scpi_serial: Rephrase NL and NL+CR line termination check.

Rearrange the check for line termination in SCPI receive data, and add a
comment in that spot. Keep related conditions together, avoid line breaks
for complex terms. This shall simplify review, and raise awareness during
maintenance. This change amends commit a0ade2f933d6.

diff --git a/src/scpi/scpi_serial.c b/src/scpi/scpi_serial.c
index f0ec4c4dfc77a4ba246e7a3f6dd4b56099827eb3..f627deefbd2d2010cf16559dd977b1099c95c1e7 100644 (file)
--- a/src/scpi/scpi_serial.c
+++ b/src/scpi/scpi_serial.c
@@ -181,22 +181,22 @@ static int scpi_serial_read_data(void *priv, char *buf, int maxlen)
 
        /* Try to read new data into the buffer. */
        ret = serial_read_nonblocking(sscpi->serial, buf, maxlen);
-
        if (ret < 0)
                return ret;
 
-       if (ret > 0) {
-               if (buf[ret - 1] == '\n') {
-                       sscpi->got_newline = TRUE;
-                       sr_spew("Received NL terminator");
-               } else if (ret > 1 &&
-                          buf[ret - 2] == '\n' && buf[ret - 1] == '\r') {
-                       sscpi->got_newline = TRUE;
-                       sr_spew("Received NL+CR terminator");
-                       ret--;
-               } else {
-                       sscpi->got_newline = FALSE;
-               }
+       /*
+        * Check for line termination at the end of the receive data.
+        * Handle the usual case of NL, as well as the unusual NL+CR
+        * combination (some GWInstek DMMs were found to do this).
+        */
+       sscpi->got_newline = FALSE;
+       if (ret >= 1 && buf[ret - 1] == '\n') {
+               sscpi->got_newline = TRUE;
+               sr_spew("Received NL terminator");
+       } else if (ret >= 2 && buf[ret - 2] == '\n' && buf[ret - 1] == '\r') {
+               ret--;
+               sscpi->got_newline = TRUE;
+               sr_spew("Received NL+CR terminator");
        }
 
        return ret;