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       1                 :            : /* ykcrc.c --- Implementation of Yubikey CRC-16 function.
       2                 :            :  *
       3                 :            :  * Written by Simon Josefsson <simon@josefsson.org>.
       4                 :            :  * Copyright (c) 2006, 2007, 2008, 2009 Yubico AB
       5                 :            :  * All rights reserved.
       6                 :            :  *
       7                 :            :  * Redistribution and use in source and binary forms, with or without
       8                 :            :  * modification, are permitted provided that the following conditions are
       9                 :            :  * met:
      10                 :            :  *
      11                 :            :  *    * Redistributions of source code must retain the above copyright
      12                 :            :  *      notice, this list of conditions and the following disclaimer.
      13                 :            :  *
      14                 :            :  *    * Redistributions in binary form must reproduce the above
      15                 :            :  *      copyright notice, this list of conditions and the following
      16                 :            :  *      disclaimer in the documentation and/or other materials provided
      17                 :            :  *      with the distribution.
      18                 :            :  *
      19                 :            :  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      20                 :            :  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      21                 :            :  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      22                 :            :  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      23                 :            :  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      24                 :            :  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      25                 :            :  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      26                 :            :  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      27                 :            :  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      28                 :            :  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      29                 :            :  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
      30                 :            :  *
      31                 :            :  */
      32                 :            : 
      33                 :            : #include "yubikey.h"
      34                 :            : 
      35                 :            : unsigned short
      36                 :            : yubikey_crc16 (const unsigned char *buf, size_t buf_size)
      37                 :          0 : {
      38                 :          0 :   unsigned short m_crc = 0xffff;
      39                 :            : 
      40         [ #  # ]:          0 :   while (buf_size--)
      41                 :            :     {
      42                 :            :       int i, j;
      43                 :          0 :       m_crc ^= (unsigned char) * buf++ & 0xFF;
      44         [ #  # ]:          0 :       for (i = 0; i < 8; i++)
      45                 :            :         {
      46                 :          0 :           j = m_crc & 1;
      47                 :          0 :           m_crc >>= 1;
      48         [ #  # ]:          0 :           if (j)
      49                 :          0 :             m_crc ^= 0x8408;
      50                 :            :         }
      51                 :            :     }
      52                 :            : 
      53                 :          0 :   return m_crc;
      54                 :            : }