Delbin: improve packet deserialization.

diff --git a/delbin.c b/delbin.c
index 406444652d1fe0d161aedb24864ff561ee532b9f..d24601fc447bde2ac8188582f7ee59272ebb367f 100644 (file)
--- a/delbin.c
+++ b/delbin.c
@@ -37,6 +37,10 @@ device was upgraded to firmware 2.5.165506 during development.
 The "data size" in the message header includes the 4 trailer bytes, so it
 is really the size of the whole message minus the header.
 
+Messages do not always start at the beginning of a packet. Every once in a
+while, the start of the next message directly follows the end of the previous
+one, in the same packet.
+
 The time before an unacknowledged message will be retransmitted by the
 device is on the order of 2 to 4 seconds.
 
@@ -524,6 +528,7 @@ static unsigned
 message_read_1(unsigned msg_id, message_t* m)
 {
        gbuint8 buf[256];
+       static gbuint8 buf_prev[256];
        gbuint8* p;
        unsigned total = 0;
        unsigned count = 0;
@@ -531,24 +536,38 @@ message_read_1(unsigned msg_id, message_t* m)
 
        for (;;) {
                for (;;) {
-                       unsigned n = packet_read(buf);
+                       unsigned n;
+                       // if last packet had extra data
+                       if (buf_prev[1]) {
+                               // try that first
+                               n = buf_prev[1] + 2;
+                               memcpy(buf, buf_prev, n);
+                               buf_prev[1] = 0;
+                       } else {
+                               n = packet_read(buf);
+                       }
                        if (n >= 10 && buf[2] == 0xdb && buf[3] == 0xfe &&
                            checksum(buf + 2, 6) == le_readu16(buf + 8))
                        {
-                               count = buf[1] - 8;
-                               total = le_readu16(buf + 6);
-                               id = le_readu16(buf + 4);
-                               message_ensure_size(m, total - 4);
-                               memcpy(m->buf, buf, 2 + buf[1]);
                                break;
                        }
                }
-               while (count < total && buf[1] == delbin_os_packet_size - 2) {
+               count = buf[1] - 8;
+               total = le_readu16(buf + 6);
+               id = le_readu16(buf + 4);
+               message_ensure_size(m, total - 4);
+               memcpy(m->buf, buf, 2 + buf[1]);
+               while (count < total) {
                        unsigned n;
                        packet_read(buf);
                        n = buf[1];
+                       // if packet has more than needed to complete message
                        if (n > total - count) {
-                               n = total - count;
+                               const unsigned n_next = n - (total - count);
+                               n -= n_next;
+                               // save the rest for next time
+                               memcpy(buf_prev + 2, buf + 2 + n, n_next);
+                               buf_prev[1] = n_next;
                        }
                        memcpy((char*)m->data + count, buf + 2, n);
                        count += n;