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unormcmp.cpp (23184B)

---

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
*
*   Copyright (C) 2001-2014, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
*******************************************************************************
*   file name:  unormcmp.cpp
*   encoding:   UTF-8
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 2004sep13
*   created by: Markus W. Scherer
*
*   unorm_compare() function moved here from unorm.cpp for better modularization.
*   Depends on both normalization and case folding.
*   Allows unorm.cpp to not depend on any character properties code.
*/

#include "unicode/utypes.h"

#if !UCONFIG_NO_NORMALIZATION

#include "unicode/unorm.h"
#include "unicode/ustring.h"
#include "cmemory.h"
#include "normalizer2impl.h"
#include "ucase.h"
#include "uprops.h"
#include "ustr_imp.h"

U_NAMESPACE_USE

/* compare canonically equivalent ------------------------------------------- */

/*
* Compare two strings for canonical equivalence.
* Further options include case-insensitive comparison and
* code point order (as opposed to code unit order).
*
* In this function, canonical equivalence is optional as well.
* If canonical equivalence is tested, then both strings must fulfill
* the FCD check.
*
* Semantically, this is equivalent to
*   strcmp[CodePointOrder](NFD(foldCase(s1)), NFD(foldCase(s2)))
* where code point order, NFD and foldCase are all optional.
*
* String comparisons almost always yield results before processing both strings
* completely.
* They are generally more efficient working incrementally instead of
* performing the sub-processing (strlen, normalization, case-folding)
* on the entire strings first.
*
* It is also unnecessary to not normalize identical characters.
*
* This function works in principle as follows:
*
* loop {
*   get one code unit c1 from s1 (-1 if end of source)
*   get one code unit c2 from s2 (-1 if end of source)
*
*   if(either string finished) {
*     return result;
*   }
*   if(c1==c2) {
*     continue;
*   }
*
*   // c1!=c2
*   try to decompose/case-fold c1/c2, and continue if one does;
*
*   // still c1!=c2 and neither decomposes/case-folds, return result
*   return c1-c2;
* }
*
* When a character decomposes, then the pointer for that source changes to
* the decomposition, pushing the previous pointer onto a stack.
* When the end of the decomposition is reached, then the code unit reader
* pops the previous source from the stack.
* (Same for case-folding.)
*
* This is complicated further by operating on variable-width UTF-16.
* The top part of the loop works on code units, while lookups for decomposition
* and case-folding need code points.
* Code points are assembled after the equality/end-of-source part.
* The source pointer is only advanced beyond all code units when the code point
* actually decomposes/case-folds.
*
* If we were on a trail surrogate unit when assembling a code point,
* and the code point decomposes/case-folds, then the decomposition/folding
* result must be compared with the part of the other string that corresponds to
* this string's lead surrogate.
* Since we only assemble a code point when hitting a trail unit when the
* preceding lead units were identical, we back up the other string by one unit
* in such a case.
*
* The optional code point order comparison at the end works with
* the same fix-up as the other code point order comparison functions.
* See ustring.c and the comment near the end of this function.
*
* Assumption: A decomposition or case-folding result string never contains
* a single surrogate. This is a safe assumption in the Unicode Standard.
* Therefore, we do not need to check for surrogate pairs across
* decomposition/case-folding boundaries.
*
* Further assumptions (see verifications tstnorm.cpp):
* The API function checks for FCD first, while the core function
* first case-folds and then decomposes. This requires that case-folding does not
* un-FCD any strings.
*
* The API function may also NFD the input and turn off decomposition.
* This requires that case-folding does not un-NFD strings either.
*
* TODO If any of the above two assumptions is violated,
* then this entire code must be re-thought.
* If this happens, then a simple solution is to case-fold both strings up front
* and to turn off UNORM_INPUT_IS_FCD.
* We already do this when not both strings are in FCD because makeFCD
* would be a partial NFD before the case folding, which does not work.
* Note that all of this is only a problem when case-folding _and_
* canonical equivalence come together.
* (Comments in unorm_compare() are more up to date than this TODO.)
*/

/* stack element for previous-level source/decomposition pointers */
struct CmpEquivLevel {
   const char16_t *start, *s, *limit;
};
typedef struct CmpEquivLevel CmpEquivLevel;

/**
* Internal option for unorm_cmpEquivFold() for decomposing.
* If not set, just do strcasecmp().
*/
#define _COMPARE_EQUIV 0x80000

/* internal function */
static int32_t
unorm_cmpEquivFold(const char16_t *s1, int32_t length1,
                  const char16_t *s2, int32_t length2,
                  uint32_t options,
                  UErrorCode *pErrorCode) {
   const Normalizer2Impl *nfcImpl;

   /* current-level start/limit - s1/s2 as current */
   const char16_t *start1, *start2, *limit1, *limit2;

   /* decomposition and case folding variables */
   const char16_t *p;
   int32_t length;

   /* stacks of previous-level start/current/limit */
   CmpEquivLevel stack1[2], stack2[2];

   /* buffers for algorithmic decompositions */
   char16_t decomp1[4], decomp2[4];

   /* case folding buffers, only use current-level start/limit */
   char16_t fold1[UCASE_MAX_STRING_LENGTH+1], fold2[UCASE_MAX_STRING_LENGTH+1];

   /* track which is the current level per string */
   int32_t level1, level2;

   /* current code units, and code points for lookups */
   UChar32 c1, c2, cp1, cp2;

   /* no argument error checking because this itself is not an API */

   /*
    * assume that at least one of the options _COMPARE_EQUIV and U_COMPARE_IGNORE_CASE is set
    * otherwise this function must behave exactly as uprv_strCompare()
    * not checking for that here makes testing this function easier
    */

   /* normalization/properties data loaded? */
   if((options&_COMPARE_EQUIV)!=0) {
       nfcImpl=Normalizer2Factory::getNFCImpl(*pErrorCode);
   } else {
       nfcImpl=nullptr;
   }
   if(U_FAILURE(*pErrorCode)) {
       return 0;
   }

   /* initialize */
   start1=s1;
   if(length1==-1) {
       limit1=nullptr;
   } else {
       limit1=s1+length1;
   }

   start2=s2;
   if(length2==-1) {
       limit2=nullptr;
   } else {
       limit2=s2+length2;
   }

   level1=level2=0;
   c1=c2=-1;

   /* comparison loop */
   for(;;) {
       /*
        * here a code unit value of -1 means "get another code unit"
        * below it will mean "this source is finished"
        */

       if(c1<0) {
           /* get next code unit from string 1, post-increment */
           for(;;) {
               if(s1==limit1 || ((c1=*s1)==0 && (limit1==nullptr || (options&_STRNCMP_STYLE)))) {
                   if(level1==0) {
                       c1=-1;
                       break;
                   }
               } else {
                   ++s1;
                   break;
               }

               /* reached end of level buffer, pop one level */
               do {
                   --level1;
                   start1=stack1[level1].start;    /*Not uninitialized*/
               } while(start1==nullptr);
               s1=stack1[level1].s;                /*Not uninitialized*/
               limit1=stack1[level1].limit;        /*Not uninitialized*/
           }
       }

       if(c2<0) {
           /* get next code unit from string 2, post-increment */
           for(;;) {
               if(s2==limit2 || ((c2=*s2)==0 && (limit2==nullptr || (options&_STRNCMP_STYLE)))) {
                   if(level2==0) {
                       c2=-1;
                       break;
                   }
               } else {
                   ++s2;
                   break;
               }

               /* reached end of level buffer, pop one level */
               do {
                   --level2;
                   start2=stack2[level2].start;    /*Not uninitialized*/
               } while(start2==nullptr);
               s2=stack2[level2].s;                /*Not uninitialized*/
               limit2=stack2[level2].limit;        /*Not uninitialized*/
           }
       }

       /*
        * compare c1 and c2
        * either variable c1, c2 is -1 only if the corresponding string is finished
        */
       if(c1==c2) {
           if(c1<0) {
               return 0;   /* c1==c2==-1 indicating end of strings */
           }
           c1=c2=-1;       /* make us fetch new code units */
           continue;
       } else if(c1<0) {
           return -1;      /* string 1 ends before string 2 */
       } else if(c2<0) {
           return 1;       /* string 2 ends before string 1 */
       }
       /* c1!=c2 && c1>=0 && c2>=0 */

       /* get complete code points for c1, c2 for lookups if either is a surrogate */
       cp1=c1;
       if(U_IS_SURROGATE(c1)) {
           char16_t c;

           if(U_IS_SURROGATE_LEAD(c1)) {
               if(s1!=limit1 && U16_IS_TRAIL(c=*s1)) {
                   /* advance ++s1; only below if cp1 decomposes/case-folds */
                   cp1=U16_GET_SUPPLEMENTARY(c1, c);
               }
           } else /* isTrail(c1) */ {
               if(start1<=(s1-2) && U16_IS_LEAD(c=*(s1-2))) {
                   cp1=U16_GET_SUPPLEMENTARY(c, c1);
               }
           }
       }

       cp2=c2;
       if(U_IS_SURROGATE(c2)) {
           char16_t c;

           if(U_IS_SURROGATE_LEAD(c2)) {
               if(s2!=limit2 && U16_IS_TRAIL(c=*s2)) {
                   /* advance ++s2; only below if cp2 decomposes/case-folds */
                   cp2=U16_GET_SUPPLEMENTARY(c2, c);
               }
           } else /* isTrail(c2) */ {
               if(start2<=(s2-2) && U16_IS_LEAD(c=*(s2-2))) {
                   cp2=U16_GET_SUPPLEMENTARY(c, c2);
               }
           }
       }

       /*
        * go down one level for each string
        * continue with the main loop as soon as there is a real change
        */

       if( level1==0 && (options&U_COMPARE_IGNORE_CASE) &&
           (length = ucase_toFullFolding(cp1, &p, options)) >= 0
       ) {
           /* cp1 case-folds to the code point "length" or to p[length] */
           if(U_IS_SURROGATE(c1)) {
               if(U_IS_SURROGATE_LEAD(c1)) {
                   /* advance beyond source surrogate pair if it case-folds */
                   ++s1;
               } else /* isTrail(c1) */ {
                   /*
                    * we got a supplementary code point when hitting its trail surrogate,
                    * therefore the lead surrogate must have been the same as in the other string;
                    * compare this decomposition with the lead surrogate in the other string
                    * remember that this simulates bulk text replacement:
                    * the decomposition would replace the entire code point
                    */
                   --s2;
                   c2=*(s2-1);
               }
           }

           /* push current level pointers */
           stack1[0].start=start1;
           stack1[0].s=s1;
           stack1[0].limit=limit1;
           ++level1;

           /* copy the folding result to fold1[] */
           if(length<=UCASE_MAX_STRING_LENGTH) {
               u_memcpy(fold1, p, length);
           } else {
               int32_t i=0;
               U16_APPEND_UNSAFE(fold1, i, length);
               length=i;
           }

           /* set next level pointers to case folding */
           start1=s1=fold1;
           limit1=fold1+length;

           /* get ready to read from decomposition, continue with loop */
           c1=-1;
           continue;
       }

       if( level2==0 && (options&U_COMPARE_IGNORE_CASE) &&
           (length = ucase_toFullFolding(cp2, &p, options)) >= 0
       ) {
           /* cp2 case-folds to the code point "length" or to p[length] */
           if(U_IS_SURROGATE(c2)) {
               if(U_IS_SURROGATE_LEAD(c2)) {
                   /* advance beyond source surrogate pair if it case-folds */
                   ++s2;
               } else /* isTrail(c2) */ {
                   /*
                    * we got a supplementary code point when hitting its trail surrogate,
                    * therefore the lead surrogate must have been the same as in the other string;
                    * compare this decomposition with the lead surrogate in the other string
                    * remember that this simulates bulk text replacement:
                    * the decomposition would replace the entire code point
                    */
                   --s1;
                   c1=*(s1-1);
               }
           }

           /* push current level pointers */
           stack2[0].start=start2;
           stack2[0].s=s2;
           stack2[0].limit=limit2;
           ++level2;

           /* copy the folding result to fold2[] */
           if(length<=UCASE_MAX_STRING_LENGTH) {
               u_memcpy(fold2, p, length);
           } else {
               int32_t i=0;
               U16_APPEND_UNSAFE(fold2, i, length);
               length=i;
           }

           /* set next level pointers to case folding */
           start2=s2=fold2;
           limit2=fold2+length;

           /* get ready to read from decomposition, continue with loop */
           c2=-1;
           continue;
       }

       if( level1<2 && (options&_COMPARE_EQUIV) &&
           nullptr != (p = nfcImpl->getDecomposition(cp1, decomp1, length))
       ) {
           /* cp1 decomposes into p[length] */
           if(U_IS_SURROGATE(c1)) {
               if(U_IS_SURROGATE_LEAD(c1)) {
                   /* advance beyond source surrogate pair if it decomposes */
                   ++s1;
               } else /* isTrail(c1) */ {
                   /*
                    * we got a supplementary code point when hitting its trail surrogate,
                    * therefore the lead surrogate must have been the same as in the other string;
                    * compare this decomposition with the lead surrogate in the other string
                    * remember that this simulates bulk text replacement:
                    * the decomposition would replace the entire code point
                    */
                   --s2;
                   c2=*(s2-1);
               }
           }

           /* push current level pointers */
           stack1[level1].start=start1;
           stack1[level1].s=s1;
           stack1[level1].limit=limit1;
           ++level1;

           /* set empty intermediate level if skipped */
           if(level1<2) {
               stack1[level1++].start=nullptr;
           }

           /* set next level pointers to decomposition */
           start1=s1=p;
           limit1=p+length;

           /* get ready to read from decomposition, continue with loop */
           c1=-1;
           continue;
       }

       if( level2<2 && (options&_COMPARE_EQUIV) &&
           nullptr != (p = nfcImpl->getDecomposition(cp2, decomp2, length))
       ) {
           /* cp2 decomposes into p[length] */
           if(U_IS_SURROGATE(c2)) {
               if(U_IS_SURROGATE_LEAD(c2)) {
                   /* advance beyond source surrogate pair if it decomposes */
                   ++s2;
               } else /* isTrail(c2) */ {
                   /*
                    * we got a supplementary code point when hitting its trail surrogate,
                    * therefore the lead surrogate must have been the same as in the other string;
                    * compare this decomposition with the lead surrogate in the other string
                    * remember that this simulates bulk text replacement:
                    * the decomposition would replace the entire code point
                    */
                   --s1;
                   c1=*(s1-1);
               }
           }

           /* push current level pointers */
           stack2[level2].start=start2;
           stack2[level2].s=s2;
           stack2[level2].limit=limit2;
           ++level2;

           /* set empty intermediate level if skipped */
           if(level2<2) {
               stack2[level2++].start=nullptr;
           }

           /* set next level pointers to decomposition */
           start2=s2=p;
           limit2=p+length;

           /* get ready to read from decomposition, continue with loop */
           c2=-1;
           continue;
       }

       /*
        * no decomposition/case folding, max level for both sides:
        * return difference result
        *
        * code point order comparison must not just return cp1-cp2
        * because when single surrogates are present then the surrogate pairs
        * that formed cp1 and cp2 may be from different string indexes
        *
        * example: { d800 d800 dc01 } vs. { d800 dc00 }, compare at second code units
        * c1=d800 cp1=10001 c2=dc00 cp2=10000
        * cp1-cp2>0 but c1-c2<0 and in fact in UTF-32 it is { d800 10001 } < { 10000 }
        *
        * therefore, use same fix-up as in ustring.c/uprv_strCompare()
        * except: uprv_strCompare() fetches c=*s while this functions fetches c=*s++
        * so we have slightly different pointer/start/limit comparisons here
        */

       if(c1>=0xd800 && c2>=0xd800 && (options&U_COMPARE_CODE_POINT_ORDER)) {
           /* subtract 0x2800 from BMP code points to make them smaller than supplementary ones */
           if(
               (c1<=0xdbff && s1!=limit1 && U16_IS_TRAIL(*s1)) ||
               (U16_IS_TRAIL(c1) && start1!=(s1-1) && U16_IS_LEAD(*(s1-2)))
           ) {
               /* part of a surrogate pair, leave >=d800 */
           } else {
               /* BMP code point - may be surrogate code point - make <d800 */
               c1-=0x2800;
           }

           if(
               (c2<=0xdbff && s2!=limit2 && U16_IS_TRAIL(*s2)) ||
               (U16_IS_TRAIL(c2) && start2!=(s2-1) && U16_IS_LEAD(*(s2-2)))
           ) {
               /* part of a surrogate pair, leave >=d800 */
           } else {
               /* BMP code point - may be surrogate code point - make <d800 */
               c2-=0x2800;
           }
       }

       return c1-c2;
   }
}

static
UBool _normalize(const Normalizer2 *n2, const char16_t *s, int32_t length,
               UnicodeString &normalized, UErrorCode *pErrorCode) {
   UnicodeString str(length<0, s, length);

   // check if s fulfill the conditions
   int32_t spanQCYes=n2->spanQuickCheckYes(str, *pErrorCode);
   if (U_FAILURE(*pErrorCode)) {
       return false;
   }
   /*
    * ICU 2.4 had a further optimization:
    * If both strings were not in FCD, then they were both NFD'ed,
    * and the _COMPARE_EQUIV option was turned off.
    * It is not entirely clear that this is valid with the current
    * definition of the canonical caseless match.
    * Therefore, ICU 2.6 removes that optimization.
    */
   if(spanQCYes<str.length()) {
       UnicodeString unnormalized=str.tempSubString(spanQCYes);
       normalized.setTo(false, str.getBuffer(), spanQCYes);
       n2->normalizeSecondAndAppend(normalized, unnormalized, *pErrorCode);
       if (U_SUCCESS(*pErrorCode)) {
           return true;
       }
   }
   return false;
}

U_CAPI int32_t U_EXPORT2
unorm_compare(const char16_t *s1, int32_t length1,
             const char16_t *s2, int32_t length2,
             uint32_t options,
             UErrorCode *pErrorCode) {
   /* argument checking */
   if(U_FAILURE(*pErrorCode)) {
       return 0;
   }
   if (s1 == nullptr || length1 < -1 || s2 == nullptr || length2 < -1) {
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
       return 0;
   }

   UnicodeString fcd1, fcd2;
   int32_t normOptions=(int32_t)(options>>UNORM_COMPARE_NORM_OPTIONS_SHIFT);
   options|=_COMPARE_EQUIV;

   /*
    * UAX #21 Case Mappings, as fixed for Unicode version 4
    * (see Jitterbug 2021), defines a canonical caseless match as
    *
    * A string X is a canonical caseless match
    * for a string Y if and only if
    * NFD(toCasefold(NFD(X))) = NFD(toCasefold(NFD(Y)))
    *
    * For better performance, we check for FCD (or let the caller tell us that
    * both strings are in FCD) for the inner normalization.
    * BasicNormalizerTest::FindFoldFCDExceptions() makes sure that
    * case-folding preserves the FCD-ness of a string.
    * The outer normalization is then only performed by unorm_cmpEquivFold()
    * when there is a difference.
    *
    * Exception: When using the Turkic case-folding option, we do perform
    * full NFD first. This is because in the Turkic case precomposed characters
    * with 0049 capital I or 0069 small i fold differently whether they
    * are first decomposed or not, so an FCD check - a check only for
    * canonical order - is not sufficient.
    */
   if(!(options&UNORM_INPUT_IS_FCD) || (options&U_FOLD_CASE_EXCLUDE_SPECIAL_I)) {
       const Normalizer2 *n2;
       if(options&U_FOLD_CASE_EXCLUDE_SPECIAL_I) {
           n2=Normalizer2::getNFDInstance(*pErrorCode);
       } else {
           n2=Normalizer2Factory::getFCDInstance(*pErrorCode);
       }
       if (U_FAILURE(*pErrorCode)) {
           return 0;
       }

       if(normOptions&UNORM_UNICODE_3_2) {
           const UnicodeSet *uni32=uniset_getUnicode32Instance(*pErrorCode);
           FilteredNormalizer2 fn2(*n2, *uni32);
           if(_normalize(&fn2, s1, length1, fcd1, pErrorCode)) {
               s1=fcd1.getBuffer();
               length1=fcd1.length();
           }
           if(_normalize(&fn2, s2, length2, fcd2, pErrorCode)) {
               s2=fcd2.getBuffer();
               length2=fcd2.length();
           }
       } else {
           if(_normalize(n2, s1, length1, fcd1, pErrorCode)) {
               s1=fcd1.getBuffer();
               length1=fcd1.length();
           }
           if(_normalize(n2, s2, length2, fcd2, pErrorCode)) {
               s2=fcd2.getBuffer();
               length2=fcd2.length();
           }
       }
   }

   if(U_SUCCESS(*pErrorCode)) {
       return unorm_cmpEquivFold(s1, length1, s2, length2, options, pErrorCode);
   } else {
       return 0;
   }
}

#endif /* #if !UCONFIG_NO_NORMALIZATION */