icuSources/common/unormcmp.cpp

   1 /*
   2 *******************************************************************************
   3 *
   4 *   Copyright (C) 2001-2010, International Business Machines
   5 *   Corporation and others.  All Rights Reserved.
   6 *
   7 *******************************************************************************
   8 *   file name:  unormcmp.cpp
   9 *   encoding:   US-ASCII
  10 *   tab size:   8 (not used)
  11 *   indentation:4
  12 *
  13 *   created on: 2004sep13
  14 *   created by: Markus W. Scherer
  15 *
  16 *   unorm_compare() function moved here from unorm.cpp for better modularization.
  17 *   Depends on both normalization and case folding.
  18 *   Allows unorm.cpp to not depend on any character properties code.
  19 */
  20
  21 #include "unicode/utypes.h"
  22
  23 #if !UCONFIG_NO_NORMALIZATION
  24
  25 #include "unicode/unorm.h"
  26 #include "unicode/ustring.h"
  27 #include "cmemory.h"
  28 #include "normalizer2impl.h"
  29 #include "ucase.h"
  30 #include "uprops.h"
  31 #include "ustr_imp.h"
  32
  33 U_NAMESPACE_USE
  34
  35 #define LENGTHOF(array) (int32_t)(sizeof(array)/sizeof((array)[0]))
  36
  37 /* compare canonically equivalent ------------------------------------------- */
  38
  39 /*
  40  * Compare two strings for canonical equivalence.
  41  * Further options include case-insensitive comparison and
  42  * code point order (as opposed to code unit order).
  43  *
  44  * In this function, canonical equivalence is optional as well.
  45  * If canonical equivalence is tested, then both strings must fulfill
  46  * the FCD check.
  47  *
  48  * Semantically, this is equivalent to
  49  *   strcmp[CodePointOrder](NFD(foldCase(s1)), NFD(foldCase(s2)))
  50  * where code point order, NFD and foldCase are all optional.
  51  *
  52  * String comparisons almost always yield results before processing both strings
  53  * completely.
  54  * They are generally more efficient working incrementally instead of
  55  * performing the sub-processing (strlen, normalization, case-folding)
  56  * on the entire strings first.
  57  *
  58  * It is also unnecessary to not normalize identical characters.
  59  *
  60  * This function works in principle as follows:
  61  *
  62  * loop {
  63  *   get one code unit c1 from s1 (-1 if end of source)
  64  *   get one code unit c2 from s2 (-1 if end of source)
  65  *
  66  *   if(either string finished) {
  67  *     return result;
  68  *   }
  69  *   if(c1==c2) {
  70  *     continue;
  71  *   }
  72  *
  73  *   // c1!=c2
  74  *   try to decompose/case-fold c1/c2, and continue if one does;
  75  *
  76  *   // still c1!=c2 and neither decomposes/case-folds, return result
  77  *   return c1-c2;
  78  * }
  79  *
  80  * When a character decomposes, then the pointer for that source changes to
  81  * the decomposition, pushing the previous pointer onto a stack.
  82  * When the end of the decomposition is reached, then the code unit reader
  83  * pops the previous source from the stack.
  84  * (Same for case-folding.)
  85  *
  86  * This is complicated further by operating on variable-width UTF-16.
  87  * The top part of the loop works on code units, while lookups for decomposition
  88  * and case-folding need code points.
  89  * Code points are assembled after the equality/end-of-source part.
  90  * The source pointer is only advanced beyond all code units when the code point
  91  * actually decomposes/case-folds.
  92  *
  93  * If we were on a trail surrogate unit when assembling a code point,
  94  * and the code point decomposes/case-folds, then the decomposition/folding
  95  * result must be compared with the part of the other string that corresponds to
  96  * this string's lead surrogate.
  97  * Since we only assemble a code point when hitting a trail unit when the
  98  * preceding lead units were identical, we back up the other string by one unit
  99  * in such a case.
 100  *
 101  * The optional code point order comparison at the end works with
 102  * the same fix-up as the other code point order comparison functions.
 103  * See ustring.c and the comment near the end of this function.
 104  *
 105  * Assumption: A decomposition or case-folding result string never contains
 106  * a single surrogate. This is a safe assumption in the Unicode Standard.
 107  * Therefore, we do not need to check for surrogate pairs across
 108  * decomposition/case-folding boundaries.
 109  *
 110  * Further assumptions (see verifications tstnorm.cpp):
 111  * The API function checks for FCD first, while the core function
 112  * first case-folds and then decomposes. This requires that case-folding does not
 113  * un-FCD any strings.
 114  *
 115  * The API function may also NFD the input and turn off decomposition.
 116  * This requires that case-folding does not un-NFD strings either.
 117  *
 118  * TODO If any of the above two assumptions is violated,
 119  * then this entire code must be re-thought.
 120  * If this happens, then a simple solution is to case-fold both strings up front
 121  * and to turn off UNORM_INPUT_IS_FCD.
 122  * We already do this when not both strings are in FCD because makeFCD
 123  * would be a partial NFD before the case folding, which does not work.
 124  * Note that all of this is only a problem when case-folding _and_
 125  * canonical equivalence come together.
 126  * (Comments in unorm_compare() are more up to date than this TODO.)
 127  */
 128
 129 /* stack element for previous-level source/decomposition pointers */
 130 struct CmpEquivLevel {
 131     const UChar *start, *s, *limit;
 132 };
 133 typedef struct CmpEquivLevel CmpEquivLevel;
 134
 135 /**
 136  * Internal option for unorm_cmpEquivFold() for decomposing.
 137  * If not set, just do strcasecmp().
 138  */
 139 #define _COMPARE_EQUIV 0x80000
 140
 141 /* internal function */
 142 static int32_t
 143 unorm_cmpEquivFold(const UChar *s1, int32_t length1,
 144                    const UChar *s2, int32_t length2,
 145                    uint32_t options,
 146                    UErrorCode *pErrorCode) {
 147     const Normalizer2Impl *nfcImpl;
 148     const UCaseProps *csp;
 149
 150     /* current-level start/limit - s1/s2 as current */
 151     const UChar *start1, *start2, *limit1, *limit2;
 152
 153     /* decomposition and case folding variables */
 154     const UChar *p;
 155     int32_t length;
 156
 157     /* stacks of previous-level start/current/limit */
 158     CmpEquivLevel stack1[2], stack2[2];
 159
 160     /* buffers for algorithmic decompositions */
 161     UChar decomp1[4], decomp2[4];
 162
 163     /* case folding buffers, only use current-level start/limit */
 164     UChar fold1[UCASE_MAX_STRING_LENGTH+1], fold2[UCASE_MAX_STRING_LENGTH+1];
 165
 166     /* track which is the current level per string */
 167     int32_t level1, level2;
 168
 169     /* current code units, and code points for lookups */
 170     UChar32 c1, c2, cp1, cp2;
 171
 172     /* no argument error checking because this itself is not an API */
 173
 174     /*
 175      * assume that at least one of the options _COMPARE_EQUIV and U_COMPARE_IGNORE_CASE is set
 176      * otherwise this function must behave exactly as uprv_strCompare()
 177      * not checking for that here makes testing this function easier
 178      */
 179
 180     /* normalization/properties data loaded? */
 181     if((options&_COMPARE_EQUIV)!=0) {
 182         nfcImpl=Normalizer2Factory::getNFCImpl(*pErrorCode);
 183     } else {
 184         nfcImpl=NULL;
 185     }
 186     if((options&U_COMPARE_IGNORE_CASE)!=0) {
 187         csp=ucase_getSingleton();
 188     } else {
 189         csp=NULL;
 190     }
 191     if(U_FAILURE(*pErrorCode)) {
 192         return 0;
 193     }
 194
 195     /* initialize */
 196     start1=s1;
 197     if(length1==-1) {
 198         limit1=NULL;
 199     } else {
 200         limit1=s1+length1;
 201     }
 202
 203     start2=s2;
 204     if(length2==-1) {
 205         limit2=NULL;
 206     } else {
 207         limit2=s2+length2;
 208     }
 209
 210     level1=level2=0;
 211     c1=c2=-1;
 212
 213     /* comparison loop */
 214     for(;;) {
 215         /*
 216          * here a code unit value of -1 means "get another code unit"
 217          * below it will mean "this source is finished"
 218          */
 219
 220         if(c1<0) {
 221             /* get next code unit from string 1, post-increment */
 222             for(;;) {
 223                 if(s1==limit1 || ((c1=*s1)==0 && (limit1==NULL || (options&_STRNCMP_STYLE)))) {
 224                     if(level1==0) {
 225                         c1=-1;
 226                         break;
 227                     }
 228                 } else {
 229                     ++s1;
 230                     break;
 231                 }
 232
 233                 /* reached end of level buffer, pop one level */
 234                 do {
 235                     --level1;
 236                     start1=stack1[level1].start;
 237                 } while(start1==NULL);
 238                 s1=stack1[level1].s;
 239                 limit1=stack1[level1].limit;
 240             }
 241         }
 242
 243         if(c2<0) {
 244             /* get next code unit from string 2, post-increment */
 245             for(;;) {
 246                 if(s2==limit2 || ((c2=*s2)==0 && (limit2==NULL || (options&_STRNCMP_STYLE)))) {
 247                     if(level2==0) {
 248                         c2=-1;
 249                         break;
 250                     }
 251                 } else {
 252                     ++s2;
 253                     break;
 254                 }
 255
 256                 /* reached end of level buffer, pop one level */
 257                 do {
 258                     --level2;
 259                     start2=stack2[level2].start;
 260                 } while(start2==NULL);
 261                 s2=stack2[level2].s;
 262                 limit2=stack2[level2].limit;
 263             }
 264         }
 265
 266         /*
 267          * compare c1 and c2
 268          * either variable c1, c2 is -1 only if the corresponding string is finished
 269          */
 270         if(c1==c2) {
 271             if(c1<0) {
 272                 return 0;   /* c1==c2==-1 indicating end of strings */
 273             }
 274             c1=c2=-1;       /* make us fetch new code units */
 275             continue;
 276         } else if(c1<0) {
 277             return -1;      /* string 1 ends before string 2 */
 278         } else if(c2<0) {
 279             return 1;       /* string 2 ends before string 1 */
 280         }
 281         /* c1!=c2 && c1>=0 && c2>=0 */
 282
 283         /* get complete code points for c1, c2 for lookups if either is a surrogate */
 284         cp1=c1;
 285         if(U_IS_SURROGATE(c1)) {
 286             UChar c;
 287
 288             if(U_IS_SURROGATE_LEAD(c1)) {
 289                 if(s1!=limit1 && U16_IS_TRAIL(c=*s1)) {
 290                     /* advance ++s1; only below if cp1 decomposes/case-folds */
 291                     cp1=U16_GET_SUPPLEMENTARY(c1, c);
 292                 }
 293             } else /* isTrail(c1) */ {
 294                 if(start1<=(s1-2) && U16_IS_LEAD(c=*(s1-2))) {
 295                     cp1=U16_GET_SUPPLEMENTARY(c, c1);
 296                 }
 297             }
 298         }
 299
 300         cp2=c2;
 301         if(U_IS_SURROGATE(c2)) {
 302             UChar c;
 303
 304             if(U_IS_SURROGATE_LEAD(c2)) {
 305                 if(s2!=limit2 && U16_IS_TRAIL(c=*s2)) {
 306                     /* advance ++s2; only below if cp2 decomposes/case-folds */
 307                     cp2=U16_GET_SUPPLEMENTARY(c2, c);
 308                 }
 309             } else /* isTrail(c2) */ {
 310                 if(start2<=(s2-2) && U16_IS_LEAD(c=*(s2-2))) {
 311                     cp2=U16_GET_SUPPLEMENTARY(c, c2);
 312                 }
 313             }
 314         }
 315
 316         /*
 317          * go down one level for each string
 318          * continue with the main loop as soon as there is a real change
 319          */
 320
 321         if( level1==0 && (options&U_COMPARE_IGNORE_CASE) &&
 322             (length=ucase_toFullFolding(csp, (UChar32)cp1, &p, options))>=0
 323         ) {
 324             /* cp1 case-folds to the code point "length" or to p[length] */
 325             if(U_IS_SURROGATE(c1)) {
 326                 if(U_IS_SURROGATE_LEAD(c1)) {
 327                     /* advance beyond source surrogate pair if it case-folds */
 328                     ++s1;
 329                 } else /* isTrail(c1) */ {
 330                     /*
 331                      * we got a supplementary code point when hitting its trail surrogate,
 332                      * therefore the lead surrogate must have been the same as in the other string;
 333                      * compare this decomposition with the lead surrogate in the other string
 334                      * remember that this simulates bulk text replacement:
 335                      * the decomposition would replace the entire code point
 336                      */
 337                     --s2;
 338                     c2=*(s2-1);
 339                 }
 340             }
 341
 342             /* push current level pointers */
 343             stack1[0].start=start1;
 344             stack1[0].s=s1;
 345             stack1[0].limit=limit1;
 346             ++level1;
 347
 348             /* copy the folding result to fold1[] */
 349             if(length<=UCASE_MAX_STRING_LENGTH) {
 350                 u_memcpy(fold1, p, length);
 351             } else {
 352                 int32_t i=0;
 353                 U16_APPEND_UNSAFE(fold1, i, length);
 354                 length=i;
 355             }
 356
 357             /* set next level pointers to case folding */
 358             start1=s1=fold1;
 359             limit1=fold1+length;
 360
 361             /* get ready to read from decomposition, continue with loop */
 362             c1=-1;
 363             continue;
 364         }
 365
 366         if( level2==0 && (options&U_COMPARE_IGNORE_CASE) &&
 367             (length=ucase_toFullFolding(csp, (UChar32)cp2, &p, options))>=0
 368         ) {
 369             /* cp2 case-folds to the code point "length" or to p[length] */
 370             if(U_IS_SURROGATE(c2)) {
 371                 if(U_IS_SURROGATE_LEAD(c2)) {
 372                     /* advance beyond source surrogate pair if it case-folds */
 373                     ++s2;
 374                 } else /* isTrail(c2) */ {
 375                     /*
 376                      * we got a supplementary code point when hitting its trail surrogate,
 377                      * therefore the lead surrogate must have been the same as in the other string;
 378                      * compare this decomposition with the lead surrogate in the other string
 379                      * remember that this simulates bulk text replacement:
 380                      * the decomposition would replace the entire code point
 381                      */
 382                     --s1;
 383                     c1=*(s1-1);
 384                 }
 385             }
 386
 387             /* push current level pointers */
 388             stack2[0].start=start2;
 389             stack2[0].s=s2;
 390             stack2[0].limit=limit2;
 391             ++level2;
 392
 393             /* copy the folding result to fold2[] */
 394             if(length<=UCASE_MAX_STRING_LENGTH) {
 395                 u_memcpy(fold2, p, length);
 396             } else {
 397                 int32_t i=0;
 398                 U16_APPEND_UNSAFE(fold2, i, length);
 399                 length=i;
 400             }
 401
 402             /* set next level pointers to case folding */
 403             start2=s2=fold2;
 404             limit2=fold2+length;
 405
 406             /* get ready to read from decomposition, continue with loop */
 407             c2=-1;
 408             continue;
 409         }
 410
 411         if( level1<2 && (options&_COMPARE_EQUIV) &&
 412             0!=(p=nfcImpl->getDecomposition((UChar32)cp1, decomp1, length))
 413         ) {
 414             /* cp1 decomposes into p[length] */
 415             if(U_IS_SURROGATE(c1)) {
 416                 if(U_IS_SURROGATE_LEAD(c1)) {
 417                     /* advance beyond source surrogate pair if it decomposes */
 418                     ++s1;
 419                 } else /* isTrail(c1) */ {
 420                     /*
 421                      * we got a supplementary code point when hitting its trail surrogate,
 422                      * therefore the lead surrogate must have been the same as in the other string;
 423                      * compare this decomposition with the lead surrogate in the other string
 424                      * remember that this simulates bulk text replacement:
 425                      * the decomposition would replace the entire code point
 426                      */
 427                     --s2;
 428                     c2=*(s2-1);
 429                 }
 430             }
 431
 432             /* push current level pointers */
 433             stack1[level1].start=start1;
 434             stack1[level1].s=s1;
 435             stack1[level1].limit=limit1;
 436             ++level1;
 437
 438             /* set empty intermediate level if skipped */
 439             if(level1<2) {
 440                 stack1[level1++].start=NULL;
 441             }
 442
 443             /* set next level pointers to decomposition */
 444             start1=s1=p;
 445             limit1=p+length;
 446
 447             /* get ready to read from decomposition, continue with loop */
 448             c1=-1;
 449             continue;
 450         }
 451
 452         if( level2<2 && (options&_COMPARE_EQUIV) &&
 453             0!=(p=nfcImpl->getDecomposition((UChar32)cp2, decomp2, length))
 454         ) {
 455             /* cp2 decomposes into p[length] */
 456             if(U_IS_SURROGATE(c2)) {
 457                 if(U_IS_SURROGATE_LEAD(c2)) {
 458                     /* advance beyond source surrogate pair if it decomposes */
 459                     ++s2;
 460                 } else /* isTrail(c2) */ {
 461                     /*
 462                      * we got a supplementary code point when hitting its trail surrogate,
 463                      * therefore the lead surrogate must have been the same as in the other string;
 464                      * compare this decomposition with the lead surrogate in the other string
 465                      * remember that this simulates bulk text replacement:
 466                      * the decomposition would replace the entire code point
 467                      */
 468                     --s1;
 469                     c1=*(s1-1);
 470                 }
 471             }
 472
 473             /* push current level pointers */
 474             stack2[level2].start=start2;
 475             stack2[level2].s=s2;
 476             stack2[level2].limit=limit2;
 477             ++level2;
 478
 479             /* set empty intermediate level if skipped */
 480             if(level2<2) {
 481                 stack2[level2++].start=NULL;
 482             }
 483
 484             /* set next level pointers to decomposition */
 485             start2=s2=p;
 486             limit2=p+length;
 487
 488             /* get ready to read from decomposition, continue with loop */
 489             c2=-1;
 490             continue;
 491         }
 492
 493         /*
 494          * no decomposition/case folding, max level for both sides:
 495          * return difference result
 496          *
 497          * code point order comparison must not just return cp1-cp2
 498          * because when single surrogates are present then the surrogate pairs
 499          * that formed cp1 and cp2 may be from different string indexes
 500          *
 501          * example: { d800 d800 dc01 } vs. { d800 dc00 }, compare at second code units
 502          * c1=d800 cp1=10001 c2=dc00 cp2=10000
 503          * cp1-cp2>0 but c1-c2<0 and in fact in UTF-32 it is { d800 10001 } < { 10000 }
 504          *
 505          * therefore, use same fix-up as in ustring.c/uprv_strCompare()
 506          * except: uprv_strCompare() fetches c=*s while this functions fetches c=*s++
 507          * so we have slightly different pointer/start/limit comparisons here
 508          */
 509
 510         if(c1>=0xd800 && c2>=0xd800 && (options&U_COMPARE_CODE_POINT_ORDER)) {
 511             /* subtract 0x2800 from BMP code points to make them smaller than supplementary ones */
 512             if(
 513                 (c1<=0xdbff && s1!=limit1 && U16_IS_TRAIL(*s1)) ||
 514                 (U16_IS_TRAIL(c1) && start1!=(s1-1) && U16_IS_LEAD(*(s1-2)))
 515             ) {
 516                 /* part of a surrogate pair, leave >=d800 */
 517             } else {
 518                 /* BMP code point - may be surrogate code point - make <d800 */
 519                 c1-=0x2800;
 520             }
 521
 522             if(
 523                 (c2<=0xdbff && s2!=limit2 && U16_IS_TRAIL(*s2)) ||
 524                 (U16_IS_TRAIL(c2) && start2!=(s2-1) && U16_IS_LEAD(*(s2-2)))
 525             ) {
 526                 /* part of a surrogate pair, leave >=d800 */
 527             } else {
 528                 /* BMP code point - may be surrogate code point - make <d800 */
 529                 c2-=0x2800;
 530             }
 531         }
 532
 533         return c1-c2;
 534     }
 535 }
 536
 537 U_CAPI int32_t U_EXPORT2
 538 unorm_compare(const UChar *s1, int32_t length1,
 539               const UChar *s2, int32_t length2,
 540               uint32_t options,
 541               UErrorCode *pErrorCode) {
 542     /* argument checking */
 543     if(U_FAILURE(*pErrorCode)) {
 544         return 0;
 545     }
 546     if(s1==0 || length1<-1 || s2==0 || length2<-1) {
 547         *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
 548         return 0;
 549     }
 550
 551     UnicodeString fcd1, fcd2;
 552     int32_t normOptions=(int32_t)(options>>UNORM_COMPARE_NORM_OPTIONS_SHIFT);
 553     options|=_COMPARE_EQUIV;
 554
 555     /*
 556      * UAX #21 Case Mappings, as fixed for Unicode version 4
 557      * (see Jitterbug 2021), defines a canonical caseless match as
 558      *
 559      * A string X is a canonical caseless match
 560      * for a string Y if and only if
 561      * NFD(toCasefold(NFD(X))) = NFD(toCasefold(NFD(Y)))
 562      *
 563      * For better performance, we check for FCD (or let the caller tell us that
 564      * both strings are in FCD) for the inner normalization.
 565      * BasicNormalizerTest::FindFoldFCDExceptions() makes sure that
 566      * case-folding preserves the FCD-ness of a string.
 567      * The outer normalization is then only performed by unorm_cmpEquivFold()
 568      * when there is a difference.
 569      *
 570      * Exception: When using the Turkic case-folding option, we do perform
 571      * full NFD first. This is because in the Turkic case precomposed characters
 572      * with 0049 capital I or 0069 small i fold differently whether they
 573      * are first decomposed or not, so an FCD check - a check only for
 574      * canonical order - is not sufficient.
 575      */
 576     if(!(options&UNORM_INPUT_IS_FCD) || (options&U_FOLD_CASE_EXCLUDE_SPECIAL_I)) {
 577         const Normalizer2 *n2;
 578         if(options&U_FOLD_CASE_EXCLUDE_SPECIAL_I) {
 579             n2=Normalizer2Factory::getNFDInstance(*pErrorCode);
 580         } else {
 581             n2=Normalizer2Factory::getFCDInstance(*pErrorCode);
 582         }
 583         if (U_FAILURE(*pErrorCode)) {
 584             return 0;
 585         }
 586
 587         // check if s1 and/or s2 fulfill the FCD conditions
 588         const UnicodeSet *uni32;
 589         if(normOptions&UNORM_UNICODE_3_2) {
 590             uni32=uniset_getUnicode32Instance(*pErrorCode);
 591         } else {
 592             uni32=NULL;  // unused
 593         }
 594         FilteredNormalizer2 fn2(*n2, *uni32);
 595         if(normOptions&UNORM_UNICODE_3_2) {
 596             n2=&fn2;
 597         }
 598
 599         UnicodeString str1(length1<0, s1, length1);
 600         UnicodeString str2(length2<0, s2, length2);
 601         int32_t spanQCYes1=n2->spanQuickCheckYes(str1, *pErrorCode);
 602         int32_t spanQCYes2=n2->spanQuickCheckYes(str2, *pErrorCode);
 603         if(U_FAILURE(*pErrorCode)) {
 604             return 0;
 605         }
 606
 607         /*
 608          * ICU 2.4 had a further optimization:
 609          * If both strings were not in FCD, then they were both NFD'ed,
 610          * and the _COMPARE_EQUIV option was turned off.
 611          * It is not entirely clear that this is valid with the current
 612          * definition of the canonical caseless match.
 613          * Therefore, ICU 2.6 removes that optimization.
 614          */
 615
 616         if(spanQCYes1<str1.length()) {
 617             UnicodeString unnormalized=str1.tempSubString(spanQCYes1);
 618             fcd1.setTo(FALSE, str1.getBuffer(), spanQCYes1);
 619             n2->normalizeSecondAndAppend(fcd1, unnormalized, *pErrorCode);
 620             s1=fcd1.getBuffer();
 621             length1=fcd1.length();
 622         }
 623         if(spanQCYes2<str2.length()) {
 624             UnicodeString unnormalized=str2.tempSubString(spanQCYes2);
 625             fcd2.setTo(FALSE, str2.getBuffer(), spanQCYes2);
 626             n2->normalizeSecondAndAppend(fcd2, unnormalized, *pErrorCode);
 627             s2=fcd2.getBuffer();
 628             length2=fcd2.length();
 629         }
 630     }
 631
 632     if(U_SUCCESS(*pErrorCode)) {
 633         return unorm_cmpEquivFold(s1, length1, s2, length2, options, pErrorCode);
 634     } else {
 635         return 0;
 636     }
 637 }
 638
 639 #endif /* #if !UCONFIG_NO_NORMALIZATION */