Simulator is just about ready for real-world testing now. Added a simulated

MOS6551 ACIA at address $C000 which does buffered input and output via the
console. Updated the README with a bit more documentation, and bumped the
version number to 0.1 because I'm impatient.

src/main/java/com/loomcom/symon/util/FifoRingBuffer.java

@@ -0,0 +1,78 @@
+package com.loomcom.symon.util;
+
+import com.loomcom.symon.exceptions.*;
+
+/**
+ * A very simple and efficient FIFO ring buffer implementation backed
+ * by an array. It can only hold only integers.
+ */
+public class FifoRingBuffer {
+
+  private int[] fifoBuffer;
+  private int readPtr = 0;
+  private int writePtr = 0;
+  private int size = 0;
+
+  public FifoRingBuffer(int size) {
+    if (size <= 0) {
+      throw new RuntimeException("Cannot create a FifoRingBuffer with size <= 0.");
+    }
+    this.size = size;
+    fifoBuffer = new int[size];
+  }
+
+  public int peek() throws FifoUnderrunException {
+    if (isEmpty()) {
+      throw new FifoUnderrunException("Buffer Underrun");
+    }
+    return fifoBuffer[readPtr];
+  }
+
+  public int pop() throws FifoUnderrunException {
+    if (isEmpty()) {
+      throw new FifoUnderrunException("Buffer Underrun");
+    }
+    int val = fifoBuffer[readPtr];
+    incrementReadPointer();
+    return val;
+  }
+
+  public boolean isEmpty() {
+    return(readPtr == writePtr);
+  }
+
+  public boolean isFull() {
+    return((readPtr == 0 && writePtr == (size - 1)) ||
+           writePtr == (readPtr - 1));
+  }
+
+  public void push(int val) {
+    fifoBuffer[writePtr] = val;
+    incrementWritePointer();
+  }
+
+  public void reset() {
+    readPtr = 0;
+    writePtr = 0;
+  }
+
+  private void incrementWritePointer() {
+    if (++writePtr == size) {
+      writePtr = 0;
+    }
+    if (writePtr == readPtr) {
+      incrementReadPointer();
+    }
+  }
+
+  private void incrementReadPointer() {
+    if (++readPtr == size) {
+      readPtr = 0;
+    }
+  }
+
+  public String toString() {
+    return "[FifoRingBuffer: size=" + size + "]";
+  }
+}
+