Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* Utility routines for FEC support |
| 2 | * Copyright 2004, Phil Karn, KA9Q |
| 3 | */ |
| 4 | |
| 5 | #include <stdio.h> |
| 6 | #include "fec.h" |
| 7 | |
| 8 | unsigned char Partab[256]; |
| 9 | int P_init; |
| 10 | |
| 11 | /* Create 256-entry odd-parity lookup table |
| 12 | * Needed only on non-ia32 machines |
| 13 | */ |
| 14 | void partab_init(void){ |
| 15 | int i,cnt,ti; |
| 16 | |
| 17 | /* Initialize parity lookup table */ |
| 18 | for(i=0;i<256;i++){ |
| 19 | cnt = 0; |
| 20 | ti = i; |
| 21 | while(ti){ |
| 22 | if(ti & 1) |
| 23 | cnt++; |
| 24 | ti >>= 1; |
| 25 | } |
| 26 | Partab[i] = cnt & 1; |
| 27 | } |
| 28 | P_init=1; |
| 29 | } |
| 30 | |
| 31 | /* Lookup table giving count of 1 bits for integers 0-255 */ |
| 32 | int Bitcnt[] = { |
| 33 | 0, 1, 1, 2, 1, 2, 2, 3, |
| 34 | 1, 2, 2, 3, 2, 3, 3, 4, |
| 35 | 1, 2, 2, 3, 2, 3, 3, 4, |
| 36 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 37 | 1, 2, 2, 3, 2, 3, 3, 4, |
| 38 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 39 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 40 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 41 | 1, 2, 2, 3, 2, 3, 3, 4, |
| 42 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 43 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 44 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 45 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 46 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 47 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 48 | 4, 5, 5, 6, 5, 6, 6, 7, |
| 49 | 1, 2, 2, 3, 2, 3, 3, 4, |
| 50 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 51 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 52 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 53 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 54 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 55 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 56 | 4, 5, 5, 6, 5, 6, 6, 7, |
| 57 | 2, 3, 3, 4, 3, 4, 4, 5, |
| 58 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 59 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 60 | 4, 5, 5, 6, 5, 6, 6, 7, |
| 61 | 3, 4, 4, 5, 4, 5, 5, 6, |
| 62 | 4, 5, 5, 6, 5, 6, 6, 7, |
| 63 | 4, 5, 5, 6, 5, 6, 6, 7, |
| 64 | 5, 6, 6, 7, 6, 7, 7, 8, |
| 65 | }; |
| 66 | |