Checking in vendor folder for ease of using go get.

vendor/golang.org/x/text/internal/colltab/collelem.go

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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 http://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 http://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
+// http://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
+}