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