base/numerics/safe_conversions.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_NUMERICS_SAFE_CONVERSIONS_H_
   6 #define BASE_NUMERICS_SAFE_CONVERSIONS_H_
   7
   8 #include <limits>
   9
  10 #include "base/logging.h"
  11 #include "base/numerics/safe_conversions_impl.h"
  12
  13 namespace base {
  14
  15 // Convenience function that returns true if the supplied value is in range
  16 // for the destination type.
  17 template <typename Dst, typename Src>
  18 inline bool IsValueInRangeForNumericType(Src value) {
  19   return internal::DstRangeRelationToSrcRange<Dst>(value) ==
  20          internal::RANGE_VALID;
  21 }
  22
  23 // checked_cast<> is analogous to static_cast<> for numeric types,
  24 // except that it CHECKs that the specified numeric conversion will not
  25 // overflow or underflow. NaN source will always trigger a CHECK.
  26 template <typename Dst, typename Src>
  27 inline Dst checked_cast(Src value) {
  28   CHECK(IsValueInRangeForNumericType<Dst>(value));
  29   return static_cast<Dst>(value);
  30 }
  31
  32 // saturated_cast<> is analogous to static_cast<> for numeric types, except
  33 // that the specified numeric conversion will saturate rather than overflow or
  34 // underflow. NaN assignment to an integral will trigger a CHECK condition.
  35 template <typename Dst, typename Src>
  36 inline Dst saturated_cast(Src value) {
  37   // Optimization for floating point values, which already saturate.
  38   if (std::numeric_limits<Dst>::is_iec559)
  39     return static_cast<Dst>(value);
  40
  41   switch (internal::DstRangeRelationToSrcRange<Dst>(value)) {
  42     case internal::RANGE_VALID:
  43       return static_cast<Dst>(value);
  44
  45     case internal::RANGE_UNDERFLOW:
  46       return std::numeric_limits<Dst>::min();
  47
  48     case internal::RANGE_OVERFLOW:
  49       return std::numeric_limits<Dst>::max();
  50
  51     // Should fail only on attempting to assign NaN to a saturated integer.
  52     case internal::RANGE_INVALID:
  53       CHECK(false);
  54       return std::numeric_limits<Dst>::max();
  55   }
  56
  57   NOTREACHED();
  58   return static_cast<Dst>(value);
  59 }
  60
  61 }  // namespace base
  62
  63 #endif  // BASE_NUMERICS_SAFE_CONVERSIONS_H_