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pkt-line: share buffer/descriptor reading implementation

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The packet_read function reads from a descriptor. The
packet_get_line function is similar, but reads from an
in-memory buffer, and uses a completely separate
implementation. This patch teaches the generic packet_read
function to accept either source, and we can do away with
packet_get_line's implementation.

There are two other differences to account for between the
old and new functions. The first is that we used to read
into a strbuf, but now read into a fixed size buffer. The
only two callers are fine with that, and in fact it
simplifies their code, since they can use the same
static-buffer interface as the rest of the packet_read_line
callers (and we provide a similar convenience wrapper for
reading from a buffer rather than a descriptor).

This is technically an externally-visible behavior change in
that we used to accept arbitrary sized packets up to 65532
bytes, and now cap out at LARGE_PACKET_MAX, 65520. In
practice this doesn't matter, as we use it only for parsing
smart-http headers (of which there is exactly one defined,
and it is small and fixed-size). And any extension headers
would be breaking the protocol to go over LARGE_PACKET_MAX
anyway.

The other difference is that packet_get_line would return
on error rather than dying. However, both callers of
packet_get_line are actually improved by dying.

The first caller does its own error checking, but we can
drop that; as a result, we'll actually get more specific
reporting about protocol breakage when packet_read dies
internally. The only downside is that packet_read will not
print the smart-http URL that failed, but that's not a big
deal; anybody not debugging can already see the remote's URL
already, and anybody debugging would want to run with
GIT_CURL_VERBOSE anyway to see way more information.

The second caller, which is just trying to skip past any
extra smart-http headers (of which there are none defined,
but which we allow to keep room for future expansion), did
not error check at all. As a result, it would treat an error
just like a flush packet. The resulting mess would generally
cause an error later in get_remote_heads, but now we get
error reporting much closer to the source of the problem.

Brown-paper-bag-fixes-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2013-02-23 17:31:34 -05:00
committed by Junio C Hamano
parent 74543a0423
commit 4981fe750b
6 changed files with 70 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
remote-curl.c
View File

@ -138,28 +138,26 @@ static struct discovery* discover_refs(const char *service)
if (maybe_smart &&
(5 <= last->len && last->buf[4] == '#') &&
!strbuf_cmp(&exp, &type)) {
char *line;
/*
* smart HTTP response; validate that the service
* pkt-line matches our request.
*/
if (packet_get_line(&buffer, &last->buf, &last->len) <= 0)
die("%s has invalid packet header", refs_url);
if (buffer.len && buffer.buf[buffer.len - 1] == '\n')
strbuf_setlen(&buffer, buffer.len - 1);
line = packet_read_line_buf(&last->buf, &last->len, NULL);
strbuf_reset(&exp);
strbuf_addf(&exp, "# service=%s", service);
if (strbuf_cmp(&exp, &buffer))
die("invalid server response; got '%s'", buffer.buf);
if (strcmp(line, exp.buf))
die("invalid server response; got '%s'", line);
strbuf_release(&exp);
/* The header can include additional metadata lines, up
* until a packet flush marker. Ignore these now, but
* in the future we might start to scan them.
*/
strbuf_reset(&buffer);
while (packet_get_line(&buffer, &last->buf, &last->len) > 0)
strbuf_reset(&buffer);
while (packet_read_line_buf(&last->buf, &last->len, NULL))
;
last->proto_git = 1;
}
@ -308,7 +306,7 @@ static size_t rpc_out(void *ptr, size_t eltsize,
if (!avail) {
rpc->initial_buffer = 0;
avail = packet_read(rpc->out, rpc->buf, rpc->alloc, 0);
avail = packet_read(rpc->out, NULL, NULL, rpc->buf, rpc->alloc, 0);
if (!avail)
return 0;
rpc->pos = 0;
@ -425,7 +423,7 @@ static int post_rpc(struct rpc_state *rpc)
break;
}
n = packet_read(rpc->out, buf, left, 0);
n = packet_read(rpc->out, NULL, NULL, buf, left, 0);
if (!n)
break;
rpc->len += n;
@ -579,7 +577,7 @@ static int rpc_service(struct rpc_state *rpc, struct discovery *heads)
rpc->hdr_accept = strbuf_detach(&buf, NULL);
while (!err) {
int n = packet_read(rpc->out, rpc->buf, rpc->alloc, 0);
int n = packet_read(rpc->out, NULL, NULL, rpc->buf, rpc->alloc, 0);
if (!n)
break;
rpc->pos = 0;