text: #include "verify.h"
  
  #include <stddef.h>
  #include <stdint.h>
  
  /*************************************************
  * Name:        verify
  *
  * Description: Compare two arrays for equality in constant time.
  *
  * Arguments:   const uint8_t *a: pointer to first byte array
  *              const uint8_t *b: pointer to second byte array
  *              size_t len:             length of the byte arrays
  *
  * Returns 0 if the byte arrays are equal, 1 otherwise
  **************************************************/
  uint8_t PQCLEAN_KYBER51290S_CLEAN_verify(const uint8_t *a, const uint8_t *b, size_t len) {
      uint64_t r;
      size_t i;
      r = 0;
  
      for (i = 0; i < len; i++) {
          r |= a[i] ^ b[i];
      }
  
      r = (-r) >> 63;
      return (uint8_t)r;
  }
  
  /*************************************************
  * Name:        cmov
  *
  * Description: Copy len bytes from x to r if b is 1;
  *              don't modify x if b is 0. Requires b to be in {0,1};
  *              assumes two's complement representation of negative integers.
  *              Runs in constant time.
  *
  * Arguments:   uint8_t *r:       pointer to output byte array
  *              const uint8_t *x: pointer to input byte array
  *              size_t len:             Amount of bytes to be copied
  *              uint8_t b:        Condition bit; has to be in {0,1}
  **************************************************/
  void PQCLEAN_KYBER51290S_CLEAN_cmov(uint8_t *r, const uint8_t *x, size_t len, uint8_t b) {
      size_t i;
  
      b = -b;
      for (i = 0; i < len; i++) {
          r[i] ^= b & (x[i] ^ r[i]);
      }
  }
  