Check in the pristine copy of ICU 4.6...

icu46/source/common/unormcmp.cpp

+/*
+*******************************************************************************
+*
+*   Copyright (C) 2001-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  unormcmp.cpp
+*   encoding:   US-ASCII
+*   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
+
+#define LENGTHOF(array) (int32_t)(sizeof(array)/sizeof((array)[0]))
+
+/* 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 UChar *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 UChar *s1, int32_t length1,
+                   const UChar *s2, int32_t length2,
+                   uint32_t options,
+                   UErrorCode *pErrorCode) {
+    const Normalizer2Impl *nfcImpl;
+    const UCaseProps *csp;
+
+    /* current-level start/limit - s1/s2 as current */
+    const UChar *start1, *start2, *limit1, *limit2;
+
+    /* decomposition and case folding variables */
+    const UChar *p;
+    int32_t length;
+
+    /* stacks of previous-level start/current/limit */
+    CmpEquivLevel stack1[2], stack2[2];
+
+    /* buffers for algorithmic decompositions */
+    UChar decomp1[4], decomp2[4];
+
+    /* case folding buffers, only use current-level start/limit */
+    UChar 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=NULL;
+    }
+    if((options&U_COMPARE_IGNORE_CASE)!=0) {
+        csp=ucase_getSingleton();
+    } else {
+        csp=NULL;
+    }
+    if(U_FAILURE(*pErrorCode)) {
+        return 0;
+    }
+
+    /* initialize */
+    start1=s1;
+    if(length1==-1) {
+        limit1=NULL;
+    } else {
+        limit1=s1+length1;
+    }
+
+    start2=s2;
+    if(length2==-1) {
+        limit2=NULL;
+    } 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==NULL || (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;
+                } while(start1==NULL);
+                s1=stack1[level1].s;
+                limit1=stack1[level1].limit;
+            }
+        }
+
+        if(c2<0) {
+            /* get next code unit from string 2, post-increment */
+            for(;;) {
+                if(s2==limit2 || ((c2=*s2)==0 && (limit2==NULL || (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;
+                } while(start2==NULL);
+                s2=stack2[level2].s;
+                limit2=stack2[level2].limit;
+            }
+        }
+
+        /*
+         * 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)) {
+            UChar 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)) {
+            UChar 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(csp, (UChar32)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(csp, (UChar32)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) &&
+            0!=(p=nfcImpl->getDecomposition((UChar32)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=NULL;
+            }
+
+            /* 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) &&
+            0!=(p=nfcImpl->getDecomposition((UChar32)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=NULL;
+            }
+
+            /* 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;
+    }
+}
+
+U_CAPI int32_t U_EXPORT2
+unorm_compare(const UChar *s1, int32_t length1,
+              const UChar *s2, int32_t length2,
+              uint32_t options,
+              UErrorCode *pErrorCode) {
+    /* argument checking */
+    if(U_FAILURE(*pErrorCode)) {
+        return 0;
+    }
+    if(s1==0 || length1<-1 || s2==0 || 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=Normalizer2Factory::getNFDInstance(*pErrorCode);
+        } else {
+            n2=Normalizer2Factory::getFCDInstance(*pErrorCode);
+        }
+        if (U_FAILURE(*pErrorCode)) {
+            return 0;
+        }
+
+        // check if s1 and/or s2 fulfill the FCD conditions
+        const UnicodeSet *uni32;
+        if(normOptions&UNORM_UNICODE_3_2) {
+            uni32=uniset_getUnicode32Instance(*pErrorCode);
+        } else {
+            uni32=NULL;  // unused
+        }
+        FilteredNormalizer2 fn2(*n2, *uni32);
+        if(normOptions&UNORM_UNICODE_3_2) {
+            n2=&fn2;
+        }
+
+        UnicodeString str1(length1<0, s1, length1);
+        UnicodeString str2(length2<0, s2, length2);
+        int32_t spanQCYes1=n2->spanQuickCheckYes(str1, *pErrorCode);
+        int32_t spanQCYes2=n2->spanQuickCheckYes(str2, *pErrorCode);
+        if(U_FAILURE(*pErrorCode)) {
+            return 0;
+        }
+
+        /*
+         * 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(spanQCYes1<str1.length()) {
+            UnicodeString unnormalized=str1.tempSubString(spanQCYes1);
+            fcd1.setTo(FALSE, str1.getBuffer(), spanQCYes1);
+            n2->normalizeSecondAndAppend(fcd1, unnormalized, *pErrorCode);
+            s1=fcd1.getBuffer();
+            length1=fcd1.length();
+        }
+        if(spanQCYes2<str2.length()) {
+            UnicodeString unnormalized=str2.tempSubString(spanQCYes2);
+            fcd2.setTo(FALSE, str2.getBuffer(), spanQCYes2);
+            n2->normalizeSecondAndAppend(fcd2, unnormalized, *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 */