Line data    Source code

       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           0 : size_t memweight(const void *ptr, size_t bytes)
      12             : {
      13           0 :         size_t ret = 0;
      14           0 :         size_t longs;
      15           0 :         const unsigned char *bitmap = ptr;
      16             : 
      17           0 :         for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
      18           0 :                         bytes--, bitmap++)
      19           0 :                 ret += hweight8(*bitmap);
      20             : 
      21           0 :         longs = bytes / sizeof(long);
      22           0 :         if (longs) {
      23           0 :                 BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
      24           0 :                 ret += bitmap_weight((unsigned long *)bitmap,
      25             :                                 longs * BITS_PER_LONG);
      26           0 :                 bytes -= longs * sizeof(long);
      27           0 :                 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           0 :         for (; bytes > 0; bytes--, bitmap++)
      35           0 :                 ret += hweight8(*bitmap);
      36             : 
      37           0 :         return ret;
      38             : }
      39             : EXPORT_SYMBOL(memweight);