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Merge pull request #31 from haskell-nix/je-printHashBytes32-bit-fiddling

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Weird bit fiddling to make `printHashBytes32` work
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John Ericson 2019-03-10 13:35:29 -04:00 committed by GitHub
commit 8cc6595803
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2 changed files with 9 additions and 2 deletions
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7
hnix-store-core/src/System/Nix/Internal/Hash.hs
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@ -150,8 +150,11 @@ newtype Digest (a :: HashAlgorithm) = Digest
printHashBytes32 :: BS.ByteString -> T.Text
printHashBytes32 c = T.pack $ concatMap char32 [nChar - 1, nChar - 2 .. 0]
where
-- The base32 encoding is 8/5's as long as the base256 digest
nChar = fromIntegral $ BS.length c * 8 `div` 5
-- The base32 encoding is 8/5's as long as the base256 digest. This `+ 1`
-- `- 1` business is a bit odd, but has always been used in C++ since the
-- base32 truncation was added in was first added in
-- d58a11e019813902b6c4547ca61a127938b2cc20.
nChar = fromIntegral $ ((BS.length c * 8 - 1) `div` 5) + 1
char32 :: Integer -> [Char]
char32 i = [digits32 V.! digitInd]

4
hnix-store-core/tests/Hash.hs
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@ -31,6 +31,10 @@ spec_hash = do
describe "hashing parity with nix-store" $ do
it "produces (base32 . sha256) of \"nix-output:foo\" the same as Nix does at the moment for placeholder \"foo\"" $
shouldBe (printAsBase32 (hash @SHA256 "nix-output:foo"))
"1x0ymrsy7yr7i9wdsqy9khmzc1yy7nvxw6rdp72yzn50285s67j5"
it "produces (base32 . sha1) of \"Hello World\" the same as the thesis" $
shouldBe (printAsBase32 (hash @SHA1 "Hello World"))
"s23c9fs0v32pf6bhmcph5rbqsyl5ak8a"