base/safe_conversions.h

/*
 * libjingle
 * Copyright 2014, Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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 */

// Borrowed from Chromium's src/base/numerics/safe_conversions.h.

#ifndef TALK_BASE_SAFE_CONVERSIONS_H_
#define TALK_BASE_SAFE_CONVERSIONS_H_

#include <limits>

#include "talk/base/common.h"
#include "talk/base/logging.h"
#include "talk/base/safe_conversions_impl.h"

namespace talk_base {

inline void Check(bool condition) {
  if (!condition) {
    LOG(LS_ERROR) << "CHECK failed.";
    Break();
    // The program should have crashed at this point.
  }
}

// Convenience function that returns true if the supplied value is in range
// for the destination type.
template <typename Dst, typename Src>
inline bool IsValueInRangeForNumericType(Src value) {
  return internal::RangeCheck<Dst>(value) == internal::TYPE_VALID;
}

// checked_cast<> is analogous to static_cast<> for numeric types,
// except that it CHECKs that the specified numeric conversion will not
// overflow or underflow. NaN source will always trigger a CHECK.
template <typename Dst, typename Src>
inline Dst checked_cast(Src value) {
  Check(IsValueInRangeForNumericType<Dst>(value));
  return static_cast<Dst>(value);
}

// saturated_cast<> is analogous to static_cast<> for numeric types, except
// that the specified numeric conversion will saturate rather than overflow or
// underflow. NaN assignment to an integral will trigger a CHECK condition.
template <typename Dst, typename Src>
inline Dst saturated_cast(Src value) {
  // Optimization for floating point values, which already saturate.
  if (std::numeric_limits<Dst>::is_iec559)
    return static_cast<Dst>(value);

  switch (internal::RangeCheck<Dst>(value)) {
    case internal::TYPE_VALID:
      return static_cast<Dst>(value);

    case internal::TYPE_UNDERFLOW:
      return std::numeric_limits<Dst>::min();

    case internal::TYPE_OVERFLOW:
      return std::numeric_limits<Dst>::max();

    // Should fail only on attempting to assign NaN to a saturated integer.
    case internal::TYPE_INVALID:
      Check(false);
      return std::numeric_limits<Dst>::max();
  }

  Check(false); // NOTREACHED();
  return static_cast<Dst>(value);
}

}  // namespace talk_base

#endif  // TALK_BASE_SAFE_CONVERSIONS_H_