1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/export.h>
3 #include <linux/bug.h>
4 #include <linux/bitmap.h>
5
6 /**
7 * memweight - count the total number of bits set in memory area
8 * @ptr: pointer to the start of the area
9 * @bytes: the size of the area
10 */
11 size_t memweight(const void *ptr, size_t bytes)
12 {
13 size_t ret = 0;
14 size_t longs;
15 const unsigned char *bitmap = ptr;
16
17 for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
18 bytes--, bitmap++)
19 ret += hweight8(*bitmap);
20
21 longs = bytes / sizeof(long);
22 if (longs) {
23 BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
24 ret += bitmap_weight((unsigned long *)bitmap,
25 longs * BITS_PER_LONG);
26 bytes -= longs * sizeof(long);
27 bitmap += longs * sizeof(long);
28 }
29 /*
30 * The reason that this last loop is distinct from the preceding
31 * bitmap_weight() call is to compute 1-bits in the last region smaller
32 * than sizeof(long) properly on big-endian systems.
33 */
34 for (; bytes > 0; bytes--, bitmap++)
35 ret += hweight8(*bitmap);
36
37 return ret;
38 }
39 EXPORT_SYMBOL(memweight);
40
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