// Copyright 2015 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. //go:generate go run gen.go // Package htmlindex maps character set encoding names to Encodings as // recommended by the W3C for use in HTML 5. See http://www.w3.org/TR/encoding. package htmlindex // TODO: perhaps have a "bare" version of the index (used by this package) that // is not pre-loaded with all encodings. Global variables in encodings prevent // the linker from being able to purge unneeded tables. This means that // referencing all encodings, as this package does for the default index, links // in all encodings unconditionally. // // This issue can be solved by either solving the linking issue (see // https://github.com/golang/go/issues/6330) or refactoring the encoding tables // (e.g. moving the tables to internal packages that do not use global // variables). // TODO: allow canonicalizing names import ( "errors" "strings" "sync" "golang.org/x/text/encoding" "golang.org/x/text/encoding/internal/identifier" "golang.org/x/text/language" ) var ( errInvalidName = errors.New("htmlindex: invalid encoding name") errUnknown = errors.New("htmlindex: unknown Encoding") errUnsupported = errors.New("htmlindex: this encoding is not supported") ) var ( matcherOnce sync.Once matcher language.Matcher ) // LanguageDefault returns the canonical name of the default encoding for a // given language. func LanguageDefault(tag language.Tag) string { matcherOnce.Do(func() { tags := []language.Tag{} for _, t := range strings.Split(locales, " ") { tags = append(tags, language.MustParse(t)) } matcher = language.NewMatcher(tags, language.PreferSameScript(true)) }) _, i, _ := matcher.Match(tag) return canonical[localeMap[i]] // Default is Windows-1252. } // Get returns an Encoding for one of the names listed in // http://www.w3.org/TR/encoding using the Default Index. Matching is case- // insensitive. func Get(name string) (encoding.Encoding, error) { x, ok := nameMap[strings.ToLower(strings.TrimSpace(name))] if !ok { return nil, errInvalidName } return encodings[x], nil } // Name reports the canonical name of the given Encoding. It will return // an error if e is not associated with a supported encoding scheme. func Name(e encoding.Encoding) (string, error) { id, ok := e.(identifier.Interface) if !ok { return "", errUnknown } mib, _ := id.ID() if mib == 0 { return "", errUnknown } v, ok := mibMap[mib] if !ok { return "", errUnsupported } return canonical[v], nil }