more efficient particles

Former-commit-id: 56dad88ecd715ad6e357e33b903851a47a358dcd
Former-commit-id: c85c0b759a447c0461563d98156f59879fa95db2

src/net/torvald/terrarum/CircularArray.kt

@@ -0,0 +1,49 @@
+package net.torvald.terrarum
+
+
+/**
+ * Notes for particle storage:
+ *      Particles does not need to be removed, just let it overwrite as their operation is rather
+ *      lightweight. So, just flagDespawn = true if it need to be "deleted" so that it won't update
+ *      anymore.
+ *
+ * Created by minjaesong on 2017-01-22.
+ */
+class CircularArray<T>(val size: Int) {
+
+    private val buffer: Array<T> = arrayOfNulls<Any>(size) as Array<T>
+    private var tail: Int = 0
+    private var head: Int = 0
+
+    val elemCount: Int
+        get() = if (tail >= head) tail - head else size
+
+    fun add(item: T) {
+        buffer[tail] = item // overwrites oldest item when eligible
+        tail = (tail + 1) % size
+        if (tail == head) {
+            head = (head + 1) % size
+        }
+    }
+
+    fun forEach(action: (T) -> Unit) {
+        if (tail >= head) { // queue not full
+            (head..tail - 1).map { buffer[it] }.forEach { action(it) }
+        }
+        else { // queue full
+            (0..size - 1).map { buffer[(it + head) % size] }.forEach { action(it) }
+        }
+    }
+
+    fun forEachConcurrent(action: (T) -> Unit) {
+        TODO()
+    }
+
+    fun forEachConcurrentWaitFor(action: (T) -> Unit) {
+        TODO()
+    }
+
+    override fun toString(): String {
+        return "CircularArray(size=" + buffer.size + ", head=" + head + ", tail=" + tail + ")"
+    }
+}