mirror of
https://github.com/danog/libtgvoip.git
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5caaaafa42
I'm now using the entire audio processing module from WebRTC as opposed to individual DSP algorithms pulled from there before. Seems to work better this way.
336 lines
13 KiB
C++
336 lines
13 KiB
C++
/*
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* Copyright 2017 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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// Minimum and maximum
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// ===================
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//
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// rtc::SafeMin(x, y)
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// rtc::SafeMax(x, y)
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//
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// (These are both constexpr.)
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//
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// Accept two arguments of either any two integral or any two floating-point
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// types, and return the smaller and larger value, respectively, with no
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// truncation or wrap-around. If only one of the input types is statically
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// guaranteed to be able to represent the result, the return type is that type;
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// if either one would do, the result type is the smaller type. (One of these
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// two cases always applies.)
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//
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// * The case with one floating-point and one integral type is not allowed,
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// because the floating-point type will have greater range, but may not
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// have sufficient precision to represent the integer value exactly.)
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//
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// Clamp (a.k.a. constrain to a given interval)
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// ============================================
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//
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// rtc::SafeClamp(x, a, b)
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//
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// Accepts three arguments of any mix of integral types or any mix of
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// floating-point types, and returns the value in the closed interval [a, b]
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// that is closest to x (that is, if x < a it returns a; if x > b it returns b;
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// and if a <= x <= b it returns x). As for SafeMin() and SafeMax(), there is
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// no truncation or wrap-around. The result type
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//
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// 1. is statically guaranteed to be able to represent the result;
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//
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// 2. is no larger than the largest of the three argument types; and
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//
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// 3. has the same signedness as the type of the third argument, if this is
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// possible without violating the First or Second Law.
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//
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// There is always at least one type that meets criteria 1 and 2. If more than
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// one type meets these criteria equally well, the result type is one of the
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// types that is smallest. Note that unlike SafeMin() and SafeMax(),
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// SafeClamp() will sometimes pick a return type that isn't the type of any of
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// its arguments.
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//
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// * In this context, a type A is smaller than a type B if it has a smaller
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// range; that is, if A::max() - A::min() < B::max() - B::min(). For
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// example, int8_t < int16_t == uint16_t < int32_t, and all integral types
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// are smaller than all floating-point types.)
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//
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// * As for SafeMin and SafeMax, mixing integer and floating-point arguments
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// is not allowed, because floating-point types have greater range than
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// integer types, but do not have sufficient precision to represent the
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// values of most integer types exactly.
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//
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// Requesting a specific return type
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// =================================
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//
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// All three functions allow callers to explicitly specify the return type as a
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// template parameter, overriding the default return type. E.g.
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//
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// rtc::SafeMin<int>(x, y) // returns an int
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//
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// If the requested type is statically guaranteed to be able to represent the
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// result, then everything's fine, and the return type is as requested. But if
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// the requested type is too small, a static_assert is triggered.
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#ifndef RTC_BASE_NUMERICS_SAFE_MINMAX_H_
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#define RTC_BASE_NUMERICS_SAFE_MINMAX_H_
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#include <limits>
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#include <type_traits>
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#include "rtc_base/checks.h"
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#include "rtc_base/numerics/safe_compare.h"
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#include "rtc_base/type_traits.h"
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namespace rtc {
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namespace safe_minmax_impl {
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// Make the range of a type available via something other than a constexpr
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// function, to work around MSVC limitations. See
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// https://blogs.msdn.microsoft.com/vcblog/2015/12/02/partial-support-for-expression-sfinae-in-vs-2015-update-1/
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template <typename T>
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struct Limits {
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static constexpr T lowest = std::numeric_limits<T>::lowest();
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static constexpr T max = std::numeric_limits<T>::max();
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};
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template <typename T, bool is_enum = std::is_enum<T>::value>
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struct UnderlyingType;
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template <typename T>
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struct UnderlyingType<T, false> {
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using type = T;
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};
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template <typename T>
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struct UnderlyingType<T, true> {
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using type = typename std::underlying_type<T>::type;
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};
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// Given two types T1 and T2, find types that can hold the smallest (in
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// ::min_t) and the largest (in ::max_t) of the two values.
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template <typename T1,
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typename T2,
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bool int1 = IsIntlike<T1>::value,
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bool int2 = IsIntlike<T2>::value>
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struct MType {
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static_assert(int1 == int2,
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"You may not mix integral and floating-point arguments");
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};
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// Specialization for when neither type is integral (and therefore presumably
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// floating-point).
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template <typename T1, typename T2>
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struct MType<T1, T2, false, false> {
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using min_t = typename std::common_type<T1, T2>::type;
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static_assert(std::is_same<min_t, T1>::value ||
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std::is_same<min_t, T2>::value,
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"");
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using max_t = typename std::common_type<T1, T2>::type;
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static_assert(std::is_same<max_t, T1>::value ||
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std::is_same<max_t, T2>::value,
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"");
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};
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// Specialization for when both types are integral.
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template <typename T1, typename T2>
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struct MType<T1, T2, true, true> {
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// The type with the lowest minimum value. In case of a tie, the type with
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// the lowest maximum value. In case that too is a tie, the types have the
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// same range, and we arbitrarily pick T1.
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using min_t = typename std::conditional<
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SafeLt(Limits<T1>::lowest, Limits<T2>::lowest),
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T1,
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typename std::conditional<
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SafeGt(Limits<T1>::lowest, Limits<T2>::lowest),
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T2,
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typename std::conditional<SafeLe(Limits<T1>::max, Limits<T2>::max),
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T1,
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T2>::type>::type>::type;
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static_assert(std::is_same<min_t, T1>::value ||
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std::is_same<min_t, T2>::value,
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"");
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// The type with the highest maximum value. In case of a tie, the types have
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// the same range (because in C++, integer types with the same maximum also
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// have the same minimum).
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static_assert(SafeNe(Limits<T1>::max, Limits<T2>::max) ||
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SafeEq(Limits<T1>::lowest, Limits<T2>::lowest),
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"integer types with the same max should have the same min");
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using max_t = typename std::
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conditional<SafeGe(Limits<T1>::max, Limits<T2>::max), T1, T2>::type;
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static_assert(std::is_same<max_t, T1>::value ||
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std::is_same<max_t, T2>::value,
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"");
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};
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// A dummy type that we pass around at compile time but never actually use.
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// Declared but not defined.
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struct DefaultType;
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// ::type is A, except we fall back to B if A is DefaultType. We static_assert
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// that the chosen type can hold all values that B can hold.
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template <typename A, typename B>
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struct TypeOr {
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using type = typename std::
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conditional<std::is_same<A, DefaultType>::value, B, A>::type;
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static_assert(SafeLe(Limits<type>::lowest, Limits<B>::lowest) &&
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SafeGe(Limits<type>::max, Limits<B>::max),
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"The specified type isn't large enough");
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static_assert(IsIntlike<type>::value == IsIntlike<B>::value &&
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std::is_floating_point<type>::value ==
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std::is_floating_point<type>::value,
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"float<->int conversions not allowed");
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};
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} // namespace safe_minmax_impl
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template <
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typename R = safe_minmax_impl::DefaultType,
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typename T1 = safe_minmax_impl::DefaultType,
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typename T2 = safe_minmax_impl::DefaultType,
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typename R2 = typename safe_minmax_impl::TypeOr<
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R,
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typename safe_minmax_impl::MType<
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typename safe_minmax_impl::UnderlyingType<T1>::type,
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typename safe_minmax_impl::UnderlyingType<T2>::type>::min_t>::type>
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constexpr R2 SafeMin(T1 a, T2 b) {
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static_assert(IsIntlike<T1>::value || std::is_floating_point<T1>::value,
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"The first argument must be integral or floating-point");
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static_assert(IsIntlike<T2>::value || std::is_floating_point<T2>::value,
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"The second argument must be integral or floating-point");
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return SafeLt(a, b) ? static_cast<R2>(a) : static_cast<R2>(b);
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}
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template <
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typename R = safe_minmax_impl::DefaultType,
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typename T1 = safe_minmax_impl::DefaultType,
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typename T2 = safe_minmax_impl::DefaultType,
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typename R2 = typename safe_minmax_impl::TypeOr<
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R,
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typename safe_minmax_impl::MType<
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typename safe_minmax_impl::UnderlyingType<T1>::type,
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typename safe_minmax_impl::UnderlyingType<T2>::type>::max_t>::type>
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constexpr R2 SafeMax(T1 a, T2 b) {
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static_assert(IsIntlike<T1>::value || std::is_floating_point<T1>::value,
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"The first argument must be integral or floating-point");
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static_assert(IsIntlike<T2>::value || std::is_floating_point<T2>::value,
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"The second argument must be integral or floating-point");
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return SafeGt(a, b) ? static_cast<R2>(a) : static_cast<R2>(b);
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}
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namespace safe_minmax_impl {
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// Given three types T, L, and H, let ::type be a suitable return value for
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// SafeClamp(T, L, H). See the docs at the top of this file for details.
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template <typename T,
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typename L,
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typename H,
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bool int1 = IsIntlike<T>::value,
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bool int2 = IsIntlike<L>::value,
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bool int3 = IsIntlike<H>::value>
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struct ClampType {
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static_assert(int1 == int2 && int1 == int3,
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"You may not mix integral and floating-point arguments");
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};
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// Specialization for when all three types are floating-point.
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template <typename T, typename L, typename H>
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struct ClampType<T, L, H, false, false, false> {
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using type = typename std::common_type<T, L, H>::type;
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};
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// Specialization for when all three types are integral.
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template <typename T, typename L, typename H>
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struct ClampType<T, L, H, true, true, true> {
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private:
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// Range of the return value. The return type must be able to represent this
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// full range.
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static constexpr auto r_min =
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SafeMax(Limits<L>::lowest, SafeMin(Limits<H>::lowest, Limits<T>::lowest));
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static constexpr auto r_max =
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SafeMin(Limits<H>::max, SafeMax(Limits<L>::max, Limits<T>::max));
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// Is the given type an acceptable return type? (That is, can it represent
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// all possible return values, and is it no larger than the largest of the
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// input types?)
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template <typename A>
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struct AcceptableType {
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private:
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static constexpr bool not_too_large = sizeof(A) <= sizeof(L) ||
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sizeof(A) <= sizeof(H) ||
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sizeof(A) <= sizeof(T);
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static constexpr bool range_contained =
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SafeLe(Limits<A>::lowest, r_min) && SafeLe(r_max, Limits<A>::max);
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public:
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static constexpr bool value = not_too_large && range_contained;
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};
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using best_signed_type = typename std::conditional<
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AcceptableType<int8_t>::value,
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int8_t,
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typename std::conditional<
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AcceptableType<int16_t>::value,
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int16_t,
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typename std::conditional<AcceptableType<int32_t>::value,
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int32_t,
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int64_t>::type>::type>::type;
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using best_unsigned_type = typename std::conditional<
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AcceptableType<uint8_t>::value,
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uint8_t,
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typename std::conditional<
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AcceptableType<uint16_t>::value,
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uint16_t,
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typename std::conditional<AcceptableType<uint32_t>::value,
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uint32_t,
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uint64_t>::type>::type>::type;
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public:
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// Pick the best type, preferring the same signedness as T but falling back
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// to the other one if necessary.
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using type = typename std::conditional<
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std::is_signed<T>::value,
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typename std::conditional<AcceptableType<best_signed_type>::value,
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best_signed_type,
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best_unsigned_type>::type,
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typename std::conditional<AcceptableType<best_unsigned_type>::value,
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best_unsigned_type,
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best_signed_type>::type>::type;
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static_assert(AcceptableType<type>::value, "");
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};
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} // namespace safe_minmax_impl
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template <
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typename R = safe_minmax_impl::DefaultType,
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typename T = safe_minmax_impl::DefaultType,
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typename L = safe_minmax_impl::DefaultType,
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typename H = safe_minmax_impl::DefaultType,
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typename R2 = typename safe_minmax_impl::TypeOr<
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R,
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typename safe_minmax_impl::ClampType<
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typename safe_minmax_impl::UnderlyingType<T>::type,
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typename safe_minmax_impl::UnderlyingType<L>::type,
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typename safe_minmax_impl::UnderlyingType<H>::type>::type>::type>
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R2 SafeClamp(T x, L min, H max) {
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static_assert(IsIntlike<H>::value || std::is_floating_point<H>::value,
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"The first argument must be integral or floating-point");
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static_assert(IsIntlike<T>::value || std::is_floating_point<T>::value,
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"The second argument must be integral or floating-point");
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static_assert(IsIntlike<L>::value || std::is_floating_point<L>::value,
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"The third argument must be integral or floating-point");
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RTC_DCHECK_LE(min, max);
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return SafeLe(x, min)
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? static_cast<R2>(min)
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: SafeGe(x, max) ? static_cast<R2>(max) : static_cast<R2>(x);
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}
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} // namespace rtc
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#endif // RTC_BASE_NUMERICS_SAFE_MINMAX_H_
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