Same runtime cost, however reduces the logic and avoids one of
the two big branches. See the DESIGN.md for more info.
Now uses these equations instead of the messy guess and correct method:
n = (N - w/8(popcount(N/(B-2w/8)) + 2)) / (B-2w/8)
off = N - (B-w2/8)n - w/8popcount(n)
This reduces the O(n^2logn) runtime to read a file to only O(nlog).
The extra O(n) did not touch the disk, so it isn't a problem until the
files become very large, but this solution comes with very little cost.
Long story short, you can find the block index + offset pair for a
CTZ linked-list with this series of formulas:
n' = floor(N / (B - 2w/8))
N' = (B - 2w/8)n' + (w/8)popcount(n')
off' = N - N'
n, off =
n'-1, off'+B if off' < 0
n', off'+(w/8)(ctz(n')+1) if off' >= 0
For the long story, you will need to see the updated DESIGN.md
Christopher Haster