1 // © 2016 and later: Unicode, Inc. and others. 2 // License & terms of use: http://www.unicode.org/copyright.html 3 /* 4 ******************************************************************************* 5 * Copyright (C) 2012-2014, International Business Machines 6 * Corporation and others. All Rights Reserved. 7 ******************************************************************************* 8 * collationfcd.h 9 * 10 * created on: 2012aug18 11 * created by: Markus W. Scherer 12 */ 13 14 #ifndef __COLLATIONFCD_H__ 15 #define __COLLATIONFCD_H__ 16 17 #include "unicode/utypes.h" 18 19 #if !UCONFIG_NO_COLLATION 20 21 #include "unicode/utf16.h" 22 23 U_NAMESPACE_BEGIN 24 25 /** 26 * Data and functions for the FCD check fast path. 27 * 28 * The fast path looks at a pair of 16-bit code units and checks 29 * whether there is an FCD boundary between them; 30 * there is if the first unit has a trailing ccc=0 (!hasTccc(first)) 31 * or the second unit has a leading ccc=0 (!hasLccc(second)), 32 * or both. 33 * When the fast path finds a possible non-boundary, 34 * then the FCD check slow path looks at the actual sequence of FCD values. 35 * 36 * This is a pure optimization. 37 * The fast path must at least find all possible non-boundaries. 38 * If the fast path is too pessimistic, it costs performance. 39 * 40 * For a pair of BMP characters, the fast path tests are precise (1 bit per character). 41 * 42 * For a supplementary code point, the two units are its lead and trail surrogates. 43 * We set hasTccc(lead)=true if any of its 1024 associated supplementary code points 44 * has lccc!=0 or tccc!=0. 45 * We set hasLccc(trail)=true for all trail surrogates. 46 * As a result, we leave the fast path if the lead surrogate might start a 47 * supplementary code point that is not FCD-inert. 48 * (So the fast path need not detect that there is a surrogate pair, 49 * nor look ahead to the next full code point.) 50 * 51 * hasLccc(lead)=true if any of its 1024 associated supplementary code points 52 * has lccc!=0, for fast boundary checking between BMP & supplementary. 53 * 54 * hasTccc(trail)=false: 55 * It should only be tested for unpaired trail surrogates which are FCD-inert. 56 */ 57 class U_I18N_API CollationFCD { 58 public: hasLccc(UChar32 c)59 static inline UBool hasLccc(UChar32 c) { 60 // assert c <= 0xffff 61 // c can be negative, e.g., U_SENTINEL from UCharIterator; 62 // that is handled in the first test. 63 int32_t i; 64 return 65 // U+0300 is the first character with lccc!=0. 66 c >= 0x300 && 67 (i = lcccIndex[c >> 5]) != 0 && 68 (lcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0; 69 } 70 hasTccc(UChar32 c)71 static inline UBool hasTccc(UChar32 c) { 72 // assert c <= 0xffff 73 // c can be negative, e.g., U_SENTINEL from UCharIterator; 74 // that is handled in the first test. 75 int32_t i; 76 return 77 // U+00C0 is the first character with tccc!=0. 78 c >= 0xc0 && 79 (i = tcccIndex[c >> 5]) != 0 && 80 (tcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0; 81 } 82 mayHaveLccc(UChar32 c)83 static inline UBool mayHaveLccc(UChar32 c) { 84 // Handles all of Unicode 0..10FFFF. 85 // c can be negative, e.g., U_SENTINEL. 86 // U+0300 is the first character with lccc!=0. 87 if(c < 0x300) { return false; } 88 if(c > 0xffff) { c = U16_LEAD(c); } 89 int32_t i; 90 return 91 (i = lcccIndex[c >> 5]) != 0 && 92 (lcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0; 93 } 94 95 /** 96 * Tibetan composite vowel signs (U+0F73, U+0F75, U+0F81) 97 * must be decomposed before reaching the core collation code, 98 * or else some sequences including them, even ones passing the FCD check, 99 * do not yield canonically equivalent results. 100 * 101 * This is a fast and imprecise test. 102 * 103 * @param c a code point 104 * @return true if c is U+0F73, U+0F75 or U+0F81 or one of several other Tibetan characters 105 */ maybeTibetanCompositeVowel(UChar32 c)106 static inline UBool maybeTibetanCompositeVowel(UChar32 c) { 107 return (c & 0x1fff01) == 0xf01; 108 } 109 110 /** 111 * Tibetan composite vowel signs (U+0F73, U+0F75, U+0F81) 112 * must be decomposed before reaching the core collation code, 113 * or else some sequences including them, even ones passing the FCD check, 114 * do not yield canonically equivalent results. 115 * 116 * They have distinct lccc/tccc combinations: 129/130 or 129/132. 117 * 118 * @param fcd16 the FCD value (lccc/tccc combination) of a code point 119 * @return true if fcd16 is from U+0F73, U+0F75 or U+0F81 120 */ isFCD16OfTibetanCompositeVowel(uint16_t fcd16)121 static inline UBool isFCD16OfTibetanCompositeVowel(uint16_t fcd16) { 122 return fcd16 == 0x8182 || fcd16 == 0x8184; 123 } 124 125 private: 126 CollationFCD(); // No instantiation. 127 128 static const uint8_t lcccIndex[2048]; 129 static const uint8_t tcccIndex[2048]; 130 static const uint32_t lcccBits[]; 131 static const uint32_t tcccBits[]; 132 }; 133 134 U_NAMESPACE_END 135 136 #endif // !UCONFIG_NO_COLLATION 137 #endif // __COLLATIONFCD_H__ 138