44 lines
1.3 KiB
C
44 lines
1.3 KiB
C
#include "parameters.h"
|
|
#include "repetition.h"
|
|
#include <immintrin.h>
|
|
#include <stddef.h>
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
/**
|
|
* @file repetition.c
|
|
* @brief Implementation of repetition codes
|
|
*/
|
|
|
|
|
|
#define MASK_N2 ((((uint64_t) 1) << PARAM_N2) - 1)
|
|
|
|
/**
|
|
* @brief Decoding the code words to a message using the repetition code
|
|
*
|
|
* We use a majority decoding. In fact we have that PARAM_N2 = 2 * PARAM_T + 1, thus,
|
|
* if the Hamming weight of the vector is greater than PARAM_T, the code word is decoded
|
|
* to 1 and 0 otherwise.
|
|
*
|
|
* @param[out] m Pointer to an array that is the message
|
|
* @param[in] em Pointer to an array that is the code word
|
|
*/
|
|
void PQCLEAN_HQC192_AVX2_repetition_code_decode(uint64_t *m, const uint64_t *em) {
|
|
size_t t = 0;
|
|
uint32_t b, bn, bi, c, cn, ci;
|
|
uint64_t cx, ones;
|
|
uint64_t mask;
|
|
|
|
for (b = 0; b < PARAM_N1N2 - PARAM_N2 + 1; b += PARAM_N2) {
|
|
bn = b >> 6;
|
|
bi = b & 63;
|
|
c = b + PARAM_N2 - 1;
|
|
cn = c >> 6;
|
|
ci = c & 63;
|
|
cx = em[cn] << (63 - ci);
|
|
mask = (uint64_t) (-((int64_t) (cn ^ (bn + 1))) >> 63); // cn != bn+1
|
|
ones = _mm_popcnt_u64(((em[bn] >> bi) & MASK_N2) | (cx & ~mask));
|
|
m[t >> 6] |= (uint64_t) ((((PARAM_T - ones) >> 31) & 1) << (t & 63));
|
|
t++;
|
|
}
|
|
}
|