From efd9905f5b08da0a913b5730180f6394d56549a5 Mon Sep 17 00:00:00 2001
From: a dinosaur <dino@a-dinosaur.com>
Date: Fri, 23 Aug 2024 09:13:42 +1000
Subject: [PATCH] generalise shared prng functionality to interfaces

---
 Sources/Voxelotl/Random/PCG32Random.swift    |  9 +++++----
 Sources/Voxelotl/Random/RandomProvider.swift | 15 +++++++++++++++
 Sources/Voxelotl/Random/Xoroshiro128.swift   | 12 +++++++++---
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/Sources/Voxelotl/Random/PCG32Random.swift b/Sources/Voxelotl/Random/PCG32Random.swift
index 3462663..f1c7532 100644
--- a/Sources/Voxelotl/Random/PCG32Random.swift
+++ b/Sources/Voxelotl/Random/PCG32Random.swift
@@ -1,5 +1,6 @@
-public struct PCG32Random: RandomProvider {
+public struct PCG32Random: RandomProvider, RandomStateAccess {
   public typealias Output = UInt32
+  public typealias StateType = (UInt64, UInt64)
 
   public static var min: UInt32 { .min }
   public static var max: UInt32 { .max }
@@ -19,12 +20,12 @@ public struct PCG32Random: RandomProvider {
     self._inc   = 0xDA3E39CB94B95BDB
   }
 
-  public init(seed: UInt64, sequence: UInt64) {
+  public init(state: (UInt64, UInt64)) {
     self.init()
-    self.seed(state: _state, sequence: sequence)
+    self.reset(state: state.0, sequence: state.1)
   }
 
-  public mutating func seed(state: UInt64, sequence: UInt64) {
+  public mutating func reset(state: UInt64, sequence: UInt64) {
     self._state = 0
     self._inc   = sequence << 1 | 0x1
     _ = next()
diff --git a/Sources/Voxelotl/Random/RandomProvider.swift b/Sources/Voxelotl/Random/RandomProvider.swift
index 110a301..f4cdbb4 100644
--- a/Sources/Voxelotl/Random/RandomProvider.swift
+++ b/Sources/Voxelotl/Random/RandomProvider.swift
@@ -6,3 +6,18 @@ public protocol RandomProvider {
 
   mutating func next() -> Output
 }
+
+public protocol RandomSeedable {
+  associatedtype SeedType: FixedWidthInteger
+
+  init(seed: SeedType)
+  mutating func seed(_ value: SeedType)
+}
+
+public protocol RandomStateAccess {
+  associatedtype StateType
+
+  var state: StateType { get set }
+
+  init(state: StateType)
+}
diff --git a/Sources/Voxelotl/Random/Xoroshiro128.swift b/Sources/Voxelotl/Random/Xoroshiro128.swift
index e6eb016..305a757 100644
--- a/Sources/Voxelotl/Random/Xoroshiro128.swift
+++ b/Sources/Voxelotl/Random/Xoroshiro128.swift
@@ -1,5 +1,7 @@
-struct Xoroshiro128Plus: RandomProvider {
+struct Xoroshiro128Plus: RandomProvider, RandomSeedable, RandomStateAccess {
   public typealias Output = UInt64
+  public typealias SeedType = UInt64
+  public typealias StateType = (UInt64, UInt64)
 
   static public var min: UInt64 { .min }
   static public var max: UInt64 { .max }
@@ -36,8 +38,10 @@ struct Xoroshiro128Plus: RandomProvider {
   }
 }
 
-struct Xoroshiro128PlusPlus: RandomProvider {
+struct Xoroshiro128PlusPlus: RandomProvider, RandomSeedable, RandomStateAccess {
   public typealias Output = UInt64
+  public typealias SeedType = UInt64
+  public typealias StateType = (UInt64, UInt64)
 
   static public var min: UInt64 { .min }
   static public var max: UInt64 { .max }
@@ -74,8 +78,10 @@ struct Xoroshiro128PlusPlus: RandomProvider {
   }
 }
 
-struct Xoroshiro128StarStar: RandomProvider {
+struct Xoroshiro128StarStar: RandomProvider, RandomSeedable, RandomStateAccess {
   public typealias Output = UInt64
+  public typealias SeedType = UInt64
+  public typealias StateType = (UInt64, UInt64)
 
   static public var min: UInt64 { .min }
   static public var max: UInt64 { .max }