pkt-line: add delim packet support

One of the design goals of protocol-v2 is to improve the semantics of
flush packets.  Currently in protocol-v1, flush packets are used both to
indicate a break in a list of packet lines as well as an indication that
one side has finished speaking.  This makes it particularly difficult
to implement proxies as a proxy would need to completely understand git
protocol instead of simply looking for a flush packet.

To do this, introduce the special deliminator packet '0001'.  A delim
packet can then be used as a deliminator between lists of packet lines
while flush packets can be reserved to indicate the end of a response.

Documentation for how this packet will be used in protocol v2 will
included in a future patch.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/pkt-line.c b/pkt-line.c
index 1881dc881392bc9de01a6158c6a9d1835a06a331..7296731cf3222946f565c97144e0f6fb2dc8850b 100644 (file)
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -91,6 +91,12 @@ void packet_flush(int fd)
        write_or_die(fd, "0000", 4);
 }
 
+void packet_delim(int fd)
+{
+       packet_trace("0001", 4, 1);
+       write_or_die(fd, "0001", 4);
+}
+
 int packet_flush_gently(int fd)
 {
        packet_trace("0000", 4, 1);
@@ -105,6 +111,12 @@ void packet_buf_flush(struct strbuf *buf)
        strbuf_add(buf, "0000", 4);
 }
 
+void packet_buf_delim(struct strbuf *buf)
+{
+       packet_trace("0001", 4, 1);
+       strbuf_add(buf, "0001", 4);
+}
+
 static void set_packet_header(char *buf, const int size)
 {
        static char hexchar[] = "0123456789abcdef";
@@ -301,6 +313,10 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
                packet_trace("0000", 4, 0);
                *pktlen = 0;
                return PACKET_READ_FLUSH;
+       } else if (len == 1) {
+               packet_trace("0001", 4, 0);
+               *pktlen = 0;
+               return PACKET_READ_DELIM;
        } else if (len < 4) {
                die("protocol error: bad line length %d", len);
        }

diff --git a/pkt-line.h b/pkt-line.h
index 11b04f026f795ebb82382d7182988b5007d34802..9570bd7a0a8759bc15876d13652b38107c0d5ed5 100644 (file)
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -20,8 +20,10 @@
  * side can't, we stay with pure read/write interfaces.
  */
 void packet_flush(int fd);
+void packet_delim(int fd);
 void packet_write_fmt(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
 void packet_buf_flush(struct strbuf *buf);
+void packet_buf_delim(struct strbuf *buf);
 void packet_write(int fd_out, const char *buf, size_t size);
 void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
 int packet_flush_gently(int fd);
@@ -75,6 +77,7 @@ enum packet_read_status {
        PACKET_READ_EOF,
        PACKET_READ_NORMAL,
        PACKET_READ_FLUSH,
+       PACKET_READ_DELIM,
 };
 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
                                                size_t *src_len, char *buffer,