replace darwin prng with higher quality prngs

Sources/Voxelotl/Random/Xoroshiro128.swift

@@ -0,0 +1,126 @@
+struct Xoroshiro128Plus: RandomProvider {
+  public typealias Output = UInt64
+
+  static public var min: UInt64 { .min }
+  static public var max: UInt64 { .max }
+
+  public var state: (UInt64, UInt64)
+
+  public init() {
+    self.state = (0, 0)
+  }
+
+  public init(state: (UInt64, UInt64)) {
+    self.state = (state.0, state.1)
+  }
+
+  public init(seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.init(state: (s0, splitMix64(seed: s0)))
+  }
+
+  public mutating func seed(_ seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.state = (s0, splitMix64(seed: s0))
+  }
+
+  public mutating func next() -> UInt64 {
+    let result = self.state.0 &+ self.state.1
+
+    let xor = state.1 ^ self.state.0
+    self.state = (
+      self.state.0.rotate(left: 24) ^ xor ^ xor &<< 16,
+      xor.rotate(left: 37))
+
+    return result
+  }
+}
+
+struct Xoroshiro128PlusPlus: RandomProvider {
+  public typealias Output = UInt64
+
+  static public var min: UInt64 { .min }
+  static public var max: UInt64 { .max }
+
+  public var state: (UInt64, UInt64)
+
+  public init() {
+    self.state = (0, 0)
+  }
+
+  public init(state: (UInt64, UInt64)) {
+    self.state = (state.0, state.1)
+  }
+
+  public init(seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.init(state: (s0, splitMix64(seed: s0)))
+  }
+
+  public mutating func seed(_ seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.state = (s0, splitMix64(seed: s0))
+  }
+
+  public mutating func next() -> UInt64 {
+    let result = (self.state.0 &+ self.state.1).rotate(left: 17) &+ self.state.0
+
+    let xor = state.1 ^ self.state.0
+    self.state = (
+      self.state.0.rotate(left: 49) ^ xor ^ xor << 21,
+      xor.rotate(left: 28))
+
+    return result
+  }
+}
+
+struct Xoroshiro128StarStar: RandomProvider {
+  public typealias Output = UInt64
+
+  static public var min: UInt64 { .min }
+  static public var max: UInt64 { .max }
+
+  public var state: (UInt64, UInt64)
+
+  public init() {
+    self.state = (0, 0)
+  }
+
+  public init(state: (UInt64, UInt64)) {
+    self.state = (state.0, state.1)
+  }
+
+  public init(seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.init(state: (s0, splitMix64(seed: s0)))
+  }
+
+  public mutating func seed(_ seed: UInt64) {
+    let s0 = splitMix64(seed: seed)
+    self.state = (s0, splitMix64(seed: s0))
+  }
+
+  public mutating func next() -> UInt64 {
+    let result = (self.state.0 &* 5).rotate(left: 7) &* 9
+
+    let xor = self.state.1 ^ self.state.0
+    self.state = (
+      self.state.0.rotate(left: 24) ^ xor ^ xor << 16,
+      xor.rotate(left: 37))
+
+    return result
+  }
+}
+
+fileprivate extension UInt64 {
+  func rotate(left count: Int) -> Self {
+    self &<< count | self &>> (Self.bitWidth &- count)
+  }
+}
+
+fileprivate func splitMix64(seed: UInt64) -> UInt64 {
+  var x = seed &+ 0x9E3779B97F4A7C15
+  x = (x ^ x &>> 30) &* 0xBF58476D1CE4E5B9
+  x = (x ^ x &>> 27) &* 0x94D049BB133111EB
+  return x ^ x &>> 31
+}