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|
{- data size display
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module DataUnits (roughSize, compareSizes) where
{- And now a rant:
-
- In the beginning, we had powers of two, and they were good.
-
- Disk drive manufacturers noticed that some powers of two were
- sorta close to some powers of ten, and that rounding down to the nearest
- power of ten allowed them to advertise their drives were bigger. This
- was sorta annoying.
-
- Then drives got big. Really, really big. This was good.
-
- Except that the small rounding error perpretrated by the drive
- manufacturers suffered the fate of a small error, and became a large
- error. This was bad.
-
- So, a committee was formed. And it arrived at a committee-like decision,
- which satisfied noone, confused everyone, and made the world an uglier
- place. As with all committees, this was meh.
-
- And the drive manufacturers happily continued selling drives that are
- increasingly smaller than you'd expect, if you don't count on your
- fingers. But that are increasingly bigger.
-
- Thus, I use units here that I loathe. Because if I didn't, people would
- be confused that their drives seem the wrong size, and other people would
- complain at me for not being standards compliant. And we call this
- progress?
-}
{- approximate display of a particular number of bytes -}
roughSize :: Bool -> Integer -> String
roughSize short i
| i < 0 = "-" ++ roughSize short (negate i)
| i >= at 8 = units 8 "yottabyte" "YB"
| i >= at 7 = units 7 "zettabyte" "ZB"
| i >= at 6 = units 6 "exabyte" "EB"
| i >= at 5 = units 5 "petabyte" "PB"
| i >= at 4 = units 4 "terabyte" "TB"
| i >= at 3 = units 3 "gigabyte" "GB"
| i >= at 2 = units 2 "megabyte" "MB"
| i >= at 1 = units 1 "kilobyte" "kB"
| otherwise = units 0 "byte" "B"
where
at :: Integer -> Integer
at n = 1000^n
chop :: Integer -> Integer
chop d = round $ (fromInteger i :: Double) / fromInteger (at d)
units d u u' = let num = chop d in
show num ++ " " ++
(if short then u' else plural num u)
plural n u
| n == 1 = u
| otherwise = u ++ "s"
compareSizes :: Bool -> Integer -> Integer -> String
compareSizes short old new
| old > new = roughSize short (old - new) ++ " smaller"
| old < new = roughSize short (new - old) ++ " larger"
| otherwise = "same"
|
