[PATCH v3 2/3] pkt-line: use string versions of functions

[Denton Liu <liu.denton@xxxxxxxxx>]

We have many cases where we are writing a control packet as a string
constant out and we need to specify the length of the string. Currently,
the length is specified as a magical `4` literal.

Change these instances to use a function that calls strlen() to
determine the length of the string removing the need to specify the
length at all. Since these functions are inline, the strlen()s should be
replaced with constants at compile-time so this should not result in any
performance penalty.

Signed-off-by: Denton Liu <liu.denton@xxxxxxxxx>
---

Notes:
    Junio, you mentioned in an earlier email[0] that write_str_in_full() and
    strbuf_addstr() each count the string length at runtime. However, I
    don't think that's true since they're both inline functions and
    strbuf_addstr() has the following comment:
    
    	/**
    	 * Add a NUL-terminated string to the buffer.
    	 *
    	 * NOTE: This function will *always* be implemented as an inline or a macro
    	 * using strlen, meaning that this is efficient to write things like:
    	 *
    	 *     strbuf_addstr(sb, "immediate string");
    	 *
    	 */
    
    so I believe that the lengths should be determined at compile-time.
    
    [0]: https://lore.kernel.org/git/xmqqeeqhxred.fsf@xxxxxxxxxxxxxxxxxxxxxx/

 pkt-line.c | 48 ++++++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 18 deletions(-)

diff --git a/pkt-line.c b/pkt-line.c
index 8f9bc68ee2..e29f427b19 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -81,49 +81,61 @@ static void packet_trace(const char *buf, unsigned int len, int write)
 	strbuf_release(&out);
 }
 
+static inline void packet_trace_str(const char *buf, int write)
+{
+	packet_trace(buf, strlen(buf), write);
+}
+
+#define control_packet_write(fd, s, errstr) \
+	do { \
+		(void)s"is a string constant"; \
+		packet_trace_str(s, 1); \
+		if (write_str_in_full((fd), s) < 0) \
+			die_errno((errstr)); \
+	} while (0)
+
 /*
  * If we buffered things up above (we don't, but we should),
  * we'd flush it here
  */
 void packet_flush(int fd)
 {
-	packet_trace("0000", 4, 1);
-	if (write_in_full(fd, "0000", 4) < 0)
-		die_errno(_("unable to write flush packet"));
+	control_packet_write(fd, "0000", _("unable to write flush packet"));
 }
 
 void packet_delim(int fd)
 {
-	packet_trace("0001", 4, 1);
-	if (write_in_full(fd, "0001", 4) < 0)
-		die_errno(_("unable to write delim packet"));
+	control_packet_write(fd, "0001", _("unable to write delim packet"));
 }
 
 void packet_response_end(int fd)
 {
-	packet_trace("0002", 4, 1);
-	if (write_in_full(fd, "0002", 4) < 0)
-		die_errno(_("unable to write stateless separator packet"));
+	control_packet_write(fd, "0002", _("unable to write stateless separator packet"));
 }
 
 int packet_flush_gently(int fd)
 {
-	packet_trace("0000", 4, 1);
-	if (write_in_full(fd, "0000", 4) < 0)
+	packet_trace_str("0000", 1);
+	if (write_str_in_full(fd, "0000") < 0)
 		return error(_("flush packet write failed"));
 	return 0;
 }
 
+#define control_packet_buf_write(buf, s) \
+	do { \
+		(void)s"is a string constant"; \
+		packet_trace_str(s, 1); \
+		strbuf_addstr((buf), s); \
+	} while (0)
+
 void packet_buf_flush(struct strbuf *buf)
 {
-	packet_trace("0000", 4, 1);
-	strbuf_add(buf, "0000", 4);
+	control_packet_buf_write(buf, "0000");
 }
 
 void packet_buf_delim(struct strbuf *buf)
 {
-	packet_trace("0001", 4, 1);
-	strbuf_add(buf, "0001", 4);
+	control_packet_buf_write(buf, "0001");
 }
 
 void set_packet_header(char *buf, int size)
@@ -337,15 +349,15 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 	if (len < 0) {
 		die(_("protocol error: bad line length character: %.4s"), linelen);
 	} else if (!len) {
-		packet_trace("0000", 4, 0);
+		packet_trace_str("0000", 0);
 		*pktlen = 0;
 		return PACKET_READ_FLUSH;
 	} else if (len == 1) {
-		packet_trace("0001", 4, 0);
+		packet_trace_str("0001", 0);
 		*pktlen = 0;
 		return PACKET_READ_DELIM;
 	} else if (len == 2) {
-		packet_trace("0002", 4, 0);
+		packet_trace_str("0002", 0);
 		*pktlen = 0;
 		return PACKET_READ_RESPONSE_END;
 	} else if (len < 4) {
-- 
2.27.0.307.g7979e895e7