Hi,

Brandon Williams wrote:

The current pkt-line API encodes the status of a pkt-line read in the
length of the read content.  An error is indicated with '-1', a flush
with '0' (which can be confusing since a return value of '0' can also
indicate an empty pkt-line), and a positive integer for the length of
the read content otherwise.  This doesn't leave much room for allowing
the addition of additional special packets in the future.

To solve this introduce 'packet_read_with_status()' which reads a packet
and returns the status of the read encoded as an 'enum packet_status'
type.  This allows for easily identifying between special and normal
packets as well as errors.  It also enables easily adding a new special
packet in the future.

Makes sense, thanks.  Using an enum return value is less opaque, too.

[...]

This function definition straddles two worlds: it is line-wrapped as
though there are a limited number of columns, but it goes far past 80
columns.

Can "make style" or a similar tool take care of rewrapping it?

 {
-	int len, ret;
+	int len;
 	char linelen[4];
 
-	ret = get_packet_data(fd, src_buf, src_len, linelen, 4, options);
-	if (ret < 0)
-		return ret;
+	if (get_packet_data(fd, src_buffer, src_len, linelen, 4, options) < 0)
+		return PACKET_READ_EOF;
+

EOF is indeed the only error that get_packet_data can return.

Could be worth a doc comment on get_packet_data to make that clearer.
It's not too important since it's static, though.

 	len = packet_length(linelen);
-	if (len < 0)
+
+	if (len < 0) {
 		die("protocol error: bad line length character: %.4s", linelen);
-	if (!len) {
+	} else if (!len) {
 		packet_trace("0000", 4, 0);
-		return 0;
+		return PACKET_READ_FLUSH;

The advertised change. Makes sense.

[...]

-	if (len >= size)
+	if ((unsigned)len >= size)
 		die("protocol error: bad line length %d", len);

The comparison is safe since we just checked that len >= 0.

Is there some static analysis that can make this kind of operation
easier?

[...]

nit: can simplify by avoiding the status temporary:

	int pktlen;

	switch (packet_read_with_status(...)) {
	case PACKET_READ_EOF:
		return -1;
	case PACKET_READ_FLUSH:
		return 0;
	case PACKET_READ_NORMAL:
		return pktlen;
	}

As a bonus, that lets static analyzers check that the cases are
exhaustive.  (On the other hand, C doesn't guarantee that an enum can
only have the values listed as enumerators.  Did we end up figuring
out a way to handle that, beyond always including a 'default: BUG()'?)

nit: do any callers treat the return value as a number?  It would be
less magical if the numbering were left to the compiler (0, 1, 2).

Thanks,
Jonathan