incubator-nuttx/libs/libc/string/lib_memcmp.c

/****************************************************************************
 * libs/libc/string/lib_memcmp.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you 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.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>
#include <sys/types.h>
#include <string.h>

#include "libc.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

#if !defined(CONFIG_LIBC_ARCH_MEMCMP) && defined(LIBC_BUILD_MEMCMP)
#undef memcmp /* See mm/README.txt */
no_builtin("memcmp")
int memcmp(FAR const void *s1, FAR const void *s2, size_t n)
{
  FAR unsigned char *p1 = (FAR unsigned char *)s1;
  FAR unsigned char *p2 = (FAR unsigned char *)s2;

  while (n-- > 0)
    {
      if (*p1 < *p2)
        {
          return -1;
        }
      else if (*p1 > *p2)
        {
          return 1;
        }

      p1++;
      p2++;
    }

  return 0;
}
#endif