Reserves the space for the next message using specified key and value sizes. This may
be used to avoid double-copy. Instead of filling the user's buffer and passing it to
pushMessage(), the user may call the reserveMessage() and fill the data directly in
the internal buffer using reservedKey and reservedValue slices. This function is used
internally by pushMessage() function.
Reserves the space for the next message using specified key and value sizes. This may be used to avoid double-copy. Instead of filling the user's buffer and passing it to pushMessage(), the user may call the reserveMessage() and fill the data directly in the internal buffer using reservedKey and reservedValue slices. This function is used internally by pushMessage() function.