diff --git a/inputsource.cpp b/inputsource.cpp
index 1fea732..24d182b 100644
--- a/inputsource.cpp
+++ b/inputsource.cpp
@@ -27,31 +27,60 @@
 
 #include <stdexcept>
 
-InputSource::InputSource(const char *filename)
+InputSource::InputSource()
 {
-    m_file = fopen(filename, "rb");
-    if (m_file == nullptr)
-        throw std::runtime_error("Error opening file");
-
-    struct stat sb;
-    if (fstat(fileno(m_file), &sb) != 0)
-        throw std::runtime_error("Error fstating file");
-    m_file_size = sb.st_size;
-    sampleCount = m_file_size / sizeof(std::complex<float>);
-
-    m_data = (std::complex<float>*)mmap(NULL, m_file_size, PROT_READ, MAP_SHARED, fileno(m_file), 0);
-    if (m_data == 0)
-        throw std::runtime_error("Error mmapping file");
 }
 
 InputSource::~InputSource()
 {
-    munmap(m_data, m_file_size);
-    fclose(m_file);
+    cleanup();
+}
+
+void InputSource::cleanup()
+{
+    if (mmapData != nullptr) {
+        munmap(mmapData, fileSize);
+        mmapData = nullptr;
+        fileSize = 0;
+    }
+
+    if (inputFile != nullptr) {
+        fclose(inputFile);
+        inputFile = nullptr;
+    }
+}
+
+void InputSource::openFile(const char *filename)
+{
+    FILE *file = fopen(filename, "rb");
+    if (file == nullptr)
+        throw std::runtime_error("Error opening file");
+
+    struct stat sb;
+    if (fstat(fileno(file), &sb) != 0)
+        throw std::runtime_error("Error fstating file");
+    off_t size = sb.st_size;
+    sampleCount = size / sizeof(std::complex<float>);
+
+    auto data = (std::complex<float>*)mmap(NULL, size, PROT_READ, MAP_SHARED, fileno(file), 0);
+    if (data == nullptr)
+        throw std::runtime_error("Error mmapping file");
+
+    cleanup();
+
+    inputFile = file;
+    fileSize = size;
+    mmapData = data;
 }
 
 std::unique_ptr<std::complex<float>[]> InputSource::getSamples(off_t start, off_t length)
 {
+    if (inputFile == nullptr)
+        return nullptr;
+
+    if (mmapData == nullptr)
+        return nullptr;
+
     if(start < 0 || length < 0)
         return nullptr;
 
@@ -59,6 +88,6 @@ std::unique_ptr<std::complex<float>[]> InputSource::getSamples(off_t start, off_
         return nullptr;
 
     std::unique_ptr<std::complex<float>[]> dest(new std::complex<float>[length]);
-    memcpy(dest.get(), &m_data[start], length * sizeof(std::complex<float>));
+    memcpy(dest.get(), &mmapData[start], length * sizeof(std::complex<float>));
     return dest;
 }
diff --git a/inputsource.h b/inputsource.h
index ea31e1e..75feeac 100644
--- a/inputsource.h
+++ b/inputsource.h
@@ -25,15 +25,16 @@
 class InputSource : public SampleSource<std::complex<float>>
 {
 private:
-    FILE *m_file;
-    off_t m_file_size;
-    off_t sampleCount;
-    std::complex<float> *m_data;
+    FILE *inputFile = nullptr;
+    off_t fileSize = 0;
+    off_t sampleCount = 0;
+    std::complex<float> *mmapData = nullptr;
 
 public:
-    InputSource(const char *filename);
+    InputSource();
     ~InputSource();
-
+    void cleanup();
+    void openFile(const char *filename);
     std::unique_ptr<std::complex<float>[]> getSamples(off_t start, off_t length);
     off_t count() {
         return sampleCount;
diff --git a/mainwindow.cpp b/mainwindow.cpp
index f7eda87..7535212 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -31,7 +31,9 @@ MainWindow::MainWindow()
     dock->setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea);
     addDockWidget(Qt::LeftDockWidgetArea, dock);
 
-    plots = new PlotView();
+    InputSource *input = new InputSource();
+
+    plots = new PlotView(input);
     setCentralWidget(plots);
 
     connect(dock, SIGNAL(fftSizeChanged(int)), plots, SLOT(setFFTSize(int)));
@@ -43,6 +45,5 @@ void MainWindow::openFile(QString fileName)
 {
     QString title="%1: %2";
     this->setWindowTitle(title.arg(QApplication::applicationName(),fileName.section('/',-1,-1)));
-    // TODO: error check, ownership
-    plots->inputSourceChanged(new InputSource(fileName.toUtf8().constData()));
+    // TODO: open a file again
 }
diff --git a/plotview.cpp b/plotview.cpp
index cabad05..a0a0582 100644
--- a/plotview.cpp
+++ b/plotview.cpp
@@ -31,8 +31,9 @@
 #include "memory_source.h"
 #include "traceplot.h"
 
-PlotView::PlotView() : cursors(this), viewRange({0, 0})
+PlotView::PlotView(InputSource *input) : cursors(this), viewRange({0, 0})
 {
+    mainSampleSource = input;
     setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
     enableCursors(false);
 }
diff --git a/plotview.h b/plotview.h
index 3c0e3a6..6f6a6c0 100644
--- a/plotview.h
+++ b/plotview.h
@@ -32,7 +32,7 @@ class PlotView : public QAbstractScrollArea
     Q_OBJECT
 
 public:
-    PlotView();
+    PlotView(InputSource *input);
 
 public slots:
     void enableCursors(bool enable);