peridot/vendor/github.com/ProtonMail/go-mime/encoding.go
2024-10-16 13:40:38 +02:00

214 lines
5.1 KiB
Go

package gomime
import (
"fmt"
"io"
"mime"
"mime/quotedprintable"
"regexp"
"strings"
"unicode/utf8"
"encoding/base64"
"golang.org/x/text/encoding"
"golang.org/x/text/encoding/htmlindex"
)
var wordDec = &mime.WordDecoder{
CharsetReader: func(charset string, input io.Reader) (io.Reader, error) {
dec, err := selectDecoder(charset)
if err != nil {
return nil, err
}
if dec == nil { // utf-8
return input, nil
}
return dec.Reader(input), nil
},
}
// expected trimmed low case
func getEncoding(charset string) (enc encoding.Encoding, err error) {
preparsed := strings.Trim(strings.ToLower(charset), " \t\r\n")
// koi
re := regexp.MustCompile("(cs)?koi[-_ ]?8?[-_ ]?(r|ru|u|uk)?$")
matches := re.FindAllStringSubmatch(preparsed, -1)
if len(matches) == 1 && len(matches[0]) == 3 {
preparsed = "koi8-"
switch matches[0][2] {
case "u", "uk":
preparsed += "u"
default:
preparsed += "r"
}
}
// windows-XXXX
re = regexp.MustCompile("(cp|(cs)?win(dows)?)[-_ ]?([0-9]{3,4})$")
matches = re.FindAllStringSubmatch(preparsed, -1)
if len(matches) == 1 && len(matches[0]) == 5 {
switch matches[0][4] {
case "874", "1250", "1251", "1252", "1253", "1254", "1255", "1256", "1257", "1258":
preparsed = "windows-" + matches[0][4]
}
}
// iso
re = regexp.MustCompile("iso[-_ ]?([0-9]{4})[-_ ]?([0-9]+|jp)?[-_ ]?(i|e)?")
matches = re.FindAllStringSubmatch(preparsed, -1)
if len(matches) == 1 && len(matches[0]) == 4 {
if matches[0][1] == "2022" && matches[0][2] == "jp" {
preparsed = "iso-2022-jp"
}
if matches[0][1] == "8859" {
switch matches[0][2] {
case "1", "2", "3", "4", "5", "7", "8", "9", "10", "11", "13", "14", "15", "16":
preparsed = "iso-8859-" + matches[0][2]
if matches[0][3] == "i" {
preparsed += "-" + matches[0][3]
}
case "":
preparsed = "iso-8859-1"
}
}
}
// latin is tricky
re = regexp.MustCompile("^(cs|csiso)?l(atin)?[-_ ]?([0-9]{1,2})$")
matches = re.FindAllStringSubmatch(preparsed, -1)
if len(matches) == 1 && len(matches[0]) == 4 {
switch matches[0][3] {
case "1":
preparsed = "windows-1252"
case "2", "3", "4", "5":
preparsed = "iso-8859-" + matches[0][3]
case "6":
preparsed = "iso-8859-10"
case "8":
preparsed = "iso-8859-14"
case "9":
preparsed = "iso-8859-15"
case "10":
preparsed = "iso-8859-16"
}
}
// missing substitutions
switch preparsed {
case "csutf8", "iso-utf-8", "utf8mb4":
preparsed = "utf-8"
case "eucjp", "ibm-eucjp":
preparsed = "euc-jp"
case "euckr", "ibm-euckr", "cp949":
preparsed = "euc-kr"
case "euccn", "ibm-euccn":
preparsed = "gbk"
case "zht16mswin950", "cp950":
preparsed = "big5"
case "csascii",
"ansi_x3.4-1968",
"ansi_x3.4-1986",
"ansi_x3.110-1983",
"cp850",
"cp858",
"us",
"iso646",
"iso-646",
"iso646-us",
"iso_646.irv:1991",
"cp367",
"ibm367",
"ibm-367",
"iso-ir-6":
preparsed = "ascii"
case "ibm852":
preparsed = "iso-8859-2"
case "iso-ir-199", "iso-celtic":
preparsed = "iso-8859-14"
case "iso-ir-226":
preparsed = "iso-8859-16"
case "macroman":
preparsed = "macintosh"
}
enc, _ = htmlindex.Get(preparsed)
if enc == nil {
err = fmt.Errorf("can not get encodig for '%s' (or '%s')", charset, preparsed)
}
return
}
func selectDecoder(charset string) (decoder *encoding.Decoder, err error) {
var enc encoding.Encoding
lcharset := strings.Trim(strings.ToLower(charset), " \t\r\n")
switch lcharset {
case "utf7", "utf-7", "unicode-1-1-utf-7":
return NewUtf7Decoder(), nil
default:
enc, err = getEncoding(lcharset)
}
if err == nil {
decoder = enc.NewDecoder()
}
return
}
// DecodeHeader if needed. Returns error if raw contains non-utf8 characters
func DecodeHeader(raw string) (decoded string, err error) {
if decoded, err = wordDec.DecodeHeader(raw); err != nil {
decoded = raw
}
if !utf8.ValidString(decoded) {
err = fmt.Errorf("header contains non utf8 chars: %v", err)
}
return
}
// EncodeHeader using quoted printable and utf8
func EncodeHeader(s string) string {
return mime.QEncoding.Encode("utf-8", s)
}
// DecodeCharset decodes the orginal using content type parameters. When
// charset missing it checks the content is utf8-valid.
func DecodeCharset(original []byte, mediaType string, contentTypeParams map[string]string) ([]byte, error) {
var decoder *encoding.Decoder
var err error
if charset, ok := contentTypeParams["charset"]; ok {
decoder, err = selectDecoder(charset)
} else {
if !strings.HasPrefix(mediaType, "text/") || utf8.Valid(original) {
return original, nil
}
err = fmt.Errorf("non-utf8 content without charset specification")
}
if err != nil {
return original, err
}
utf8, err := decoder.Bytes(original)
if err != nil {
return original, err
}
return utf8, nil
}
// DecodeContentEncoding wraps the reader with decoder based on content encoding
func DecodeContentEncoding(r io.Reader, contentEncoding string) (d io.Reader) {
switch strings.ToLower(contentEncoding) {
case "quoted-printable":
d = quotedprintable.NewReader(r)
case "base64":
d = base64.NewDecoder(base64.StdEncoding, r)
case "7bit", "8bit", "binary", "": // Nothing to do
d = r
}
return
}