diff --git a/src/readonlybuffer.cpp b/src/readonlybuffer.cpp
new file mode 100644
--- /dev/null
+++ b/src/readonlybuffer.cpp
@@ -0,0 +1,86 @@
+/*
+  Copyright © 2017 Hasan Yavuz Özderya
+
+  This file is part of serialplot.
+
+  serialplot 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.
+
+  serialplot 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 serialplot.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <QtGlobal>
+
+#include "readonlybuffer.h"
+
+ReadOnlyBuffer::ReadOnlyBuffer(const FrameBuffer* source) :
+    ReadOnlyBuffer(source, 0, source->size())
+{
+    // empty
+}
+
+ReadOnlyBuffer::ReadOnlyBuffer(const FrameBuffer* source, unsigned start, unsigned n)
+{
+    Q_ASSERT(source->size() > 0);
+    Q_ASSERT(start + n <= source->size());
+
+    _size = n;
+    data = new double[_size];
+
+    for (unsigned i = 0; i < n; i++)
+    {
+        data[i] = source->sample(start + i);
+    }
+
+    /// if not exact copy of source re-calculate limits
+    if (start == 0 && n == source->size())
+    {
+        _limits = source->limits();
+    }
+    else
+    {
+        // TODO: code duplication with RingBuffer::updateLimits, consider reuse
+        _limits.start = data[0];
+        _limits.end = data[0];
+
+        for (unsigned i = 0; i < _size; i++)
+        {
+            if (data[i] > _limits.end)
+            {
+                _limits.end = data[i];
+            }
+            else if (data[i] < _limits.start)
+            {
+                _limits.start = data[i];
+            }
+        }
+    }
+}
+
+ReadOnlyBuffer::~ReadOnlyBuffer()
+{
+    delete[] data;
+}
+
+unsigned ReadOnlyBuffer::size() const
+{
+    return _size;
+}
+
+double ReadOnlyBuffer::sample(unsigned i) const
+{
+    return data[i];
+}
+
+Range ReadOnlyBuffer::limits() const
+{
+    return _limits;
+}