/usr/share/gocode/src/golang.org/x/text/secure/precis/context.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 | // Copyright 2016 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 precis
import "errors"
// This file contains tables and code related to context rules.
type catBitmap uint16
const (
// These bits, once set depending on the current value, are never unset.
bJapanese catBitmap = 1 << iota
bArabicIndicDigit
bExtendedArabicIndicDigit
// These bits are set on each iteration depending on the current value.
bJoinStart
bJoinMid
bJoinEnd
bVirama
bLatinSmallL
bGreek
bHebrew
// These bits indicated which of the permanent bits need to be set at the
// end of the checks.
bMustHaveJapn
permanent = bJapanese | bArabicIndicDigit | bExtendedArabicIndicDigit | bMustHaveJapn
)
const finalShift = 10
var errContext = errors.New("precis: contextual rule violated")
func init() {
// Programmatically set these required bits as, manually setting them seems
// too error prone.
for i, ct := range categoryTransitions {
categoryTransitions[i].keep |= permanent
categoryTransitions[i].accept |= ct.term
}
}
var categoryTransitions = []struct {
keep catBitmap // mask selecting which bits to keep from the previous state
set catBitmap // mask for which bits to set for this transition
// These bitmaps are used for rules that require lookahead.
// term&accept == term must be true, which is enforced programmatically.
term catBitmap // bits accepted as termination condition
accept catBitmap // bits that pass, but not sufficient as termination
// The rule function cannot take a *context as an argument, as it would
// cause the context to escape, adding significant overhead.
rule func(beforeBits catBitmap) (doLookahead bool, err error)
}{
joiningL: {set: bJoinStart},
joiningD: {set: bJoinStart | bJoinEnd},
joiningT: {keep: bJoinStart, set: bJoinMid},
joiningR: {set: bJoinEnd},
viramaModifier: {set: bVirama},
viramaJoinT: {set: bVirama | bJoinMid},
latinSmallL: {set: bLatinSmallL},
greek: {set: bGreek},
greekJoinT: {set: bGreek | bJoinMid},
hebrew: {set: bHebrew},
hebrewJoinT: {set: bHebrew | bJoinMid},
japanese: {set: bJapanese},
katakanaMiddleDot: {set: bMustHaveJapn},
zeroWidthNonJoiner: {
term: bJoinEnd,
accept: bJoinMid,
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bVirama != 0 {
return false, nil
}
if before&bJoinStart == 0 {
return false, errContext
}
return true, nil
},
},
zeroWidthJoiner: {
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bVirama == 0 {
err = errContext
}
return false, err
},
},
middleDot: {
term: bLatinSmallL,
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bLatinSmallL == 0 {
return false, errContext
}
return true, nil
},
},
greekLowerNumeralSign: {
set: bGreek,
term: bGreek,
rule: func(before catBitmap) (doLookAhead bool, err error) {
return true, nil
},
},
hebrewPreceding: {
set: bHebrew,
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bHebrew == 0 {
err = errContext
}
return false, err
},
},
arabicIndicDigit: {
set: bArabicIndicDigit,
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bExtendedArabicIndicDigit != 0 {
err = errContext
}
return false, err
},
},
extendedArabicIndicDigit: {
set: bExtendedArabicIndicDigit,
rule: func(before catBitmap) (doLookAhead bool, err error) {
if before&bArabicIndicDigit != 0 {
err = errContext
}
return false, err
},
},
}
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