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
23U_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 */
57class U_I18N_API CollationFCD {
58public:
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
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
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 */
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 */
121 static inline UBool isFCD16OfTibetanCompositeVowel(uint16_t fcd16) {
122 return fcd16 == 0x8182 || fcd16 == 0x8184;
123 }
124
125private:
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
134U_NAMESPACE_END
135
136#endif // !UCONFIG_NO_COLLATION
137#endif // __COLLATIONFCD_H__
138