mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-22 17:01:14 +00:00
![Akinobu Mita](/assets/img/avatar_default.png)
memweight() is the function that counts the total number of bits set in memory area. Unlike bitmap_weight(), memweight() takes pointer and size in bytes to specify a memory area which does not need to be aligned to long-word boundary. [akpm@linux-foundation.org: rename `w' to `ret'] Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: Anders Larsen <al@alarsen.net> Cc: Alasdair Kergon <agk@redhat.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Jan Kara <jack@suse.cz> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Matthew Wilcox <matthew@wil.cx> Cc: Mauro Carvalho Chehab <mchehab@infradead.org> Cc: Tony Luck <tony.luck@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
38 lines
999 B
C
38 lines
999 B
C
#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);
|