utils.c

#include "utils.h"

#include <linux/types.h>
#include <linux/slab.h> 

#include "GF.h"
#include "poly.h"

uint8_t complement(uint8_t a, uint8_t p) {
  return (p - a) % p;
}

// Assume p is a prime.
int8_t inverse(int8_t a, int8_t p) {
  int8_t t = 0;
  int8_t new_t = 1;
  int8_t r = p;
  int8_t new_r = a;

  int8_t q;
  int8_t tmp;
  while (new_r != 0) {
    q = r / new_r;

    tmp = new_t;
    new_t = t - q * new_t;
    t = tmp;

    tmp = new_r;
    new_r = r - q * new_r;
    r = tmp;
  }
  t = (t < 0) ? (t + p) : t;
  return t;
}

uint64_t fpow(uint8_t base, uint8_t exp) {
  uint64_t res = 1;
  while (exp > 0) {
    if ((exp % 2) != 0) {
      res *= base;
    }
    base *= base;
    exp = exp / 2;
  }
  return res;
}

void *xkmalloc(size_t size) {
  void *res = kmalloc(size, GFP_KERNEL);
  if (!res)
    return NULL;
  return res;
}

void *xkcalloc(size_t nmemb, size_t size) {
  void *res = kcalloc(nmemb, size, GFP_KERNEL);
  if (!res)
    return NULL;
  return res;
}