LXR linux/fs/ext4/bitmap.c

   1/*
   2 *  linux/fs/ext4/bitmap.c
   3 *
   4 * Copyright (C) 1992, 1993, 1994, 1995
   5 * Remy Card (card@masi.ibp.fr)
   6 * Laboratoire MASI - Institut Blaise Pascal
   7 * Universite Pierre et Marie Curie (Paris VI)
   8 */
   9
  10#include <linux/buffer_head.h>
  11#include <linux/jbd2.h>
  12#include <linux/ext4_fs.h>
  13
  14#ifdef EXT4FS_DEBUG
  15
  16static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
  17
  18unsigned long ext4_count_free (struct buffer_head * map, unsigned int numchars)
  19{
  20        unsigned int i;
  21        unsigned long sum = 0;
  22
  23        if (!map)
  24                return (0);
  25        for (i = 0; i < numchars; i++)
  26                sum += nibblemap[map->b_data[i] & 0xf] +
  27                        nibblemap[(map->b_data[i] >> 4) & 0xf];
  28        return (sum);
  29}
  30
  31#endif  /*  EXT4FS_DEBUG  */
  32
  33