summaryrefslogtreecommitdiff
path: root/Build/source/libs/icu-xetex/i18n/unicode/msgfmt.h
blob: 815cabbb94458ba445fa0d7eaf9e988b5906c86c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
/*
* Copyright (C) 1997-2006, International Business Machines Corporation and others. All Rights Reserved.
********************************************************************************
*
* File MSGFMT.H
*
* Modification History:
*
*   Date        Name        Description
*   02/19/97    aliu        Converted from java.
*   03/20/97    helena      Finished first cut of implementation.
*   07/22/98    stephen     Removed operator!= (defined in Format)
*   08/19/2002  srl         Removing Javaisms
********************************************************************************
*/

#ifndef MSGFMT_H
#define MSGFMT_H

#include "unicode/utypes.h"

/**
 * \file 
 * \brief C++ API: Formats messages in a language-neutral way.
 */
 
#if !UCONFIG_NO_FORMATTING

#include "unicode/format.h"
#include "unicode/locid.h"
#include "unicode/parseerr.h"

U_NAMESPACE_BEGIN

class NumberFormat;
class DateFormat;

/**
 *
 * A MessageFormat produces concatenated messages in a
 * language-neutral way.  It should be used for all string
 * concatenations that are visible to end users.
 * <P>
 * A MessageFormat contains an array of <EM>subformats</EM> arranged
 * within a <EM>template string</EM>.  Together, the subformats and
 * template string determine how the MessageFormat will operate during
 * formatting and parsing.
 * <P>
 * Typically, both the subformats and the template string are
 * specified at once in a <EM>pattern</EM>.  By using different
 * patterns for different locales, messages may be localized.
 * <P>
 * During formatting, the MessageFormat takes an array of arguments
 * and produces a user-readable string.  Each argument is a
 * Formattable object; they may be passed in in an array, or as a
 * single Formattable object which itself contains an array.  Each
 * argument is matched up with its corresponding subformat, which then
 * formats it into a string.  The resultant strings are then assembled
 * within the string template of the MessageFormat to produce the
 * final output string.
 * <P>
 * During parsing, an input string is matched against the string
 * template of the MessageFormat to produce an array of Formattable
 * objects.  Plain text of the template string is matched directly
 * against intput text.  At each position in the template string where
 * a subformat is located, the subformat is called to parse the
 * corresponding segment of input text to produce an output argument.
 * In this way, an array of arguments is created which together
 * constitute the parse result.
 * <P>
 * Parsing may fail or produce unexpected results in a number of
 * circumstances.
 * <UL>
 * <LI>If one of the arguments does not occur in the pattern, it
 * will be returned as a default Formattable.
 * <LI>If the format of an argument is loses information, such as with
 * a choice format where a large number formats to "many", then the
 * parse may not correspond to the originally formatted argument.
 * <LI>MessageFormat does not handle ChoiceFormat recursion during
 * parsing; such parses will fail.
 * <LI>Parsing will not always find a match (or the correct match) if
 * some part of the parse is ambiguous.  For example, if the pattern
 * "{1},{2}" is used with the string arguments {"a,b", "c"}, it will
 * format as "a,b,c".  When the result is parsed, it will return {"a",
 * "b,c"}.
 * <LI>If a single argument is formatted more than once in the string,
 * then the rightmost subformat in the pattern string will produce the
 * parse result; prior subformats with the same argument index will
 * have no effect.
 * </UL>
 * Here are some examples of usage:
 * <P>
 * Example 1:
 * <pre>
 * \code
 *     UErrorCode success = U_ZERO_ERROR;
 *     GregorianCalendar cal(success);
 *     Formattable arguments[] = {
 *         7L,
 *         Formattable( (Date) cal.getTime(success), Formattable::kIsDate),
 *         "a disturbance in the Force"
 *     };
 *
 *     UnicodeString result;
 *     MessageFormat::format(
 *          "At {1,time} on {1,date}, there was {2} on planet {0,number}.",
 *          arguments, 3, result, success );
 *
 *     cout << "result: " << result << endl;
 *     //<output>: At 4:34:20 PM on 23-Mar-98, there was a disturbance
 *     //             in the Force on planet 7.
 * \endcode
 * </pre>
 * Typically, the message format will come from resources, and the
 * arguments will be dynamically set at runtime.
 * <P>
 * Example 2:
 * <pre>
 *  \code
 *     success = U_ZERO_ERROR;
 *     Formattable testArgs[] = {3L, "MyDisk"};
 *
 *     MessageFormat form(
 *         "The disk \"{1}\" contains {0} file(s).", success );
 *
 *     UnicodeString string;
 *     FieldPosition fpos = 0;
 *     cout << "format: " << form.format(testArgs, 2, string, fpos, success ) << endl;
 *
 *     // output, with different testArgs:
 *     // output: The disk "MyDisk" contains 0 file(s).
 *     // output: The disk "MyDisk" contains 1 file(s).
 *     // output: The disk "MyDisk" contains 1,273 file(s).
 *  \endcode
 *  </pre>
 *
 *  The pattern is of the following form.  Legend:
 *  <pre>
 * \code
 *       {optional item}
 *       (group that may be repeated)*
 * \endcode
 *  </pre>
 *  Do not confuse optional items with items inside quotes braces, such
 *  as this: "{".  Quoted braces are literals.
 *  <pre>
 *  \code
 *       messageFormatPattern := string ( "{" messageFormatElement "}" string )*
 *
 *       messageFormatElement := argumentIndex { "," elementFormat }
 *
 *       elementFormat := "time" { "," datetimeStyle }
 *                      | "date" { "," datetimeStyle }
 *                      | "number" { "," numberStyle }
 *                      | "choice" "," choiceStyle
 *
 *       datetimeStyle := "short"
 *                      | "medium"
 *                      | "long"
 *                      | "full"
 *                      | dateFormatPattern
 *
 *       numberStyle :=   "currency"
 *                      | "percent"
 *                      | "integer"
 *                      | numberFormatPattern
 *
 *       choiceStyle :=   choiceFormatPattern
 * \endcode
 * </pre>
 * If there is no elementFormat, then the argument must be a string,
 * which is substituted. If there is no dateTimeStyle or numberStyle,
 * then the default format is used (e.g.  NumberFormat::createInstance(),
 * DateFormat::createTimeInstance(DateFormat::kDefault, ...) or DateFormat::createDateInstance(DateFormat::kDefault, ...). For
 * a ChoiceFormat, the pattern must always be specified, since there
 * is no default.
 * <P>
 * In strings, single quotes can be used to quote syntax characters.
 * A literal single quote is represented by '', both within and outside
 * of single-quoted segments.  Inside a
 * messageFormatElement, quotes are <EM>not</EM> removed. For example,
 * {1,number,$'#',##} will produce a number format with the pound-sign
 * quoted, with a result such as: "$#31,45".
 * <P>
 * If a pattern is used, then unquoted braces in the pattern, if any,
 * must match: that is, "ab {0} de" and "ab '}' de" are ok, but "ab
 * {0'}' de" and "ab } de" are not.
 * <p>
 * <dl><dt><b>Warning:</b><dd>The rules for using quotes within message
 * format patterns unfortunately have shown to be somewhat confusing.
 * In particular, it isn't always obvious to localizers whether single
 * quotes need to be doubled or not. Make sure to inform localizers about
 * the rules, and tell them (for example, by using comments in resource
 * bundle source files) which strings will be processed by MessageFormat.
 * Note that localizers may need to use single quotes in translated
 * strings where the original version doesn't have them.
 * <br>Note also that the simplest way to avoid the problem is to
 * use the real apostrophe (single quote) character U+2019 (') for
 * human-readable text, and to use the ASCII apostrophe (U+0027 ' )
 * only in program syntax, like quoting in MessageFormat.
 * See the annotations for U+0027 Apostrophe in The Unicode Standard.</p>
 * </dl>
 * <P>
 * The argumentIndex is a non-negative integer, which corresponds to the
 * index of the arguments presented in an array to be formatted.  The
 * first argument has argumentIndex 0.
 * <P>
 * It is acceptable to have unused arguments in the array.  With missing
 * arguments or arguments that are not of the right class for the
 * specified format, a failing UErrorCode result is set.
 * <P>
 * For more sophisticated patterns, you can use a ChoiceFormat to get
 * output:
 * <pre>
 * \code
 *     UErrorCode success = U_ZERO_ERROR;
 *     MessageFormat* form("The disk \"{1}\" contains {0}.", success);
 *     double filelimits[] = {0,1,2};
 *     UnicodeString filepart[] = {"no files","one file","{0,number} files"};
 *     ChoiceFormat* fileform = new ChoiceFormat(filelimits, filepart, 3);
 *     form.setFormat(1, *fileform); // NOT zero, see below
 *
 *     Formattable testArgs[] = {1273L, "MyDisk"};
 *
 *     UnicodeString string;
 *     FieldPosition fpos = 0;
 *     cout << form.format(testArgs, 2, string, fpos, success) << endl;
 *
 *     // output, with different testArgs
 *     // output: The disk "MyDisk" contains no files.
 *     // output: The disk "MyDisk" contains one file.
 *     // output: The disk "MyDisk" contains 1,273 files.
 * \endcode
 * </pre>
 * You can either do this programmatically, as in the above example,
 * or by using a pattern (see ChoiceFormat for more information) as in:
 * <pre>
 * \code
 *    form.applyPattern(
 *      "There {0,choice,0#are no files|1#is one file|1<are {0,number,integer} files}.");
 * \endcode
 * </pre>
 * <P>
 * <EM>Note:</EM> As we see above, the string produced by a ChoiceFormat in
 * MessageFormat is treated specially; occurences of '{' are used to
 * indicated subformats, and cause recursion.  If you create both a
 * MessageFormat and ChoiceFormat programmatically (instead of using
 * the string patterns), then be careful not to produce a format that
 * recurses on itself, which will cause an infinite loop.
 * <P>
 * <EM>Note:</EM> Subformats are numbered by their order in the pattern.
 * This is <EM>not</EM> the same as the argumentIndex.
 * <pre>
 * \code
 *    For example: with "abc{2}def{3}ghi{0}...",
 *
 *    format0 affects the first variable {2}
 *    format1 affects the second variable {3}
 *    format2 affects the second variable {0}
 * \endcode
 * </pre>
 *
 * <p><em>User subclasses are not supported.</em> While clients may write
 * subclasses, such code will not necessarily work and will not be
 * guaranteed to work stably from release to release.
 */
class U_I18N_API MessageFormat : public Format {
public:
    /**
     * Enum type for kMaxFormat.
     * @obsolete ICU 3.0.  The 10-argument limit was removed as of ICU 2.6,
     * rendering this enum type obsolete.
     */
    enum EFormatNumber {
        /**
         * The maximum number of arguments.
         * @obsolete ICU 3.0.  The 10-argument limit was removed as of ICU 2.6,
         * rendering this constant obsolete.
         */
        kMaxFormat = 10
    };

    /**
     * Constructs a new MessageFormat using the given pattern and the
     * default locale.
     *
     * @param pattern   Pattern used to construct object.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @stable ICU 2.0
     */
    MessageFormat(const UnicodeString& pattern,
                  UErrorCode &status);

    /**
     * Constructs a new MessageFormat using the given pattern and locale.
     * @param pattern   Pattern used to construct object.
     * @param newLocale The locale to use for formatting dates and numbers.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @stable ICU 2.0
     */
    MessageFormat(const UnicodeString& pattern,
                  const Locale& newLocale,
                        UErrorCode& status);
    /**
     * Constructs a new MessageFormat using the given pattern and locale.
     * @param pattern   Pattern used to construct object.
     * @param newLocale The locale to use for formatting dates and numbers.
     * @param parseError Struct to recieve information on position 
     *                   of error within the pattern.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @stable ICU 2.0
     */
    MessageFormat(const UnicodeString& pattern,
                  const Locale& newLocale,
                  UParseError& parseError,
                  UErrorCode& status);
    /**
     * Constructs a new MessageFormat from an existing one.
     * @stable ICU 2.0
     */
    MessageFormat(const MessageFormat&);

    /**
     * Assignment operator.
     * @stable ICU 2.0
     */
    const MessageFormat& operator=(const MessageFormat&);

    /**
     * Destructor.
     * @stable ICU 2.0
     */
    virtual ~MessageFormat();

    /**
     * Clones this Format object polymorphically.  The caller owns the
     * result and should delete it when done.
     * @stable ICU 2.0
     */
    virtual Format* clone(void) const;

    /**
     * Returns true if the given Format objects are semantically equal.
     * Objects of different subclasses are considered unequal.
     * @param other  the object to be compared with.
     * @return       true if the given Format objects are semantically equal.
     * @stable ICU 2.0
     */
    virtual UBool operator==(const Format& other) const;

    /**
     * Sets the locale. This locale is used for fetching default number or date
     * format information.
     * @param theLocale    the new locale value to be set.
     * @stable ICU 2.0
     */
    virtual void setLocale(const Locale& theLocale);

    /**
     * Gets the locale. This locale is used for fetching default number or date
     * format information.
     * @return    the locale of the object.
     * @stable ICU 2.0
     */
    virtual const Locale& getLocale(void) const;

    /**
     * Applies the given pattern string to this message format.
     *
     * @param pattern   The pattern to be applied.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @stable ICU 2.0
     */
    virtual void applyPattern(const UnicodeString& pattern,
                              UErrorCode& status);
    /**
     * Applies the given pattern string to this message format.
     *
     * @param pattern    The pattern to be applied.
     * @param parseError Struct to recieve information on position 
     *                   of error within pattern.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @stable ICU 2.0
     */
    virtual void applyPattern(const UnicodeString& pattern,
                             UParseError& parseError,
                             UErrorCode& status);

    /**
     * Returns a pattern that can be used to recreate this object.
     *
     * @param appendTo  Output parameter to receive the pattern.
     *                  Result is appended to existing contents.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    virtual UnicodeString& toPattern(UnicodeString& appendTo) const;

    /**
     * Sets subformats.
     * See the class description about format numbering.
     * The caller should not delete the Format objects after this call.
     * <EM>The array formatsToAdopt is not itself adopted.</EM> Its
     * ownership is retained by the caller. If the call fails because
     * memory cannot be allocated, then the formats will be deleted
     * by this method, and this object will remain unchanged.
     * 
     * @stable ICU 2.0
     * @param formatsToAdopt    the format to be adopted.
     * @param count             the size of the array.
     */
    virtual void adoptFormats(Format** formatsToAdopt, int32_t count);

    /**
     * Sets subformats.
     * See the class description about format numbering.
     * Each item in the array is cloned into the internal array.
     * If the call fails because memory cannot be allocated, then this
     * object will remain unchanged.
     * 
     * @stable ICU 2.0
     * @param newFormats the new format to be set.
     * @param cnt        the size of the array.
     */
    virtual void setFormats(const Format** newFormats,int32_t cnt);


    /**
     * Sets one subformat.
     * See the class description about format numbering.
     * The caller should not delete the Format object after this call.
     * If the number is over the number of formats already set,
     * the item will be deleted and ignored.
     * @stable ICU 2.0
     * @param formatNumber     index of the subformat.
     * @param formatToAdopt    the format to be adopted.
     */
    virtual void adoptFormat(int32_t formatNumber, Format* formatToAdopt);

    /**
     * Sets one subformat.
     * See the class description about format numbering.
     * If the number is over the number of formats already set,
     * the item will be ignored.
     * @param formatNumber     index of the subformat.
     * @param format    the format to be set.
     * @stable ICU 2.0
     */
    virtual void setFormat(int32_t formatNumber, const Format& format);

    /**
     * Gets an array of subformats of this object.  The returned array
     * should not be deleted by the caller, nor should the pointers
     * within the array.  The array and its contents remain valid only
     * until the next call to any method of this class is made with
     * this object.  See the class description about format numbering.
     * @param count output parameter to receive the size of the array
     * @return an array of count Format* objects, or NULL if out of
     * memory.  Any or all of the array elements may be NULL.
     * @stable ICU 2.0
     */
    virtual const Format** getFormats(int32_t& count) const;

    /**
     * Formats the given array of arguments into a user-readable string.
     * Does not take ownership of the Formattable* array or its contents.
     *
     * @param source    An array of objects to be formatted.
     * @param count     The number of elements of 'source'.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param ignore    Not used; inherited from base class API.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(  const Formattable* source,
                            int32_t count,
                            UnicodeString& appendTo,
                            FieldPosition& ignore,
                            UErrorCode& status) const;

    /**
     * Formats the given array of arguments into a user-readable string
     * using the given pattern.
     *
     * @param pattern   The pattern.
     * @param arguments An array of objects to be formatted.
     * @param count     The number of elements of 'source'.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    static UnicodeString& format(   const UnicodeString& pattern,
                                    const Formattable* arguments,
                                    int32_t count,
                                    UnicodeString& appendTo,
                                    UErrorCode& status);

    /**
     * Formats the given array of arguments into a user-readable
     * string.  The array must be stored within a single Formattable
     * object of type kArray. If the Formattable object type is not of
     * type kArray, then returns a failing UErrorCode.
     *
     * @param obj       A Formattable of type kArray containing
     *                  arguments to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    virtual UnicodeString& format(const Formattable& obj,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode& status) const;

    /**
     * Formats the given array of arguments into a user-readable
     * string.  The array must be stored within a single Formattable
     * object of type kArray. If the Formattable object type is not of
     * type kArray, then returns a failing UErrorCode.
     *
     * @param obj       The object to format
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(const Formattable& obj,
                          UnicodeString& appendTo,
                          UErrorCode& status) const;

    /**
     * Parses the given string into an array of output arguments.
     *
     * @param source    String to be parsed.
     * @param pos       On input, starting position for parse. On output,
     *                  final position after parse.  Unchanged if parse
     *                  fails.
     * @param count     Output parameter to receive the number of arguments
     *                  parsed.
     * @return an array of parsed arguments.  The caller owns both
     * the array and its contents.
     * @stable ICU 2.0
     */
    virtual Formattable* parse( const UnicodeString& source,
                                ParsePosition& pos,
                                int32_t& count) const;

    /**
     * Parses the given string into an array of output arguments.
     *
     * @param source    String to be parsed.
     * @param count     Output param to receive size of returned array.
     * @param status    Input/output error code.  If the
     *                  pattern cannot be parsed, set to failure code.
     * @return an array of parsed arguments.  The caller owns both
     * the array and its contents.
     * @stable ICU 2.0
     */
    virtual Formattable* parse( const UnicodeString& source,
                                int32_t& count,
                                UErrorCode& status) const;

    /**
     * Parses the given string into an array of output arguments
     * stored within a single Formattable of type kArray.
     *
     * @param source    The string to be parsed into an object.
     * @param result    Formattable to be set to the parse result.
     *                  If parse fails, return contents are undefined.
     * @param pos       On input, starting position for parse. On output,
     *                  final position after parse.  Unchanged if parse
     *                  fails.
     * @stable ICU 2.0
     */
    virtual void parseObject(const UnicodeString& source,
                             Formattable& result,
                             ParsePosition& pos) const;

    /**
     * Convert an 'apostrophe-friendly' pattern into a standard
     * pattern.  Standard patterns treat all apostrophes as
     * quotes, which is problematic in some languages, e.g. 
     * French, where apostrophe is commonly used.  This utility
     * assumes that only an unpaired apostrophe immediately before
     * a brace is a true quote.  Other unpaired apostrophes are paired,
     * and the resulting standard pattern string is returned.
     *
     * <p><b>Note</b> it is not guaranteed that the returned pattern
     * is indeed a valid pattern.  The only effect is to convert
     * between patterns having different quoting semantics.
     *
     * @param pattern the 'apostrophe-friendly' patttern to convert
     * @param status    Input/output error code.  If the pattern
     *                  cannot be parsed, the failure code is set.
     * @return the standard equivalent of the original pattern
     * @stable ICU 3.4
     */
    static UnicodeString autoQuoteApostrophe(const UnicodeString& pattern, 
        UErrorCode& status);

    /**
     * Returns a unique class ID POLYMORPHICALLY.  Pure virtual override.
     * This method is to implement a simple version of RTTI, since not all
     * C++ compilers support genuine RTTI.  Polymorphic operator==() and
     * clone() methods call this method.
     *
     * @return          The class ID for this object. All objects of a
     *                  given class have the same class ID.  Objects of
     *                  other classes have different class IDs.
     * @stable ICU 2.0
     */
    virtual UClassID getDynamicClassID(void) const;

    /**
     * Return the class ID for this class.  This is useful only for
     * comparing to a return value from getDynamicClassID().  For example:
     * <pre>
     * .   Base* polymorphic_pointer = createPolymorphicObject();
     * .   if (polymorphic_pointer->getDynamicClassID() ==
     * .      Derived::getStaticClassID()) ...
     * </pre>
     * @return          The class ID for all objects of this class.
     * @stable ICU 2.0
     */
    static UClassID U_EXPORT2 getStaticClassID(void);
    
private:

    Locale              fLocale;
    UnicodeString       fPattern;
    Format**            formatAliases; // see getFormats
    int32_t             formatAliasesCapacity;

    MessageFormat(); // default constructor not implemented

    /*
     * A structure representing one subformat of this MessageFormat.
     * Each subformat has a Format object, an offset into the plain
     * pattern text fPattern, and an argument number.  The argument
     * number corresponds to the array of arguments to be formatted.
     * @internal
     */
    class Subformat {
    public:
        /**
         * @internal 
         */
        Format* format; // formatter
        /**
         * @internal 
         */
        int32_t offset; // offset into fPattern
        /**
         * @internal 
         */
        int32_t arg;    // 0-based argument number

        /**
         * Clone that.format and assign it to this.format
         * Do NOT delete this.format
         * @internal
         */
        Subformat& operator=(const Subformat& that) {
            format = that.format ? that.format->clone() : NULL;
            offset = that.offset;
            arg = that.arg;
            return *this;
        }

        /**
         * @internal 
         */
        UBool operator==(const Subformat& that) const {
            // Do cheap comparisons first
            return offset == that.offset &&
                   arg == that.arg &&
                   ((format == that.format) || // handles NULL
                    (*format == *that.format));
        }

        /**
         * @internal
         */
        UBool operator!=(const Subformat& that) const {
            return !operator==(that);
        }
    };

    /**
     * A MessageFormat contains an array of subformats.  This array
     * needs to grow dynamically if the MessageFormat is modified.
     */
    Subformat* subformats;
    int32_t    subformatCount;
    int32_t    subformatCapacity;

    /**
     * A MessageFormat formats an array of arguments.  Each argument
     * has an expected type, based on the pattern.  For example, if
     * the pattern contains the subformat "{3,number,integer}", then
     * we expect argument 3 to have type Formattable::kLong.  This
     * array needs to grow dynamically if the MessageFormat is
     * modified.
     */
    Formattable::Type* argTypes;
    int32_t            argTypeCount;
    int32_t            argTypeCapacity;

    // Variable-size array management
    UBool allocateSubformats(int32_t capacity);
    UBool allocateArgTypes(int32_t capacity);

    /**
     * Default Format objects used when no format is specified and a
     * numeric or date argument is formatted.  These are volatile
     * cache objects maintained only for performance.  They do not
     * participate in operator=(), copy constructor(), nor
     * operator==().
     */
    NumberFormat* defaultNumberFormat;
    DateFormat*   defaultDateFormat;

    /**
     * Method to retrieve default formats (or NULL on failure).
     * These are semantically const, but may modify *this.
     */
    const NumberFormat* getDefaultNumberFormat(UErrorCode&) const;
    const DateFormat*   getDefaultDateFormat(UErrorCode&) const;

    /**
     * Finds the word s, in the keyword list and returns the located index.
     * @param s the keyword to be searched for.
     * @param list the list of keywords to be searched with.
     * @return the index of the list which matches the keyword s.
     */
    static int32_t findKeyword( const UnicodeString& s,
                                const UChar * const *list);

    /**
     * Formats the array of arguments and copies the result into the
     * result buffer, updates the field position.
     *
     * @param arguments The formattable objects array.
     * @param cnt       The array count.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param status    Field position status.
     * @param recursionProtection
     *                  Initially zero. Bits 0..9 are used to indicate
     *                  that a parameter has already been seen, to
     *                  avoid recursion.  Currently unused.
     * @param success   The error code status.
     * @return          Reference to 'appendTo' parameter.
     */
    UnicodeString&  format( const Formattable* arguments,
                            int32_t cnt,
                            UnicodeString& appendTo,
                            FieldPosition& status,
                            int32_t recursionProtection,
                            UErrorCode& success) const;

    void             makeFormat(int32_t offsetNumber,
                                UnicodeString* segments,
                                UParseError& parseError,
                                UErrorCode& success);

    /**
     * Convenience method that ought to be in NumberFormat
     */
    NumberFormat* createIntegerFormat(const Locale& locale, UErrorCode& status) const;

    /**
     * Checks the range of the source text to quote the special
     * characters, { and ' and copy to target buffer.
     * @param source
     * @param start the text offset to start the process of in the source string
     * @param end the text offset to end the process of in the source string
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     */
    static void copyAndFixQuotes(const UnicodeString& appendTo, int32_t start, int32_t end, UnicodeString& target);

    /**
     * Returns array of argument types in the parsed pattern 
     * for use in C API.  Only for the use of umsg_vformat().  Not
     * for public consumption.
     * @param listCount  Output parameter to receive the size of array
     * @return           The array of formattable types in the pattern
     * @internal
     */
    const Formattable::Type* getArgTypeList(int32_t& listCount) const {
        listCount = argTypeCount;
        return argTypes; 
    }

    friend class MessageFormatAdapter; // getFormatTypeList() access
};

inline UnicodeString&
MessageFormat::format(const Formattable& obj,
                      UnicodeString& appendTo,
                      UErrorCode& status) const {
    return Format::format(obj, appendTo, status);
}
U_NAMESPACE_END

#endif /* #if !UCONFIG_NO_FORMATTING */

#endif // _MSGFMT
//eof