text: /*
   * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
   * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this list of
   *    conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice, this list
   *    of conditions and the following disclaimer in the documentation and/or other materials
   *    provided with the distribution.
   *
   * 3. Neither the name of the copyright holder nor the names of its contributors may be used
   *    to endorse or promote products derived from this software without specific prior written
   *    permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "los_strnlen_user.h"
  #include "los_user_get.h"
  #include "los_vm_map.h"
  
  
  INT32 LOS_StrnlenUser(const CHAR *src, INT32 count)
  {
      CHAR character;
      INT32 maxCount;
      INT32 i;
      size_t offset = 0;
  
      if ((!LOS_IsUserAddress((VADDR_T)(UINTPTR)src)) || (count <= 0)) {
          return 0;
      }
  
      maxCount = (LOS_IsUserAddressRange((VADDR_T)(UINTPTR)src, (size_t)count)) ? \
                  count : (USER_ASPACE_TOP_MAX - (UINTPTR)src);
  
      for (i = 0; i < maxCount; ++i) {
          if (LOS_GetUser(&character, src + offset) != LOS_OK) {
              return 0;
          }
          ++offset;
          if (character == '\0') {
              return offset;
          }
      }
  
      return count + 1;
  }
  
  