blob: e35fc877189302fb880b6339cf8f71ce9668d201 [file] [log] [blame]
Akinobu Mita639b9e32012-07-30 14:40:55 -07001#include <linux/export.h>
2#include <linux/bug.h>
3#include <linux/bitmap.h>
4
5/**
6 * memweight - count the total number of bits set in memory area
7 * @ptr: pointer to the start of the area
8 * @bytes: the size of the area
9 */
10size_t memweight(const void *ptr, size_t bytes)
11{
12 size_t ret = 0;
13 size_t longs;
14 const unsigned char *bitmap = ptr;
15
16 for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
17 bytes--, bitmap++)
18 ret += hweight8(*bitmap);
19
20 longs = bytes / sizeof(long);
21 if (longs) {
22 BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
23 ret += bitmap_weight((unsigned long *)bitmap,
24 longs * BITS_PER_LONG);
25 bytes -= longs * sizeof(long);
26 bitmap += longs * sizeof(long);
27 }
28 /*
29 * The reason that this last loop is distinct from the preceding
30 * bitmap_weight() call is to compute 1-bits in the last region smaller
31 * than sizeof(long) properly on big-endian systems.
32 */
33 for (; bytes > 0; bytes--, bitmap++)
34 ret += hweight8(*bitmap);
35
36 return ret;
37}
38EXPORT_SYMBOL(memweight);