This is the v1 version, had the v2 before.

backend/backendutil/bodystructure.go

@@ -0,0 +1,117 @@
+package backendutil
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"io/ioutil"
+	"mime"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+type countReader struct {
+	r          io.Reader
+	bytes      uint32
+	newlines   uint32
+	endsWithLF bool
+}
+
+func (r *countReader) Read(b []byte) (int, error) {
+	n, err := r.r.Read(b)
+	r.bytes += uint32(n)
+	if n != 0 {
+		r.newlines += uint32(bytes.Count(b[:n], []byte{'\n'}))
+		r.endsWithLF = b[n-1] == '\n'
+	}
+	// If the stream does not end with a newline - count missing newline.
+	if err == io.EOF {
+		if !r.endsWithLF {
+			r.newlines++
+		}
+	}
+	return n, err
+}
+
+// FetchBodyStructure computes a message's body structure from its content.
+func FetchBodyStructure(header textproto.Header, body io.Reader, extended bool) (*imap.BodyStructure, error) {
+	bs := new(imap.BodyStructure)
+
+	mediaType, mediaParams, err := mime.ParseMediaType(header.Get("Content-Type"))
+	if err == nil {
+		typeParts := strings.SplitN(mediaType, "/", 2)
+		bs.MIMEType = typeParts[0]
+		if len(typeParts) == 2 {
+			bs.MIMESubType = typeParts[1]
+		}
+		bs.Params = mediaParams
+	} else {
+		bs.MIMEType = "text"
+		bs.MIMESubType = "plain"
+	}
+
+	bs.Id = header.Get("Content-Id")
+	bs.Description = header.Get("Content-Description")
+	bs.Encoding = header.Get("Content-Transfer-Encoding")
+
+	if mr := multipartReader(header, body); mr != nil {
+		var parts []*imap.BodyStructure
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				return nil, err
+			}
+
+			pbs, err := FetchBodyStructure(p.Header, p, extended)
+			if err != nil {
+				return nil, err
+			}
+			parts = append(parts, pbs)
+		}
+		bs.Parts = parts
+	} else {
+		countedBody := countReader{r: body}
+		needLines := false
+		if bs.MIMEType == "message" && bs.MIMESubType == "rfc822" {
+			// This will result in double-buffering if body is already a
+			// bufio.Reader (most likely it is). :\
+			bufBody := bufio.NewReader(&countedBody)
+			subMsgHdr, err := textproto.ReadHeader(bufBody)
+			if err != nil {
+				return nil, err
+			}
+			bs.Envelope, err = FetchEnvelope(subMsgHdr)
+			if err != nil {
+				return nil, err
+			}
+			bs.BodyStructure, err = FetchBodyStructure(subMsgHdr, bufBody, extended)
+			if err != nil {
+				return nil, err
+			}
+			needLines = true
+		} else if bs.MIMEType == "text" {
+			needLines = true
+		}
+		if _, err := io.Copy(ioutil.Discard, &countedBody); err != nil {
+			return nil, err
+		}
+		bs.Size = countedBody.bytes
+		if needLines {
+			bs.Lines = countedBody.newlines
+		}
+	}
+
+	if extended {
+		bs.Extended = true
+		bs.Disposition, bs.DispositionParams, _ = mime.ParseMediaType(header.Get("Content-Disposition"))
+
+		// TODO: bs.Language, bs.Location
+		// TODO: bs.MD5
+	}
+
+	return bs, nil
+}