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git-upload-pack: Support sending multiple ACK messages

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The current fetch/upload protocol works like this:

- client sends revs it wants to have via "want" messages
- client sends a flush message (message with len 0)
- client sends revs it has via "have" messages
- after one window (32 revs), a flush is sent
- after each subsequent window, a flush is sent, and an ACK/NAK is received.
        (NAK means that server does not have any of the transmitted revs;
         ACK sends also the sha1 of the rev server has)
 - when the first ACK is received, client sends "done", and does not expect
        any further messages

One special case, though:

- if no ACK is received (only NAK's), and client runs out of revs to send,
        "done" is sent, and server sends just one more "NAK"

A smarter scheme, which actually has a chance to detect more than one
common rev, would be to send more than just one ACK. This patch implements
the server side of the following extension to the protocol:

- client sends at least one "want" message with "multi_ack" appended, like

        "want 1234567890123456789012345678901234567890 multi_ack"

- if the server understands that extension, it will send ACK messages for all
        revs it has, not just the first one

- server appends "continue" to the ACK messages like

        "ACK 1234567890123456789012345678901234567890 continue"

        until it has MAX_HAS-1 revs. In this manner, client knows when to
        stop sending revs by checking for the substring "continue" (and
        further knows that server understands multi_ack)

In this manner, the protocol stays backwards compatible, since both client
must send "want ... multi_ack" and server must answer with "ACK ...
continue" to enable the extension.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Johannes Schindelin 2005-10-23 03:37:45 +02:00 committed by Junio C Hamano
parent 794f9fe7db
commit 0f8fdc3958
1 changed files with 15 additions and 22 deletions
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37
upload-pack.c
View file

@ -10,7 +10,7 @@ static const char upload_pack_usage[] = "git-upload-pack [--strict] [--timeout=n
#define THEY_HAVE (1U << 0)
#define MAX_HAS 256
#define MAX_NEEDS 256
static int nr_has = 0, nr_needs = 0;
static int nr_has = 0, nr_needs = 0, multi_ack = 0;
static unsigned char has_sha1[MAX_HAS][20];
static unsigned char needs_sha1[MAX_NEEDS][20];
static unsigned int timeout = 0;
@ -124,39 +124,28 @@ static int get_common_commits(void)
reset_timeout();
if (!len) {
packet_write(1, "NAK\n");
if (multi_ack || nr_has == 0)
packet_write(1, "NAK\n");
continue;
}
len = strip(line, len);
if (!strncmp(line, "have ", 5)) {
if (got_sha1(line+5, sha1)) {
packet_write(1, "ACK %s\n", sha1_to_hex(sha1));
break;
}
if (got_sha1(line+5, sha1) &&
(multi_ack || nr_has == 1))
packet_write(1, "ACK %s%s\n",
sha1_to_hex(sha1),
multi_ack && nr_has < MAX_HAS ?
" continue" : "");
continue;
}
if (!strcmp(line, "done")) {
if (nr_has > 0)
return 0;
packet_write(1, "NAK\n");
return -1;
}
die("git-upload-pack: expected SHA1 list, got '%s'", line);
}
for (;;) {
len = packet_read_line(0, line, sizeof(line));
reset_timeout();
if (!len)
continue;
len = strip(line, len);
if (!strncmp(line, "have ", 5)) {
got_sha1(line+5, sha1);
continue;
}
if (!strcmp(line, "done"))
break;
die("git-upload-pack: expected SHA1 list, got '%s'", line);
}
return 0;
}
static int receive_needs(void)
@ -185,6 +174,10 @@ static int receive_needs(void)
if (strncmp("want ", line, 5) || get_sha1_hex(line+5, sha1_buf))
die("git-upload-pack: protocol error, "
"expected to get sha, not '%s'", line);
if (strstr(line+45, "multi_ack"))
multi_ack = 1;
needs++;
}
}