1 files changed, 133 insertions, 0 deletions
diff --git a/sideband.c b/sideband.c
new file mode 100644
index 0000000000..6d7f943e43
--- /dev/null
+++ b/sideband.c
@@ -0,0 +1,133 @@
+#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 "        "
+
+int recv_sideband(const char *me, int in_stream, int out)
+{
+	const char *suffix;
+	char buf[LARGE_PACKET_MAX + 1];
+	struct strbuf outbuf = STRBUF_INIT;
+	int retval = 0;
+
+	if (isatty(2) && !is_terminal_dumb())
+		suffix = ANSI_SUFFIX;
+	else
+		suffix = DUMB_SUFFIX;
+
+	while (!retval) {
+		const char *b, *brk;
+		int band, len;
+		len = packet_read(in_stream, NULL, NULL, buf, LARGE_PACKET_MAX, 0);
+		if (len == 0)
+			break;
+		if (len < 1) {
+			strbuf_addf(&outbuf,
+				    "%s%s: protocol error: no band designator",
+				    outbuf.len ? "\n" : "", me);
+			retval = SIDEBAND_PROTOCOL_ERROR;
+			break;
+		}
+		band = buf[0] & 0xff;
+		buf[len] = '\0';
+		len--;
+		switch (band) {
+		case 3:
+			strbuf_addf(&outbuf, "%s%s%s", outbuf.len ? "\n" : "",
+				    PREFIX, buf + 1);
+			retval = SIDEBAND_REMOTE_ERROR;
+			break;
+		case 2:
+			b = buf + 1;
+
+			/*
+			 * Append a suffix to each nonempty line to clear the
+			 * end of the screen line.
+			 *
+			 * The output is accumulated in a buffer and
+			 * each line is printed to stderr using
+			 * write(2) to ensure inter-process atomicity.
+			 */
+			while ((brk = strpbrk(b, "\n\r"))) {
+				int linelen = brk - b;
+
+				if (!outbuf.len)
+					strbuf_addstr(&outbuf, PREFIX);
+				if (linelen > 0) {
+					strbuf_addf(&outbuf, "%.*s%s%c",
+						    linelen, b, suffix, *brk);
+				} else {
+					strbuf_addch(&outbuf, *brk);
+				}
+				xwrite(2, outbuf.buf, outbuf.len);
+				strbuf_reset(&outbuf);
+
+				b = brk + 1;
+			}
+
+			if (*b)
+				strbuf_addf(&outbuf, "%s%s",
+					    outbuf.len ? "" : PREFIX, b);
+			break;
+		case 1:
+			write_or_die(out, buf + 1, len);
+			break;
+		default:
+			strbuf_addf(&outbuf, "%s%s: protocol error: bad band #%d",
+				    outbuf.len ? "\n" : "", me, band);
+			retval = SIDEBAND_PROTOCOL_ERROR;
+			break;
+		}
+	}
+
+	if (outbuf.len) {
+		strbuf_addch(&outbuf, '\n');
+		xwrite(2, outbuf.buf, outbuf.len);
+	}
+	strbuf_release(&outbuf);
+	return retval;
+}
+
+/*
+ * fd is connected to the remote side; send the sideband data
+ * over multiplexed packet stream.
+ */
+void send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max)
+{
+	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) {
+			xsnprintf(hdr, sizeof(hdr), "%04x", n + 5);
+			hdr[4] = band;
+			write_or_die(fd, hdr, 5);
+		} else {
+			xsnprintf(hdr, sizeof(hdr), "%04x", n + 4);
+			write_or_die(fd, hdr, 4);
+		}
+		write_or_die(fd, p, n);
+		p += n;
+		sz -= n;
+	}
+}