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Do all hashing math in UInt32

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This commit is contained in:
Justin Mazzocchi 2020-09-06 16:56:21 -07:00
parent 9e8b91e23b
commit bb44676a73
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GPG key ID: E223E6937AAFB01C
2 changed files with 14 additions and 14 deletions
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19
CodableBloomFilter/Sources/CodableBloomFilter/DeterministicHasher.swift
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@ -12,9 +12,9 @@ public enum DeterministicHasher: String, Codable {
extension DeterministicHasher {
func apply(_ hashable: DeterministicallyHashable) -> Int {
Array(hashable.hashableData)
.map(Int.init)
.reduce(offsetBasis, hash)
Int(Array(hashable.hashableData)
.map(UInt32.init)
.reduce(offsetBasis, hash))
}
}
@ -22,10 +22,9 @@ extension DeterministicHasher {
// http://www.isthe.com/chongo/tech/comp/fnv/
private extension DeterministicHasher {
static let fnvPrime = 16777619
static let u32mod = 2 << 31
static let fnvPrime: UInt32 = 16777619
var offsetBasis: Int {
var offsetBasis: UInt32 {
switch self {
case .djb2, .djb2a: return 5381
case .sdbm: return 0
@ -33,18 +32,18 @@ private extension DeterministicHasher {
}
}
func hash(result: Int, next: Int) -> Int {
func hash(result: UInt32, next: UInt32) -> UInt32 {
switch self {
case .djb2:
return (result << 5) &+ result &+ next
case .djb2a:
return ((result << 5) &+ result ^ next) % Self.u32mod
return (result << 5) &+ result ^ next
case .sdbm:
return next &+ (result << 6) &+ (result << 16) &- result
case .fnv1:
return (result * Self.fnvPrime % Self.u32mod) ^ next
return (result &* Self.fnvPrime) ^ next
case .fnv1a:
return (result ^ next) * Self.fnvPrime % Self.u32mod
return (result ^ next) &* Self.fnvPrime
}
}
}

9
CodableBloomFilter/Tests/CodableBloomFilterTests/CodableBloomFilterTests.swift
View file

@ -4,12 +4,13 @@
import XCTest
final class CodableBloomFilterTests: XCTestCase {
func testHashers() {
XCTAssertEqual(DeterministicHasher.djb2.apply("hash"), 6385287881)
XCTAssertEqual(DeterministicHasher.djb2.apply("hash"), 2090320585)
XCTAssertEqual(DeterministicHasher.djb2a.apply("hash"), 2087809207)
XCTAssertEqual(DeterministicHasher.sdbm.apply("hash"), 29358318056884782)
XCTAssertEqual(DeterministicHasher.fnv1.apply("hash"), 0xd7918815)
XCTAssertEqual(DeterministicHasher.fnv1a.apply("hash"), 0xcec577d1)
XCTAssertEqual(DeterministicHasher.sdbm.apply("hash"), 385600046)
XCTAssertEqual(DeterministicHasher.fnv1.apply("hash"), 3616638997)
XCTAssertEqual(DeterministicHasher.fnv1a.apply("hash"), 3469047761)
}
func testContains() {