js/src/vm/Uint8Clamped.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 vm_Uint8Clamped_h
   8 #define vm_Uint8Clamped_h
   9
  10 #include <stdint.h>
  11
  12 namespace js {
  13
  14 extern uint32_t ClampDoubleToUint8(const double x);
  15
  16 struct uint8_clamped {
  17   uint8_t val;
  18
  19   uint8_clamped() = default;
  20   uint8_clamped(const uint8_clamped& other) = default;
  21
  22   // invoke our assignment helpers for constructor conversion
  23   explicit uint8_clamped(uint8_t x) { *this = x; }
  24   explicit uint8_clamped(uint16_t x) { *this = x; }
  25   explicit uint8_clamped(uint32_t x) { *this = x; }
  26   explicit uint8_clamped(uint64_t x) { *this = x; }
  27   explicit uint8_clamped(int8_t x) { *this = x; }
  28   explicit uint8_clamped(int16_t x) { *this = x; }
  29   explicit uint8_clamped(int32_t x) { *this = x; }
  30   explicit uint8_clamped(int64_t x) { *this = x; }
  31   explicit uint8_clamped(double x) { *this = x; }
  32
  33   uint8_clamped& operator=(const uint8_clamped& x) = default;
  34
  35   uint8_clamped& operator=(uint8_t x) {
  36     val = x;
  37     return *this;
  38   }
  39
  40   uint8_clamped& operator=(uint16_t x) {
  41     val = (x > 255) ? 255 : uint8_t(x);
  42     return *this;
  43   }
  44
  45   uint8_clamped& operator=(uint32_t x) {
  46     val = (x > 255) ? 255 : uint8_t(x);
  47     return *this;
  48   }
  49
  50   uint8_clamped& operator=(uint64_t x) {
  51     val = (x > 255) ? 255 : uint8_t(x);
  52     return *this;
  53   }
  54
  55   uint8_clamped& operator=(int8_t x) {
  56     val = (x >= 0) ? uint8_t(x) : 0;
  57     return *this;
  58   }
  59
  60   uint8_clamped& operator=(int16_t x) {
  61     val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
  62     return *this;
  63   }
  64
  65   uint8_clamped& operator=(int32_t x) {
  66     val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
  67     return *this;
  68   }
  69
  70   uint8_clamped& operator=(int64_t x) {
  71     val = (x >= 0) ? ((x < 255) ? uint8_t(x) : 255) : 0;
  72     return *this;
  73   }
  74
  75   uint8_clamped& operator=(const double x) {
  76     val = uint8_t(ClampDoubleToUint8(x));
  77     return *this;
  78   }
  79
  80   operator uint8_t() const { return val; }
  81
  82   void staticAsserts() {
  83     static_assert(sizeof(uint8_clamped) == 1,
  84                   "uint8_clamped must be layout-compatible with uint8_t");
  85   }
  86 };
  87
  88 /* Note that we can't use std::numeric_limits here due to uint8_clamped. */
  89 template <typename T>
  90 inline constexpr bool TypeIsFloatingPoint() {
  91   return false;
  92 }
  93 template <>
  94 inline constexpr bool TypeIsFloatingPoint<float>() {
  95   return true;
  96 }
  97 template <>
  98 inline constexpr bool TypeIsFloatingPoint<double>() {
  99   return true;
 100 }
 101
 102 template <typename T>
 103 inline constexpr bool TypeIsUnsigned() {
 104   return false;
 105 }
 106 template <>
 107 inline constexpr bool TypeIsUnsigned<uint8_t>() {
 108   return true;
 109 }
 110 template <>
 111 inline constexpr bool TypeIsUnsigned<uint16_t>() {
 112   return true;
 113 }
 114 template <>
 115 inline constexpr bool TypeIsUnsigned<uint32_t>() {
 116   return true;
 117 }
 118
 119 }  // namespace js
 120
 121 #endif  // vm_Uint8Clamped_h