Retro68/gcc/libgo/go/unicode/letter.go

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2012-03-27 23:13:14 +00:00
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package unicode provides data and functions to test some properties of
// Unicode code points.
package unicode
const (
MaxRune = '\U0010FFFF' // Maximum valid Unicode code point.
ReplacementChar = '\uFFFD' // Represents invalid code points.
MaxASCII = '\u007F' // maximum ASCII value.
MaxLatin1 = '\u00FF' // maximum Latin-1 value.
)
// RangeTable defines a set of Unicode code points by listing the ranges of
// code points within the set. The ranges are listed in two slices
// to save space: a slice of 16-bit ranges and a slice of 32-bit ranges.
// The two slices must be in sorted order and non-overlapping.
// Also, R32 should contain only values >= 0x10000 (1<<16).
type RangeTable struct {
R16 []Range16
R32 []Range32
}
// Range16 represents of a range of 16-bit Unicode code points. The range runs from Lo to Hi
// inclusive and has the specified stride.
type Range16 struct {
Lo uint16
Hi uint16
Stride uint16
}
// Range32 represents of a range of Unicode code points and is used when one or
// more of the values will not fit in 16 bits. The range runs from Lo to Hi
// inclusive and has the specified stride. Lo and Hi must always be >= 1<<16.
type Range32 struct {
Lo uint32
Hi uint32
Stride uint32
}
// CaseRange represents a range of Unicode code points for simple (one
// code point to one code point) case conversion.
// The range runs from Lo to Hi inclusive, with a fixed stride of 1. Deltas
// are the number to add to the code point to reach the code point for a
// different case for that character. They may be negative. If zero, it
// means the character is in the corresponding case. There is a special
// case representing sequences of alternating corresponding Upper and Lower
// pairs. It appears with a fixed Delta of
// {UpperLower, UpperLower, UpperLower}
// The constant UpperLower has an otherwise impossible delta value.
type CaseRange struct {
Lo uint32
Hi uint32
Delta d
}
// SpecialCase represents language-specific case mappings such as Turkish.
// Methods of SpecialCase customize (by overriding) the standard mappings.
type SpecialCase []CaseRange
// BUG(r): There is no mechanism for full case folding, that is, for
// characters that involve multiple runes in the input or output.
// Indices into the Delta arrays inside CaseRanges for case mapping.
const (
UpperCase = iota
LowerCase
TitleCase
MaxCase
)
type d [MaxCase]rune // to make the CaseRanges text shorter
// If the Delta field of a CaseRange is UpperLower or LowerUpper, it means
// this CaseRange represents a sequence of the form (say)
// Upper Lower Upper Lower.
const (
UpperLower = MaxRune + 1 // (Cannot be a valid delta.)
)
// is16 uses binary search to test whether rune is in the specified slice of 16-bit ranges.
func is16(ranges []Range16, r uint16) bool {
// binary search over ranges
lo := 0
hi := len(ranges)
for lo < hi {
m := lo + (hi-lo)/2
range_ := ranges[m]
if range_.Lo <= r && r <= range_.Hi {
return (r-range_.Lo)%range_.Stride == 0
}
if r < range_.Lo {
hi = m
} else {
lo = m + 1
}
}
return false
}
// is32 uses binary search to test whether rune is in the specified slice of 32-bit ranges.
func is32(ranges []Range32, r uint32) bool {
// binary search over ranges
lo := 0
hi := len(ranges)
for lo < hi {
m := lo + (hi-lo)/2
range_ := ranges[m]
if range_.Lo <= r && r <= range_.Hi {
return (r-range_.Lo)%range_.Stride == 0
}
if r < range_.Lo {
hi = m
} else {
lo = m + 1
}
}
return false
}
// Is tests whether rune is in the specified table of ranges.
func Is(rangeTab *RangeTable, r rune) bool {
// common case: rune is ASCII or Latin-1.
if uint32(r) <= MaxLatin1 {
// Only need to check R16, since R32 is always >= 1<<16.
r16 := uint16(r)
for _, r := range rangeTab.R16 {
if r16 > r.Hi {
continue
}
if r16 < r.Lo {
return false
}
return (r16-r.Lo)%r.Stride == 0
}
return false
}
r16 := rangeTab.R16
if len(r16) > 0 && r <= rune(r16[len(r16)-1].Hi) {
return is16(r16, uint16(r))
}
r32 := rangeTab.R32
if len(r32) > 0 && r >= rune(r32[0].Lo) {
return is32(r32, uint32(r))
}
return false
}
// IsUpper reports whether the rune is an upper case letter.
func IsUpper(r rune) bool {
// See comment in IsGraphic.
if uint32(r) <= MaxLatin1 {
return properties[uint8(r)]&pLu != 0
}
return Is(Upper, r)
}
// IsLower reports whether the rune is a lower case letter.
func IsLower(r rune) bool {
// See comment in IsGraphic.
if uint32(r) <= MaxLatin1 {
return properties[uint8(r)]&pLl != 0
}
return Is(Lower, r)
}
// IsTitle reports whether the rune is a title case letter.
func IsTitle(r rune) bool {
if r <= MaxLatin1 {
return false
}
return Is(Title, r)
}
// to maps the rune using the specified case mapping.
func to(_case int, r rune, caseRange []CaseRange) rune {
if _case < 0 || MaxCase <= _case {
return ReplacementChar // as reasonable an error as any
}
// binary search over ranges
lo := 0
hi := len(caseRange)
for lo < hi {
m := lo + (hi-lo)/2
cr := caseRange[m]
if rune(cr.Lo) <= r && r <= rune(cr.Hi) {
delta := rune(cr.Delta[_case])
if delta > MaxRune {
// In an Upper-Lower sequence, which always starts with
// an UpperCase letter, the real deltas always look like:
// {0, 1, 0} UpperCase (Lower is next)
// {-1, 0, -1} LowerCase (Upper, Title are previous)
// The characters at even offsets from the beginning of the
// sequence are upper case; the ones at odd offsets are lower.
// The correct mapping can be done by clearing or setting the low
// bit in the sequence offset.
// The constants UpperCase and TitleCase are even while LowerCase
// is odd so we take the low bit from _case.
return rune(cr.Lo) + ((r-rune(cr.Lo))&^1 | rune(_case&1))
}
return r + delta
}
if r < rune(cr.Lo) {
hi = m
} else {
lo = m + 1
}
}
return r
}
// To maps the rune to the specified case: UpperCase, LowerCase, or TitleCase.
func To(_case int, r rune) rune {
return to(_case, r, CaseRanges)
}
// ToUpper maps the rune to upper case.
func ToUpper(r rune) rune {
if r <= MaxASCII {
if 'a' <= r && r <= 'z' {
r -= 'a' - 'A'
}
return r
}
return To(UpperCase, r)
}
// ToLower maps the rune to lower case.
func ToLower(r rune) rune {
if r <= MaxASCII {
if 'A' <= r && r <= 'Z' {
r += 'a' - 'A'
}
return r
}
return To(LowerCase, r)
}
// ToTitle maps the rune to title case.
func ToTitle(r rune) rune {
if r <= MaxASCII {
if 'a' <= r && r <= 'z' { // title case is upper case for ASCII
r -= 'a' - 'A'
}
return r
}
return To(TitleCase, r)
}
// ToUpper maps the rune to upper case giving priority to the special mapping.
func (special SpecialCase) ToUpper(r rune) rune {
r1 := to(UpperCase, r, []CaseRange(special))
if r1 == r {
r1 = ToUpper(r)
}
return r1
}
// ToTitle maps the rune to title case giving priority to the special mapping.
func (special SpecialCase) ToTitle(r rune) rune {
r1 := to(TitleCase, r, []CaseRange(special))
if r1 == r {
r1 = ToTitle(r)
}
return r1
}
// ToLower maps the rune to lower case giving priority to the special mapping.
func (special SpecialCase) ToLower(r rune) rune {
r1 := to(LowerCase, r, []CaseRange(special))
if r1 == r {
r1 = ToLower(r)
}
return r1
}
// caseOrbit is defined in tables.go as []foldPair. Right now all the
// entries fit in uint16, so use uint16. If that changes, compilation
// will fail (the constants in the composite literal will not fit in uint16)
// and the types here can change to uint32.
type foldPair struct {
From uint16
To uint16
}
// SimpleFold iterates over Unicode code points equivalent under
// the Unicode-defined simple case folding. Among the code points
// equivalent to rune (including rune itself), SimpleFold returns the
// smallest rune >= r if one exists, or else the smallest rune >= 0.
//
// For example:
// SimpleFold('A') = 'a'
// SimpleFold('a') = 'A'
//
// SimpleFold('K') = 'k'
// SimpleFold('k') = '\u212A' (Kelvin symbol, )
// SimpleFold('\u212A') = 'K'
//
// SimpleFold('1') = '1'
//
func SimpleFold(r rune) rune {
// Consult caseOrbit table for special cases.
lo := 0
hi := len(caseOrbit)
for lo < hi {
m := lo + (hi-lo)/2
if rune(caseOrbit[m].From) < r {
lo = m + 1
} else {
hi = m
}
}
if lo < len(caseOrbit) && rune(caseOrbit[lo].From) == r {
return rune(caseOrbit[lo].To)
}
// No folding specified. This is a one- or two-element
// equivalence class containing rune and ToLower(rune)
// and ToUpper(rune) if they are different from rune.
if l := ToLower(r); l != r {
return l
}
return ToUpper(r)
}