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 "ext4.h"
  13
  14 static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
  15
  16 unsigned int ext4_count_free(char *bitmap, unsigned int numchars)
  17 {
  18         unsigned int i, sum = 0;
  19
  20         for (i = 0; i < numchars; i++)
  21                 sum += nibblemap[bitmap[i] & 0xf] +
  22                         nibblemap[(bitmap[i] >> 4) & 0xf];
  23         return sum;
  24 }
  25