| 1 | |
| 2 | #include <linux/export.h>
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| 3 | #include <linux/bug.h>
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| 4 | #include <linux/bitmap.h>
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| 5 |
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| 6 | |
| 7 | * memweight - count the total number of bits set in memory area
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| 8 | * @ptr: pointer to the start of the area
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| 9 | * @bytes: the size of the area
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| 10 |
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| 11 | size_t memweight(const void *ptr, size_t bytes)
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| 12 | {
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| 13 | size_t ret = 0;
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| 14 | size_t longs;
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| 15 | const unsigned char *bitmap = ptr;
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| 16 |
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| 17 | for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
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| 18 | bytes--, bitmap++)
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| 19 | ret += hweight8(*bitmap);
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| 20 |
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| 21 | longs = bytes / sizeof(long);
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| 22 | if (longs) {
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| 23 | BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
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| 24 | ret += bitmap_weight((unsigned long *)bitmap,
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| 25 | longs * BITS_PER_LONG);
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| 26 | bytes -= longs * sizeof(long);
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| 27 | bitmap += longs * sizeof(long);
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| 28 | }
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| 29 | |
| 30 | * The reason that this last loop is distinct from the preceding
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| 31 | * bitmap_weight() call is to compute 1-bits in the last region smaller
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| 32 | * than sizeof(long) properly on big-endian systems.
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| 33 |
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| 34 | for (; bytes > 0; bytes--, bitmap++)
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| 35 | ret += hweight8(*bitmap);
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| 36 |
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| 37 | return ret;
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| 38 | }
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| 39 | EXPORT_SYMBOL(memweight);
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