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TOMOYO Linux Cross Reference
Linux/lib/memweight.c

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  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((unsigned long *)bitmap,
 25                                 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 

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