Revert "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)
Will reland in two different commits to preserve git blame history.
BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org
Change-Id: I550da8525aeb9c5b8f96338fcf1c9714f3dcdab1
Reviewed-on: https://chromium-review.googlesource.com/554610
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18820}diff --git a/webrtc/base/mathutils.h b/webrtc/base/mathutils.h
index 9e5c3ca..3c70e76 100644
--- a/webrtc/base/mathutils.h
+++ b/webrtc/base/mathutils.h
@@ -11,9 +11,29 @@
#ifndef WEBRTC_BASE_MATHUTILS_H_
#define WEBRTC_BASE_MATHUTILS_H_
+#include <math.h>
+#include <type_traits>
-// This header is deprecated and is just left here temporarily during
-// refactoring. See https://bugs.webrtc.org/7634 for more details.
-#include "webrtc/rtc_base/mathutils.h"
+#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_BASE_MATHUTILS_H_