Motown: Add new Ratio and LinearFunction classes to media/common/cpp.

mojo/services/media/common/cpp/linear_function.cc

Index: mojo/services/media/common/cpp/linear_function.cc
diff --git a/mojo/services/media/common/cpp/linear_function.cc b/mojo/services/media/common/cpp/linear_function.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ec662e7f687f4d1150a25014a03f49a87384f9c6
--- /dev/null
+++ b/mojo/services/media/common/cpp/linear_function.cc
@@ -0,0 +1,31 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <limits>
+#include <utility>
+
+#include "mojo/public/cpp/environment/logging.h"
+#include "mojo/services/media/common/cpp/linear_function.h"
+
+namespace mojo {
+namespace media {
+
+// static
+int64_t LinearFunction::Apply(int64_t domain_basis,
+                              int64_t range_basis,
+                              const Ratio& slope,  // range_delta / domain_delta
+                              int64_t domain_input) {
+  return slope.Scale(domain_input - domain_basis) + range_basis;
+}
+
+// static
+LinearFunction LinearFunction::Compose(const LinearFunction& bc,
+                                       const LinearFunction& ab,
+                                       bool exact) {
+  return LinearFunction(ab.domain_basis(), bc.Apply(ab.range_basis()),
+                        Ratio::Product(ab.slope(), bc.slope(), exact));
+}
+
+}  // namespace media
+}  // namespace mojo