Trivial: make sptps_receive_data_datagram() a little more readable.

The new code updates variables as stuff is being consumed, so that the
reader doesn't have to do that in his head.

diff --git a/src/sptps.c b/src/sptps.c
index e5946ed6fd8cc8cb9211141063f159188e0c6e8f..d6e6d417e1d752c9cd474921422cc7708cf3ac2c 100644 (file)
--- a/src/sptps.c
+++ b/src/sptps.c
@@ -447,6 +447,7 @@ static bool sptps_receive_data_datagram(sptps_t *s, const char *data, size_t len
        uint32_t seqno;
        memcpy(&seqno, data, 4);
        seqno = ntohl(seqno);
+       data += 4; len -= 4;
 
        if(!s->instate) {
                if(seqno != s->inseqno)
@@ -454,38 +455,39 @@ static bool sptps_receive_data_datagram(sptps_t *s, const char *data, size_t len
 
                s->inseqno = seqno + 1;
 
-               uint8_t type = data[4];
+               uint8_t type = *(data++); len--;
 
                if(type != SPTPS_HANDSHAKE)
                        return error(s, EIO, "Application record received before handshake finished");
 
-               return receive_handshake(s, data + 5, len - 5);
+               return receive_handshake(s, data, len);
        }
 
        // Decrypt
 
        char buffer[len];
-
        size_t outlen;
-
-       if(!chacha_poly1305_decrypt(s->incipher, seqno, data + 4, len - 4, buffer, &outlen))
+       if(!chacha_poly1305_decrypt(s->incipher, seqno, data, len, buffer, &outlen))
                return error(s, EIO, "Failed to decrypt and verify packet");
 
        if(!sptps_check_seqno(s, seqno, true))
                return false;
 
        // Append a NULL byte for safety.
-       buffer[len - 20] = 0;
+       buffer[outlen] = 0;
+
+       data = buffer;
+       len = outlen;
 
-       uint8_t type = buffer[0];
+       uint8_t type = *(data++); len--;
 
        if(type < SPTPS_HANDSHAKE) {
                if(!s->instate)
                        return error(s, EIO, "Application record received before handshake finished");
-               if(!s->receive_record(s->handle, type, buffer + 1, len - 21))
+               if(!s->receive_record(s->handle, type, data, len))
                        return false;
        } else if(type == SPTPS_HANDSHAKE) {
-               if(!receive_handshake(s, buffer + 1, len - 21))
+               if(!receive_handshake(s, data, len))
                        return false;
        } else {
                return error(s, EIO, "Invalid record type %d", type);