roundandclip.h

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// Copyright 2017-2020, Schlumberger
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
//Adapted from: Zgy/PlatformLib/RoundAndClip.h and others.
#pragma once
 
#include <cstdint>
#include <cmath>
#include <limits>
 
namespace InternalZGY {
#if 0
}
#endif
 
static inline bool IsFiniteD(double val)
{
  return std::isfinite(val);
}
 
template <typename T> inline bool IsFiniteT(T /*value*/)
{
  return true;
}
 
template <> inline bool IsFiniteT<float>(float value)
{
  return std::isfinite(value);
}
 
template <> inline bool IsFiniteT<double>(double value)
{
  return std::isfinite(value);
}
 
template <> inline bool IsFiniteT<long double>(long double value)
{
  return std::isfinite(static_cast<double>(value));
}
 
template <typename T> inline bool IsNanT(T /*value*/)
{
  return false;
}
 
template <> inline bool IsNanT<float>(float value)
{
  return std::isnan(value);
}
 
template <> inline bool IsNanT<double>(double value)
{
  return std::isnan(value);
}
 
template <> inline bool IsNanT<long double>(long double value)
{
  return std::isnan(static_cast<double>(value));
}
 
static inline std::int32_t RoundD2I(double d)
{
  return d>0 ? (int)(d+0.5) : (int)(d-0.5);
}
 
template <typename T>
T RoundAndClip(double value)
{
  // Can skip this (and avoid an annoying warning on windows)
  // if we are sure that all floating types are explicitly
  // specialized below. Or replace it with an assert.
  // But an assert could be even worse due to the performance hit.
  if (!std::numeric_limits<T>::is_integer)
    return static_cast<T>(value);
 
  // Be careful changing this code, it is more subtle than it looks.
  // If T is a 64-bit integer, this has greater precision than a double.
  // E.g. for T == unsigned long long and an input value of, say,
  // 2^64+1 this is clearly outside the valid range (max 2^64-1).
  // But both those values end up being rounded to 2^64 when assigned
  // to a double. So if the test used the more intuitive > instead of
  // >= it would fail. And the assignment at the end would overflow,
  // resulting in a hardware dependant result. 0x8000000000000000 on
  // Pentium. NaNs are supposed to fail both tests; in this case I want
  // the 0x8xx result as a fallback in case the caller didn't remove NaNs.
 
  if (value <= (double)std::numeric_limits<T>::min())
    return std::numeric_limits<T>::min();
  if (value >= (double)std::numeric_limits<T>::max())
    return std::numeric_limits<T>::max();
 
  // Since C++ by default rounds toward zero, we need special handling.
  // In the general case we cannot use RoundD2I(), and round() is slow.
  if (value < 0)
    return static_cast<T>(value - 0.5);
  return static_cast<T>(value + 0.5);
}
 
template <typename T>
T RoundAndClip(double value, T nan)
{
  if (!std::numeric_limits<T>::is_integer)
    return static_cast<T>(value);
  else if (IsNanT(value))
    return nan;
  else
    return RoundAndClip<T>(value);
}
 
} // namespace