40 lines
1.0 KiB
C
40 lines
1.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/export.h>
|
|
#include <linux/bug.h>
|
|
#include <linux/bitmap.h>
|
|
|
|
/**
|
|
* memweight - count the total number of bits set in memory area
|
|
* @ptr: pointer to the start of the area
|
|
* @bytes: the size of the area
|
|
*/
|
|
size_t memweight(const void *ptr, size_t bytes)
|
|
{
|
|
size_t ret = 0;
|
|
size_t longs;
|
|
const unsigned char *bitmap = ptr;
|
|
|
|
for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
|
|
bytes--, bitmap++)
|
|
ret += hweight8(*bitmap);
|
|
|
|
longs = bytes / sizeof(long);
|
|
if (longs) {
|
|
BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
|
|
ret += bitmap_weight((unsigned long *)bitmap,
|
|
longs * BITS_PER_LONG);
|
|
bytes -= longs * sizeof(long);
|
|
bitmap += longs * sizeof(long);
|
|
}
|
|
/*
|
|
* The reason that this last loop is distinct from the preceding
|
|
* bitmap_weight() call is to compute 1-bits in the last region smaller
|
|
* than sizeof(long) properly on big-endian systems.
|
|
*/
|
|
for (; bytes > 0; bytes--, bitmap++)
|
|
ret += hweight8(*bitmap);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(memweight);
|