text: /*
   *
   *    Copyright (c) 2013-2017 Nest Labs, Inc.
   *    All rights reserved.
   *
   *    Licensed under the Apache License, Version 2.0 (the "License");
   *    you may not use this file except in compliance with the License.
   *    You may obtain a copy of the License at
   *
   *        http://www.apache.org/licenses/LICENSE-2.0
   *
   *    Unless required by applicable law or agreed to in writing, software
   *    distributed under the License is distributed on an "AS IS" BASIS,
   *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *    See the License for the specific language governing permissions and
   *    limitations under the License.
   */
  
  /**
   *    @file
   *      This file implements general purpose cryptographic functions for the Weave layer.
   *
   */
  
  #include <string.h>
  
  #include "WeaveCrypto.h"
  
  namespace nl {
  namespace Weave {
  namespace Crypto {
  
  /**
   * Compares the first `len` bytes of memory area `buf1` and memory area `buf2`.
   *
   * The time taken by this function is independent of the data in memory areas `buf1` and `buf2`.
   *
   * @param[in]  buf1   Pointer to a memory block.
   *
   * @param[in]  buf2   Pointer to a memory block.
   *
   * @param[in]  len    Size of memory area to compare in bytes.
   *
   * @retval  true      if first \c len bytes of memory area \c buf1 and \c buf2 are equal.
   * @retval  false     otherwise.
   *
   */
  bool ConstantTimeCompare(const uint8_t *buf1, const uint8_t *buf2, uint16_t len)
  {
      uint8_t c = 0;
      for (uint16_t i = 0; i < len; i++)
          c |= buf1[i] ^ buf2[i];
      return c == 0;
  }
  
  /**
   * Clears the first `len` bytes of memory area `buf`.
   *
   * In this implementation first `len` bytes of memory area `buf` are filled with zeros.
   *
   * @param[in]  buf     Pointer to a memory buffer holding secret data that should be cleared.
   *
   * @param[in]  len     Specifies secret data size in bytes.
   *
   */
  NL_DLL_EXPORT void ClearSecretData(uint8_t *buf, uint32_t len)
  {
      memset(buf, 0, len);
  }
  
  } // namespace Crypto
  } // namespace Weave
  } // namespace nl
  