blob: e35fc877189302fb880b6339cf8f71ce9668d201
1 | #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 | */ |
10 | size_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 | } |
38 | EXPORT_SYMBOL(memweight); |
39 |