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 */
11size_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}
39EXPORT_SYMBOL(memweight);

 
 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 */
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);