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Speed up Squawk Decode

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Re-write to avoid multiple reads of the same memory variable.
This commit is contained in:
Malcolm Robb 2013-04-15 22:12:40 +01:00
parent 6619d21970
commit 96afd52cb0
1 changed files with 19 additions and 14 deletions
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dump1090.c
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@ -1112,21 +1112,26 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
*
* For more info: http://en.wikipedia.org/wiki/Gillham_code */
{
int a,b,c,d;
int decIdentity = 0;
unsigned char rawIdentity;
a = ((msg[3] & 0x80) >> 5) |
((msg[2] & 0x02) >> 0) |
((msg[2] & 0x08) >> 3);
b = ((msg[3] & 0x02) << 1) |
((msg[3] & 0x08) >> 2) |
((msg[3] & 0x20) >> 5);
c = ((msg[2] & 0x01) << 2) |
((msg[2] & 0x04) >> 1) |
((msg[2] & 0x10) >> 4);
d = ((msg[3] & 0x01) << 2) |
((msg[3] & 0x04) >> 1) |
((msg[3] & 0x10) >> 4);
mm->identity = a*1000 + b*100 + c*10 + d;
rawIdentity = msg[2];
if (rawIdentity & 0x01) {decIdentity += 40;} // C4
if (rawIdentity & 0x02) {decIdentity += 2000;} // A2
if (rawIdentity & 0x04) {decIdentity += 20;} // C2
if (rawIdentity & 0x08) {decIdentity += 1000;} // A1
if (rawIdentity & 0x10) {decIdentity += 10;} // C1
rawIdentity = msg[3];
if (rawIdentity & 0x01) {decIdentity += 4;} // D4
if (rawIdentity & 0x02) {decIdentity += 400;} // B4
if (rawIdentity & 0x04) {decIdentity += 2;} // D2
if (rawIdentity & 0x08) {decIdentity += 200;} // B2
if (rawIdentity & 0x10) {decIdentity += 1;} // D1
if (rawIdentity & 0x20) {decIdentity += 100;} // B1
if (rawIdentity & 0x80) {decIdentity += 4000;} // A4
mm->identity = decIdentity;
}
/* DF 11 & 17: try to populate our ICAO addresses whitelist.