This commit lets clients receive multipart/byteranges responses (see
RFC 7233, Appendix A) for erasure-coded objects. Clients can already
do this for replicated objects, so this brings EC closer to feature
parity (ha!).
GetOrHeadHandler got a base class extracted from it that treats an
HTTP response as a sequence of byte-range responses. This way, it can
continue to yield whole fragments, not just N-byte pieces of the raw
HTTP response, since an N-byte piece of a multipart/byteranges
response is pretty much useless.
There are a couple of bonus fixes in here, too. For starters, download
resuming now works on multipart/byteranges responses. Before, it only
worked on 200 responses or 206 responses for a single byte
range. Also, BufferedHTTPResponse grew a readline() method.
Also, the MIME response for replicated objects got tightened up a
little. Before, it had some leading and trailing CRLFs which, while
allowed by RFC 7233, provide no benefit. Now, both replicated and EC
multipart/byteranges avoid extraneous bytes. This let me re-use the
Content-Length calculation in swob instead of having to either hack
around it or add extraneous whitespace to match.
Change-Id: I16fc65e0ec4e356706d327bdb02a3741e36330a0
4f2ed8bcd0