initial commit, 4.5 stable

thirdparty/icu4c/common/bmpset.cpp

@@ -0,0 +1,741 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+******************************************************************************
+*
+*   Copyright (C) 2007-2012, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+******************************************************************************
+*   file name:  bmpset.cpp
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2007jan29
+*   created by: Markus W. Scherer
+*/
+
+#include "unicode/utypes.h"
+#include "unicode/uniset.h"
+#include "unicode/utf8.h"
+#include "unicode/utf16.h"
+#include "cmemory.h"
+#include "bmpset.h"
+#include "uassert.h"
+
+U_NAMESPACE_BEGIN
+
+BMPSet::BMPSet(const int32_t *parentList, int32_t parentListLength) :
+        list(parentList), listLength(parentListLength) {
+    uprv_memset(latin1Contains, 0, sizeof(latin1Contains));
+    uprv_memset(table7FF, 0, sizeof(table7FF));
+    uprv_memset(bmpBlockBits, 0, sizeof(bmpBlockBits));
+
+    /*
+     * Set the list indexes for binary searches for
+     * U+0800, U+1000, U+2000, .., U+F000, U+10000.
+     * U+0800 is the first 3-byte-UTF-8 code point. Lower code points are
+     * looked up in the bit tables.
+     * The last pair of indexes is for finding supplementary code points.
+     */
+    list4kStarts[0]=findCodePoint(0x800, 0, listLength-1);
+    int32_t i;
+    for(i=1; i<=0x10; ++i) {
+        list4kStarts[i]=findCodePoint(i<<12, list4kStarts[i-1], listLength-1);
+    }
+    list4kStarts[0x11]=listLength-1;
+    containsFFFD=containsSlow(0xfffd, list4kStarts[0xf], list4kStarts[0x10]);
+
+    initBits();
+    overrideIllegal();
+}
+
+BMPSet::BMPSet(const BMPSet &otherBMPSet, const int32_t *newParentList, int32_t newParentListLength) :
+        containsFFFD(otherBMPSet.containsFFFD),
+        list(newParentList), listLength(newParentListLength) {
+    uprv_memcpy(latin1Contains, otherBMPSet.latin1Contains, sizeof(latin1Contains));
+    uprv_memcpy(table7FF, otherBMPSet.table7FF, sizeof(table7FF));
+    uprv_memcpy(bmpBlockBits, otherBMPSet.bmpBlockBits, sizeof(bmpBlockBits));
+    uprv_memcpy(list4kStarts, otherBMPSet.list4kStarts, sizeof(list4kStarts));
+}
+
+BMPSet::~BMPSet() {
+}
+
+/*
+ * Set bits in a bit rectangle in "vertical" bit organization.
+ * start<limit<=0x800
+ */
+static void set32x64Bits(uint32_t table[64], int32_t start, int32_t limit) {
+    U_ASSERT(start<limit);
+    U_ASSERT(limit<=0x800);
+
+    int32_t lead=start>>6;  // Named for UTF-8 2-byte lead byte with upper 5 bits.
+    int32_t trail=start&0x3f;  // Named for UTF-8 2-byte trail byte with lower 6 bits.
+
+    // Set one bit indicating an all-one block.
+    uint32_t bits = static_cast<uint32_t>(1) << lead;
+    if((start+1)==limit) {  // Single-character shortcut.
+        table[trail]|=bits;
+        return;
+    }
+
+    int32_t limitLead=limit>>6;
+    int32_t limitTrail=limit&0x3f;
+
+    if(lead==limitLead) {
+        // Partial vertical bit column.
+        while(trail<limitTrail) {
+            table[trail++]|=bits;
+        }
+    } else {
+        // Partial vertical bit column,
+        // followed by a bit rectangle,
+        // followed by another partial vertical bit column.
+        if(trail>0) {
+            do {
+                table[trail++]|=bits;
+            } while(trail<64);
+            ++lead;
+        }
+        if(lead<limitLead) {
+            bits = ~((static_cast<unsigned>(1) << lead) - 1);
+            if(limitLead<0x20) {
+                bits &= (static_cast<unsigned>(1) << limitLead) - 1;
+            }
+            for(trail=0; trail<64; ++trail) {
+                table[trail]|=bits;
+            }
+        }
+        // limit<=0x800. If limit==0x800 then limitLead=32 and limitTrail=0.
+        // In that case, bits=1<<limitLead is undefined but the bits value
+        // is not used because trail<limitTrail is already false.
+        bits = static_cast<uint32_t>(1) << ((limitLead == 0x20) ? (limitLead - 1) : limitLead);
+        for(trail=0; trail<limitTrail; ++trail) {
+            table[trail]|=bits;
+        }
+    }
+}
+
+void BMPSet::initBits() {
+    UChar32 start, limit;
+    int32_t listIndex=0;
+
+    // Set latin1Contains[].
+    do {
+        start=list[listIndex++];
+        if(listIndex<listLength) {
+            limit=list[listIndex++];
+        } else {
+            limit=0x110000;
+        }
+        if(start>=0x100) {
+            break;
+        }
+        do {
+            latin1Contains[start++]=1;
+        } while(start<limit && start<0x100);
+    } while(limit<=0x100);
+
+    // Find the first range overlapping with (or after) 80..FF again,
+    // to include them in table7FF as well.
+    for(listIndex=0;;) {
+        start=list[listIndex++];
+        if(listIndex<listLength) {
+            limit=list[listIndex++];
+        } else {
+            limit=0x110000;
+        }
+        if(limit>0x80) {
+            if(start<0x80) {
+                start=0x80;
+            }
+            break;
+        }
+    }
+
+    // Set table7FF[].
+    while(start<0x800) {
+        set32x64Bits(table7FF, start, limit<=0x800 ? limit : 0x800);
+        if(limit>0x800) {
+            start=0x800;
+            break;
+        }
+
+        start=list[listIndex++];
+        if(listIndex<listLength) {
+            limit=list[listIndex++];
+        } else {
+            limit=0x110000;
+        }
+    }
+
+    // Set bmpBlockBits[].
+    int32_t minStart=0x800;
+    while(start<0x10000) {
+        if(limit>0x10000) {
+            limit=0x10000;
+        }
+
+        if(start<minStart) {
+            start=minStart;
+        }
+        if(start<limit) {  // Else: Another range entirely in a known mixed-value block.
+            if(start&0x3f) {
+                // Mixed-value block of 64 code points.
+                start>>=6;
+                bmpBlockBits[start&0x3f]|=0x10001<<(start>>6);
+                start=(start+1)<<6;  // Round up to the next block boundary.
+                minStart=start;      // Ignore further ranges in this block.
+            }
+            if(start<limit) {
+                if(start<(limit&~0x3f)) {
+                    // Multiple all-ones blocks of 64 code points each.
+                    set32x64Bits(bmpBlockBits, start>>6, limit>>6);
+                }
+
+                if(limit&0x3f) {
+                    // Mixed-value block of 64 code points.
+                    limit>>=6;
+                    bmpBlockBits[limit&0x3f]|=0x10001<<(limit>>6);
+                    limit=(limit+1)<<6;  // Round up to the next block boundary.
+                    minStart=limit;      // Ignore further ranges in this block.
+                }
+            }
+        }
+
+        if(limit==0x10000) {
+            break;
+        }
+
+        start=list[listIndex++];
+        if(listIndex<listLength) {
+            limit=list[listIndex++];
+        } else {
+            limit=0x110000;
+        }
+    }
+}
+
+/*
+ * Override some bits and bytes to the result of contains(FFFD)
+ * for faster validity checking at runtime.
+ * No need to set 0 values where they were reset to 0 in the constructor
+ * and not modified by initBits().
+ * (table7FF[] 0..7F, bmpBlockBits[] 0..7FF)
+ * Need to set 0 values for surrogates D800..DFFF.
+ */
+void BMPSet::overrideIllegal() {
+    uint32_t bits, mask;
+    int32_t i;
+
+    if(containsFFFD) {
+        bits=3;                 // Lead bytes 0xC0 and 0xC1.
+        for(i=0; i<64; ++i) {
+            table7FF[i]|=bits;
+        }
+
+        bits=1;                 // Lead byte 0xE0.
+        for(i=0; i<32; ++i) {   // First half of 4k block.
+            bmpBlockBits[i]|=bits;
+        }
+
+        mask= static_cast<uint32_t>(~(0x10001<<0xd));   // Lead byte 0xED.
+        bits=1<<0xd;
+        for(i=32; i<64; ++i) {  // Second half of 4k block.
+            bmpBlockBits[i]=(bmpBlockBits[i]&mask)|bits;
+        }
+    } else {
+        mask= static_cast<uint32_t>(~(0x10001<<0xd));   // Lead byte 0xED.
+        for(i=32; i<64; ++i) {  // Second half of 4k block.
+            bmpBlockBits[i]&=mask;
+        }
+    }
+}
+
+int32_t BMPSet::findCodePoint(UChar32 c, int32_t lo, int32_t hi) const {
+    /* Examples:
+                                       findCodePoint(c)
+       set              list[]         c=0 1 3 4 7 8
+       ===              ==============   ===========
+       []               [110000]         0 0 0 0 0 0
+       [\u0000-\u0003]  [0, 4, 110000]   1 1 1 2 2 2
+       [\u0004-\u0007]  [4, 8, 110000]   0 0 0 1 1 2
+       [:Any:]          [0, 110000]      1 1 1 1 1 1
+     */
+
+    // Return the smallest i such that c < list[i].  Assume
+    // list[len - 1] == HIGH and that c is legal (0..HIGH-1).
+    if (c < list[lo])
+        return lo;
+    // High runner test.  c is often after the last range, so an
+    // initial check for this condition pays off.
+    if (lo >= hi || c >= list[hi-1])
+        return hi;
+    // invariant: c >= list[lo]
+    // invariant: c < list[hi]
+    for (;;) {
+        int32_t i = (lo + hi) >> 1;
+        if (i == lo) {
+            break; // Found!
+        } else if (c < list[i]) {
+            hi = i;
+        } else {
+            lo = i;
+        }
+    }
+    return hi;
+}
+
+UBool
+BMPSet::contains(UChar32 c) const {
+    if (static_cast<uint32_t>(c) <= 0xff) {
+        return latin1Contains[c];
+    } else if (static_cast<uint32_t>(c) <= 0x7ff) {
+        return (table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) != 0;
+    } else if (static_cast<uint32_t>(c) < 0xd800 || (c >= 0xe000 && c <= 0xffff)) {
+        int lead=c>>12;
+        uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+        if(twoBits<=1) {
+            // All 64 code points with the same bits 15..6
+            // are either in the set or not.
+            return twoBits;
+        } else {
+            // Look up the code point in its 4k block of code points.
+            return containsSlow(c, list4kStarts[lead], list4kStarts[lead+1]);
+        }
+    } else if (static_cast<uint32_t>(c) <= 0x10ffff) {
+        // surrogate or supplementary code point
+        return containsSlow(c, list4kStarts[0xd], list4kStarts[0x11]);
+    } else {
+        // Out-of-range code points get false, consistent with long-standing
+        // behavior of UnicodeSet::contains(c).
+        return false;
+    }
+}
+
+/*
+ * Check for sufficient length for trail unit for each surrogate pair.
+ * Handle single surrogates as surrogate code points as usual in ICU.
+ */
+const char16_t *
+BMPSet::span(const char16_t *s, const char16_t *limit, USetSpanCondition spanCondition) const {
+    char16_t c, c2;
+
+    if(spanCondition) {
+        // span
+        do {
+            c=*s;
+            if(c<=0xff) {
+                if(!latin1Contains[c]) {
+                    break;
+                }
+            } else if(c<=0x7ff) {
+                if ((table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) == 0) {
+                    break;
+                }
+            } else if(c<0xd800 || c>=0xe000) {
+                int lead=c>>12;
+                uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+                if(twoBits<=1) {
+                    // All 64 code points with the same bits 15..6
+                    // are either in the set or not.
+                    if(twoBits==0) {
+                        break;
+                    }
+                } else {
+                    // Look up the code point in its 4k block of code points.
+                    if(!containsSlow(c, list4kStarts[lead], list4kStarts[lead+1])) {
+                        break;
+                    }
+                }
+            } else if(c>=0xdc00 || (s+1)==limit || (c2=s[1])<0xdc00 || c2>=0xe000) {
+                // surrogate code point
+                if(!containsSlow(c, list4kStarts[0xd], list4kStarts[0xe])) {
+                    break;
+                }
+            } else {
+                // surrogate pair
+                if(!containsSlow(U16_GET_SUPPLEMENTARY(c, c2), list4kStarts[0x10], list4kStarts[0x11])) {
+                    break;
+                }
+                ++s;
+            }
+        } while(++s<limit);
+    } else {
+        // span not
+        do {
+            c=*s;
+            if(c<=0xff) {
+                if(latin1Contains[c]) {
+                    break;
+                }
+            } else if(c<=0x7ff) {
+                if ((table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) != 0) {
+                    break;
+                }
+            } else if(c<0xd800 || c>=0xe000) {
+                int lead=c>>12;
+                uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+                if(twoBits<=1) {
+                    // All 64 code points with the same bits 15..6
+                    // are either in the set or not.
+                    if(twoBits!=0) {
+                        break;
+                    }
+                } else {
+                    // Look up the code point in its 4k block of code points.
+                    if(containsSlow(c, list4kStarts[lead], list4kStarts[lead+1])) {
+                        break;
+                    }
+                }
+            } else if(c>=0xdc00 || (s+1)==limit || (c2=s[1])<0xdc00 || c2>=0xe000) {
+                // surrogate code point
+                if(containsSlow(c, list4kStarts[0xd], list4kStarts[0xe])) {
+                    break;
+                }
+            } else {
+                // surrogate pair
+                if(containsSlow(U16_GET_SUPPLEMENTARY(c, c2), list4kStarts[0x10], list4kStarts[0x11])) {
+                    break;
+                }
+                ++s;
+            }
+        } while(++s<limit);
+    }
+    return s;
+}
+
+/* Symmetrical with span(). */
+const char16_t *
+BMPSet::spanBack(const char16_t *s, const char16_t *limit, USetSpanCondition spanCondition) const {
+    char16_t c, c2;
+
+    if(spanCondition) {
+        // span
+        for(;;) {
+            c=*(--limit);
+            if(c<=0xff) {
+                if(!latin1Contains[c]) {
+                    break;
+                }
+            } else if(c<=0x7ff) {
+                if ((table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) == 0) {
+                    break;
+                }
+            } else if(c<0xd800 || c>=0xe000) {
+                int lead=c>>12;
+                uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+                if(twoBits<=1) {
+                    // All 64 code points with the same bits 15..6
+                    // are either in the set or not.
+                    if(twoBits==0) {
+                        break;
+                    }
+                } else {
+                    // Look up the code point in its 4k block of code points.
+                    if(!containsSlow(c, list4kStarts[lead], list4kStarts[lead+1])) {
+                        break;
+                    }
+                }
+            } else if(c<0xdc00 || s==limit || (c2=*(limit-1))<0xd800 || c2>=0xdc00) {
+                // surrogate code point
+                if(!containsSlow(c, list4kStarts[0xd], list4kStarts[0xe])) {
+                    break;
+                }
+            } else {
+                // surrogate pair
+                if(!containsSlow(U16_GET_SUPPLEMENTARY(c2, c), list4kStarts[0x10], list4kStarts[0x11])) {
+                    break;
+                }
+                --limit;
+            }
+            if(s==limit) {
+                return s;
+            }
+        }
+    } else {
+        // span not
+        for(;;) {
+            c=*(--limit);
+            if(c<=0xff) {
+                if(latin1Contains[c]) {
+                    break;
+                }
+            } else if(c<=0x7ff) {
+                if ((table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) != 0) {
+                    break;
+                }
+            } else if(c<0xd800 || c>=0xe000) {
+                int lead=c>>12;
+                uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+                if(twoBits<=1) {
+                    // All 64 code points with the same bits 15..6
+                    // are either in the set or not.
+                    if(twoBits!=0) {
+                        break;
+                    }
+                } else {
+                    // Look up the code point in its 4k block of code points.
+                    if(containsSlow(c, list4kStarts[lead], list4kStarts[lead+1])) {
+                        break;
+                    }
+                }
+            } else if(c<0xdc00 || s==limit || (c2=*(limit-1))<0xd800 || c2>=0xdc00) {
+                // surrogate code point
+                if(containsSlow(c, list4kStarts[0xd], list4kStarts[0xe])) {
+                    break;
+                }
+            } else {
+                // surrogate pair
+                if(containsSlow(U16_GET_SUPPLEMENTARY(c2, c), list4kStarts[0x10], list4kStarts[0x11])) {
+                    break;
+                }
+                --limit;
+            }
+            if(s==limit) {
+                return s;
+            }
+        }
+    }
+    return limit+1;
+}
+
+/*
+ * Precheck for sufficient trail bytes at end of string only once per span.
+ * Check validity.
+ */
+const uint8_t *
+BMPSet::spanUTF8(const uint8_t *s, int32_t length, USetSpanCondition spanCondition) const {
+    const uint8_t *limit=s+length;
+    uint8_t b=*s;
+    if(U8_IS_SINGLE(b)) {
+        // Initial all-ASCII span.
+        if(spanCondition) {
+            do {
+                if(!latin1Contains[b] || ++s==limit) {
+                    return s;
+                }
+                b=*s;
+            } while(U8_IS_SINGLE(b));
+        } else {
+            do {
+                if(latin1Contains[b] || ++s==limit) {
+                    return s;
+                }
+                b=*s;
+            } while(U8_IS_SINGLE(b));
+        }
+        length = static_cast<int32_t>(limit - s);
+    }
+
+    if(spanCondition!=USET_SPAN_NOT_CONTAINED) {
+        spanCondition=USET_SPAN_CONTAINED;  // Pin to 0/1 values.
+    }
+
+    const uint8_t *limit0=limit;
+
+    /*
+     * Make sure that the last 1/2/3/4-byte sequence before limit is complete
+     * or runs into a lead byte.
+     * In the span loop compare s with limit only once
+     * per multi-byte character.
+     *
+     * Give a trailing illegal sequence the same value as the result of contains(FFFD),
+     * including it if that is part of the span, otherwise set limit0 to before
+     * the truncated sequence.
+     */
+    b=*(limit-1);
+    if (static_cast<int8_t>(b) < 0) {
+        // b>=0x80: lead or trail byte
+        if(b<0xc0) {
+            // single trail byte, check for preceding 3- or 4-byte lead byte
+            if(length>=2 && (b=*(limit-2))>=0xe0) {
+                limit-=2;
+                if(containsFFFD!=spanCondition) {
+                    limit0=limit;
+                }
+            } else if(b<0xc0 && b>=0x80 && length>=3 && (b=*(limit-3))>=0xf0) {
+                // 4-byte lead byte with only two trail bytes
+                limit-=3;
+                if(containsFFFD!=spanCondition) {
+                    limit0=limit;
+                }
+            }
+        } else {
+            // lead byte with no trail bytes
+            --limit;
+            if(containsFFFD!=spanCondition) {
+                limit0=limit;
+            }
+        }
+    }
+
+    uint8_t t1, t2, t3;
+
+    while(s<limit) {
+        b=*s;
+        if(U8_IS_SINGLE(b)) {
+            // ASCII
+            if(spanCondition) {
+                do {
+                    if(!latin1Contains[b]) {
+                        return s;
+                    } else if(++s==limit) {
+                        return limit0;
+                    }
+                    b=*s;
+                } while(U8_IS_SINGLE(b));
+            } else {
+                do {
+                    if(latin1Contains[b]) {
+                        return s;
+                    } else if(++s==limit) {
+                        return limit0;
+                    }
+                    b=*s;
+                } while(U8_IS_SINGLE(b));
+            }
+        }
+        ++s;  // Advance past the lead byte.
+        if(b>=0xe0) {
+            if(b<0xf0) {
+                if( /* handle U+0000..U+FFFF inline */
+                    (t1 = static_cast<uint8_t>(s[0] - 0x80)) <= 0x3f &&
+                    (t2 = static_cast<uint8_t>(s[1] - 0x80)) <= 0x3f
+                ) {
+                    b&=0xf;
+                    uint32_t twoBits=(bmpBlockBits[t1]>>b)&0x10001;
+                    if(twoBits<=1) {
+                        // All 64 code points with this lead byte and middle trail byte
+                        // are either in the set or not.
+                        if (twoBits != static_cast<uint32_t>(spanCondition)) {
+                            return s-1;
+                        }
+                    } else {
+                        // Look up the code point in its 4k block of code points.
+                        UChar32 c=(b<<12)|(t1<<6)|t2;
+                        if(containsSlow(c, list4kStarts[b], list4kStarts[b+1]) != spanCondition) {
+                            return s-1;
+                        }
+                    }
+                    s+=2;
+                    continue;
+                }
+            } else if( /* handle U+10000..U+10FFFF inline */
+                (t1 = static_cast<uint8_t>(s[0] - 0x80)) <= 0x3f &&
+                (t2 = static_cast<uint8_t>(s[1] - 0x80)) <= 0x3f &&
+                (t3 = static_cast<uint8_t>(s[2] - 0x80)) <= 0x3f
+            ) {
+                // Give an illegal sequence the same value as the result of contains(FFFD).
+                UChar32 c = (static_cast<UChar32>(b - 0xf0) << 18) | (static_cast<UChar32>(t1) << 12) | (t2 << 6) | t3;
+                if( (   (0x10000<=c && c<=0x10ffff) ?
+                            containsSlow(c, list4kStarts[0x10], list4kStarts[0x11]) :
+                            containsFFFD
+                    ) != spanCondition
+                ) {
+                    return s-1;
+                }
+                s+=3;
+                continue;
+            }
+        } else {
+            if( /* handle U+0000..U+07FF inline */
+                b>=0xc0 &&
+                (t1 = static_cast<uint8_t>(*s - 0x80)) <= 0x3f
+            ) {
+                if (static_cast<USetSpanCondition>((table7FF[t1] & (static_cast<uint32_t>(1) << (b & 0x1f))) != 0) != spanCondition) {
+                    return s-1;
+                }
+                ++s;
+                continue;
+            }
+        }
+
+        // Give an illegal sequence the same value as the result of contains(FFFD).
+        // Handle each byte of an illegal sequence separately to simplify the code;
+        // no need to optimize error handling.
+        if(containsFFFD!=spanCondition) {
+            return s-1;
+        }
+    }
+
+    return limit0;
+}
+
+/*
+ * While going backwards through UTF-8 optimize only for ASCII.
+ * Unlike UTF-16, UTF-8 is not forward-backward symmetrical, that is, it is not
+ * possible to tell from the last byte in a multi-byte sequence how many
+ * preceding bytes there should be. Therefore, going backwards through UTF-8
+ * is much harder than going forward.
+ */
+int32_t
+BMPSet::spanBackUTF8(const uint8_t *s, int32_t length, USetSpanCondition spanCondition) const {
+    if(spanCondition!=USET_SPAN_NOT_CONTAINED) {
+        spanCondition=USET_SPAN_CONTAINED;  // Pin to 0/1 values.
+    }
+
+    uint8_t b;
+
+    do {
+        b=s[--length];
+        if(U8_IS_SINGLE(b)) {
+            // ASCII sub-span
+            if(spanCondition) {
+                do {
+                    if(!latin1Contains[b]) {
+                        return length+1;
+                    } else if(length==0) {
+                        return 0;
+                    }
+                    b=s[--length];
+                } while(U8_IS_SINGLE(b));
+            } else {
+                do {
+                    if(latin1Contains[b]) {
+                        return length+1;
+                    } else if(length==0) {
+                        return 0;
+                    }
+                    b=s[--length];
+                } while(U8_IS_SINGLE(b));
+            }
+        }
+
+        int32_t prev=length;
+        UChar32 c;
+        // trail byte: collect a multi-byte character
+        // (or  lead byte in last-trail position)
+        c=utf8_prevCharSafeBody(s, 0, &length, b, -3);
+        // c is a valid code point, not ASCII, not a surrogate
+        if(c<=0x7ff) {
+            if (static_cast<USetSpanCondition>((table7FF[c & 0x3f] & (static_cast<uint32_t>(1) << (c >> 6))) != 0) != spanCondition) {
+                return prev+1;
+            }
+        } else if(c<=0xffff) {
+            int lead=c>>12;
+            uint32_t twoBits=(bmpBlockBits[(c>>6)&0x3f]>>lead)&0x10001;
+            if(twoBits<=1) {
+                // All 64 code points with the same bits 15..6
+                // are either in the set or not.
+                if (twoBits != static_cast<uint32_t>(spanCondition)) {
+                    return prev+1;
+                }
+            } else {
+                // Look up the code point in its 4k block of code points.
+                if(containsSlow(c, list4kStarts[lead], list4kStarts[lead+1]) != spanCondition) {
+                    return prev+1;
+                }
+            }
+        } else {
+            if(containsSlow(c, list4kStarts[0x10], list4kStarts[0x11]) != spanCondition) {
+                return prev+1;
+            }
+        }
+    } while(length>0);
+    return 0;
+}
+
+U_NAMESPACE_END