BITMAP_BITREMAP(9) Basic Kernel Library Functions BITMAP_BITREMAP(9)
NAME bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
SYNOPSIS int bitmap_bitremap(int oldbit, const unsigned long * old, const unsigned long * new, int bits);
ARGUMENTS oldbit bit position to be mapped
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.
The positions of unset bits in old are mapped to themselves (the identify map).
Apply the above specified mapping to bit position oldbit, returning the new bit position.
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 oldbit is 5, then this routine returns 13.
COPYRIGHT Kernel Hackers Manual 2.6. July 2015 BITMAP_BITREMAP(9)