1 files changed, 39 insertions, 0 deletions
diff --git a/third_party/libwebrtc/webrtc/rtc_base/numerics/mathutils.h b/third_party/libwebrtc/webrtc/rtc_base/numerics/mathutils.h
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index 0000000000..5036c8fecb
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+++ b/third_party/libwebrtc/webrtc/rtc_base/numerics/mathutils.h
@@ -0,0 +1,39 @@
+/*
+ *  Copyright 2005 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef RTC_BASE_NUMERICS_MATHUTILS_H_
+#define RTC_BASE_NUMERICS_MATHUTILS_H_
+
+#include <math.h>
+#include <type_traits>
+
+#include "rtc_base/checks.h"
+
+#ifndef M_PI
+#define M_PI 3.14159265359f
+#endif
+
+// Given two numbers |x| and |y| such that x >= y, computes the difference
+// x - y without causing undefined behavior due to signed overflow.
+template <typename T>
+typename std::make_unsigned<T>::type unsigned_difference(T x, T y) {
+  static_assert(
+      std::is_signed<T>::value,
+      "Function unsigned_difference is only meaningful for signed types.");
+  RTC_DCHECK_GE(x, y);
+  typedef typename std::make_unsigned<T>::type unsigned_type;
+  // int -> unsigned conversion repeatedly adds UINT_MAX + 1 until the number
+  // can be represented as an unsigned. Since we know that the actual
+  // difference x - y can be represented as an unsigned, it is sufficient to
+  // compute the difference modulo UINT_MAX + 1, i.e using unsigned arithmetic.
+  return static_cast<unsigned_type>(x) - static_cast<unsigned_type>(y);
+}
+
+#endif  // RTC_BASE_NUMERICS_MATHUTILS_H_