rss-tools/vendor/golang.org/x/text/encoding/htmlindex/htmlindex.go (view raw)
| 1 | // Copyright 2015 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 | //go:generate go run gen.go |
| 6 | |
| 7 | // Package htmlindex maps character set encoding names to Encodings as |
| 8 | // recommended by the W3C for use in HTML 5. See http://www.w3.org/TR/encoding. |
| 9 | package htmlindex |
| 10 | |
| 11 | // TODO: perhaps have a "bare" version of the index (used by this package) that |
| 12 | // is not pre-loaded with all encodings. Global variables in encodings prevent |
| 13 | // the linker from being able to purge unneeded tables. This means that |
| 14 | // referencing all encodings, as this package does for the default index, links |
| 15 | // in all encodings unconditionally. |
| 16 | // |
| 17 | // This issue can be solved by either solving the linking issue (see |
| 18 | // https://github.com/golang/go/issues/6330) or refactoring the encoding tables |
| 19 | // (e.g. moving the tables to internal packages that do not use global |
| 20 | // variables). |
| 21 | |
| 22 | // TODO: allow canonicalizing names |
| 23 | |
| 24 | import ( |
| 25 | "errors" |
| 26 | "strings" |
| 27 | "sync" |
| 28 | |
| 29 | "golang.org/x/text/encoding" |
| 30 | "golang.org/x/text/encoding/internal/identifier" |
| 31 | "golang.org/x/text/language" |
| 32 | ) |
| 33 | |
| 34 | var ( |
| 35 | errInvalidName = errors.New("htmlindex: invalid encoding name") |
| 36 | errUnknown = errors.New("htmlindex: unknown Encoding") |
| 37 | errUnsupported = errors.New("htmlindex: this encoding is not supported") |
| 38 | ) |
| 39 | |
| 40 | var ( |
| 41 | matcherOnce sync.Once |
| 42 | matcher language.Matcher |
| 43 | ) |
| 44 | |
| 45 | // LanguageDefault returns the canonical name of the default encoding for a |
| 46 | // given language. |
| 47 | func LanguageDefault(tag language.Tag) string { |
| 48 | matcherOnce.Do(func() { |
| 49 | tags := []language.Tag{} |
| 50 | for _, t := range strings.Split(locales, " ") { |
| 51 | tags = append(tags, language.MustParse(t)) |
| 52 | } |
| 53 | matcher = language.NewMatcher(tags, language.PreferSameScript(true)) |
| 54 | }) |
| 55 | _, i, _ := matcher.Match(tag) |
| 56 | return canonical[localeMap[i]] // Default is Windows-1252. |
| 57 | } |
| 58 | |
| 59 | // Get returns an Encoding for one of the names listed in |
| 60 | // http://www.w3.org/TR/encoding using the Default Index. Matching is case- |
| 61 | // insensitive. |
| 62 | func Get(name string) (encoding.Encoding, error) { |
| 63 | x, ok := nameMap[strings.ToLower(strings.TrimSpace(name))] |
| 64 | if !ok { |
| 65 | return nil, errInvalidName |
| 66 | } |
| 67 | return encodings[x], nil |
| 68 | } |
| 69 | |
| 70 | // Name reports the canonical name of the given Encoding. It will return |
| 71 | // an error if e is not associated with a supported encoding scheme. |
| 72 | func Name(e encoding.Encoding) (string, error) { |
| 73 | id, ok := e.(identifier.Interface) |
| 74 | if !ok { |
| 75 | return "", errUnknown |
| 76 | } |
| 77 | mib, _ := id.ID() |
| 78 | if mib == 0 { |
| 79 | return "", errUnknown |
| 80 | } |
| 81 | v, ok := mibMap[mib] |
| 82 | if !ok { |
| 83 | return "", errUnsupported |
| 84 | } |
| 85 | return canonical[v], nil |
| 86 | } |