Update vendor/

vendor/github.com/emersion/go-message/charset/charset.go

@@ -0,0 +1,57 @@
+// Package charset provides functions to decode and encode charsets.
+package charset
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"golang.org/x/text/encoding"
+	"golang.org/x/text/encoding/charmap"
+	"golang.org/x/text/encoding/japanese"
+	"golang.org/x/text/encoding/simplifiedchinese"
+	"golang.org/x/text/encoding/traditionalchinese"
+)
+
+var charsets = map[string]encoding.Encoding{
+	"big5":         traditionalchinese.Big5,
+	"euc-jp":       japanese.EUCJP,
+	"gbk":          simplifiedchinese.GBK,
+	"gb2312":       simplifiedchinese.GBK,     // as GBK is a superset of HZGB2312, so just use GBK
+	"gb18030":      simplifiedchinese.GB18030, // GB18030 Use for parse QQ business mail message
+	"iso-2022-jp":  japanese.ISO2022JP,
+	"iso-8859-1":   charmap.ISO8859_1,
+	"iso-8859-2":   charmap.ISO8859_2,
+	"iso-8859-3":   charmap.ISO8859_3,
+	"iso-8859-4":   charmap.ISO8859_4,
+	"iso-8859-9":   charmap.ISO8859_9,
+	"iso-8859-10":  charmap.ISO8859_10,
+	"iso-8859-13":  charmap.ISO8859_13,
+	"iso-8859-14":  charmap.ISO8859_14,
+	"iso-8859-15":  charmap.ISO8859_15,
+	"iso-8859-16":  charmap.ISO8859_16,
+	"koi8-r":       charmap.KOI8R,
+	"shift_jis":    japanese.ShiftJIS,
+	"windows-1250": charmap.Windows1250,
+	"windows-1251": charmap.Windows1251,
+	"windows-1252": charmap.Windows1252,
+}
+
+// Reader returns an io.Reader that converts the provided charset to UTF-8.
+func Reader(charset string, input io.Reader) (io.Reader, error) {
+	charset = strings.ToLower(charset)
+	// "ascii" is not in the spec but is common
+	if charset == "utf-8" || charset == "us-ascii" || charset == "ascii" {
+		return input, nil
+	}
+	if enc, ok := charsets[charset]; ok {
+		return enc.NewDecoder().Reader(input), nil
+	}
+	return nil, fmt.Errorf("unhandled charset %q", charset)
+}
+
+// RegisterEncoding registers an encoding. This is intended to be called from
+// the init function in packages that want to support additional charsets.
+func RegisterEncoding(name string, enc encoding.Encoding) {
+	charsets[name] = enc
+}