Move some more numeric utility code from rtc_base/ to rtc_base/numerics/
Specifically, I'm moving
histogram_percentile_counter.h
mathutils.h
mod_ops.h
moving_max_counter.h
They shouldn't be part of the API, and moving them to an appropriate
subdirectory of rtc_base/ is a good way to keep track of that.
BUG=webrtc:8445
Change-Id: I78a999984a27ef935be2d7c3136475d5f209adda
Reviewed-on: https://webrtc-review.googlesource.com/20870
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20832}diff --git a/rtc_base/numerics/mathutils.h b/rtc_base/numerics/mathutils.h
new file mode 100644
index 0000000..5036c8f
--- /dev/null
+++ b/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_