libs/libc/misc/lib_log2floor.c

/****************************************************************************
 * libs/libc/misc/lib_log2floor.c
 *
 * 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/lib/math32.h>

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

/****************************************************************************
 * Name: log2floor
 *
 * Description:
 *   Calculate the down-rounded (truncated) power-of-two for input.
 *
 * Input Parameters:
 *   x - Argument to calculate the power-of-two from.
 *
 * Returned Value:
 *   Power-of-two for argument, rounded (truncated) down.
 *
 ****************************************************************************/

uintptr_t log2floor(uintptr_t x)
{
  uintptr_t pot = 0;

  for (; x > 1; x >>= 1)
    {
      pot++;
    }

  return pot;
}