mfbt/IntegerTypeTraits.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_IntegerTypeTraits_h
   8 #define mozilla_IntegerTypeTraits_h
   9
  10 #include <stddef.h>
  11 #include <stdint.h>
  12 #include <type_traits>
  13
  14 namespace mozilla {
  15
  16 namespace detail {
  17
  18 /**
  19  * StdintTypeForSizeAndSignedness returns the stdint integer type
  20  * of given size (can be 1, 2, 4 or 8) and given signedness
  21  * (false means unsigned, true means signed).
  22  */
  23 template <size_t Size, bool Signedness>
  24 struct StdintTypeForSizeAndSignedness;
  25
  26 template <>
  27 struct StdintTypeForSizeAndSignedness<1, true> {
  28   typedef int8_t Type;
  29 };
  30
  31 template <>
  32 struct StdintTypeForSizeAndSignedness<1, false> {
  33   typedef uint8_t Type;
  34 };
  35
  36 template <>
  37 struct StdintTypeForSizeAndSignedness<2, true> {
  38   typedef int16_t Type;
  39 };
  40
  41 template <>
  42 struct StdintTypeForSizeAndSignedness<2, false> {
  43   typedef uint16_t Type;
  44 };
  45
  46 template <>
  47 struct StdintTypeForSizeAndSignedness<4, true> {
  48   typedef int32_t Type;
  49 };
  50
  51 template <>
  52 struct StdintTypeForSizeAndSignedness<4, false> {
  53   typedef uint32_t Type;
  54 };
  55
  56 template <>
  57 struct StdintTypeForSizeAndSignedness<8, true> {
  58   typedef int64_t Type;
  59 };
  60
  61 template <>
  62 struct StdintTypeForSizeAndSignedness<8, false> {
  63   typedef uint64_t Type;
  64 };
  65
  66 }  // namespace detail
  67
  68 template <size_t Size>
  69 struct UnsignedStdintTypeForSize
  70     : detail::StdintTypeForSizeAndSignedness<Size, false> {};
  71
  72 template <size_t Size>
  73 struct SignedStdintTypeForSize
  74     : detail::StdintTypeForSizeAndSignedness<Size, true> {};
  75
  76 template <typename IntegerType>
  77 struct PositionOfSignBit {
  78   static_assert(std::is_integral_v<IntegerType>,
  79                 "PositionOfSignBit is only for integral types");
  80   // 8 here should be CHAR_BIT from limits.h, but the world has moved on.
  81   static const size_t value = 8 * sizeof(IntegerType) - 1;
  82 };
  83
  84 }  // namespace mozilla
  85
  86 #endif  // mozilla_IntegerTypeTraits_h