Performant, low-memory multipart/mime library for building and parsing email bodies in Go.
Status: Work In Progress
Simple create a struct containing the parts as needed. Attach an io.Reader and file contents (or a network connection) will be streamed without requiring everything to be loaded into memory.
// Assuming this is some type of io.Reader or io.ReadCloser
var openfilehandle io.ReadCloser
parts := mimestream.Parts{
mimestream.Alternative{
Parts: []mimestream.Part{
mimestream.Text{
Text: "This is the text that goes in the plain part.",
},
mimestream.Text{
ContentType: mimestream.TextHTML,
Text: "<p>This is the text that goes in the plain part.</p>",
},
},
},
mimestream.File{
Name: "filename.jpg",
Inline: true,
Reader: openfilehandle,
Closer: openfilehandle,
},
mimestream.File{
Name: "payload.json",
Reader: strings.NewReader(`{"one":1,"two":2}`),
},
}
// Destination could be file or network connection, here we just throw it away
mr := multipart.NewWriter(ioutil.Discard)
err = parts.Into(mr)
if err != nil {
log.Fatal(err)
}
Reading emails is done with a simple callback that provides a place to stream each part to a destination. In the example below we simply read everything.
// Assume mailreader is a network connection or email file
var mailreader io.Reader
err = HandleEmailFromReader(mailreader, func(header textproto.MIMEHeader, body io.Reader) (err error) {
maxbytes := 1024 * 1024
var b []byte
b, err = ioutil.ReadAll(io.LimitReader(body, maxbytes))
if err != nil {
return
}
fmt.Printf("Part Header: %v\n", header)
fmt.Printf("Part body: %q\n", b)
return
})
- More Tests
- Support writing nested parts
- Multipart mixed and alternative
Most multipart/mime handling by both email and MIME libraries in Go requires everything to be loaded into memory. I wanted to be able to create mime bodies without needing much memory.
Here are some of the following problems this package addresses:
- Requires memory equal to mime content (+ encoding)
- Uses string building to construct envelope (instead of using
encoding/mime)
Similar libraries
- https://tools.ietf.org/html/rfc2046
- @emersion has many Go packages for Email and related things.
- Collection of Go projects that deal with email, SMTP, IMAP, and other related tasks