refactor, implement LCG

LCG ... Linear Congruential Generator

src/commonMain/kotlin/com/infendro/random/prng/LCG.kt

@@ -0,0 +1,34 @@
+package com.infendro.random.prng
+
+import com.infendro.bytearray.padStart
+import com.infendro.bytearray.toUByteArray
+import com.infendro.bytearray.toULong
+import kotlin.math.min
+import kotlin.properties.Delegates
+
+class LCG internal constructor() : PRNG() {
+    private val a: ULong = 25214903917UL
+    private val c: ULong = 11UL
+    private val m: ULong = 1UL shl 48
+
+    private var x: ULong by Delegates.notNull()
+
+    override fun seed(
+        seed: UByteArray,
+    ) {
+        val s = seed.padStart(8, 0x00U).takeLast(8).toUByteArray()
+        x = s.toULong() % m
+    }
+
+    override fun generate(
+        count: Int,
+    ): UByteArray {
+        return buildList {
+            while (size < count) {
+                x = (a * x + c) % m
+
+                addAll(x.toUByteArray().takeLast(min(count - size, 6)))
+            }
+        }.toUByteArray()
+    }
+}

src/commonMain/kotlin/com/infendro/random/prng/PRNG.kt

@@ -0,0 +1,27 @@
+package com.infendro.random.prng
+
+import com.infendro.bytearray.toInt
+import kotlin.random.Random
+
+abstract class PRNG : Random() {
+    abstract fun seed(
+        seed: UByteArray,
+    )
+
+    abstract fun generate(
+        count: Int,
+    ): UByteArray
+
+    override fun nextBits(
+        bitCount: Int,
+    ): Int {
+        if (bitCount !in 0..32) throw Exception()
+        if (bitCount == 0) return 0
+
+        return generate(4).toInt() ushr (32 - bitCount)
+    }
+
+    companion object {
+        fun LCG() = com.infendro.random.prng.LCG()
+    }
+}