| 1 | // SPDX-License-Identifier: GPL-2.0 |
|---|---|
| 2 | #include <linux/export.h> |
| 3 | #include <linux/bug.h> |
| 4 | #include <linux/bitmap.h> |
| 5 | |
| 6 | /** |
| 7 | * memweight - count the total number of bits set in memory area |
| 8 | * @ptr: pointer to the start of the area |
| 9 | * @bytes: the size of the area |
| 10 | */ |
| 11 | size_t memweight(const void *ptr, size_t bytes) |
| 12 | { |
| 13 | size_t ret = 0; |
| 14 | size_t longs; |
| 15 | const unsigned char *bitmap = ptr; |
| 16 | |
| 17 | for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); |
| 18 | bytes--, bitmap++) |
| 19 | ret += hweight8(*bitmap); |
| 20 | |
| 21 | longs = bytes / sizeof(long); |
| 22 | if (longs) { |
| 23 | BUG_ON(longs >= INT_MAX / BITS_PER_LONG); |
| 24 | ret += bitmap_weight(src: (unsigned long *)bitmap, |
| 25 | nbits: longs * BITS_PER_LONG); |
| 26 | bytes -= longs * sizeof(long); |
| 27 | bitmap += longs * sizeof(long); |
| 28 | } |
| 29 | /* |
| 30 | * The reason that this last loop is distinct from the preceding |
| 31 | * bitmap_weight() call is to compute 1-bits in the last region smaller |
| 32 | * than sizeof(long) properly on big-endian systems. |
| 33 | */ |
| 34 | for (; bytes > 0; bytes--, bitmap++) |
| 35 | ret += hweight8(*bitmap); |
| 36 | |
| 37 | return ret; |
| 38 | } |
| 39 | EXPORT_SYMBOL(memweight); |
| 40 |