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