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RUM-7937 Use deterministic random ids
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18 changes: 18 additions & 0 deletions
18
DatadogSessionReplay/Sources/Recorder/Utilities/Int64+SessionReplay.swift
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,18 @@ | ||
| /* | ||
| * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0. | ||
| * This product includes software developed at Datadog (https://www.datadoghq.com/). | ||
| * Copyright 2019-Present Datadog, Inc. | ||
| */ | ||
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| #if os(iOS) | ||
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| import Foundation | ||
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| @_spi(Internal) | ||
| public extension Int64 { | ||
| static func positiveRandom<T>(using generator: inout T) -> Int64 where T: RandomNumberGenerator { | ||
| .random(in: 0..<Int64.max, using: &generator) | ||
| } | ||
| } | ||
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| #endif |
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DatadogSessionReplay/Sources/Recorder/Utilities/Xoshiro.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| /* | ||
| * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0. | ||
| * This product includes software developed at Datadog (https://www.datadoghq.com/). | ||
| * Copyright 2019-Present Datadog, Inc. | ||
| */ | ||
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| import Foundation | ||
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| /// http://xoshiro.di.unimi.it | ||
| /// by David Blackman and Sebastiano Vigna | ||
| internal struct XoshiroRandomNumberGenerator: RandomNumberGenerator { | ||
| typealias StateType = (UInt64, UInt64, UInt64, UInt64) | ||
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| private var state: StateType = (0, 0, 0, 0) | ||
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| internal init(seed: StateType) { | ||
| self.state = seed | ||
| } | ||
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| internal init<T>(seed: T) where T: FixedWidthInteger { | ||
| self.state = ( | ||
| UInt64(seed), | ||
| UInt64(seed), | ||
| UInt64(seed), | ||
| UInt64(seed) | ||
| ) | ||
| } | ||
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| internal mutating func next() -> UInt64 { | ||
| // Derived from public domain implementation of xoshiro256**: | ||
| let x = state.1 &* 5 | ||
| let result = ((x &<< 7) | (x &>> 57)) &* 9 | ||
| let t = state.1 &<< 17 | ||
| state.2 ^= state.0 | ||
| state.3 ^= state.1 | ||
| state.1 ^= state.2 | ||
| state.0 ^= state.3 | ||
| state.2 ^= t | ||
| state.3 = (state.3 &<< 45) | (state.3 &>> 19) | ||
| return result | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| /* | ||
| * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0. | ||
| * This product includes software developed at Datadog (https://www.datadoghq.com/). | ||
| * Copyright 2019-Present Datadog, Inc. | ||
| */ | ||
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| import XCTest | ||
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| @_spi(Internal) | ||
| @testable import DatadogSessionReplay | ||
| @testable import TestUtilities | ||
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| class XoshiroTests: XCTestCase { | ||
| func testRandomnValues() { | ||
| let seed: XoshiroRandomNumberGenerator.StateType = (.mockRandom(), .mockRandom(), .mockRandom(), .mockRandom()) | ||
| var g1 = XoshiroRandomNumberGenerator(seed: seed) | ||
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| let a = g1.next() | ||
| let b = g1.next() | ||
| let c = g1.next() | ||
| let d = g1.next() | ||
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| XCTAssert(a != b && a != c && a != d && b != c && b != d && c != d, "Technically, we *could* get a collision...") | ||
| } | ||
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| func testDeterministicValues() { | ||
| let seed: XoshiroRandomNumberGenerator.StateType = (.mockRandom(), .mockRandom(), .mockRandom(), .mockRandom()) | ||
| var g1 = XoshiroRandomNumberGenerator(seed: seed) | ||
| var g2 = XoshiroRandomNumberGenerator(seed: seed) | ||
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| for _ in 0..<1_000 { | ||
| XCTAssert(g1.next() == g2.next()) | ||
| } | ||
| } | ||
| } |