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RIOT/sys/hashes/hashes.c 2.08 KB
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  /**
   * This file contains some simple hash function
   *
   * Copyright (C) 2013 Freie Universitรคt Berlin
   *
   * 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.
   */
  
  /**
   * @file
   * @author      Jason Linehan <patientulysses@gmail.com>
   * @author      Christian Mehlis <mehlis@inf.fu-berlin.de>
   */
  
  #include "hashes.h"
  
  uint32_t djb2_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 5381;
  
      for (size_t i = 0; i < len; i++) {
          hash = hash * 33 + buf[i];
      }
  
      return hash;
  }
  
  uint32_t sdbm_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 0;
  
      for (size_t i = 0; i < len; i++) {
          hash = buf[i] + (hash << 6) + (hash << 16) - hash;
      }
  
      return hash;
  }
  
  uint32_t kr_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 0;
  
      for (size_t i = 0; i < len; i++) {
          hash += buf[i];
      }
  
      return hash;
  }
  
  uint32_t sax_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 0;
  
      for (size_t i = 0; i < len; i++) {
          hash ^= (hash << 5) + (hash >> 2) + buf[i];
      }
  
      return hash;
  }
  
  uint32_t dek_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 7919; /* prime */
  
      for (size_t i = 0; i < len; i++) {
          hash = (hash << 5) ^ (hash >> 27) ^ buf[i];
      }
  
      return hash;
  }
  
  uint32_t fnv_hash(const uint8_t *buf, size_t len)
  {
      uint32_t FNV_PRIME = 0x811C9DC5;
      uint32_t hash = 0;
  
      for (size_t i = 0; i < len; i++) {
          hash *= FNV_PRIME;
          hash ^= buf[i];
      }
  
      return hash;
  }
  
  uint32_t rotating_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 0;
  
      for (size_t i = 0; i < len; i++) {
          hash = (hash << 4) ^ (hash >> 28) ^ buf[i];
      }
  
      return hash;
  }
  
  uint32_t one_at_a_time_hash(const uint8_t *buf, size_t len)
  {
      uint32_t hash = 786431; /* prime */
  
      for (size_t i = 0; i < len; i++) {
          hash += buf[i];
          hash += hash << 10;
          hash ^= hash >> 6;
      }
      hash += hash << 3;
      hash ^= hash >> 11;
      hash += hash << 15;
      return hash;
  }