327 lines
8.6 KiB
Go
327 lines
8.6 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package unicode provides data and functions to test some properties of
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// Unicode code points.
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package unicode
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const (
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MaxRune = 0x10FFFF // Maximum valid Unicode code point.
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ReplacementChar = 0xFFFD // Represents invalid code points.
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MaxASCII = 0x7F // maximum ASCII value.
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MaxLatin1 = 0xFF // maximum Latin-1 value.
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)
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// RangeTable defines a set of Unicode code points by listing the ranges of
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// code points within the set. The ranges are listed in two slices
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// to save space: a slice of 16-bit ranges and a slice of 32-bit ranges.
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// The two slices must be in sorted order and non-overlapping.
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// Also, R32 should contain only values >= 0x10000 (1<<16).
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type RangeTable struct {
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R16 []Range16
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R32 []Range32
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}
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// Range16 represents of a range of 16-bit Unicode code points. The range runs from Lo to Hi
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// inclusive and has the specified stride.
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type Range16 struct {
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Lo uint16
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Hi uint16
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Stride uint16
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}
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// Range32 represents of a range of Unicode code points and is used when one or
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// more of the values will not fit in 16 bits. The range runs from Lo to Hi
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// inclusive and has the specified stride. Lo and Hi must always be >= 1<<16.
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type Range32 struct {
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Lo uint32
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Hi uint32
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Stride uint32
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}
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// CaseRange represents a range of Unicode code points for simple (one
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// code point to one code point) case conversion.
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// The range runs from Lo to Hi inclusive, with a fixed stride of 1. Deltas
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// are the number to add to the code point to reach the code point for a
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// different case for that character. They may be negative. If zero, it
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// means the character is in the corresponding case. There is a special
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// case representing sequences of alternating corresponding Upper and Lower
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// pairs. It appears with a fixed Delta of
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// {UpperLower, UpperLower, UpperLower}
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// The constant UpperLower has an otherwise impossible delta value.
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type CaseRange struct {
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Lo uint32
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Hi uint32
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Delta d
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}
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// SpecialCase represents language-specific case mappings such as Turkish.
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// Methods of SpecialCase customize (by overriding) the standard mappings.
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type SpecialCase []CaseRange
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//BUG(r): Provide a mechanism for full case folding (those that involve
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// multiple runes in the input or output).
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// Indices into the Delta arrays inside CaseRanges for case mapping.
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const (
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UpperCase = iota
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LowerCase
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TitleCase
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MaxCase
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)
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type d [MaxCase]rune // to make the CaseRanges text shorter
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// If the Delta field of a CaseRange is UpperLower or LowerUpper, it means
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// this CaseRange represents a sequence of the form (say)
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// Upper Lower Upper Lower.
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const (
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UpperLower = MaxRune + 1 // (Cannot be a valid delta.)
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)
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// is16 uses binary search to test whether rune is in the specified slice of 16-bit ranges.
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func is16(ranges []Range16, r uint16) bool {
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// binary search over ranges
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lo := 0
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hi := len(ranges)
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for lo < hi {
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m := lo + (hi-lo)/2
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range_ := ranges[m]
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if range_.Lo <= r && r <= range_.Hi {
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return (r-range_.Lo)%range_.Stride == 0
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}
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if r < range_.Lo {
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hi = m
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} else {
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lo = m + 1
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}
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}
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return false
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}
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// is32 uses binary search to test whether rune is in the specified slice of 32-bit ranges.
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func is32(ranges []Range32, r uint32) bool {
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// binary search over ranges
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lo := 0
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hi := len(ranges)
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for lo < hi {
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m := lo + (hi-lo)/2
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range_ := ranges[m]
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if range_.Lo <= r && r <= range_.Hi {
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return (r-range_.Lo)%range_.Stride == 0
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}
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if r < range_.Lo {
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hi = m
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} else {
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lo = m + 1
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}
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}
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return false
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}
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// Is tests whether rune is in the specified table of ranges.
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func Is(rangeTab *RangeTable, r rune) bool {
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// common case: rune is ASCII or Latin-1.
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if uint32(r) <= MaxLatin1 {
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// Only need to check R16, since R32 is always >= 1<<16.
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r16 := uint16(r)
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for _, r := range rangeTab.R16 {
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if r16 > r.Hi {
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continue
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}
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if r16 < r.Lo {
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return false
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}
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return (r16-r.Lo)%r.Stride == 0
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}
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return false
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}
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r16 := rangeTab.R16
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if len(r16) > 0 && r <= rune(r16[len(r16)-1].Hi) {
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return is16(r16, uint16(r))
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}
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r32 := rangeTab.R32
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if len(r32) > 0 && r >= rune(r32[0].Lo) {
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return is32(r32, uint32(r))
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}
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return false
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}
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// IsUpper reports whether the rune is an upper case letter.
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func IsUpper(r rune) bool {
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// See comment in IsGraphic.
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if uint32(r) <= MaxLatin1 {
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return properties[uint8(r)]&pLu != 0
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}
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return Is(Upper, r)
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}
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// IsLower reports whether the rune is a lower case letter.
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func IsLower(r rune) bool {
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// See comment in IsGraphic.
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if uint32(r) <= MaxLatin1 {
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return properties[uint8(r)]&pLl != 0
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}
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return Is(Lower, r)
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}
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// IsTitle reports whether the rune is a title case letter.
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func IsTitle(r rune) bool {
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if r <= MaxLatin1 {
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return false
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}
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return Is(Title, r)
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}
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// to maps the rune using the specified case mapping.
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func to(_case int, r rune, caseRange []CaseRange) rune {
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if _case < 0 || MaxCase <= _case {
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return ReplacementChar // as reasonable an error as any
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}
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// binary search over ranges
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lo := 0
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hi := len(caseRange)
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for lo < hi {
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m := lo + (hi-lo)/2
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cr := caseRange[m]
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if rune(cr.Lo) <= r && r <= rune(cr.Hi) {
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delta := rune(cr.Delta[_case])
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if delta > MaxRune {
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// In an Upper-Lower sequence, which always starts with
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// an UpperCase letter, the real deltas always look like:
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// {0, 1, 0} UpperCase (Lower is next)
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// {-1, 0, -1} LowerCase (Upper, Title are previous)
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// The characters at even offsets from the beginning of the
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// sequence are upper case; the ones at odd offsets are lower.
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// The correct mapping can be done by clearing or setting the low
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// bit in the sequence offset.
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// The constants UpperCase and TitleCase are even while LowerCase
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// is odd so we take the low bit from _case.
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return rune(cr.Lo) + ((r-rune(cr.Lo))&^1 | rune(_case&1))
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}
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return r + delta
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}
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if r < rune(cr.Lo) {
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hi = m
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} else {
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lo = m + 1
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}
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}
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return r
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}
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// To maps the rune to the specified case: UpperCase, LowerCase, or TitleCase.
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func To(_case int, r rune) rune {
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return to(_case, r, CaseRanges)
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}
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// ToUpper maps the rune to upper case.
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func ToUpper(r rune) rune {
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if r <= MaxASCII {
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if 'a' <= r && r <= 'z' {
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r -= 'a' - 'A'
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}
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return r
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}
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return To(UpperCase, r)
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}
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// ToLower maps the rune to lower case.
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func ToLower(r rune) rune {
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if r <= MaxASCII {
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if 'A' <= r && r <= 'Z' {
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r += 'a' - 'A'
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}
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return r
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}
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return To(LowerCase, r)
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}
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// ToTitle maps the rune to title case.
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func ToTitle(r rune) rune {
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if r <= MaxASCII {
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if 'a' <= r && r <= 'z' { // title case is upper case for ASCII
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r -= 'a' - 'A'
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}
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return r
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}
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return To(TitleCase, r)
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}
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// ToUpper maps the rune to upper case giving priority to the special mapping.
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func (special SpecialCase) ToUpper(r rune) rune {
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r1 := to(UpperCase, r, []CaseRange(special))
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if r1 == r {
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r1 = ToUpper(r)
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}
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return r1
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}
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// ToTitle maps the rune to title case giving priority to the special mapping.
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func (special SpecialCase) ToTitle(r rune) rune {
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r1 := to(TitleCase, r, []CaseRange(special))
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if r1 == r {
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r1 = ToTitle(r)
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}
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return r1
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}
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// ToLower maps the rune to lower case giving priority to the special mapping.
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func (special SpecialCase) ToLower(r rune) rune {
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r1 := to(LowerCase, r, []CaseRange(special))
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if r1 == r {
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r1 = ToLower(r)
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}
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return r1
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}
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// caseOrbit is defined in tables.go as []foldPair. Right now all the
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// entries fit in uint16, so use uint16. If that changes, compilation
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// will fail (the constants in the composite literal will not fit in uint16)
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// and the types here can change to uint32.
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type foldPair struct {
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From uint16
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To uint16
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}
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// SimpleFold iterates over Unicode code points equivalent under
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// the Unicode-defined simple case folding. Among the code points
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// equivalent to rune (including rune itself), SimpleFold returns the
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// smallest r >= rune if one exists, or else the smallest r >= 0.
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//
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// For example:
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// SimpleFold('A') = 'a'
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// SimpleFold('a') = 'A'
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//
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// SimpleFold('K') = 'k'
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// SimpleFold('k') = '\u212A' (Kelvin symbol, K)
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// SimpleFold('\u212A') = 'K'
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//
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// SimpleFold('1') = '1'
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//
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func SimpleFold(r rune) rune {
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// Consult caseOrbit table for special cases.
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lo := 0
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hi := len(caseOrbit)
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for lo < hi {
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m := lo + (hi-lo)/2
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if rune(caseOrbit[m].From) < r {
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lo = m + 1
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} else {
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hi = m
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}
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}
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if lo < len(caseOrbit) && rune(caseOrbit[lo].From) == r {
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return rune(caseOrbit[lo].To)
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}
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// No folding specified. This is a one- or two-element
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// equivalence class containing rune and ToLower(rune)
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// and ToUpper(rune) if they are different from rune.
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if l := ToLower(r); l != r {
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return l
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}
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return ToUpper(r)
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}
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