# HG changeset patch
# User Hasan Yavuz ÖZDERYA <hy@ozderya.net>
# Date 2017-12-12 03:29:00
# Node ID b2f0d61c350726719401bc7b13b3641e380b5e38
# Parent  41cf55d3a08c96eeae17d178f24d3021d4051d3d

added read only buffer for use with snapshots

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;
+}
diff --git a/src/readonlybuffer.h b/src/readonlybuffer.h
new file mode 100644
--- /dev/null
+++ b/src/readonlybuffer.h
@@ -0,0 +1,57 @@
+/*
+  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/>.
+*/
+
+#ifndef READONLYBUFFER_H
+#define READONLYBUFFER_H
+
+// IMPORTANT TODO: rename to "framebuffer.h" when stream work is done.
+#include "framebuffer2.h"
+
+/// A read only frame buffer used for storing snapshot data. Main advantage of
+/// this compared to `RingBuffer` is that reading data should be somewhat
+/// faster.
+class ReadOnlyBuffer : public FrameBuffer
+{
+public:
+    /// Creates a buffer with data copied from `source`. Source buffer cannot be
+    /// empty.
+    ReadOnlyBuffer(const FrameBuffer* source);
+
+    /// Creates a buffer from a slice of the `source`.
+    ///
+    /// @param start start of the slice
+    /// @param n number of samples
+    ///
+    /// @important (start + n) should be smaller or equal than `source->size()`,
+    /// otherwise it's an error.
+    ReadOnlyBuffer(const FrameBuffer* source, unsigned start, unsigned n);
+
+    ~ReadOnlyBuffer();
+
+    virtual unsigned size() const;
+    virtual double sample(unsigned i) const;
+    virtual Range limits() const;
+
+private:
+    double* data;    ///< data storage
+    unsigned _size;  ///< data size
+    Range _limits;   ///< limits cache
+};
+
+#endif // READONLYBUFFER_H
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -30,6 +30,7 @@ add_executable(Test EXCLUDE_FROM_ALL
   ../src/indexbuffer.cpp
   ../src/linindexbuffer.cpp
   ../src/ringbuffer.cpp
+  ../src/readonlybuffer.cpp
   )
 add_test(NAME test1 COMMAND Test)
 qt5_use_modules(Test Widgets)
diff --git a/tests/test.cpp b/tests/test.cpp
--- a/tests/test.cpp
+++ b/tests/test.cpp
@@ -25,6 +25,7 @@
 #include "indexbuffer.h"
 #include "linindexbuffer.h"
 #include "ringbuffer.h"
+#include "readonlybuffer.h"
 
 TEST_CASE("samplepack with no X", "[memory]")
 {
@@ -364,3 +365,35 @@ TEST_CASE("RingBuffer clear", "[memory, 
     REQUIRE(lim.start == 0.);
     REQUIRE(lim.end == 0.);
 }
+
+TEST_CASE("ReadOnlyBuffer", "[memory, buffer]")
+{
+    IndexBuffer source(10);
+
+    ReadOnlyBuffer buf(&source);
+
+    REQUIRE(buf.size() == 10);
+    auto lim = buf.limits();
+    REQUIRE(lim.start == 0.);
+    REQUIRE(lim.end == 9.);
+    for (unsigned i = 0; i < 10; i++)
+    {
+        REQUIRE(buf.sample(i) == i);
+    }
+}
+
+TEST_CASE("ReadOnlyBuffer sliced constructor", "[memory, buffer]")
+{
+    IndexBuffer source(10);
+
+    ReadOnlyBuffer buf(&source, 5, 4);
+
+    REQUIRE(buf.size() == 4);
+    auto lim = buf.limits();
+    REQUIRE(lim.start == 5.);
+    REQUIRE(lim.end == 8.);
+    for (unsigned i = 0; i < 4; i++)
+    {
+        REQUIRE(buf.sample(i) == (i + 5));
+    }
+}