the
70       * decimal point are implied.
71       *
72       * Equivalently, the represented value is given by f * 10^decimalAt.  Here
73       * f is a value 0.1 <= f < 1 arrived at by placing the digits in Digits to
74       * the right of the decimal.
75       *
76       * DigitList is normalized, so if it is non-zero, figits[0] is non-zero.  We
77       * don't allow denormalized numbers because our exponent is effectively of
78       * unlimited magnitude.  The count value contains the number of significant
79       * digits present in digits[].
80       *
81       * Zero is represented by any DigitList with count == 0 or with each digits[i]
82       * for all i <= count == '0'.
83       */
84      public int decimalAt = 0;
85      public int count = 0;
86      public char[] digits = new char[MAX_COUNT];
87  
88      private char[] data;
89  
90      /**
91       * Return true if the represented number is zero.
92       */
93      boolean isZero() {
94          for (int i=0; i < count; ++i) {
95              if (digits[i] != '0') {
96                  return false;
97              }
98          }
99          return true;
100     }
101 
102     /**
103      * Clears out the digits.
104      * Use before appending them.
105      * Typically, you set a series of digits with append, then at the point
106      * you hit the decimal point, you set myDigitList.decimalAt = myDigitList.count;
107      * then go on appending digits.
108      */
109     public void clear () {
110         decimalAt = 0;
111         count = 0;
112     }
113 
114     /**
115      * Appends a digit to the list, extending the list when necessary.
116      */
117     public void append(char digit) {
118         if (count == digits.length) {
119             char[] data = new char[count + 100];
120             System.arraycopy(digits, 0, data, 0, count);
121             digits = data;
122         }
123         digits[count++] = digit;
124     }
125 
126     /**
127      * Utility routine to get the value of the digit list
128      * If (count == 0) this throws a NumberFormatException, which
129      * mimics Long.parseLong().
130      */
131     public final double getDouble() {
132         if (count == 0) {
133             return 0.0;
134         }
135 
136         StringBuffer   temp = getStringBuffer();
137         temp.append('.');
138         temp.append(digits, 0, count);
139         temp.append('E');
140         temp.append(decimalAt);
141         return Double.parseDouble(temp.toString());
142     }
143 
144     /**
145      * Utility routine to get the value of the digit list.
146      * If (count == 0) this returns 0, unlike Long.parseLong().
147      */
148     public final long getLong() {
149         // for now, simple implementation; later, do proper IEEE native stuff
150 
151         if (count == 0) {
152             return 0;
153         }
154 
155         // We have to check for this, because this is the one NEGATIVE value
156         // we represent.  If we tried to just pass the digits off to parseLong,
157         // we'd get a parse failure.
158         if (isLongMIN_VALUE()) {
159             return Long.MIN_VALUE;
160         }
161 
162         StringBuffer   temp = getStringBuffer();
163         temp.append(digits, 0, count);
164         for (int i = count; i < decimalAt; ++i) {
165             temp.append('0');
166         }
167         return Long.parseLong(temp.toString());
168     }
169 
170     public final BigDecimal   getBigDecimal() {
171         if (count == 0) {
172             if (decimalAt == 0) {
173                 return BigDecimal.ZERO;
174             } else {
175                 return new BigDecimal  ("0E" + decimalAt);
176             }
177         }
178 
179         StringBuffer   temp = new StringBuffer  (count + 12);
180         temp.append('.');
181         temp.append(digits, 0, count);
182         temp.append('E');
183         temp.append(decimalAt);
184         return new BigDecimal  (temp.toString());
185     }
186 
187     /**
188      * Return true if the number represented by this object can fit into
189      * a long.
190      * @param isPositive true if this number should be regarded as positive
191      * @param ignoreNegativeZero true if -0 should be regarded as identical to
192      * +0; otherwise they are considered distinct
193      * @return true if this number fits into a Java long
194      */
195     boolean fitsIntoLong(boolean isPositive, boolean ignoreNegativeZero) {
196         // Figure out if the result will fit in a long.  We have to
197         // first look for nonzero digits after the decimal point;
198         // then check the size.  If the digit count is 18 or less, then
199         // the value can definitely be represented as a long.  If it is 19
200         // then it may be too large.
201 
202         // Trim trailing zeros.  This does not change the represented value.
203         while (count > 0 && digits[count - 1] == '0') {
204             --count;
205         }
206 
207         if (count == 0) {
208             // Positive zero fits into a long, but negative zero can only
209             // be represented as a double. - bug 4162852
210             return isPositive || ignoreNegativeZero;
211         }
212 
213         if (decimalAt < count || decimalAt > MAX_COUNT) {
214             return false;
215         }
216 
217         if (decimalAt < MAX_COUNT) return true;
218 
219         // At this point we have decimalAt == count, and count == MAX_COUNT.
220         // The number will overflow if it is larger than 9223372036854775807
221         // or smaller than -9223372036854775808.
222         for (int i=0; i<count; ++i) {
223             char dig = digits[i], max = LONG_MIN_REP[i];
224             if (dig > max) return false;
225             if (dig < max) return true;
226         }
227 
228         // At this point the first count digits match.  If decimalAt is less
229         // than count, then the remaining digits are zero, and we return true.
230         if (count < decimalAt) return true;
231 
232         // Now we have a representation of Long.MIN_VALUE, without the leading
233         // negative sign.  If this represents a positive value, then it does
234         // not fit; otherwise it fits.
235         return !isPositive;
236     }
237 
238     /**
239      * Set the digit list to a representation of the given double value.
240      * This method supports fixed-point notation.
241      * @param source Value to be converted; must not be Inf, -Inf, Nan,
242      * or a value <= 0.
243      * @param maximumFractionDigits The most fractional digits which should
244      * be converted.
245      */
246     public final void set(double source, int maximumFractionDigits) {
247         set(source, maximumFractionDigits, true);
248     }
249 
250     /**
251      * Set the digit list to a representation of the given double value.
252      * This method supports both fixed-point and exponential notation.
253      * @param source Value to be converted; must not be Inf, -Inf, Nan,
254      * or a value <= 0.
255      * @param maximumDigits The most fractional or total digits which should
256      * be converted.
257      * @param fixedPoint If true, then maximumDigits is the maximum
258      * fractional digits to be converted.  If false, total digits.
259      */
260     final void set(double source, int maximumDigits, boolean fixedPoint) {
261         set(Double.toString(source), maximumDigits, fixedPoint);
262     }
263 
264     /**
265      * Generate a representation of the form DDDDD, DDDDD.DDDDD, or
266      * DDDDDE+/-DDDDD.
267      */
268     final void set(String   s, int maximumDigits, boolean fixedPoint) {
269         int len = s.length();
270         char[] source = getDataChars(len);
271         s.getChars(0, len, source, 0);
272 
273         decimalAt = -1;
274         count = 0;
275         int exponent = 0;
276         // Number of zeros between decimal point and first non-zero digit after
277         // decimal point, for numbers < 1.
278         int leadingZerosAfterDecimal = 0;
279         boolean nonZeroDigitSeen = false;
280 
281         for (int i = 0; i < len; ) {
282             char c = source[i++];
283             if (c == '.') {
284                 decimalAt = count;
285             } else if (c == 'e' || c == 'E') {
286                 exponent = parseInt(source, i, len);
287                 break;
288             } else {
289                 if (!nonZeroDigitSeen) {
290                     nonZeroDigitSeen = (c != '0');
291                     if (!nonZeroDigitSeen && decimalAt != -1)
292                         ++leadingZerosAfterDecimal;
293                 }
294                 if (nonZeroDigitSeen) {
295                     digits[count++] = c;
296                 }
297             }
298         }
299         if (decimalAt == -1) {
300             decimalAt = count;
301         }
302         if (nonZeroDigitSeen) {
303             decimalAt += exponent - leadingZerosAfterDecimal;
304         }
305 
306         if (fixedPoint) {
307             // The negative of the exponent represents the number of leading
308             // zeros between the decimal and the first non-zero digit, for
309             // a value < 0.1 (e.g., for 0.00123, -decimalAt == 2).  If this
310             // is more than the maximum fraction digits, then we have an underflow
311             // for the printed representation.
312             if (-decimalAt > maximumDigits) {
313                 // Handle an underflow to zero when we round something like
314                 // 0.0009 to 2 fractional digits.
315                 count = 0;
316                 return;
317             } else if (-decimalAt == maximumDigits) {
318                 // If we round 0.0009 to 3 fractional digits, then we have to
319                 // create a new one digit in the least significant location.
320                 if (shouldRoundUp(0)) {
321                     count = 1;
322                     ++decimalAt;
323                     digits[0] = '1';
324                 } else {
325                     count = 0;
326                 }
327                 return;
328             }
329             // else fall through
330         }
331 
332         // Eliminate trailing zeros.
333         while (count > 1 && digits[count - 1] == '0') {
334             --count;
335         }
336 
337         // Eliminate digits beyond maximum digits to be displayed.
338         // Round up if appropriate.
339         round(fixedPoint ? (maximumDigits + decimalAt) : maximumDigits);
340     }
341 
342     /**
343      * Round the representation to the given number of digits.
344      * @param maximumDigits The maximum number of digits to be shown.
345      * Upon return, count will be less than or equal to maximumDigits.
346      */
347     private final void round(int maximumDigits) {
348         // Eliminate digits beyond maximum digits to be displayed.
349         // Round up if appropriate.
350         if (maximumDigits >= 0 && maximumDigits < count) {
351             if (shouldRoundUp(maximumDigits)) {
352                 // Rounding up involved incrementing digits from LSD to MSD.
353                 // In most cases this is simple, but in a worst case situation
354                 // (9999..99) we have to adjust the decimalAt value.
355                 for (;;) {
356                     --maximumDigits;
357                     if (maximumDigits < 0) {
358                         // We have all 9's, so we increment to a single digit
359                         // of one and adjust the exponent.
360                         digits[0] = '1';
361                         ++decimalAt;
362                         maximumDigits = 0; // Adjust the count
363                         break;
364                     }
365 
366                     ++digits[maximumDigits];
367                     if (digits[maximumDigits] <= '9') break;
368                     // digits[maximumDigits] = '0'; // Unnecessary since we'll truncate this
369                 }
370                 ++maximumDigits; // Increment for use as count
371             }
372             count = maximumDigits;
373 
374             // Eliminate trailing zeros.
375             while (count > 1 && digits[count-1] == '0') {
376                 --count;
377             }
378         }
379     }
380 
381 
382     /**
383      * Return true if truncating the representation to the given number
384      * of digits will result in an increment to the last digit.  This
385      * method implements half-even rounding, the default rounding mode.
386      * [bnf]
387      * @param maximumDigits the number of digits to keep, from 0 to
388      * <code>count-1</code>.  If 0, then all digits are rounded away, and
389      * this method returns true if a one should be generated (e.g., formatting
390      * 0.09 with "#.#").
391      * @return true if digit <code>maximumDigits-1</code> should be
392      * incremented
393      */
394     private boolean shouldRoundUp(int maximumDigits) {
395         boolean increment = false;
396         // Implement IEEE half-even rounding
397         if (maximumDigits < count) {
398             if (digits[maximumDigits] > '5') {
399                 return true;
400             } else if (digits[maximumDigits] == '5' ) {
401                 for (int i=maximumDigits+1; i<count; ++i) {
402                     if (digits[i] != '0') {
403                         return true;
404                     }
405                 }
406                 return maximumDigits > 0 && (digits[maximumDigits-1] % 2 != 0);
407             }
408         }
409         return false;
410     }
411 
412     /**
413      * Utility routine to set the value of the digit list from a long
414      */
415     public final void set(long source) {
416         set(source, 0);
417     }
418 
419     /**
420      * Set the digit list to a representation of the given long value.
421      * @param source Value to be converted; must be >= 0 or ==
422      * Long.MIN_VALUE.
423      * @param maximumDigits The most digits which should be converted.
424      * If maximumDigits is lower than the number of significant digits
425      * in source, the representation will be rounded.  Ignored if <= 0.
426      */
427     public final void set(long source, int maximumDigits) {
428         // This method does not expect a negative number. However,
429         // "source" can be a Long.MIN_VALUE (-9223372036854775808),
430         // if the number being formatted is a Long.MIN_VALUE.  In that
431         // case, it will be formatted as -Long.MIN_VALUE, a number
432         // which is outside the legal range of a long, but which can
433         // be represented by DigitList.
434         if (source <= 0) {
435             if (source == Long.MIN_VALUE) {
436                 decimalAt = count = MAX_COUNT;
437                 System.arraycopy(LONG_MIN_REP, 0, digits, 0, count);
438             } else {
439                 decimalAt = count = 0; // Values <= 0 format as zero
440             }
441         } else {
442             // Rewritten to improve performance.  I used to call
443             // Long.toString(), which was about 4x slower than this code.
444             int left = MAX_COUNT;
445             int right;
446             while (source > 0) {
447                 digits[--left] = (char)('0' + (source % 10));
448                 source /= 10;
449             }
450             decimalAt = MAX_COUNT - left;
451             // Don't copy trailing zeros.  We are guaranteed that there is at
452             // least one non-zero digit, so we don't have to check lower bounds.
453             for (right = MAX_COUNT - 1; digits[right] == '0'; --right)
454                 ;
455             count = right - left + 1;
456             System.arraycopy(digits, left, digits, 0, count);
457         }
458         if (maximumDigits > 0) round(maximumDigits);
459     }
460 
461     /**
462      * Set the digit list to a representation of the given BigDecimal value.
463      * This method supports both fixed-point and exponential notation.
464      * @param source Value to be converted; must not be a value <= 0.
465      * @param maximumDigits The most fractional or total digits which should
466      * be converted.
467      * @param fixedPoint If true, then maximumDigits is the maximum
468      * fractional digits to be converted.  If false, total digits.
469      */
470     final void set(BigDecimal   source, int maximumDigits, boolean fixedPoint) {
471         String   s = source.toString();
472         extendDigits(s.length());
473 
474         set(s, maximumDigits, fixedPoint);
475     }
476 
477     /**
478      * Set the digit list to a representation of the given BigInteger value.
479      * @param source Value to be converted; must be >= 0.
480      * @param maximumDigits The most digits which should be converted.
481      * If maximumDigits is lower than the number of significant digits
482      * in source, the representation will be rounded.  Ignored if <= 0.
483      */
484     final void set(BigInteger   source, int maximumDigits) {
485         String   s = source.toString();
486         int len = s.length();
487         extendDigits(len);
488         s.getChars(0, len, digits, 0);
489 
490         decimalAt = len;
491         int right;
492         for (right = len - 1; right >= 0 && digits[right] == '0'; --right)
493             ;
494         count = right + 1;
495 
496         if (maximumDigits > 0) {
497             round(maximumDigits);
498         }
499     }
500 
501     /**
502      * equality test between two digit lists.
503      */
504     public boolean equals(Object   obj) {
505         if (this == obj)                      // quick check
506             return true;
507         if (!(obj instanceof DigitList  ))         // (1) same object?
508             return false;
509         DigitList   other = (DigitList  ) obj;
510         if (count != other.count ||
511         decimalAt != other.decimalAt)
512             return false;
513         for (int i = 0; i < count; i++)
514             if (digits[i] != other.digits[i])
515                 return false;
516         return true;
517     }
518 
519     /**
520      * Generates the hash code for the digit list.
521      */
522     public int hashCode() {
523         int hashcode = decimalAt;
524 
525         for (int i = 0; i < count; i++) {
526             hashcode = hashcode * 37 + digits[i];
527         }
528 
529         return hashcode;
530     }
531 
532     /**
533      * Creates a copy of this object.
534      * @return a clone of this instance.
535      */
536     public Object   clone() {
537         try {
538             DigitList   other = (DigitList  ) super.clone();
539             char[] newDigits = new char[digits.length];
540             System.arraycopy(digits, 0, newDigits, 0, digits.length);
541             other.digits = newDigits;
542             return other;
543         } catch (CloneNotSupportedException   e) {
544             throw new InternalError  ();
545         }
546     }
547 
548     /**
549      * Returns true if this DigitList represents Long.MIN_VALUE;
550      * false, otherwise.  This is required so that getLong() works.
551      */
552     private boolean isLongMIN_VALUE() {
553         if (decimalAt != count || count != MAX_COUNT) {
554             return false;
555         }
556 
557         for (int i = 0; i < count; ++i) {
558             if (digits[i] != LONG_MIN_REP[i]) return false;
559         }
560 
561         return true;
562     }
563 
564     private static final int parseInt(char[] str, int offset, int strLen) {
565         char c;
566         boolean positive = true;
567         if ((c = str[offset]) == '-') {
568             positive = false;
569             offset++;
570         } else if (c == '+') {
571             offset++;
572         }
573 
574         int value = 0;
575         while (offset < strLen) {
576             c = str[offset++];
577             if (c >= '0' && c <= '9') {
578                 value = value * 10 + (c - '0');
579             } else {
580                 break;
581             }
582         }
583         return positive ? value : -value;
584     }
585 
586     // The digit part of -9223372036854775808L
587     private static final char[] LONG_MIN_REP = "9223372036854775808".toCharArray();
588 
589     public String   toString() {
590         if (isZero()) {
591             return "0";
592         }
593         StringBuffer   buf = getStringBuffer();
594         buf.append("0.");
595         buf.append(digits, 0, count);
596         buf.append("x10^");
597         buf.append(decimalAt);
598         return buf.toString();
599     }
600 
601     private StringBuffer   tempBuffer;
602 
603     private StringBuffer   getStringBuffer() {
604         if (tempBuffer == null) {
605             tempBuffer = new StringBuffer  (MAX_COUNT);
606         } else {
607             tempBuffer.setLength(0);
608         }
609         return tempBuffer;
610     }
611 
612     private void extendDigits(int len) {
613         if (len > digits.length) {
614             digits = new char[len];
615         }
616     }
617 
618     private final char[] getDataChars(int length) {
619         if (data == null || data.length < length) {
620             data = new char[length];
621         }
622         return data;
623     }
624 }
625
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