Merge "Fix issue #28602068: Add count to job scheduler stats" into nyc-dev am: d90be6cccc am: 9071cacdbe

am: 9b560795e2

* commit '9b560795e292a9701848e0b0603c7edc68b8bc1d':
  Fix issue #28602068: Add count to job scheduler stats

Change-Id: If3d2f01c1e0aacdcf7ef44eeef46ea84dbfb3b32

core/java/com/android/internal/util/RingBufferIndices.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.internal.util;
+
+/**
+ * Helper class for implementing a ring buffer.  This supplies the indices, you supply
+ * the array(s).
+ */
+public class RingBufferIndices {
+    private final int mCapacity;
+
+    // The first valid element and the next open slot.
+    private int mStart;
+    private int mSize;
+
+    /**
+     * Create ring buffer of the given capacity.
+     */
+    public RingBufferIndices(int capacity) {
+        mCapacity = capacity;
+    }
+
+    /**
+     * Add a new item to the ring buffer.  If the ring buffer is full, this
+     * replaces the oldest item.
+     * @return Returns the index at which the new item appears, for placing in your array.
+     */
+    public int add() {
+        if (mSize < mCapacity) {
+            final int pos = mSize;
+            mSize++;
+            return pos;
+        }
+        int pos = mStart;
+        mStart++;
+        if (mStart == mCapacity) {
+            mStart = 0;
+        }
+        return pos;
+    }
+
+    /**
+     * Clear the ring buffer.
+     */
+    public void clear() {
+        mStart = 0;
+        mSize = 0;
+    }
+
+    /**
+     * Return the current size of the ring buffer.
+     */
+    public int size() {
+        return mSize;
+    }
+
+    /**
+     * Convert a position in the ring buffer that is [0..size()] to an offset
+     * in the array(s) containing the ring buffer items.
+     */
+    public int indexOf(int pos) {
+        int index = mStart + pos;
+        if (index >= mCapacity) {
+            index -= mCapacity;
+        }
+        return index;
+    }
+}