Add qt_real_to_fraction() helper function.

Private API meant to be used by plugins whose backends expect frame
rate values represented by a ratio.
The function implementation was moved from the AVFoundation plugin
to the QtMultimedia library.

Change-Id: I555b9d5da5ca3bae88992ed03501869fb731e45f
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

1 files changed, 81 insertions, 0 deletions

diff --git a/src/multimedia/qmultimediautils.cpp b/src/multimedia/qmultimediautils.cpp
new file mode 100644
index 000000000..6635e755d
--- /dev/null
+++ b/src/multimedia/qmultimediautils.cpp
@@ -0,0 +1,81 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qmultimediautils_p.h"
+
+QT_BEGIN_NAMESPACE
+
+void qt_real_to_fraction(qreal value, int *numerator, int *denominator)
+{
+    if (!numerator || !denominator)
+        return;
+
+    const int dMax = 1000;
+    int n1 = 0, d1 = 1, n2 = 1, d2 = 1;
+    qreal mid = 0.;
+    while (d1 <= dMax && d2 <= dMax) {
+        mid = qreal(n1 + n2) / (d1 + d2);
+
+        if (qAbs(value - mid) < 0.000001) {
+            if (d1 + d2 <= dMax) {
+                *numerator = n1 + n2;
+                *denominator = d1 + d2;
+                return;
+            } else if (d2 > d1) {
+                *numerator = n2;
+                *denominator = d2;
+                return;
+            } else {
+                *numerator = n1;
+                *denominator = d1;
+                return;
+            }
+        } else if (value > mid) {
+            n1 = n1 + n2;
+            d1 = d1 + d2;
+        } else {
+            n2 = n1 + n2;
+            d2 = d1 + d2;
+        }
+    }
+
+    if (d1 > dMax) {
+        *numerator = n2;
+        *denominator = d2;
+    } else {
+        *numerator = n1;
+        *denominator = d1;
+    }
+}
+
+QT_END_NAMESPACE