bitmap_bitremap — Apply map defined by a pair of bitmaps to a single bit


int bitmap_bitremap (int oldbit,
 const unsigned long * old,
 const unsigned long * new,
 int bits);


int oldbit

bit position to be mapped

const unsigned long * old

defines domain of map

const unsigned long * new

defines range of map

int bits

number of bits in each of these bitmaps


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.