Reland "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)
Reland the base->rtc_base without adding stub headers (will be
done in follow-up CL). This preserves git blame history of all files.
BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org
Change-Id: Iea3bb6f3f67b8374c96337b63e8f5aa3e6181012
Reviewed-on: https://chromium-review.googlesource.com/554611
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18821}diff --git a/webrtc/rtc_base/mathutils.h b/webrtc/rtc_base/mathutils.h
new file mode 100644
index 0000000..3882c32
--- /dev/null
+++ b/webrtc/rtc_base/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 WEBRTC_RTC_BASE_MATHUTILS_H_
+#define WEBRTC_RTC_BASE_MATHUTILS_H_
+
+#include <math.h>
+#include <type_traits>
+
+#include "webrtc/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 // WEBRTC_RTC_BASE_MATHUTILS_H_