golang：通过电子邮件发送存储为Google Appengine blobstore blob的图像

Question

I'm trying to read a JPEG file stored in the GAE blobstore back into a byte array using the following code:

info,_  := blobstore.Stat(context,appengine.BlobKey(request.FormValue("blobkey")))
image   := make([]byte,info.Size)
reader  := blobstore.NewReader(context,appengine.BlobKey(request.FormValue("blobkey")))
n,nerr  := reader.Read(image)

The image is stored correctly i.e. it can be served using blobstore.Send(...).

And the above code sort of works (in that it does read back the blob data) but it converts any 0x0a byte into a 0x0d 0x0a pair (i.e. LF into CR LF).

Is there a way in Go to work around this behaviour (without writing a filter to convert 0x0d0a back to 0x0a) ?

EDIT:

It turns out the problem is not with Blobstore.Reader at all, but with the attachment encoding in mail.py on the dev appserver.

Answer 1

The mail attachment handling on the dev appserver does not correctly encode image data. If the attachment data is known to be binary, a partial workaround is to add the line:

encoders.encode_base64(mime_attachment)

after the line

mime_attachment.set_payload(attachment.data())

in the file

google/appengine/api/mail.py

Using a MIMEImage attachment for an image content type would be a better solution but causes a 'LazyImporter object is not callable' error.