Function sample_slices 

pub fn sample_slices(len: usize) -> usize

Number of slices the sample of a block of len bytes has: one per 128 KiB, at least 8 (a 1 MiB block gives 8 slices = 64 KiB) and at most 32 (256 KiB at 4 MiB and above). A block prefix must not be used instead: blocks concatenate chunks of several files and a prefix predicts the wrong codec on a third of the benchmark blocks (measured, see the plan).