/
decoders.go
194 lines (170 loc) · 5.25 KB
/
decoders.go
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package letters
import (
"bytes"
"encoding/base64"
"fmt"
"io"
"io/ioutil"
"mime"
"mime/multipart"
"mime/quotedprintable"
"strings"
"golang.org/x/net/html/charset"
"golang.org/x/text/encoding"
"golang.org/x/text/transform"
)
func decodeHeader(s string) (string, error) {
CharsetReader := func(label string, input io.Reader) (io.Reader, error) {
enc, _ := charset.Lookup(label)
if enc == nil {
normalizedLabel := strings.Replace(label, "windows-", "cp", -1)
enc, _ = charset.Lookup(normalizedLabel)
}
if enc == nil {
return nil, fmt.Errorf(
"letters.decoders.decodeHeader.CharsetReader: cannot lookup encoding %s",
label)
}
return enc.NewDecoder().Reader(input), nil
}
mimeDecoder := mime.WordDecoder{CharsetReader: CharsetReader}
decodedHeader, err := mimeDecoder.DecodeHeader(s)
if err != nil {
return decodedHeader, fmt.Errorf(
"letters.decoders.decodeHeader: cannot decode MIME-word-encoded header %q: %w",
s,
err)
}
return decodedHeader, nil
}
func decodeContent(
content io.Reader,
e encoding.Encoding,
cte ContentTransferEncoding,
) (io.Reader, error) {
var contentReader io.Reader
contentBytes, err := ioutil.ReadAll(content)
if err != nil && err != io.ErrUnexpectedEOF {
return nil, fmt.Errorf(
"letters.decoders.decodeContent: cannot decode content: %w",
err)
}
switch cte {
case cteBase64:
decoded := base64.NewDecoder(base64.StdEncoding, bytes.NewReader(contentBytes))
b, err := ioutil.ReadAll(decoded)
if err == io.ErrUnexpectedEOF {
decoded = base64.NewDecoder(base64.RawStdEncoding, bytes.NewReader(contentBytes))
b, err = ioutil.ReadAll(decoded)
if err != nil {
return nil, fmt.Errorf(
"letters.decoders.decodeContent: cannot decode raw-std-base64-encoded content: %w",
err)
}
} else if err != nil {
return nil, fmt.Errorf(
"letters.decoders.decodeContent: cannot decode std-base64-encoded content: %w",
err)
}
contentReader = bytes.NewReader(b)
case cteQuotedPrintable:
decoded := quotedprintable.NewReader(bytes.NewReader(contentBytes))
b, err := ioutil.ReadAll(decoded)
if err != nil {
return nil, fmt.Errorf(
"letters.decoders.decodeContent: cannot decode quoted-printable-encoded content: %w",
err)
}
contentReader = bytes.NewReader(b)
default:
contentReader = bytes.NewReader(contentBytes)
}
if e != nil {
contentReader = transform.NewReader(
contentReader,
e.NewDecoder(),
)
}
return contentReader, nil
}
func decodeInlineFile(part *multipart.Part, cte ContentTransferEncoding) (InlineFile, error) {
var ifl InlineFile
cid, err := decodeHeader(part.Header.Get("Content-Id"))
if err != nil {
return ifl, fmt.Errorf(
"letters.decoders.decodeInlineFile: cannot decode Content-ID header for inline attachment: %w",
err)
}
decoded, err := decodeContent(part, nil, cte)
if err != nil {
return ifl, fmt.Errorf(
"letters.decoders.decodeInlineFile: cannot decode inline attachment content: %w",
err)
}
ifl.ContentID = strings.Trim(cid, "<>")
ifl.Data, err = ioutil.ReadAll(decoded)
if err != nil {
return ifl, fmt.Errorf(
"letters.decoders.decodeInlineFile: cannot read inline attachment data: %w",
err)
}
ifl.ContentType, err = parseContentTypeHeader(part.Header.Get("Content-Type"))
if err != nil {
return ifl, fmt.Errorf(
"letters.decoders.decodeInlineFile: cannot parse Content-Type of inline attachment: %w",
err)
}
ifl.ContentDisposition, err = parseContentDisposition(part.Header.Get("Content-Disposition"))
if err != nil {
return ifl, fmt.Errorf(
"letters.decoders.decodeInlineFile: cannot parse Content-Disposition of inline attachment: %w",
err)
}
return ifl, nil
}
func decodeAttachmentFileFromBody(body io.Reader, headers Headers, cte ContentTransferEncoding) (AttachedFile, error) {
var afl AttachedFile
decoded, err := decodeContent(body, nil, cte)
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachmentFileFromBody: cannot decode attached file content: %w",
err)
}
afl.ContentType = headers.ContentType
afl.ContentDisposition = headers.ContentDisposition
afl.Data, err = ioutil.ReadAll(decoded)
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachmentFileFromBody: cannot read attached file data: %w",
err)
}
return afl, nil
}
func decodeAttachedFileFromPart(part *multipart.Part, cte ContentTransferEncoding) (AttachedFile, error) {
var afl AttachedFile
decoded, err := decodeContent(part, nil, cte)
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachedFileFromPart: cannot decode attached file content: %w",
err)
}
afl.ContentType, err = parseContentTypeHeader(part.Header.Get("Content-Type"))
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachedFileFromPart: cannot parse Content-Type of attached file: %w",
err)
}
afl.ContentDisposition, err = parseContentDisposition(part.Header.Get("Content-Disposition"))
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachedFileFromPart: cannot parse Content-Disposition of attached file: %w",
err)
}
afl.Data, err = ioutil.ReadAll(decoded)
if err != nil {
return afl, fmt.Errorf(
"letters.decoders.decodeAttachedFileFromPart: cannot read attached file data: %w",
err)
}
return afl, nil
}