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https://github.com/torvalds/linux
23 October 2021, 00:29:24 UTC
Revision 872f8edeb6bdadc9fd8c832f1a295610ad664a07 authored by Linus Torvalds on 16 July 2021, 20:35:04 UTC, committed by Linus Torvalds on 16 July 2021, 20:35:04 UTC 
Merge tag 'docs-5.14-2' of git://git.lwn.net/linux
 
Pull documentation fixes from Jonathan Corbet:
 "A handful of fixes in and around documentation.

  Some funky quotes in LICENSES/dual/CC-BY-4.0 were giving spdxcheck.py
  grief; that has been fixed on both ends. Also a couple of features
  updates and one docs build fix"

* tag 'docs-5.14-2' of git://git.lwn.net/linux:
  docs/zh_CN: add a missing space character
  Documentation/features: Add THREAD_INFO_IN_TASK feature matrix
  Documentation/features: Update the ARCH_HAS_TICK_BROADCAST entry
  LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"
  scripts/spdxcheck.py: Strictly read license files in utf-8
2 parent s 0d18c12 + 530c437
Raw File
Tip revision: 872f8edeb6bdadc9fd8c832f1a295610ad664a07 authored by Linus Torvalds on 16 July 2021, 20:35:04 UTC
Merge tag 'docs-5.14-2' of git://git.lwn.net/linux
Tip revision: 872f8ed
memweight.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);
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