136 lines
4.7 KiB
C++
136 lines
4.7 KiB
C++
/*
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*******************************************************************************
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* Copyright (C) 2012-2014, International Business Machines
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* Corporation and others. All Rights Reserved.
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*******************************************************************************
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* collationfcd.h
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*
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* created on: 2012aug18
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* created by: Markus W. Scherer
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*/
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#ifndef __COLLATIONFCD_H__
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#define __COLLATIONFCD_H__
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#include "unicode/utypes.h"
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#if !UCONFIG_NO_COLLATION
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#include "unicode/utf16.h"
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U_NAMESPACE_BEGIN
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/**
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* Data and functions for the FCD check fast path.
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*
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* The fast path looks at a pair of 16-bit code units and checks
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* whether there is an FCD boundary between them;
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* there is if the first unit has a trailing ccc=0 (!hasTccc(first))
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* or the second unit has a leading ccc=0 (!hasLccc(second)),
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* or both.
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* When the fast path finds a possible non-boundary,
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* then the FCD check slow path looks at the actual sequence of FCD values.
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*
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* This is a pure optimization.
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* The fast path must at least find all possible non-boundaries.
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* If the fast path is too pessimistic, it costs performance.
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*
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* For a pair of BMP characters, the fast path tests are precise (1 bit per character).
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*
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* For a supplementary code point, the two units are its lead and trail surrogates.
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* We set hasTccc(lead)=true if any of its 1024 associated supplementary code points
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* has lccc!=0 or tccc!=0.
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* We set hasLccc(trail)=true for all trail surrogates.
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* As a result, we leave the fast path if the lead surrogate might start a
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* supplementary code point that is not FCD-inert.
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* (So the fast path need not detect that there is a surrogate pair,
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* nor look ahead to the next full code point.)
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*
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* hasLccc(lead)=true if any of its 1024 associated supplementary code points
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* has lccc!=0, for fast boundary checking between BMP & supplementary.
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*
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* hasTccc(trail)=false:
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* It should only be tested for unpaired trail surrogates which are FCD-inert.
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*/
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class U_I18N_API CollationFCD {
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public:
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static inline UBool hasLccc(UChar32 c) {
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// assert c <= 0xffff
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// c can be negative, e.g., U_SENTINEL from UCharIterator;
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// that is handled in the first test.
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int32_t i;
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return
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// U+0300 is the first character with lccc!=0.
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c >= 0x300 &&
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(i = lcccIndex[c >> 5]) != 0 &&
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(lcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0;
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}
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static inline UBool hasTccc(UChar32 c) {
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// assert c <= 0xffff
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// c can be negative, e.g., U_SENTINEL from UCharIterator;
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// that is handled in the first test.
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int32_t i;
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return
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// U+00C0 is the first character with tccc!=0.
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c >= 0xc0 &&
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(i = tcccIndex[c >> 5]) != 0 &&
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(tcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0;
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}
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static inline UBool mayHaveLccc(UChar32 c) {
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// Handles all of Unicode 0..10FFFF.
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// c can be negative, e.g., U_SENTINEL.
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// U+0300 is the first character with lccc!=0.
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if(c < 0x300) { return FALSE; }
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if(c > 0xffff) { c = U16_LEAD(c); }
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int32_t i;
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return
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(i = lcccIndex[c >> 5]) != 0 &&
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(lcccBits[i] & ((uint32_t)1 << (c & 0x1f))) != 0;
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}
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/**
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* Tibetan composite vowel signs (U+0F73, U+0F75, U+0F81)
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* must be decomposed before reaching the core collation code,
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* or else some sequences including them, even ones passing the FCD check,
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* do not yield canonically equivalent results.
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*
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* This is a fast and imprecise test.
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*
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* @param c a code point
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* @return TRUE if c is U+0F73, U+0F75 or U+0F81 or one of several other Tibetan characters
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*/
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static inline UBool maybeTibetanCompositeVowel(UChar32 c) {
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return (c & 0x1fff01) == 0xf01;
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}
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/**
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* Tibetan composite vowel signs (U+0F73, U+0F75, U+0F81)
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* must be decomposed before reaching the core collation code,
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* or else some sequences including them, even ones passing the FCD check,
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* do not yield canonically equivalent results.
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*
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* They have distinct lccc/tccc combinations: 129/130 or 129/132.
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*
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* @param fcd16 the FCD value (lccc/tccc combination) of a code point
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* @return TRUE if fcd16 is from U+0F73, U+0F75 or U+0F81
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*/
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static inline UBool isFCD16OfTibetanCompositeVowel(uint16_t fcd16) {
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return fcd16 == 0x8182 || fcd16 == 0x8184;
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}
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private:
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CollationFCD(); // No instantiation.
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static const uint8_t lcccIndex[2048];
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static const uint8_t tcccIndex[2048];
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static const uint32_t lcccBits[];
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static const uint32_t tcccBits[];
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};
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U_NAMESPACE_END
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#endif // !UCONFIG_NO_COLLATION
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#endif // __COLLATIONFCD_H__
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