icuSources/common/unicode/edits.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3
   4 // edits.h
   5 // created: 2016dec30 Markus W. Scherer
   6
   7 #ifndef __EDITS_H__
   8 #define __EDITS_H__
   9
  10 #include "unicode/utypes.h"
  11 #include "unicode/uobject.h"
  12
  13 /**
  14  * \file
  15  * \brief C++ API: C++ class Edits for low-level string transformations on styled text.
  16  */
  17
  18 #if U_SHOW_CPLUSPLUS_API
  19 U_NAMESPACE_BEGIN
  20
  21 class UnicodeString;
  22
  23 /**
  24  * Records lengths of string edits but not replacement text. Supports replacements, insertions, deletions
  25  * in linear progression. Does not support moving/reordering of text.
  26  *
  27  * There are two types of edits: <em>change edits</em> and <em>no-change edits</em>. Add edits to
  28  * instances of this class using {@link #addReplace(int, int)} (for change edits) and
  29  * {@link #addUnchanged(int)} (for no-change edits). Change edits are retained with full granularity,
  30  * whereas adjacent no-change edits are always merged together. In no-change edits, there is a one-to-one
  31  * mapping between code points in the source and destination strings.
  32  *
  33  * After all edits have been added, instances of this class should be considered immutable, and an
  34  * {@link Edits::Iterator} can be used for queries.
  35  *
  36  * There are four flavors of Edits::Iterator:
  37  *
  38  * <ul>
  39  * <li>{@link #getFineIterator()} retains full granularity of change edits.
  40  * <li>{@link #getFineChangesIterator()} retains full granularity of change edits, and when calling
  41  * next() on the iterator, skips over no-change edits (unchanged regions).
  42  * <li>{@link #getCoarseIterator()} treats adjacent change edits as a single edit. (Adjacent no-change
  43  * edits are automatically merged during the construction phase.)
  44  * <li>{@link #getCoarseChangesIterator()} treats adjacent change edits as a single edit, and when
  45  * calling next() on the iterator, skips over no-change edits (unchanged regions).
  46  * </ul>
  47  *
  48  * For example, consider the string "abcßDeF", which case-folds to "abcssdef". This string has the
  49  * following fine edits:
  50  * <ul>
  51  * <li>abc ⇨ abc (no-change)
  52  * <li>ß ⇨ ss (change)
  53  * <li>D ⇨ d (change)
  54  * <li>e ⇨ e (no-change)
  55  * <li>F ⇨ f (change)
  56  * </ul>
  57  * and the following coarse edits (note how adjacent change edits get merged together):
  58  * <ul>
  59  * <li>abc ⇨ abc (no-change)
  60  * <li>ßD ⇨ ssd (change)
  61  * <li>e ⇨ e (no-change)
  62  * <li>F ⇨ f (change)
  63  * </ul>
  64  *
  65  * The "fine changes" and "coarse changes" iterators will step through only the change edits when their
  66  * {@link Edits::Iterator#next()} methods are called. They are identical to the non-change iterators when
  67  * their {@link Edits::Iterator#findSourceIndex(int)} or {@link Edits::Iterator#findDestinationIndex(int)}
  68  * methods are used to walk through the string.
  69  *
  70  * For examples of how to use this class, see the test <code>TestCaseMapEditsIteratorDocs</code> in
  71  * UCharacterCaseTest.java.
  72  *
  73  * An Edits object tracks a separate UErrorCode, but ICU string transformation functions
  74  * (e.g., case mapping functions) merge any such errors into their API's UErrorCode.
  75  *
  76  * @stable ICU 59
  77  */
  78 class U_COMMON_API Edits U_FINAL : public UMemory {
  79 public:
  80     /**
  81      * Constructs an empty object.
  82      * @stable ICU 59
  83      */
  84     Edits() :
  85             array(stackArray), capacity(STACK_CAPACITY), length(0), delta(0), numChanges(0),
  86             errorCode_(U_ZERO_ERROR) {}
  87     /**
  88      * Copy constructor.
  89      * @param other source edits
  90      * @draft ICU 60
  91      */
  92     Edits(const Edits &other) :
  93             array(stackArray), capacity(STACK_CAPACITY), length(other.length),
  94             delta(other.delta), numChanges(other.numChanges),
  95             errorCode_(other.errorCode_) {
  96         copyArray(other);
  97     }
  98     /**
  99      * Move constructor, might leave src empty.
 100      * This object will have the same contents that the source object had.
 101      * @param src source edits
 102      * @draft ICU 60
 103      */
 104     Edits(Edits &&src) U_NOEXCEPT :
 105             array(stackArray), capacity(STACK_CAPACITY), length(src.length),
 106             delta(src.delta), numChanges(src.numChanges),
 107             errorCode_(src.errorCode_) {
 108         moveArray(src);
 109     }
 110
 111     /**
 112      * Destructor.
 113      * @stable ICU 59
 114      */
 115     ~Edits();
 116
 117     /**
 118      * Assignment operator.
 119      * @param other source edits
 120      * @return *this
 121      * @draft ICU 60
 122      */
 123     Edits &operator=(const Edits &other);
 124
 125     /**
 126      * Move assignment operator, might leave src empty.
 127      * This object will have the same contents that the source object had.
 128      * The behavior is undefined if *this and src are the same object.
 129      * @param src source edits
 130      * @return *this
 131      * @draft ICU 60
 132      */
 133     Edits &operator=(Edits &&src) U_NOEXCEPT;
 134
 135     /**
 136      * Resets the data but may not release memory.
 137      * @stable ICU 59
 138      */
 139     void reset() U_NOEXCEPT;
 140
 141     /**
 142      * Adds a no-change edit: a record for an unchanged segment of text.
 143      * Normally called from inside ICU string transformation functions, not user code.
 144      * @stable ICU 59
 145      */
 146     void addUnchanged(int32_t unchangedLength);
 147     /**
 148      * Adds a change edit: a record for a text replacement/insertion/deletion.
 149      * Normally called from inside ICU string transformation functions, not user code.
 150      * @stable ICU 59
 151      */
 152     void addReplace(int32_t oldLength, int32_t newLength);
 153     /**
 154      * Sets the UErrorCode if an error occurred while recording edits.
 155      * Preserves older error codes in the outErrorCode.
 156      * Normally called from inside ICU string transformation functions, not user code.
 157      * @param outErrorCode Set to an error code if it does not contain one already
 158      *                  and an error occurred while recording edits.
 159      *                  Otherwise unchanged.
 160      * @return TRUE if U_FAILURE(outErrorCode)
 161      * @stable ICU 59
 162      */
 163     UBool copyErrorTo(UErrorCode &outErrorCode);
 164
 165     /**
 166      * How much longer is the new text compared with the old text?
 167      * @return new length minus old length
 168      * @stable ICU 59
 169      */
 170     int32_t lengthDelta() const { return delta; }
 171     /**
 172      * @return TRUE if there are any change edits
 173      * @stable ICU 59
 174      */
 175     UBool hasChanges() const { return numChanges != 0; }
 176
 177 #ifndef U_HIDE_DRAFT_API
 178     /**
 179      * @return the number of change edits
 180      * @draft ICU 60
 181      */
 182     int32_t numberOfChanges() const { return numChanges; }
 183 #endif  // U_HIDE_DRAFT_API
 184
 185     /**
 186      * Access to the list of edits.
 187      *
 188      * At any moment in time, an instance of this class points to a single edit: a "window" into a span
 189      * of the source string and the corresponding span of the destination string. The source string span
 190      * starts at {@link #sourceIndex()} and runs for {@link #oldLength()} chars; the destination string
 191      * span starts at {@link #destinationIndex()} and runs for {@link #newLength()} chars.
 192      *
 193      * The iterator can be moved between edits using the {@link #next()}, {@link #findSourceIndex(int)},
 194      * and {@link #findDestinationIndex(int)} methods. Calling any of these methods mutates the iterator
 195      * to make it point to the corresponding edit.
 196      *
 197      * For more information, see the documentation for {@link Edits}.
 198      *
 199      * @see getCoarseIterator
 200      * @see getFineIterator
 201      * @stable ICU 59
 202      */
 203     struct U_COMMON_API Iterator U_FINAL : public UMemory {
 204         /**
 205          * Default constructor, empty iterator.
 206          * @draft ICU 60
 207          */
 208         Iterator() :
 209                 array(nullptr), index(0), length(0),
 210                 remaining(0), onlyChanges_(FALSE), coarse(FALSE),
 211                 dir(0), changed(FALSE), oldLength_(0), newLength_(0),
 212                 srcIndex(0), replIndex(0), destIndex(0) {}
 213         /**
 214          * Copy constructor.
 215          * @stable ICU 59
 216          */
 217         Iterator(const Iterator &other) = default;
 218         /**
 219          * Assignment operator.
 220          * @stable ICU 59
 221          */
 222         Iterator &operator=(const Iterator &other) = default;
 223
 224         /**
 225          * Advances the iterator to the next edit.
 226          * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 227          *                  or else the function returns immediately. Check for U_FAILURE()
 228          *                  on output or use with function chaining. (See User Guide for details.)
 229          * @return TRUE if there is another edit
 230          * @stable ICU 59
 231          */
 232         UBool next(UErrorCode &errorCode) { return next(onlyChanges_, errorCode); }
 233
 234         /**
 235          * Moves the iterator to the edit that contains the source index.
 236          * The source index may be found in a no-change edit
 237          * even if normal iteration would skip no-change edits.
 238          * Normal iteration can continue from a found edit.
 239          *
 240          * The iterator state before this search logically does not matter.
 241          * (It may affect the performance of the search.)
 242          *
 243          * The iterator state after this search is undefined
 244          * if the source index is out of bounds for the source string.
 245          *
 246          * @param i source index
 247          * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 248          *                  or else the function returns immediately. Check for U_FAILURE()
 249          *                  on output or use with function chaining. (See User Guide for details.)
 250          * @return TRUE if the edit for the source index was found
 251          * @stable ICU 59
 252          */
 253         UBool findSourceIndex(int32_t i, UErrorCode &errorCode) {
 254             return findIndex(i, TRUE, errorCode) == 0;
 255         }
 256
 257 #ifndef U_HIDE_DRAFT_API
 258         /**
 259          * Moves the iterator to the edit that contains the destination index.
 260          * The destination index may be found in a no-change edit
 261          * even if normal iteration would skip no-change edits.
 262          * Normal iteration can continue from a found edit.
 263          *
 264          * The iterator state before this search logically does not matter.
 265          * (It may affect the performance of the search.)
 266          *
 267          * The iterator state after this search is undefined
 268          * if the source index is out of bounds for the source string.
 269          *
 270          * @param i destination index
 271          * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 272          *                  or else the function returns immediately. Check for U_FAILURE()
 273          *                  on output or use with function chaining. (See User Guide for details.)
 274          * @return TRUE if the edit for the destination index was found
 275          * @draft ICU 60
 276          */
 277         UBool findDestinationIndex(int32_t i, UErrorCode &errorCode) {
 278             return findIndex(i, FALSE, errorCode) == 0;
 279         }
 280
 281         /**
 282          * Computes the destination index corresponding to the given source index.
 283          * If the source index is inside a change edit (not at its start),
 284          * then the destination index at the end of that edit is returned,
 285          * since there is no information about index mapping inside a change edit.
 286          *
 287          * (This means that indexes to the start and middle of an edit,
 288          * for example around a grapheme cluster, are mapped to indexes
 289          * encompassing the entire edit.
 290          * The alternative, mapping an interior index to the start,
 291          * would map such an interval to an empty one.)
 292          *
 293          * This operation will usually but not always modify this object.
 294          * The iterator state after this search is undefined.
 295          *
 296          * @param i source index
 297          * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 298          *                  or else the function returns immediately. Check for U_FAILURE()
 299          *                  on output or use with function chaining. (See User Guide for details.)
 300          * @return destination index; undefined if i is not 0..string length
 301          * @draft ICU 60
 302          */
 303         int32_t destinationIndexFromSourceIndex(int32_t i, UErrorCode &errorCode);
 304
 305         /**
 306          * Computes the source index corresponding to the given destination index.
 307          * If the destination index is inside a change edit (not at its start),
 308          * then the source index at the end of that edit is returned,
 309          * since there is no information about index mapping inside a change edit.
 310          *
 311          * (This means that indexes to the start and middle of an edit,
 312          * for example around a grapheme cluster, are mapped to indexes
 313          * encompassing the entire edit.
 314          * The alternative, mapping an interior index to the start,
 315          * would map such an interval to an empty one.)
 316          *
 317          * This operation will usually but not always modify this object.
 318          * The iterator state after this search is undefined.
 319          *
 320          * @param i destination index
 321          * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 322          *                  or else the function returns immediately. Check for U_FAILURE()
 323          *                  on output or use with function chaining. (See User Guide for details.)
 324          * @return source index; undefined if i is not 0..string length
 325          * @draft ICU 60
 326          */
 327         int32_t sourceIndexFromDestinationIndex(int32_t i, UErrorCode &errorCode);
 328 #endif  // U_HIDE_DRAFT_API
 329
 330         /**
 331          * Returns whether the edit currently represented by the iterator is a change edit.
 332          *
 333          * @return TRUE if this edit replaces oldLength() units with newLength() different ones.
 334          *         FALSE if oldLength units remain unchanged.
 335          * @stable ICU 59
 336          */
 337         UBool hasChange() const { return changed; }
 338
 339         /**
 340          * The length of the current span in the source string, which starts at {@link #sourceIndex}.
 341          *
 342          * @return the number of units in the original string which are replaced or remain unchanged.
 343          * @stable ICU 59
 344          */
 345         int32_t oldLength() const { return oldLength_; }
 346
 347         /**
 348          * The length of the current span in the destination string, which starts at
 349          * {@link #destinationIndex}, or in the replacement string, which starts at
 350          * {@link #replacementIndex}.
 351          *
 352          * @return the number of units in the modified string, if hasChange() is TRUE.
 353          *         Same as oldLength if hasChange() is FALSE.
 354          * @stable ICU 59
 355          */
 356         int32_t newLength() const { return newLength_; }
 357
 358         /**
 359          * The start index of the current span in the source string; the span has length
 360          * {@link #oldLength}.
 361          *
 362          * @return the current index into the source string
 363          * @stable ICU 59
 364          */
 365         int32_t sourceIndex() const { return srcIndex; }
 366
 367         /**
 368          * The start index of the current span in the replacement string; the span has length
 369          * {@link #newLength}. Well-defined only if the current edit is a change edit.
 370          * <p>
 371          * The <em>replacement string</em> is the concatenation of all substrings of the destination
 372          * string corresponding to change edits.
 373          * <p>
 374          * This method is intended to be used together with operations that write only replacement
 375          * characters (e.g., {@link CaseMap#omitUnchangedText()}). The source string can then be modified
 376          * in-place.
 377          *
 378          * @return the current index into the replacement-characters-only string,
 379          *         not counting unchanged spans
 380          * @stable ICU 59
 381          */
 382         int32_t replacementIndex() const {
 383             // TODO: Throw an exception if we aren't in a change edit?
 384             return replIndex;
 385         }
 386
 387         /**
 388          * The start index of the current span in the destination string; the span has length
 389          * {@link #newLength}.
 390          *
 391          * @return the current index into the full destination string
 392          * @stable ICU 59
 393          */
 394         int32_t destinationIndex() const { return destIndex; }
 395
 396 #ifndef U_HIDE_INTERNAL_API
 397         /**
 398          * A string representation of the current edit represented by the iterator for debugging. You
 399          * should not depend on the contents of the return string.
 400          * @internal
 401          */
 402         UnicodeString& toString(UnicodeString& appendTo) const;
 403 #endif  // U_HIDE_INTERNAL_API
 404
 405     private:
 406         friend class Edits;
 407
 408         Iterator(const uint16_t *a, int32_t len, UBool oc, UBool crs);
 409
 410         int32_t readLength(int32_t head);
 411         void updateNextIndexes();
 412         void updatePreviousIndexes();
 413         UBool noNext();
 414         UBool next(UBool onlyChanges, UErrorCode &errorCode);
 415         UBool previous(UErrorCode &errorCode);
 416         /** @return -1: error or i<0; 0: found; 1: i>=string length */
 417         int32_t findIndex(int32_t i, UBool findSource, UErrorCode &errorCode);
 418
 419         const uint16_t *array;
 420         int32_t index, length;
 421         // 0 if we are not within compressed equal-length changes.
 422         // Otherwise the number of remaining changes, including the current one.
 423         int32_t remaining;
 424         UBool onlyChanges_, coarse;
 425
 426         int8_t dir;  // iteration direction: back(<0), initial(0), forward(>0)
 427         UBool changed;
 428         int32_t oldLength_, newLength_;
 429         int32_t srcIndex, replIndex, destIndex;
 430     };
 431
 432     /**
 433      * Returns an Iterator for coarse-grained change edits
 434      * (adjacent change edits are treated as one).
 435      * Can be used to perform simple string updates.
 436      * Skips no-change edits.
 437      * @return an Iterator that merges adjacent changes.
 438      * @stable ICU 59
 439      */
 440     Iterator getCoarseChangesIterator() const {
 441         return Iterator(array, length, TRUE, TRUE);
 442     }
 443
 444     /**
 445      * Returns an Iterator for coarse-grained change and no-change edits
 446      * (adjacent change edits are treated as one).
 447      * Can be used to perform simple string updates.
 448      * Adjacent change edits are treated as one edit.
 449      * @return an Iterator that merges adjacent changes.
 450      * @stable ICU 59
 451      */
 452     Iterator getCoarseIterator() const {
 453         return Iterator(array, length, FALSE, TRUE);
 454     }
 455
 456     /**
 457      * Returns an Iterator for fine-grained change edits
 458      * (full granularity of change edits is retained).
 459      * Can be used for modifying styled text.
 460      * Skips no-change edits.
 461      * @return an Iterator that separates adjacent changes.
 462      * @stable ICU 59
 463      */
 464     Iterator getFineChangesIterator() const {
 465         return Iterator(array, length, TRUE, FALSE);
 466     }
 467
 468     /**
 469      * Returns an Iterator for fine-grained change and no-change edits
 470      * (full granularity of change edits is retained).
 471      * Can be used for modifying styled text.
 472      * @return an Iterator that separates adjacent changes.
 473      * @stable ICU 59
 474      */
 475     Iterator getFineIterator() const {
 476         return Iterator(array, length, FALSE, FALSE);
 477     }
 478
 479 #ifndef U_HIDE_DRAFT_API
 480     /**
 481      * Merges the two input Edits and appends the result to this object.
 482      *
 483      * Consider two string transformations (for example, normalization and case mapping)
 484      * where each records Edits in addition to writing an output string.<br>
 485      * Edits ab reflect how substrings of input string a
 486      * map to substrings of intermediate string b.<br>
 487      * Edits bc reflect how substrings of intermediate string b
 488      * map to substrings of output string c.<br>
 489      * This function merges ab and bc such that the additional edits
 490      * recorded in this object reflect how substrings of input string a
 491      * map to substrings of output string c.
 492      *
 493      * If unrelated Edits are passed in where the output string of the first
 494      * has a different length than the input string of the second,
 495      * then a U_ILLEGAL_ARGUMENT_ERROR is reported.
 496      *
 497      * @param ab reflects how substrings of input string a
 498      *     map to substrings of intermediate string b.
 499      * @param bc reflects how substrings of intermediate string b
 500      *     map to substrings of output string c.
 501      * @param errorCode ICU error code. Its input value must pass the U_SUCCESS() test,
 502      *                  or else the function returns immediately. Check for U_FAILURE()
 503      *                  on output or use with function chaining. (See User Guide for details.)
 504      * @return *this, with the merged edits appended
 505      * @draft ICU 60
 506      */
 507     Edits &mergeAndAppend(const Edits &ab, const Edits &bc, UErrorCode &errorCode);
 508 #endif  // U_HIDE_DRAFT_API
 509
 510 private:
 511     void releaseArray() U_NOEXCEPT;
 512     Edits &copyArray(const Edits &other);
 513     Edits &moveArray(Edits &src) U_NOEXCEPT;
 514
 515     void setLastUnit(int32_t last) { array[length - 1] = (uint16_t)last; }
 516     int32_t lastUnit() const { return length > 0 ? array[length - 1] : 0xffff; }
 517
 518     void append(int32_t r);
 519     UBool growArray();
 520
 521     static const int32_t STACK_CAPACITY = 100;
 522     uint16_t *array;
 523     int32_t capacity;
 524     int32_t length;
 525     int32_t delta;
 526     int32_t numChanges;
 527     UErrorCode errorCode_;
 528     uint16_t stackArray[STACK_CAPACITY];
 529 };
 530
 531 U_NAMESPACE_END
 532 #endif // U_SHOW_CPLUSPLUS_API
 533
 534 #endif  // __EDITS_H__