在Go中解析电子邮件标题

Question

How I can read some headers from an email message in Go?

Usually I would use ReadMIMEHeader(), but sadly not everybody has read all the relevant RFCs and for some messages I get output like:

malformed MIME header line: name="7DDA4_foo_9E5D72.zip"

I narrowed the culprit to be

Content-Type: application/x-zip-compressed; x-unix-mode=0600;
name="7DDA4_foo_9E5D72.zip"

instead of

Content-Type: application/x-zip-compressed; x-unix-mode=0600; 
  name="7DDA4_foo_9E5D72.zip"

in the source of the message.

Go Playground example

What is the correct way of parsing the headers correctly, regardless if indented or not?

Answer 1

Given that the message is malformed, I would fix it through a separate piece of code that reformats the message:

func fixBrokenMime(r_ io.Reader, w io.WriteCloser) {
    r := bufio.NewScanner(bufio.NewReader(r_))
    for r.Scan() {
        line := r.Text()
        if len(line) > 0 && line[0] != ' ' && strings.IndexByte(line, ':') < 0 {
            line = " " + line
        }
        w.Write([]byte(line+"
"))
    }
    w.Close()
}

Playground: http://play.golang.org/p/OZsXT7pmtN

Obviously, you may want a different heuristic. I assumed that a line that is not indented and doesn't contain ":", must be indented.