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RIOT/sys/net/gnrc/netif/gnrc_netif_addr_from_str.c 1.87 KB
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  /*
   * Copyright (C) 2015 Martine Lenders <mlenders@inf.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.
   */
  
  /**
   * @{
   *
   * @file
   */
  
  #include "net/gnrc/netif.h"
  
  static inline int _dehex(char c, int default_)
  {
      if ('0' <= c && c <= '9') {
          return c - '0';
      }
      else if ('A' <= c && c <= 'F') {
          return c - 'A' + 10;
      }
      else if ('a' <= c && c <= 'f') {
          return c - 'a' + 10;
      }
      else {
          return default_;
      }
  }
  
  size_t gnrc_netif_addr_from_str(uint8_t *out, size_t out_len, const char *str)
  {
      /* Walk over str from the end. */
      /* Take two chars a time as one hex value (%hhx). */
      /* Leading zeros can be omitted. */
      /* Every non-hexadimal character is a delimiter. */
      /* Leading, tailing and adjacent delimiters are forbidden. */
  
      const char *end_str = str;
      uint8_t *out_end = out;
      size_t count = 0;
      int assert_cell = 1;
  
      if (!str || !*str) {
          return 0;
      }
      while (end_str[1]) {
          ++end_str;
      }
  
      while (end_str >= str) {
          int a = 0, b = _dehex(*end_str--, -1);
          if (b < 0) {
              if (assert_cell) {
                  return 0;
              }
              else {
                  assert_cell = 1;
                  continue;
              }
          }
          assert_cell = 0;
  
          if (end_str >= str) {
              a = _dehex(*end_str--, 0);
          }
  
          if (++count > out_len) {
              return 0;
          }
          *out_end++ = (a << 4) | b;
      }
      if (assert_cell) {
          return 0;
      }
      /* out is reversed */
  
      while (out < --out_end) {
          uint8_t tmp = *out_end;
          *out_end = *out;
          *out++ = tmp;
      }
  
      return count;
  }
  
  /** @} */