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refactor: tidy up DecodeCharset

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This commit is contained in:
James Houlahan
2020-05-08 09:54:11 +02:00
parent 37f4e46bdc
commit f87ca36ffd
4 changed files with 64 additions and 47 deletions
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50
pkg/mime/encoding.go
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@ -18,7 +18,6 @@
package pmmime
import (
"bytes"
"fmt"
"io"
"mime"
@ -29,10 +28,10 @@ import (
"encoding/base64"
"github.com/pkg/errors"
"golang.org/x/text/encoding"
"golang.org/x/text/encoding/charmap"
"golang.org/x/text/encoding/htmlindex"
"golang.org/x/text/transform"
)
var wordDec = &mime.WordDecoder{
@ -161,7 +160,7 @@ func getEncoding(charset string) (enc encoding.Encoding, err error) {
enc, _ = htmlindex.Get(preparsed)
if enc == nil {
err = fmt.Errorf("can not get encodig for '%s' (or '%s')", charset, preparsed)
err = fmt.Errorf("can not get encoding for '%s' (or '%s')", charset, preparsed)
}
return
}
@ -202,41 +201,34 @@ func EncodeHeader(s string) string {
// If it isn't, it checks whether the content is valid latin1 (iso-8859-1), and if so,
// reencodes it as utf-8.
func DecodeCharset(original []byte, contentTypeParams map[string]string) ([]byte, error) {
var decoder *encoding.Decoder
var err error
// If the charset is specified, use that.
if charset, ok := contentTypeParams["charset"]; ok {
decoder, err = selectDecoder(charset)
} else if utf8.Valid(original) {
decoder, err := selectDecoder(charset)
if err != nil {
return original, errors.Wrap(err, "unknown charset was specified")
}
return decoder.Bytes(original)
}
// The charset was not specified. First try utf8.
if utf8.Valid(original) {
return original, nil
} else if decoded, err = charmap.ISO8859_1.NewDecoder().Bytes(original); err == nil {
return decoded, nil
} else {
err = fmt.Errorf("non-utf8 content without charset specification")
}
// Fallback to latin1.
// In future this should fallback to whatever default encoding user specified.
decoded, err := charmap.ISO8859_1.NewDecoder().Bytes(original)
if err != nil {
return original, err
return original, errors.Wrap(err, "failed to decode as latin1")
}
utf8 := make([]byte, len(original))
nDst, nSrc, err := decoder.Transform(utf8, original, false)
for err == transform.ErrShortDst {
if nDst < 1 {
nDst = 1
}
if nSrc < 1 {
nSrc = 1
}
utf8 = make([]byte, (nDst/nSrc+1)*len(original))
nDst, nSrc, err = decoder.Transform(utf8, original, false)
// If the decoded string is not valid utf8, it wasn't latin1, so give up.
if !utf8.Valid(decoded) {
return original, errors.Wrap(err, "failed to decode as latin1")
}
if err != nil {
return original, err
}
utf8 = bytes.Trim(utf8, "\x00")
return utf8, nil
return decoded, nil
}
// DecodeContentEncoding wraps the reader with decoder based on content encoding.