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convert key2file and file2key to use builder and attoparsec

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The new parser is significantly stricter than the old one:

The old file2key allowed the fields to come in any order,
but the new one requires the fixed order that git-annex has always used.
Hopefully this will not cause any breakage.

And the old file2key allowed eg SHA1-m1-m2-m3-m4-m5-m6--xxxx
while the new does not allow duplication of fields. This could potentially
improve security, because allowing lots of extra junk like that in a key
could potentially be used in a SHA1 collision attack, although the current
attacks need binary data and not this kind of structured numeric data.

Speed improved of course, and fairly substantially, in microbenchmarks:

benchmarking old/key2file
time                 2.264 μs   (2.257 μs .. 2.273 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 2.265 μs   (2.260 μs .. 2.275 μs)
std dev              21.17 ns   (13.06 ns .. 39.26 ns)

benchmarking new/key2file'
time                 1.744 μs   (1.741 μs .. 1.747 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.745 μs   (1.742 μs .. 1.751 μs)
std dev              13.55 ns   (9.099 ns .. 21.89 ns)

benchmarking old/file2key
time                 6.114 μs   (6.102 μs .. 6.129 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 6.118 μs   (6.106 μs .. 6.143 μs)
std dev              55.00 ns   (30.08 ns .. 100.2 ns)

benchmarking new/file2key'
time                 1.791 μs   (1.782 μs .. 1.801 μs)
                     1.000 R²   (0.999 R² .. 1.000 R²)
mean                 1.792 μs   (1.785 μs .. 1.804 μs)
std dev              32.46 ns   (20.59 ns .. 50.82 ns)
variance introduced by outliers: 19% (moderately inflated)
This commit is contained in:
Joey Hess 2019-01-11 16:33:42 -04:00
parent b552551b33
commit 151562b537
No known key found for this signature in database
GPG key ID: DB12DB0FF05F8F38
2 changed files with 93 additions and 69 deletions
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Types/Key.hs
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@ -12,8 +12,6 @@ module Types.Key where
import qualified Data.ByteString as S
import qualified Data.ByteString.Char8 as S8
import qualified Data.ByteString.Lazy as L
import Data.ByteString.Builder
import System.Posix.Types
{- A Key has a unique name, which is derived from a particular backend,