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 /* Helpers to manipulate integer types that don't fit in TypeTraits.h */
   8
   9 #ifndef mozilla_IntegerTypeTraits_h
  10 #define mozilla_IntegerTypeTraits_h
  11
  12 #include <stddef.h>
  13 #include <stdint.h>
  14 #include <type_traits>
  15
  16 namespace mozilla {
  17
  18 namespace detail {
  19
  20 /**
  21  * StdintTypeForSizeAndSignedness returns the stdint integer type
  22  * of given size (can be 1, 2, 4 or 8) and given signedness
  23  * (false means unsigned, true means signed).
  24  */
  25 template <size_t Size, bool Signedness>
  26 struct StdintTypeForSizeAndSignedness;
  27
  28 template <>
  29 struct StdintTypeForSizeAndSignedness<1, true> {
  30   typedef int8_t Type;
  31 };
  32
  33 template <>
  34 struct StdintTypeForSizeAndSignedness<1, false> {
  35   typedef uint8_t Type;
  36 };
  37
  38 template <>
  39 struct StdintTypeForSizeAndSignedness<2, true> {
  40   typedef int16_t Type;
  41 };
  42
  43 template <>
  44 struct StdintTypeForSizeAndSignedness<2, false> {
  45   typedef uint16_t Type;
  46 };
  47
  48 template <>
  49 struct StdintTypeForSizeAndSignedness<4, true> {
  50   typedef int32_t Type;
  51 };
  52
  53 template <>
  54 struct StdintTypeForSizeAndSignedness<4, false> {
  55   typedef uint32_t Type;
  56 };
  57
  58 template <>
  59 struct StdintTypeForSizeAndSignedness<8, true> {
  60   typedef int64_t Type;
  61 };
  62
  63 template <>
  64 struct StdintTypeForSizeAndSignedness<8, false> {
  65   typedef uint64_t Type;
  66 };
  67
  68 }  // namespace detail
  69
  70 template <size_t Size>
  71 struct UnsignedStdintTypeForSize
  72     : detail::StdintTypeForSizeAndSignedness<Size, false> {};
  73
  74 template <size_t Size>
  75 struct SignedStdintTypeForSize
  76     : detail::StdintTypeForSizeAndSignedness<Size, true> {};
  77
  78 template <typename IntegerType>
  79 struct PositionOfSignBit {
  80   static_assert(std::is_integral_v<IntegerType>,
  81                 "PositionOfSignBit is only for integral types");
  82   // 8 here should be CHAR_BIT from limits.h, but the world has moved on.
  83   static const size_t value = 8 * sizeof(IntegerType) - 1;
  84 };
  85
  86 }  // namespace mozilla
  87
  88 #endif  // mozilla_IntegerTypeTraits_h