int main( int argc, char *argv[] ) {
unsigned char test[] = "abcd";
fprintf( stdout, "check '%s' of size %lu output: %u\n", "lol", sizeof test, checksum_crc16( test, sizeof test ) );
exit( EXIT_SUCCESS );
}
int msg_send( msg_t *msg )
{
unsigned char header[MSG_PREAMBLE_LEN + 3];
unsigned char checksum[2];
unsigned short crc;
int i, res;
// Preamble
for ( i = 0; i < MSG_PREAMBLE_LEN; i++ ) header[i] = MSG_PREAMBLE_BYTE;
// Command ID
header[MSG_PREAMBLE_LEN] = msg->id;
// Length
header[MSG_PREAMBLE_LEN + 1] = lo( msg->len );
header[MSG_PREAMBLE_LEN + 2] = hi( msg->len );
// Checksum
crc = checksum_crc16( header, 6 );
crc = checksum_update_crc16( msg->data, msg->len, crc );
checksum[0] = lo( crc );
checksum[1] = hi( crc );
if ( interface->write )
{
unsigned char *buf = malloc( 6 + msg->len + 2 ); // 6+2 fixes (PREAMBLE, ID, PAILOAD / ... / CRC)
memcpy( buf, header, 6 );
memcpy( buf + 6, msg->data, msg->len );
memcpy( buf + 6 + msg->len, (unsigned char *) &crc, 2 );
res = interface->write( buf, 6 + msg->len + 2 );
if ( res < 6 + msg->len + 2 )
{
interface->close();
quit( "Failed to submit message checksum" );
}
free( buf );
// The following implementation doesn't work:
//
// // Submit header
// res = interface->write( header, 6 );
// if ( res < 6 )
// {
// interface->close();
// quit( "Failed to submit message header" );
// }
//
// // Submit payload
// res = interface->write( msg->data, msg->len );
// if ( res < msg->len )
// {
// interface->close();
// quit( "Failed to submit message payload" );
// }
//
// res = interface->write( (unsigned char *) &crc, 2 );
// if ( res < sizeof( crc ) )
// {
// interface->close();
// quit( "Failed to submit message checksum" );
// }
// unsigned short check = checksum_crc16( header, 6 );
// check = checksum_update_crc16( msg->data, msg->len, check );
// check = checksum_update_crc16( (unsigned char *) &crc, sizeof( short ), check );
return msg->len + 8;
}
return -1;
}