Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* Fast Reed-Solomon encoder for (255,223) CCSDS code on PowerPC G4/G5 using Altivec instructions |
| 2 | * Copyright 2004, Phil Karn KA9Q |
| 3 | * May be used under the terms of the GNU Lesser General Public License (LGPL) |
| 4 | */ |
| 5 | #include <stdio.h> |
| 6 | #include <string.h> |
| 7 | #include "fixed.h" |
| 8 | |
| 9 | /* Lookup table for feedback multiplications |
| 10 | * These are the low half of the coefficients. Since the generator polynomial is |
| 11 | * palindromic, we form it by reversing these on the fly |
| 12 | */ |
| 13 | static union { vector unsigned char v; unsigned char c[16]; } table[256]; |
| 14 | |
| 15 | static vector unsigned char reverse = (vector unsigned char)(0,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1); |
| 16 | static vector unsigned char shift_right = (vector unsigned char)(15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30); |
| 17 | |
| 18 | extern data_t CCSDS_alpha_to[]; |
| 19 | extern data_t CCSDS_index_of[]; |
| 20 | extern data_t CCSDS_poly[]; |
| 21 | |
| 22 | void rs_init_av(){ |
| 23 | int i,j; |
| 24 | |
| 25 | /* The PowerPC is big-endian, so the low-order byte of each vector contains the highest order term in the polynomial */ |
| 26 | for(j=0;j<16;j++){ |
| 27 | table[0].c[j] = 0; |
| 28 | for(i=1;i<256;i++){ |
| 29 | table[i].c[16-j-1] = CCSDS_alpha_to[MODNN(CCSDS_poly[j+1] + CCSDS_index_of[i])]; |
| 30 | } |
| 31 | } |
| 32 | #if 0 |
| 33 | for(i=0;i<256;i++){ |
| 34 | printf("table[%3d] = %3vu\n",i,table[i].v); |
| 35 | } |
| 36 | #endif |
| 37 | } |
| 38 | |
| 39 | void encode_rs_av(unsigned char *data,unsigned char *parity,int pad){ |
| 40 | union { vector unsigned char v[2]; unsigned char c[32]; } shift_register; |
| 41 | int i; |
| 42 | |
| 43 | shift_register.v[0] = (vector unsigned char)(0); |
| 44 | shift_register.v[1] = (vector unsigned char)(0); |
| 45 | |
| 46 | for(i=0;i<NN-NROOTS-pad;i++){ |
| 47 | vector unsigned char feedback0,feedback1; |
| 48 | unsigned char f; |
| 49 | |
| 50 | f = data[i] ^ shift_register.c[31]; |
| 51 | feedback1 = table[f].v; |
| 52 | feedback0 = vec_perm(feedback1,feedback1,reverse); |
| 53 | |
| 54 | /* Shift right one byte */ |
| 55 | shift_register.v[1] = vec_perm(shift_register.v[0],shift_register.v[1],shift_right) ^ feedback1; |
| 56 | shift_register.v[0] = vec_sro(shift_register.v[0],(vector unsigned char)(8)) ^ feedback0; |
| 57 | shift_register.c[0] = f; |
| 58 | } |
| 59 | for(i=0;i<NROOTS;i++) |
| 60 | parity[NROOTS-i-1] = shift_register.c[i]; |
| 61 | } |