[gpsd-dev] [PATCH v2 1/1] gps2udp: add a 'pack' mode

[Ferry Huberts]

From: Ferry Huberts <address@hidden>

-p flush-phrase Will pack all sentences that start with a '$' character
   in a single packet. The packet will be sent when a sentence is
   received from the gpsd daemon that starts with the flush-phrase.

Signed-off-by: Ferry Huberts <address@hidden>
---
 gps2udp.c   | 41 ++++++++++++++++++++++++++++++++++++++---
 gps2udp.xml |  4 ++++
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/gps2udp.c b/gps2udp.c
index ac816bc..563c01f 100644
--- a/gps2udp.c
+++ b/gps2udp.c
@@ -78,8 +78,10 @@ static bool aisonly = false;
 }
 /address@hidden@*/
 
-static int send_udp (char *nmeastring, size_t ind)
+static int send_udp (char *flush_phrase, unsigned int flush_phrase_len, char 
*nmeastring, size_t ind)
 {
+    static char pack_buffer[16384];
+    static unsigned int pack_buffer_len = 0;
     char message [255];
     char *buffer;
     int  channel;
@@ -105,6 +107,26 @@ static int send_udp (char *nmeastring, size_t ind)
     buffer[ind] = '\r'; ind++;
     buffer[ind] = '\0';
 
+    /*
+     * Only pack when a flush-phrase is defined and when the current sentence
+     * starts with a '$'
+     */
+    if (flush_phrase && buffer[0] == '$') {
+      strcpy(&pack_buffer[pack_buffer_len], buffer);
+      pack_buffer_len += ind;
+      if (strncmp(buffer, flush_phrase, flush_phrase_len) &&
+          (pack_buffer_len < (sizeof(pack_buffer) - sizeof(message)))) {
+        /* the current sentence doesn't start with the flush-phrase _and_
+         * there is enough space in the pack buffer for another sentence */
+        return 0;
+      }
+
+      /* send out the pack buffer */
+      buffer = pack_buffer;
+      ind = pack_buffer_len;
+      pack_buffer_len = 0;
+    }
+
     /* send message on udp channel */
     /address@hidden@*/
     for (channel=0; channel < udpchannel; channel ++) {
@@ -182,6 +204,9 @@ static void usage(void)
                  "-a Select !AISDM message only.\n"
                  "-c [count] exit after count packets.\n"
                  "-b Run in background as a daemon.\n" 
+                 "-p flush-phrase Will pack all sentences that start with a 
'$' character\n"
+                 "   in a single packet. The packet will be sent when a 
sentence is\n"
+                 "   received from the gpsd daemon that starts with the 
flush-phrase.\n"
                  "-d [0-2] 1 display sent packets, 2 ignored packets.\n" 
                  "-v Print version and exit.\n\n"
                  "You must specify one, or more, of -r, -R, or -w\n"
@@ -354,12 +379,14 @@ static unsigned int AISGetInt(unsigned char *bitbytes, 
unsigned int sp, unsigned
 int main(int argc, char **argv)
 {
     bool daemonize = false;
+    char * flush_phrase = NULL;
+    unsigned int flush_phrase_len = 0;
     long count = -1;
     int option;
     char *udphostport[MAX_UDP_DEST];
 
     flags = WATCH_ENABLE;
-    while ((option = getopt(argc, argv, "?habnjvc:l:u:d:")) != -1)
+    while ((option = getopt(argc, argv, "?habnjvc:l:u:p:d:")) != -1)
     {
        switch (option) {
        case 'd':
@@ -397,6 +424,14 @@ int main(int argc, char **argv)
                udphostport[udpchannel++] = optarg;
             }
             break;
+       case 'p':
+               flush_phrase = strdup(optarg);
+               flush_phrase_len = strlen(flush_phrase);
+               if (!flush_phrase_len || flush_phrase[0] != '$') {
+                       (void) fprintf(stderr, "gps2udp: flush-phrase must 
start with '$' character\n");
+                       exit (1);
+               }
+               break;
        case 'v':
            (void)fprintf(stderr, "%s: %s (revision %s)\n",
                          argv[0], VERSION, REVISION);
@@ -483,7 +518,7 @@ int main(int argc, char **argv)
 
            // send to all UDP destinations
            if (udpchannel > 0)
-               (void)send_udp(buffer, (size_t)len);
+               (void)send_udp(flush_phrase, flush_phrase_len, buffer, 
(size_t)len);
 
            // if we count messages check it now
            if (count >= 0) {
diff --git a/gps2udp.xml b/gps2udp.xml
index 8f0f588..4ef8a9d 100644
--- a/gps2udp.xml
+++ b/gps2udp.xml
@@ -28,6 +28,7 @@ BSD terms apply: see the file COPYING in the distribution 
root for details.
       <arg choice='opt'>-a</arg>
       <arg choice='opt'>-u <replaceable>hostname:udpport</replaceable></arg>
       <arg choice='opt'>-c <replaceable>count</replaceable></arg>
+      <arg choice='opt'>-p <replaceable>flush-phrase</replaceable></arg>
       <arg choice='opt'>-d <replaceable>1|2</replaceable></arg>
       <arg choice='opt'>-v</arg>
       <group>
@@ -85,6 +86,9 @@ destinations).</para>
 <para>-b causes <application>gps2udp</application> to run as a daemon.</para>
 <para>-c [count] causes [count] sentences to be output.
 <application>gps2udp</application> will then exit gracefully.</para>
+<para>-p flush-phrase Will pack all sentences that start with a '$' character
+in a single packet. The packet will be sent when a sentence is received from
+the gpsd daemon that starts with the flush-phrase.</para>
 
 <para>-d 1 prints sent packet on stdout.</para>
 <para>-v prints the version, then exits.</para>
-- 
1.8.4.2