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// Copyright 2012 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 colltab
import (
"fmt"
"unicode"
)
// Level identifies the collation comparison level.
// The primary level corresponds to the basic sorting of text.
// The secondary level corresponds to accents and related linguistic elements.
// The tertiary level corresponds to casing and related concepts.
// The quaternary level is derived from the other levels by the
// various algorithms for handling variable elements.
type Level int
const (
Primary Level = iota
Secondary
Tertiary
Quaternary
Identity
NumLevels
)
const (
defaultSecondary = 0x20
defaultTertiary = 0x2
maxTertiary = 0x1F
MaxQuaternary = 0x1FFFFF // 21 bits.
)
// Elem is a representation of a collation element. This API provides ways to encode
// and decode Elems. Implementations of collation tables may use values greater
// or equal to PrivateUse for their own purposes. However, these should never be
// returned by AppendNext.
type Elem uint32
const (
maxCE Elem = 0xAFFFFFFF
PrivateUse = minContract
minContract = 0xC0000000
maxContract = 0xDFFFFFFF
minExpand = 0xE0000000
maxExpand = 0xEFFFFFFF
minDecomp = 0xF0000000
)
type ceType int
const (
ceNormal ceType = iota // ceNormal includes implicits (ce == 0)
ceContractionIndex // rune can be a start of a contraction
ceExpansionIndex // rune expands into a sequence of collation elements
ceDecompose // rune expands using NFKC decomposition
)
func (ce Elem) ctype() ceType {
if ce <= maxCE {
return ceNormal
}
if ce <= maxContract {
return ceContractionIndex
} else {
if ce <= maxExpand {
return ceExpansionIndex
}
return ceDecompose
}
panic("should not reach here")
return ceType(-1)
}
// For normal collation elements, we assume that a collation element either has
// a primary or non-default secondary value, not both.
// Collation elements with a primary value are of the form
// 01pppppp pppppppp ppppppp0 ssssssss
// - p* is primary collation value
// - s* is the secondary collation value
// 00pppppp pppppppp ppppppps sssttttt, where
// - p* is primary collation value
// - s* offset of secondary from default value.
// - t* is the tertiary collation value
// 100ttttt cccccccc pppppppp pppppppp
// - t* is the tertiar collation value
// - c* is the canonical combining class
// - p* is the primary collation value
// Collation elements with a secondary value are of the form
// 1010cccc ccccssss ssssssss tttttttt, where
// - c* is the canonical combining class
// - s* is the secondary collation value
// - t* is the tertiary collation value
// 11qqqqqq qqqqqqqq qqqqqqq0 00000000
// - q* quaternary value
const (
ceTypeMask = 0xC0000000
ceTypeMaskExt = 0xE0000000
ceIgnoreMask = 0xF00FFFFF
ceType1 = 0x40000000
ceType2 = 0x00000000
ceType3or4 = 0x80000000
ceType4 = 0xA0000000
ceTypeQ = 0xC0000000
Ignore = ceType4
firstNonPrimary = 0x80000000
lastSpecialPrimary = 0xA0000000
secondaryMask = 0x80000000
hasTertiaryMask = 0x40000000
primaryValueMask = 0x3FFFFE00
maxPrimaryBits = 21
compactPrimaryBits = 16
maxSecondaryBits = 12
maxTertiaryBits = 8
maxCCCBits = 8
maxSecondaryCompactBits = 8
maxSecondaryDiffBits = 4
maxTertiaryCompactBits = 5
primaryShift = 9
compactSecondaryShift = 5
minCompactSecondary = defaultSecondary - 4
)
func makeImplicitCE(primary int) Elem {
return ceType1 | Elem(primary<<primaryShift) | defaultSecondary
}
// MakeElem returns an Elem for the given values. It will return an error
// if the given combination of values is invalid.
func MakeElem(primary, secondary, tertiary int, ccc uint8) (Elem, error) {
if w := primary; w >= 1<<maxPrimaryBits || w < 0 {
return 0, fmt.Errorf("makeCE: primary weight out of bounds: %x >= %x", w, 1<<maxPrimaryBits)
}
if w := secondary; w >= 1<<maxSecondaryBits || w < 0 {
return 0, fmt.Errorf("makeCE: secondary weight out of bounds: %x >= %x", w, 1<<maxSecondaryBits)
}
if w := tertiary; w >= 1<<maxTertiaryBits || w < 0 {
return 0, fmt.Errorf("makeCE: tertiary weight out of bounds: %x >= %x", w, 1<<maxTertiaryBits)
}
ce := Elem(0)
if primary != 0 {
if ccc != 0 {
if primary >= 1<<compactPrimaryBits {
return 0, fmt.Errorf("makeCE: primary weight with non-zero CCC out of bounds: %x >= %x", primary, 1<<compactPrimaryBits)
}
if secondary != defaultSecondary {
return 0, fmt.Errorf("makeCE: cannot combine non-default secondary value (%x) with non-zero CCC (%x)", secondary, ccc)
}
ce = Elem(tertiary << (compactPrimaryBits + maxCCCBits))
ce |= Elem(ccc) << compactPrimaryBits
ce |= Elem(primary)
ce |= ceType3or4
} else if tertiary == defaultTertiary {
if secondary >= 1<<maxSecondaryCompactBits {
return 0, fmt.Errorf("makeCE: secondary weight with non-zero primary out of bounds: %x >= %x", secondary, 1<<maxSecondaryCompactBits)
}
ce = Elem(primary<<(maxSecondaryCompactBits+1) + secondary)
ce |= ceType1
} else {
d := secondary - defaultSecondary + maxSecondaryDiffBits
if d >= 1<<maxSecondaryDiffBits || d < 0 {
return 0, fmt.Errorf("makeCE: secondary weight diff out of bounds: %x < 0 || %x > %x", d, d, 1<<maxSecondaryDiffBits)
}
if tertiary >= 1<<maxTertiaryCompactBits {
return 0, fmt.Errorf("makeCE: tertiary weight with non-zero primary out of bounds: %x > %x", tertiary, 1<<maxTertiaryCompactBits)
}
ce = Elem(primary<<maxSecondaryDiffBits + d)
ce = ce<<maxTertiaryCompactBits + Elem(tertiary)
}
} else {
ce = Elem(secondary<<maxTertiaryBits + tertiary)
ce += Elem(ccc) << (maxSecondaryBits + maxTertiaryBits)
ce |= ceType4
}
return ce, nil
}
// MakeQuaternary returns an Elem with the given quaternary value.
func MakeQuaternary(v int) Elem {
return ceTypeQ | Elem(v<<primaryShift)
}
// Mask sets weights for any level smaller than l to 0.
// The resulting Elem can be used to test for equality with
// other Elems to which the same mask has been applied.
func (ce Elem) Mask(l Level) uint32 {
return 0
}
// CCC returns the canonical combining class associated with the underlying character,
// if applicable, or 0 otherwise.
func (ce Elem) CCC() uint8 {
if ce&ceType3or4 != 0 {
if ce&ceType4 == ceType3or4 {
return uint8(ce >> 16)
}
return uint8(ce >> 20)
}
return 0
}
// Primary returns the primary collation weight for ce.
func (ce Elem) Primary() int {
if ce >= firstNonPrimary {
if ce > lastSpecialPrimary {
return 0
}
return int(uint16(ce))
}
return int(ce&primaryValueMask) >> primaryShift
}
// Secondary returns the secondary collation weight for ce.
func (ce Elem) Secondary() int {
switch ce & ceTypeMask {
case ceType1:
return int(uint8(ce))
case ceType2:
return minCompactSecondary + int((ce>>compactSecondaryShift)&0xF)
case ceType3or4:
if ce < ceType4 {
return defaultSecondary
}
return int(ce>>8) & 0xFFF
case ceTypeQ:
return 0
}
panic("should not reach here")
}
// Tertiary returns the tertiary collation weight for ce.
func (ce Elem) Tertiary() uint8 {
if ce&hasTertiaryMask == 0 {
if ce&ceType3or4 == 0 {
return uint8(ce & 0x1F)
}
if ce&ceType4 == ceType4 {
return uint8(ce)
}
return uint8(ce>>24) & 0x1F // type 2
} else if ce&ceTypeMask == ceType1 {
return defaultTertiary
}
// ce is a quaternary value.
return 0
}
func (ce Elem) updateTertiary(t uint8) Elem {
if ce&ceTypeMask == ceType1 {
// convert to type 4
nce := ce & primaryValueMask
nce |= Elem(uint8(ce)-minCompactSecondary) << compactSecondaryShift
ce = nce
} else if ce&ceTypeMaskExt == ceType3or4 {
ce &= ^Elem(maxTertiary << 24)
return ce | (Elem(t) << 24)
} else {
// type 2 or 4
ce &= ^Elem(maxTertiary)
}
return ce | Elem(t)
}
// Quaternary returns the quaternary value if explicitly specified,
// 0 if ce == Ignore, or MaxQuaternary otherwise.
// Quaternary values are used only for shifted variants.
func (ce Elem) Quaternary() int {
if ce&ceTypeMask == ceTypeQ {
return int(ce&primaryValueMask) >> primaryShift
} else if ce&ceIgnoreMask == Ignore {
return 0
}
return MaxQuaternary
}
// Weight returns the collation weight for the given level.
func (ce Elem) Weight(l Level) int {
switch l {
case Primary:
return ce.Primary()
case Secondary:
return ce.Secondary()
case Tertiary:
return int(ce.Tertiary())
case Quaternary:
return ce.Quaternary()
}
return 0 // return 0 (ignore) for undefined levels.
}
// For contractions, collation elements are of the form
// 110bbbbb bbbbbbbb iiiiiiii iiiinnnn, where
// - n* is the size of the first node in the contraction trie.
// - i* is the index of the first node in the contraction trie.
// - b* is the offset into the contraction collation element table.
// See contract.go for details on the contraction trie.
const (
maxNBits = 4
maxTrieIndexBits = 12
maxContractOffsetBits = 13
)
func splitContractIndex(ce Elem) (index, n, offset int) {
n = int(ce & (1<<maxNBits - 1))
ce >>= maxNBits
index = int(ce & (1<<maxTrieIndexBits - 1))
ce >>= maxTrieIndexBits
offset = int(ce & (1<<maxContractOffsetBits - 1))
return
}
// For expansions, Elems are of the form 11100000 00000000 bbbbbbbb bbbbbbbb,
// where b* is the index into the expansion sequence table.
const maxExpandIndexBits = 16
func splitExpandIndex(ce Elem) (index int) {
return int(uint16(ce))
}
// Some runes can be expanded using NFKD decomposition. Instead of storing the full
// sequence of collation elements, we decompose the rune and lookup the collation
// elements for each rune in the decomposition and modify the tertiary weights.
// The Elem, in this case, is of the form 11110000 00000000 wwwwwwww vvvvvvvv, where
// - v* is the replacement tertiary weight for the first rune,
// - w* is the replacement tertiary weight for the second rune,
// Tertiary weights of subsequent runes should be replaced with maxTertiary.
// See https://www.unicode.org/reports/tr10/#Compatibility_Decompositions for more details.
func splitDecompose(ce Elem) (t1, t2 uint8) {
return uint8(ce), uint8(ce >> 8)
}
const (
// These constants were taken from https://www.unicode.org/versions/Unicode6.0.0/ch12.pdf.
minUnified rune = 0x4E00
maxUnified = 0x9FFF
minCompatibility = 0xF900
maxCompatibility = 0xFAFF
minRare = 0x3400
maxRare = 0x4DBF
)
const (
commonUnifiedOffset = 0x10000
rareUnifiedOffset = 0x20000 // largest rune in common is U+FAFF
otherOffset = 0x50000 // largest rune in rare is U+2FA1D
illegalOffset = otherOffset + int(unicode.MaxRune)
maxPrimary = illegalOffset + 1
)
// implicitPrimary returns the primary weight for the a rune
// for which there is no entry for the rune in the collation table.
// We take a different approach from the one specified in
// https://unicode.org/reports/tr10/#Implicit_Weights,
// but preserve the resulting relative ordering of the runes.
func implicitPrimary(r rune) int {
if unicode.Is(unicode.Ideographic, r) {
if r >= minUnified && r <= maxUnified {
// The most common case for CJK.
return int(r) + commonUnifiedOffset
}
if r >= minCompatibility && r <= maxCompatibility {
// This will typically not hit. The DUCET explicitly specifies mappings
// for all characters that do not decompose.
return int(r) + commonUnifiedOffset
}
return int(r) + rareUnifiedOffset
}
return int(r) + otherOffset
}