// 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);