函数源码

Linux Kernel

v5.5.9

Brick Technologies Co., Ltd

Source File:lib\bitmap.c Create Date:2022-07-27 07:17:20
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// SPDX-License-Identifier: GPL-2.0-only
/*
 * lib/bitmap.c
 * Helper functions for bitmap.h.
 */
#include <linux/export.h>
#include <linux/thread_info.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/uaccess.h>
 
#include <asm/page.h>
 
#include "kstrtox.h"
 
/**
 * DOC: bitmap introduction
 *
 * bitmaps provide an array of bits, implemented using an an
 * array of unsigned longs.  The number of valid bits in a
 * given bitmap does _not_ need to be an exact multiple of
 * BITS_PER_LONG.
 *
 * The possible unused bits in the last, partially used word
 * of a bitmap are 'don't care'.  The implementation makes
 * no particular effort to keep them zero.  It ensures that
 * their value will not affect the results of any operation.
 * The bitmap operations that return Boolean (bitmap_empty,
 * for example) or scalar (bitmap_weight, for example) results
 * carefully filter out these unused bits from impacting their
 * results.
 *
 * The byte ordering of bitmaps is more natural on little
 * endian architectures.  See the big-endian headers
 * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
 * for the best explanations of this ordering.
 */
 
int __bitmap_equal(const unsigned long *bitmap1,
        const unsigned long *bitmap2, unsigned int bits)
{
    unsigned int k, lim = bits/BITS_PER_LONG;
    for (k = 0; k < lim; ++k)
        if (bitmap1[k] != bitmap2[k])
            return 0;
 
    if (bits % BITS_PER_LONG)
        if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
            return 0;
 
    return 1;
}