We have released a new feature for IMAP stores: get and fetch messages in a single operation. This will avoid one round-trip to the server.

Let’s say we want to get the flags for the messages UID 2 to 6. Until today, we used to write the following code:

vmime::shared_ptr <vmime::net::folder> f = /* ... */;

vmime::net::messageSet mset(vmime::net::messageSet::byUID(2, 6));

vmime::net::fetchAttributes attribs;
attribs.add(vmime::net::fetchAttributes::FLAGS);

std::vector <vmime::shared_ptr <vmime::net::message> >
    msgs = f->getMessages(mset);

f->fetchMessages(msgs, attribs);

// ...do something with msg[n]->getFlags()...

This resulted into the following IMAP client-server dialog, with two FETCH commands in sequence:

C: a005 UID FETCH 2:6 UID                <-- getMessages()
S: * 1 FETCH (UID 2 MODSEQ (1268172))
S: * 2 FETCH (UID 3 MODSEQ (1268417))
S: * 3 FETCH (UID 4 MODSEQ (1268417))
S: * 4 FETCH (UID 5 MODSEQ (1268312))
S: * 5 FETCH (UID 6 MODSEQ (1268417))
S: a005 OK Success
C: a006 FETCH 1:5 (FLAGS)                <-- fetchMessages()
S: * 1 FETCH (MODSEQ (1268172) FLAGS (NotJunk $NotJunk \Seen))
S: * 2 FETCH (MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: * 3 FETCH (MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: * 4 FETCH (MODSEQ (1268312) FLAGS (NotJunk $NotJunk \Seen))
S: * 5 FETCH (MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: a006 OK Success

With the new getAndFetchMessages() method, we can now write:

vmime::shared_ptr <vmime::net::folder> f = /* ... */;

vmime::net::messageSet mset(vmime::net::messageSet::byUID(2, 6));

vmime::net::fetchAttributes attribs;
attribs.add(vmime::net::fetchAttributes::FLAGS);

std::vector <vmime::shared_ptr <vmime::net::message> >
    msgs = f->getAndFetchMessages(mset, attribs);

// ...do something with msg[n]->getFlags()...

Here is now the dialog between the client and the server:

C: a006 UID FETCH 2:6 (FLAGS UID MODSEQ) 
S: * 1 FETCH (UID 2 MODSEQ (1268172) FLAGS (NotJunk $NotJunk \Seen))
S: * 2 FETCH (UID 3 MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: * 3 FETCH (UID 4 MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: * 4 FETCH (UID 5 MODSEQ (1268312) FLAGS (NotJunk $NotJunk \Seen))
S: * 5 FETCH (UID 6 MODSEQ (1268417) FLAGS (NotJunk $NotJunk \Seen))
S: a006 OK Success

That is, one round-trip to the server saved. Please note that this will work with any fetch attribute, and should also work with any IMAP-compliant server!