C:\test\C>bufswap 536870912 268435456 2   ### 2^29 2^28
size:536870912 offset;268435456
[         0          1 ...  268435454    268435455 ^  268435456    268435457   ...  536870910  536870911 ]
[ 268435456  268435457 ...  536870910    536870911 ^          0            1   ...  268435454  268435455 ]
iterative: swaps:536870912 took 4.364767872 secs.

[         0          1 ...  268435454    268435455 ^  268435456    268435457   ...  536870910  536870911 ]
[ 268435456  268435457 ...  536870910    536870911 ^          0            1   ...  268435454  268435455 ]
recursive: swaps:268435456 took 2.476348362 secs.