FGFS-4.1/gr-air-modes
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Rewrite CRC to use bytewise CRC instead of bitwise. ~8x faster.

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This commit is contained in:
Nick Foster
2013-08-19 16:40:02 -07:00
parent 4d2587574a
commit b7627fa2d4
3 changed files with 39 additions and 137 deletions
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6
lib/slicer_impl.cc
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@@ -172,7 +172,11 @@ int air_modes::slicer_impl::work(int noutput_items,
if(rx_packet.type == Short_Packet && rx_packet.message_type != 11 && rx_packet.numlowconf > 0) {continue;}
if(rx_packet.message_type == 11 && rx_packet.numlowconf >= 10) {continue;}
rx_packet.crc = modes_check_crc(rx_packet.data, packet_length);
rx_packet.crc = modes_check_crc(rx_packet.data, (packet_length/8)-3);
unsigned int ap = rx_packet.data[packet_length/8-3] << 16
| rx_packet.data[packet_length/8-2] << 8
| rx_packet.data[packet_length/8-1] << 0;
rx_packet.crc ^= ap;
//crc for packets that aren't type 11 or type 17 is encoded with the transponder ID, which we don't know
//therefore we toss 'em if there's syndrome