implement optimizations

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

@@ -0,0 +1,16 @@
+package com.infendro.random
+
+import kotlin.random.Random
+
+abstract class PRNG : Random() {
+    abstract fun seed(seed: ByteArray)
+
+    protected abstract fun generate(): Int
+
+    override fun nextBits(bitCount: Int): Int {
+        require(bitCount in 0..32)
+
+        if (bitCount == 0) return 0
+        return generate() ushr (32 - bitCount)
+    }
+}