1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/export.h>
4 #include <linux/bitmap.h>
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
11 size_t memweight(const void *ptr, size_t bytes)
15 const unsigned char *bitmap = ptr;
17 for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
19 ret += hweight8(*bitmap);
21 longs = bytes / sizeof(long);
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);
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.
34 for (; bytes > 0; bytes--, bitmap++)
35 ret += hweight8(*bitmap);
39 EXPORT_SYMBOL(memweight);