add_with_saturate.h

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#ifndef INCLUDE_ADD_WITH_SATURATE_H_
#define INCLUDE_ADD_WITH_SATURATE_H_
 
/*
   Copyright (c) 2018, 2024, Oracle and/or its affiliates.
 
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   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
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   permission to link the program and your derivative works with the
   separately licensed software that they have either included with
   the program or referenced in the documentation.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
/**
  @file include/add_with_saturate.h
  Some utilities for saturating add.
 */
 
#include <limits>
#include <type_traits>
 
// Returns a + b, saturated to the range of a.
template <class T, class U>
inline T AddWithSaturate(T a, U b) {
  static_assert(!std::is_signed<T>::value, "values must be unsigned");
  static_assert(!std::is_signed<U>::value, "values must be unsigned");
 
  auto result = a + b;
  if (result < a || result > std::numeric_limits<T>::max()) {
    // Value wrapped around or was promoted to a larger type; saturate to the
    // maximum value.
    return std::numeric_limits<T>::max();
  }
  return result;
}
 
// Effectively does b += a; with saturation.
template <class T, class U>
inline void AddWithSaturate(T a, U *b) {
  *b = AddWithSaturate(*b, a);
}
 
#endif  // INCLUDE_ADD_WITH_SATURATE_H_