centos man page for bitmap_remap

BITMAP_REMAP(9) 					  Basic Kernel Library Functions					   BITMAP_REMAP(9)

NAME
       bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap

SYNOPSIS
       void bitmap_remap(unsigned long * dst, const unsigned long * src, const unsigned long * old, const unsigned long * new, int bits);

ARGUMENTS
       dst
	   remapped result

       src
	   subset to be remapped

       old
	   defines domain of map

       new
	   defines range of map

       bits
	   number of bits in each of these bitmaps

DESCRIPTION
       Let old and new define a mapping of bit positions, such that whatever position is held by the n-th set bit in old is mapped to the n-th set
       bit in new. In the more general case, allowing for the possibility that the weight 'w' of new is less than the weight of old, map the
       position of the n-th set bit in old to the position of the m-th set bit in new, where m == n % w.

       If either of the old and new bitmaps are empty, or if src and dst point to the same location, then this routine copies src to dst.

       The positions of unset bits in old are mapped to themselves (the identify map).

       Apply the above specified mapping to src, placing the result in dst, clearing any bits previously set in dst.

       For example, lets say that old has bits 4 through 7 set, and new has bits 12 through 15 set. This defines the mapping of bit position 4 to
       12, 5 to 13, 6 to 14 and 7 to 15, and of all other bit positions unchanged. So if say src comes into this routine with bits 1, 5 and 7 set,
       then dst should leave with bits 1, 13 and 15 set.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							   BITMAP_REMAP(9)