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39 lines
1.0 KiB
39 lines
1.0 KiB
// 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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