/*
   * Copyright (C) 2015 Nico von Geyso <nico.geyso@fu-berlin.de>
   * Copyright (C) 2015 René Kijewski <rene.kijewski@fu-berlin.de>
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  #include "crypto/helper.h"
  
  void crypto_block_inc_ctr(uint8_t block[16], int L)
  {
      uint8_t *b = &block[15];
      for (int i = 0; i < L; ++i, --b) {
          if (++*b != 0) {
              break;
          }
      }
  }
  
  int crypto_equals(uint8_t *a, uint8_t *b, size_t len)
  {
      uint8_t diff = 0;
      for (size_t i = 0; i < len; ++i, ++a, ++b) {
          diff |= (*a ^ *b);
      }
  
      diff |= (diff >> 1) | (diff << 7);
      diff |= (diff >> 2) | (diff << 6);
      diff |= (diff >> 4) | (diff << 4);
      ++diff;
  
      return diff;
  }