Rotating a bitmap 90 degrees

Question

I have a one 64-bit integer, which I need to rotate 90 degrees in 8 x 8 area (preferably with straight bit-manipulation). I cannot figure out any handy algorith

Answer 1

If an if-powered loop is acceptable, the formula for bits is simple enough:

8>>Column - Row - 1

Column and Row are 0-indexed.

This gives you this mapping:

 7 15 23 31 39 47 55 63
 6 14 22 ...
 5 ...
 4 ...
 3 ...
 2 ...
 1 ...
 0  8 16 24 32 40 48 54