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This commit is contained in:
Joey Yakimowich-Payne 2020-02-13 08:02:20 -07:00
commit ae108f7a56
3 changed files with 19 additions and 9 deletions
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2
lib/pure/collections/hashcommon.nim
View file

@ -52,7 +52,7 @@ proc rawGetKnownHC[X, A](t: X, key: A, hc: Hash): int {.inline.} =
rawGetKnownHCImpl() rawGetKnownHCImpl()
template genHashImpl(key, hc: typed) = template genHashImpl(key, hc: typed) =
hc = hash(key, targetBits=lastSetBit(maxHash(t))) hc = hash(key, targetBits=lastSetBit(maxHash(t).uint))
if hc == 0: # This almost never taken branch should be very predictable. if hc == 0: # This almost never taken branch should be very predictable.
hc = 314159265 # Value doesn't matter; Any non-zero favorite is fine. hc = 314159265 # Value doesn't matter; Any non-zero favorite is fine.

14
lib/pure/hashes.nim
View file

@ -117,11 +117,11 @@ const
defaultSeedB = (1734880652122947187'u64).uint defaultSeedB = (1734880652122947187'u64).uint
template computeIntegerHash(x, numBits, seedA, seedB): Hash = template computeIntegerHash(x, numBits, seedA, seedB): Hash =
cast[Hash]((seedA*cast[uint](x) + seedB) shr (sizeof(x)*8 - targetBits*8)) cast[Hash]((seedA*cast[uint](x) + seedB) shr (sizeof(x)*8 - numBits*8))
proc hash*( proc hash*(
x: int, x: int,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =
@ -130,7 +130,7 @@ proc hash*(
proc hash*( proc hash*(
x: int64, x: int64,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =
@ -139,7 +139,7 @@ proc hash*(
proc hash*( proc hash*(
x: uint, x: uint,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =
@ -148,7 +148,7 @@ proc hash*(
proc hash*( proc hash*(
x: uint64, x: uint64,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =
@ -157,7 +157,7 @@ proc hash*(
proc hash*( proc hash*(
x: char, x: char,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =
@ -166,7 +166,7 @@ proc hash*(
proc hash*[T: Ordinal]( proc hash*[T: Ordinal](
x: T, x: T,
targetBits = sizeof(uint).uint32, targetBits: SomeUnsignedInt = sizeof(uint),
seedA = defaultSeedA, seedA = defaultSeedA,
seedB = defaultSeedB seedB = defaultSeedB
): Hash {.inline.} = ): Hash {.inline.} =

12
tests/collections/thashsets.nim
View file

@ -1,4 +1,4 @@
import sets, hashes, algorithm import sets, hashes, algorithm, bitops
block setEquality: block setEquality:
@ -120,3 +120,13 @@ block hashForOrderdSet:
reversed = !$reversed reversed = !$reversed
doAssert hash(r) == reversed doAssert hash(r) == reversed
doAssert hash(s1) != reversed doAssert hash(s1) != reversed
block hashDoesntHaveLowerBitsCleared:
let num32 = 0xFFFF.uint32
let bits = num32.lastBitSet
let h1 = hash(0xFFFFFFFF00000000'u64, targetBits=bits)
let h2 = hash(0x2345123400000000'u64, targetBits=bits)
doAssert (h1 and num32) != (h2 and num32)