Added log ring buffer

app/src/main/java/eu/faircode/email/RingBuffer.java

@@ -0,0 +1,56 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2021 by Marcel Bokhorst (M66B)
+*/
+
+public class RingBuffer<T> {
+    private T[] buffer;
+    private int count = 0;
+    private int out = 0;
+    private int in = 0;
+
+    public RingBuffer(int capacity) {
+        buffer = (T[]) new Object[capacity];
+    }
+
+    public synchronized void push(T item) {
+        if (count == buffer.length)
+            pop();
+
+        buffer[in] = item;
+        in = (in + 1) % buffer.length;
+        count++;
+    }
+
+    public synchronized T pop() {
+        T item = buffer[out];
+        buffer[out] = null;
+        count--;
+        out = (out + 1) % buffer.length;
+        return item;
+    }
+
+    public synchronized boolean isEmpty() {
+        return (count == 0);
+    }
+
+    public synchronized int size() {
+        return count;
+    }
+}