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RIOT/sys/include/net/inet_csum.h 2.49 KB
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  /*
   * Copyright (C) 2015 Martine Lenders <mlenders@inf.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.
   */
  
  /**
   * @defgroup    net_inet_csum    Internet Checksum
   * @ingroup     net
   * @brief   Provides a function to calculate the Internet Checksum
   * @{
   *
   * @file
   * @brief   Internet Checksum definitions
   *
   * @author  Martine Lenders <mlenders@inf.fu-berlin.de>
   */
  #ifndef NET_INET_CSUM_H
  #define NET_INET_CSUM_H
  
  #include <inttypes.h>
  #include <stddef.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * @brief   Calculates the unnormalized Internet Checksum of @p buf, where the
   *          buffer provides a slice of the full checksum domain, calculated in order.
   *
   * @see <a href="https://tools.ietf.org/html/rfc1071">
   *          RFC 1071
   *      </a>
   *
   * @details The Internet Checksum is not normalized (i. e. its 1's complement
   *          was not taken of the result) to use it for further calculation.
   *          This function handles padding an odd number of bytes across the full domain.
   *
   * @param[in] sum       An initial value for the checksum.
   * @param[in] buf       A buffer.
   * @param[in] len       Length of @p buf in byte.
   * @param[in] accum_len Accumulated length of checksum domain that has already
   *                      been checksummed.
   *
   * @return  The unnormalized Internet Checksum of @p buf.
   */
  uint16_t inet_csum_slice(uint16_t sum, const uint8_t *buf, uint16_t len, size_t accum_len);
  
  /**
   * @brief   Calculates the unnormalized Internet Checksum of @p buf, where the
   *          buffer provides a standalone domain for the checksum.
   *
   * @see <a href="https://tools.ietf.org/html/rfc1071">
   *          RFC 1071
   *      </a>
   *
   * @details The Internet Checksum is not normalized (i. e. its 1's complement
   *          was not taken of the result) to use it for further calculation.
   *          This function, rather than inet_csum_slice(), has been used historically
   *          when we are not concerned with padding for an odd number of bytes.
   *
   *
   * @param[in] sum       An initial value for the checksum.
   * @param[in] buf       A buffer.
   * @param[in] len       Length of @p buf in byte.
   *
   * @return  The unnormalized Internet Checksum of @p buf.
   */
  static inline uint16_t inet_csum(uint16_t sum, const uint8_t *buf, uint16_t len) {
      return inet_csum_slice(sum, buf, len, 0);
  }
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* NET_INET_CSUM_H */
  /** @} */