safe_conversions.h

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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
// Slightly adapted for inclusion in V8.
// Copyright 2014 the V8 project authors. All rights reserved.
 
#ifndef V8_BASE_SAFE_CONVERSIONS_H_
#define V8_BASE_SAFE_CONVERSIONS_H_
 
#include <limits>
 
#include "src/base/safe_conversions_impl.h"
 
namespace v8 {
namespace base {
 
// 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::DstRangeRelationToSrcRange<Dst>(value) ==
         internal::RANGE_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::DstRangeRelationToSrcRange<Dst>(value)) {
    case internal::RANGE_VALID:
      return static_cast<Dst>(value);
 
    case internal::RANGE_UNDERFLOW:
      return std::numeric_limits<Dst>::min();
 
    case internal::RANGE_OVERFLOW:
      return std::numeric_limits<Dst>::max();
 
    // Should fail only on attempting to assign NaN to a saturated integer.
    case internal::RANGE_INVALID:
      CHECK(false);
      return std::numeric_limits<Dst>::max();
  }
 
  UNREACHABLE();
  return static_cast<Dst>(value);
}
 
}  // namespace base
}  // namespace v8
 
#endif  // V8_BASE_SAFE_CONVERSIONS_H_