git/sideband.c
Jeff King 4981fe750b pkt-line: share buffer/descriptor reading implementation
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>
2013-02-24 00:14:15 -08:00

153 lines
3.4 KiB
C

#include "cache.h"
#include "pkt-line.h"
#include "sideband.h"
/*
* Receive multiplexed output stream over git native protocol.
* in_stream is the input stream from the remote, which carries data
* in pkt_line format with band designator. Demultiplex it into out
* and err and return error appropriately. Band #1 carries the
* primary payload. Things coming over band #2 is not necessarily
* error; they are usually informative message on the standard error
* stream, aka "verbose"). A message over band #3 is a signal that
* the remote died unexpectedly. A flush() concludes the stream.
*/
#define PREFIX "remote:"
#define ANSI_SUFFIX "\033[K"
#define DUMB_SUFFIX " "
#define FIX_SIZE 10 /* large enough for any of the above */
int recv_sideband(const char *me, int in_stream, int out)
{
unsigned pf = strlen(PREFIX);
unsigned sf;
char buf[LARGE_PACKET_MAX + 2*FIX_SIZE];
char *suffix, *term;
int skip_pf = 0;
memcpy(buf, PREFIX, pf);
term = getenv("TERM");
if (term && strcmp(term, "dumb"))
suffix = ANSI_SUFFIX;
else
suffix = DUMB_SUFFIX;
sf = strlen(suffix);
while (1) {
int band, len;
len = packet_read(in_stream, NULL, NULL, buf + pf, LARGE_PACKET_MAX, 0);
if (len == 0)
break;
if (len < 1) {
fprintf(stderr, "%s: protocol error: no band designator\n", me);
return SIDEBAND_PROTOCOL_ERROR;
}
band = buf[pf] & 0xff;
len--;
switch (band) {
case 3:
buf[pf] = ' ';
buf[pf+1+len] = '\0';
fprintf(stderr, "%s\n", buf);
return SIDEBAND_REMOTE_ERROR;
case 2:
buf[pf] = ' ';
do {
char *b = buf;
int brk = 0;
/*
* If the last buffer didn't end with a line
* break then we should not print a prefix
* this time around.
*/
if (skip_pf) {
b += pf+1;
} else {
len += pf+1;
brk += pf+1;
}
/* Look for a line break. */
for (;;) {
brk++;
if (brk > len) {
brk = 0;
break;
}
if (b[brk-1] == '\n' ||
b[brk-1] == '\r')
break;
}
/*
* Let's insert a suffix to clear the end
* of the screen line if a line break was
* found. Also, if we don't skip the
* prefix, then a non-empty string must be
* present too.
*/
if (brk > (skip_pf ? 0 : (pf+1 + 1))) {
char save[FIX_SIZE];
memcpy(save, b + brk, sf);
b[brk + sf - 1] = b[brk - 1];
memcpy(b + brk - 1, suffix, sf);
fprintf(stderr, "%.*s", brk + sf, b);
memcpy(b + brk, save, sf);
len -= brk;
} else {
int l = brk ? brk : len;
fprintf(stderr, "%.*s", l, b);
len -= l;
}
skip_pf = !brk;
memmove(buf + pf+1, b + brk, len);
} while (len);
continue;
case 1:
write_or_die(out, buf + pf+1, len);
continue;
default:
fprintf(stderr, "%s: protocol error: bad band #%d\n",
me, band);
return SIDEBAND_PROTOCOL_ERROR;
}
}
return 0;
}
/*
* fd is connected to the remote side; send the sideband data
* over multiplexed packet stream.
*/
ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max)
{
ssize_t ssz = sz;
const char *p = data;
while (sz) {
unsigned n;
char hdr[5];
n = sz;
if (packet_max - 5 < n)
n = packet_max - 5;
if (0 <= band) {
sprintf(hdr, "%04x", n + 5);
hdr[4] = band;
write_or_die(fd, hdr, 5);
} else {
sprintf(hdr, "%04x", n + 4);
write_or_die(fd, hdr, 4);
}
write_or_die(fd, p, n);
p += n;
sz -= n;
}
return ssz;
}