atomic write for sideband remote messages

It has been a few times that I ended up with such a confusing display:

|remote: Generating pack...
|remote: Done counting 17 objects.
|remote: Result has 9 objects.
|remote: Deltifying 9 objects.
|remote:  100% (9/9) done
|remote: Unpacking 9 objects
|Total 9, written 9 (delta 8), reused 0 (delta 0)
| 100% (9/9) done

The confusion can be avoided in most cases by writing the remote message
in one go to prevent interleacing with local messages.  The buffer
declaration has been moved inside recv_sideband() to avoid extra string
copies.

Signed-off-by: Nicolas Pitre <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Nicolas Pitre

builtin-archive.c

@@ -75,7 +75,7 @@ static int run_remote_archiver(const char *remote, int argc,
 		die("git-archive: expected a flush");
 
 	/* Now, start reading from fd[0] and spit it out to stdout */
-	rv = recv_sideband("archive", fd[0], 1, 2, buf, sizeof(buf));
+	rv = recv_sideband("archive", fd[0], 1, 2);
 	close(fd[0]);
 	rv |= finish_connect(pid);
 

fetch-clone.c

@@ -115,12 +115,10 @@ static pid_t setup_sideband(int sideband, const char *me, int fd[2], int xd[2])
 		die("%s: unable to fork off sideband demultiplexer", me);
 	if (!side_pid) {
 		/* subprocess */
-		char buf[LARGE_PACKET_MAX];
-
 		close(fd[0]);
 		if (xd[0] != xd[1])
 			close(xd[1]);
-		if (recv_sideband(me, xd[0], fd[1], 2, buf, sizeof(buf)))
+		if (recv_sideband(me, xd[0], fd[1], 2))
 			exit(1);
 		exit(0);
 	}

sideband.c

@@ -11,36 +11,40 @@
  * stream, aka "verbose").  A message over band #3 is a signal that
  * the remote died unexpectedly.  A flush() concludes the stream.
  */
-int recv_sideband(const char *me, int in_stream, int out, int err, char *buf, int bufsz)
+int recv_sideband(const char *me, int in_stream, int out, int err)
 {
+	char buf[7 + LARGE_PACKET_MAX + 1];
+	strcpy(buf, "remote:");
 	while (1) {
-		int len = packet_read_line(in_stream, buf, bufsz);
+		int band, len;
+		len	= packet_read_line(in_stream, buf+7, LARGE_PACKET_MAX);
 		if (len == 0)
 			break;
 		if (len < 1) {
 			len = sprintf(buf, "%s: protocol error: no band designator\n", me);
 			safe_write(err, buf, len);
 			return SIDEBAND_PROTOCOL_ERROR;
 		}
+		band = buf[7] & 0xff;
 		len--;
-		switch (buf[0] & 0xFF) {
+		switch (band) {
 		case 3:
-			safe_write(err, "remote: ", 8);
-			safe_write(err, buf+1, len);
-			safe_write(err, "\n", 1);
+			buf[7] = ' ';
+			buf[8+len] = '\n';
+			safe_write(err, buf, 8+len+1);
 			return SIDEBAND_REMOTE_ERROR;
 		case 2:
-			safe_write(err, "remote: ", 8);
-			safe_write(err, buf+1, len);
+			buf[7] = ' ';
+			safe_write(err, buf, 8+len);
 			continue;
 		case 1:
-			safe_write(out, buf+1, len);
+			safe_write(out, buf+8, len);
 			continue;
 		default:
-			len = sprintf(buf + 1,
+			len = sprintf(buf,
 				      "%s: protocol error: bad band #%d\n",
-				      me, buf[0] & 0xFF);
-			safe_write(err, buf+1, len);
+				      me, band);
+			safe_write(err, buf, len);
 			return SIDEBAND_PROTOCOL_ERROR;
 		}
 	}

sideband.h

@@ -7,7 +7,7 @@
 #define DEFAULT_PACKET_MAX 1000
 #define LARGE_PACKET_MAX 65520
 
-int recv_sideband(const char *me, int in_stream, int out, int err, char *, int);
+int recv_sideband(const char *me, int in_stream, int out, int err);
 ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max);
 
 #endif