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