/usr/share/gocode/src/golang.org/x/text/cases/gen_trieval.go is in golang-golang-x-text-dev 0.0~git20170627.0.6353ef0-1ubuntu2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 | // Copyright 2014 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.
// +build ignore
package main
// This file contains definitions for interpreting the trie value of the case
// trie generated by "go run gen*.go". It is shared by both the generator
// program and the resultant package. Sharing is achieved by the generator
// copying gen_trieval.go to trieval.go and changing what's above this comment.
// info holds case information for a single rune. It is the value returned
// by a trie lookup. Most mapping information can be stored in a single 16-bit
// value. If not, for example when a rune is mapped to multiple runes, the value
// stores some basic case data and an index into an array with additional data.
//
// The per-rune values have the following format:
//
// if (exception) {
// 15..5 unsigned exception index
// 4 unused
// } else {
// 15..8 XOR pattern or index to XOR pattern for case mapping
// Only 13..8 are used for XOR patterns.
// 7 inverseFold (fold to upper, not to lower)
// 6 index: interpret the XOR pattern as an index
// or isMid if case mode is cIgnorableUncased.
// 5..4 CCC: zero (normal or break), above or other
// }
// 3 exception: interpret this value as an exception index
// (TODO: is this bit necessary? Probably implied from case mode.)
// 2..0 case mode
//
// For the non-exceptional cases, a rune must be either uncased, lowercase or
// uppercase. If the rune is cased, the XOR pattern maps either a lowercase
// rune to uppercase or an uppercase rune to lowercase (applied to the 10
// least-significant bits of the rune).
//
// See the definitions below for a more detailed description of the various
// bits.
type info uint16
const (
casedMask = 0x0003
fullCasedMask = 0x0007
ignorableMask = 0x0006
ignorableValue = 0x0004
inverseFoldBit = 1 << 7
isMidBit = 1 << 6
exceptionBit = 1 << 3
exceptionShift = 5
numExceptionBits = 11
xorIndexBit = 1 << 6
xorShift = 8
// There is no mapping if all xor bits and the exception bit are zero.
hasMappingMask = 0xff80 | exceptionBit
)
// The case mode bits encodes the case type of a rune. This includes uncased,
// title, upper and lower case and case ignorable. (For a definition of these
// terms see Chapter 3 of The Unicode Standard Core Specification.) In some rare
// cases, a rune can be both cased and case-ignorable. This is encoded by
// cIgnorableCased. A rune of this type is always lower case. Some runes are
// cased while not having a mapping.
//
// A common pattern for scripts in the Unicode standard is for upper and lower
// case runes to alternate for increasing rune values (e.g. the accented Latin
// ranges starting from U+0100 and U+1E00 among others and some Cyrillic
// characters). We use this property by defining a cXORCase mode, where the case
// mode (always upper or lower case) is derived from the rune value. As the XOR
// pattern for case mappings is often identical for successive runes, using
// cXORCase can result in large series of identical trie values. This, in turn,
// allows us to better compress the trie blocks.
const (
cUncased info = iota // 000
cTitle // 001
cLower // 010
cUpper // 011
cIgnorableUncased // 100
cIgnorableCased // 101 // lower case if mappings exist
cXORCase // 11x // case is cLower | ((rune&1) ^ x)
maxCaseMode = cUpper
)
func (c info) isCased() bool {
return c&casedMask != 0
}
func (c info) isCaseIgnorable() bool {
return c&ignorableMask == ignorableValue
}
func (c info) isNotCasedAndNotCaseIgnorable() bool {
return c&fullCasedMask == 0
}
func (c info) isCaseIgnorableAndNotCased() bool {
return c&fullCasedMask == cIgnorableUncased
}
func (c info) isMid() bool {
return c&(fullCasedMask|isMidBit) == isMidBit|cIgnorableUncased
}
// The case mapping implementation will need to know about various Canonical
// Combining Class (CCC) values. We encode two of these in the trie value:
// cccZero (0) and cccAbove (230). If the value is cccOther, it means that
// CCC(r) > 0, but not 230. A value of cccBreak means that CCC(r) == 0 and that
// the rune also has the break category Break (see below).
const (
cccBreak info = iota << 4
cccZero
cccAbove
cccOther
cccMask = cccBreak | cccZero | cccAbove | cccOther
)
const (
starter = 0
above = 230
iotaSubscript = 240
)
// The exceptions slice holds data that does not fit in a normal info entry.
// The entry is pointed to by the exception index in an entry. It has the
// following format:
//
// Header
// byte 0:
// 7..6 unused
// 5..4 CCC type (same bits as entry)
// 3 unused
// 2..0 length of fold
//
// byte 1:
// 7..6 unused
// 5..3 length of 1st mapping of case type
// 2..0 length of 2nd mapping of case type
//
// case 1st 2nd
// lower -> upper, title
// upper -> lower, title
// title -> lower, upper
//
// Lengths with the value 0x7 indicate no value and implies no change.
// A length of 0 indicates a mapping to zero-length string.
//
// Body bytes:
// case folding bytes
// lowercase mapping bytes
// uppercase mapping bytes
// titlecase mapping bytes
// closure mapping bytes (for NFKC_Casefold). (TODO)
//
// Fallbacks:
// missing fold -> lower
// missing title -> upper
// all missing -> original rune
//
// exceptions starts with a dummy byte to enforce that there is no zero index
// value.
const (
lengthMask = 0x07
lengthBits = 3
noChange = 0
)
// References to generated trie.
var trie = newCaseTrie(0)
var sparse = sparseBlocks{
values: sparseValues[:],
offsets: sparseOffsets[:],
}
// Sparse block lookup code.
// valueRange is an entry in a sparse block.
type valueRange struct {
value uint16
lo, hi byte
}
type sparseBlocks struct {
values []valueRange
offsets []uint16
}
// lookup returns the value from values block n for byte b using binary search.
func (s *sparseBlocks) lookup(n uint32, b byte) uint16 {
lo := s.offsets[n]
hi := s.offsets[n+1]
for lo < hi {
m := lo + (hi-lo)/2
r := s.values[m]
if r.lo <= b && b <= r.hi {
return r.value
}
if b < r.lo {
hi = m
} else {
lo = m + 1
}
}
return 0
}
// lastRuneForTesting is the last rune used for testing. Everything after this
// is boring.
const lastRuneForTesting = rune(0x1FFFF)
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