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/mod_ops.h b/webrtc/rtc_base/mod_ops.h
new file mode 100644
index 0000000..d51f127
--- /dev/null
+++ b/webrtc/rtc_base/mod_ops.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2016 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_MOD_OPS_H_
+#define WEBRTC_RTC_BASE_MOD_OPS_H_
+
+#include <limits>
+#include <type_traits>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+template <unsigned long M> // NOLINT
+inline unsigned long Add(unsigned long a, unsigned long b) { // NOLINT
+ RTC_DCHECK_LT(a, M);
+ unsigned long t = M - b % M; // NOLINT
+ unsigned long res = a - t; // NOLINT
+ if (t > a)
+ return res + M;
+ return res;
+}
+
+template <unsigned long M> // NOLINT
+inline unsigned long Subtract(unsigned long a, unsigned long b) { // NOLINT
+ RTC_DCHECK_LT(a, M);
+ unsigned long sub = b % M; // NOLINT
+ if (a < sub)
+ return M - (sub - a);
+ return a - sub;
+}
+
+// Calculates the forward difference between two wrapping numbers.
+//
+// Example:
+// uint8_t x = 253;
+// uint8_t y = 2;
+//
+// ForwardDiff(x, y) == 5
+//
+// 252 253 254 255 0 1 2 3
+// #################################################
+// | | x | | | | | y | |
+// #################################################
+// |----->----->----->----->----->
+//
+// ForwardDiff(y, x) == 251
+//
+// 252 253 254 255 0 1 2 3
+// #################################################
+// | | x | | | | | y | |
+// #################################################
+// -->-----> |----->---
+//
+template <typename T, T M>
+inline T ForwardDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ RTC_DCHECK_LT(a, M);
+ RTC_DCHECK_LT(b, M);
+ return a <= b ? b - a : M - (a - b);
+}
+
+template <typename T>
+inline T ForwardDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ return b - a;
+}
+
+// Calculates the reverse difference between two wrapping numbers.
+//
+// Example:
+// uint8_t x = 253;
+// uint8_t y = 2;
+//
+// ReverseDiff(y, x) == 5
+//
+// 252 253 254 255 0 1 2 3
+// #################################################
+// | | x | | | | | y | |
+// #################################################
+// <-----<-----<-----<-----<-----|
+//
+// ReverseDiff(x, y) == 251
+//
+// 252 253 254 255 0 1 2 3
+// #################################################
+// | | x | | | | | y | |
+// #################################################
+// ---<-----| |<-----<--
+//
+template <typename T, T M>
+inline T ReverseDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ RTC_DCHECK_LT(a, M);
+ RTC_DCHECK_LT(b, M);
+ return b <= a ? a - b : M - (b - a);
+}
+
+template <typename T>
+inline T ReverseDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ return a - b;
+}
+
+// Calculates the minimum distance between to wrapping numbers.
+//
+// The minimum distance is defined as min(ForwardDiff(a, b), ReverseDiff(a, b))
+template <typename T, T M>
+inline T MinDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ return std::min(ForwardDiff<T, M>(a, b), ReverseDiff<T, M>(a, b));
+}
+
+template <typename T>
+inline T MinDiff(T a, T b) {
+ static_assert(std::is_unsigned<T>::value,
+ "Type must be an unsigned integer.");
+ return std::min(ForwardDiff(a, b), ReverseDiff(a, b));
+}
+
+} // namespace webrtc
+
+#endif // WEBRTC_RTC_BASE_MOD_OPS_H_