rss-tools/vendor/golang.org/x/text/internal/language/match.go (view raw)
| 1 | // Copyright 2013 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package language |
| 6 | |
| 7 | import "errors" |
| 8 | |
| 9 | type scriptRegionFlags uint8 |
| 10 | |
| 11 | const ( |
| 12 | isList = 1 << iota |
| 13 | scriptInFrom |
| 14 | regionInFrom |
| 15 | ) |
| 16 | |
| 17 | func (t *Tag) setUndefinedLang(id Language) { |
| 18 | if t.LangID == 0 { |
| 19 | t.LangID = id |
| 20 | } |
| 21 | } |
| 22 | |
| 23 | func (t *Tag) setUndefinedScript(id Script) { |
| 24 | if t.ScriptID == 0 { |
| 25 | t.ScriptID = id |
| 26 | } |
| 27 | } |
| 28 | |
| 29 | func (t *Tag) setUndefinedRegion(id Region) { |
| 30 | if t.RegionID == 0 || t.RegionID.Contains(id) { |
| 31 | t.RegionID = id |
| 32 | } |
| 33 | } |
| 34 | |
| 35 | // ErrMissingLikelyTagsData indicates no information was available |
| 36 | // to compute likely values of missing tags. |
| 37 | var ErrMissingLikelyTagsData = errors.New("missing likely tags data") |
| 38 | |
| 39 | // addLikelySubtags sets subtags to their most likely value, given the locale. |
| 40 | // In most cases this means setting fields for unknown values, but in some |
| 41 | // cases it may alter a value. It returns an ErrMissingLikelyTagsData error |
| 42 | // if the given locale cannot be expanded. |
| 43 | func (t Tag) addLikelySubtags() (Tag, error) { |
| 44 | id, err := addTags(t) |
| 45 | if err != nil { |
| 46 | return t, err |
| 47 | } else if id.equalTags(t) { |
| 48 | return t, nil |
| 49 | } |
| 50 | id.RemakeString() |
| 51 | return id, nil |
| 52 | } |
| 53 | |
| 54 | // specializeRegion attempts to specialize a group region. |
| 55 | func specializeRegion(t *Tag) bool { |
| 56 | if i := regionInclusion[t.RegionID]; i < nRegionGroups { |
| 57 | x := likelyRegionGroup[i] |
| 58 | if Language(x.lang) == t.LangID && Script(x.script) == t.ScriptID { |
| 59 | t.RegionID = Region(x.region) |
| 60 | } |
| 61 | return true |
| 62 | } |
| 63 | return false |
| 64 | } |
| 65 | |
| 66 | // Maximize returns a new tag with missing tags filled in. |
| 67 | func (t Tag) Maximize() (Tag, error) { |
| 68 | return addTags(t) |
| 69 | } |
| 70 | |
| 71 | func addTags(t Tag) (Tag, error) { |
| 72 | // We leave private use identifiers alone. |
| 73 | if t.IsPrivateUse() { |
| 74 | return t, nil |
| 75 | } |
| 76 | if t.ScriptID != 0 && t.RegionID != 0 { |
| 77 | if t.LangID != 0 { |
| 78 | // already fully specified |
| 79 | specializeRegion(&t) |
| 80 | return t, nil |
| 81 | } |
| 82 | // Search matches for und-script-region. Note that for these cases |
| 83 | // region will never be a group so there is no need to check for this. |
| 84 | list := likelyRegion[t.RegionID : t.RegionID+1] |
| 85 | if x := list[0]; x.flags&isList != 0 { |
| 86 | list = likelyRegionList[x.lang : x.lang+uint16(x.script)] |
| 87 | } |
| 88 | for _, x := range list { |
| 89 | // Deviating from the spec. See match_test.go for details. |
| 90 | if Script(x.script) == t.ScriptID { |
| 91 | t.setUndefinedLang(Language(x.lang)) |
| 92 | return t, nil |
| 93 | } |
| 94 | } |
| 95 | } |
| 96 | if t.LangID != 0 { |
| 97 | // Search matches for lang-script and lang-region, where lang != und. |
| 98 | if t.LangID < langNoIndexOffset { |
| 99 | x := likelyLang[t.LangID] |
| 100 | if x.flags&isList != 0 { |
| 101 | list := likelyLangList[x.region : x.region+uint16(x.script)] |
| 102 | if t.ScriptID != 0 { |
| 103 | for _, x := range list { |
| 104 | if Script(x.script) == t.ScriptID && x.flags&scriptInFrom != 0 { |
| 105 | t.setUndefinedRegion(Region(x.region)) |
| 106 | return t, nil |
| 107 | } |
| 108 | } |
| 109 | } else if t.RegionID != 0 { |
| 110 | count := 0 |
| 111 | goodScript := true |
| 112 | tt := t |
| 113 | for _, x := range list { |
| 114 | // We visit all entries for which the script was not |
| 115 | // defined, including the ones where the region was not |
| 116 | // defined. This allows for proper disambiguation within |
| 117 | // regions. |
| 118 | if x.flags&scriptInFrom == 0 && t.RegionID.Contains(Region(x.region)) { |
| 119 | tt.RegionID = Region(x.region) |
| 120 | tt.setUndefinedScript(Script(x.script)) |
| 121 | goodScript = goodScript && tt.ScriptID == Script(x.script) |
| 122 | count++ |
| 123 | } |
| 124 | } |
| 125 | if count == 1 { |
| 126 | return tt, nil |
| 127 | } |
| 128 | // Even if we fail to find a unique Region, we might have |
| 129 | // an unambiguous script. |
| 130 | if goodScript { |
| 131 | t.ScriptID = tt.ScriptID |
| 132 | } |
| 133 | } |
| 134 | } |
| 135 | } |
| 136 | } else { |
| 137 | // Search matches for und-script. |
| 138 | if t.ScriptID != 0 { |
| 139 | x := likelyScript[t.ScriptID] |
| 140 | if x.region != 0 { |
| 141 | t.setUndefinedRegion(Region(x.region)) |
| 142 | t.setUndefinedLang(Language(x.lang)) |
| 143 | return t, nil |
| 144 | } |
| 145 | } |
| 146 | // Search matches for und-region. If und-script-region exists, it would |
| 147 | // have been found earlier. |
| 148 | if t.RegionID != 0 { |
| 149 | if i := regionInclusion[t.RegionID]; i < nRegionGroups { |
| 150 | x := likelyRegionGroup[i] |
| 151 | if x.region != 0 { |
| 152 | t.setUndefinedLang(Language(x.lang)) |
| 153 | t.setUndefinedScript(Script(x.script)) |
| 154 | t.RegionID = Region(x.region) |
| 155 | } |
| 156 | } else { |
| 157 | x := likelyRegion[t.RegionID] |
| 158 | if x.flags&isList != 0 { |
| 159 | x = likelyRegionList[x.lang] |
| 160 | } |
| 161 | if x.script != 0 && x.flags != scriptInFrom { |
| 162 | t.setUndefinedLang(Language(x.lang)) |
| 163 | t.setUndefinedScript(Script(x.script)) |
| 164 | return t, nil |
| 165 | } |
| 166 | } |
| 167 | } |
| 168 | } |
| 169 | |
| 170 | // Search matches for lang. |
| 171 | if t.LangID < langNoIndexOffset { |
| 172 | x := likelyLang[t.LangID] |
| 173 | if x.flags&isList != 0 { |
| 174 | x = likelyLangList[x.region] |
| 175 | } |
| 176 | if x.region != 0 { |
| 177 | t.setUndefinedScript(Script(x.script)) |
| 178 | t.setUndefinedRegion(Region(x.region)) |
| 179 | } |
| 180 | specializeRegion(&t) |
| 181 | if t.LangID == 0 { |
| 182 | t.LangID = _en // default language |
| 183 | } |
| 184 | return t, nil |
| 185 | } |
| 186 | return t, ErrMissingLikelyTagsData |
| 187 | } |
| 188 | |
| 189 | func (t *Tag) setTagsFrom(id Tag) { |
| 190 | t.LangID = id.LangID |
| 191 | t.ScriptID = id.ScriptID |
| 192 | t.RegionID = id.RegionID |
| 193 | } |
| 194 | |
| 195 | // minimize removes the region or script subtags from t such that |
| 196 | // t.addLikelySubtags() == t.minimize().addLikelySubtags(). |
| 197 | func (t Tag) minimize() (Tag, error) { |
| 198 | t, err := minimizeTags(t) |
| 199 | if err != nil { |
| 200 | return t, err |
| 201 | } |
| 202 | t.RemakeString() |
| 203 | return t, nil |
| 204 | } |
| 205 | |
| 206 | // minimizeTags mimics the behavior of the ICU 51 C implementation. |
| 207 | func minimizeTags(t Tag) (Tag, error) { |
| 208 | if t.equalTags(Und) { |
| 209 | return t, nil |
| 210 | } |
| 211 | max, err := addTags(t) |
| 212 | if err != nil { |
| 213 | return t, err |
| 214 | } |
| 215 | for _, id := range [...]Tag{ |
| 216 | {LangID: t.LangID}, |
| 217 | {LangID: t.LangID, RegionID: t.RegionID}, |
| 218 | {LangID: t.LangID, ScriptID: t.ScriptID}, |
| 219 | } { |
| 220 | if x, err := addTags(id); err == nil && max.equalTags(x) { |
| 221 | t.setTagsFrom(id) |
| 222 | break |
| 223 | } |
| 224 | } |
| 225 | return t, nil |
| 226 | } |