onlineupdate/inc/Char16.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 /* Implements a UTF-16 character type. */
   8
   9 #ifndef mozilla_Char16_h
  10 #define mozilla_Char16_h
  11
  12 #ifdef __cplusplus
  13
  14 /*
  15  * C++11 introduces a char16_t type and support for UTF-16 string and character
  16  * literals. C++11's char16_t is a distinct builtin type. Technically, char16_t
  17  * is a 16-bit code unit of a Unicode code point, not a "character".
  18  */
  19
  20 #ifdef _WIN32
  21 # define MOZ_USE_CHAR16_WRAPPER
  22 # include <cstdint>
  23   /**
  24    * Win32 API extensively uses wchar_t, which is represented by a separated
  25    * builtin type than char16_t per spec. It's not the case for MSVC prior to
  26    * MSVC 2015, but other compilers follow the spec. We want to mix wchar_t and
  27    * char16_t on Windows builds. This class is supposed to make it easier. It
  28    * stores char16_t const pointer, but provides implicit casts for wchar_t as
  29    * well. On other platforms, we simply use
  30    * |typedef const char16_t* char16ptr_t|. Here, we want to make the class as
  31    * similar to this typedef, including providing some casts that are allowed
  32    * by the typedef.
  33    */
  34 class char16ptr_t
  35 {
  36 private:
  37   const char16_t* mPtr;
  38   static_assert(sizeof(char16_t) == sizeof(wchar_t),
  39                 "char16_t and wchar_t sizes differ");
  40
  41 public:
  42   char16ptr_t(const char16_t* aPtr) : mPtr(aPtr) {}
  43   char16ptr_t(const wchar_t* aPtr) :
  44     mPtr(reinterpret_cast<const char16_t*>(aPtr))
  45   {}
  46
  47   /* Without this, nullptr assignment would be ambiguous. */
  48   constexpr char16ptr_t(decltype(nullptr)) : mPtr(nullptr) {}
  49
  50   operator const char16_t*() const
  51   {
  52     return mPtr;
  53   }
  54   operator const wchar_t*() const
  55   {
  56     return reinterpret_cast<const wchar_t*>(mPtr);
  57   }
  58   operator const void*() const
  59   {
  60     return mPtr;
  61   }
  62   operator bool() const
  63   {
  64     return mPtr != nullptr;
  65   }
  66
  67   /* Explicit cast operators to allow things like (char16_t*)str. */
  68   explicit operator char16_t*() const
  69   {
  70     return const_cast<char16_t*>(mPtr);
  71   }
  72   explicit operator wchar_t*() const
  73   {
  74     return const_cast<wchar_t*>(static_cast<const wchar_t*>(*this));
  75   }
  76   explicit operator int() const
  77   {
  78     return reinterpret_cast<intptr_t>(mPtr);
  79   }
  80   explicit operator unsigned int() const
  81   {
  82     return reinterpret_cast<uintptr_t>(mPtr);
  83   }
  84   explicit operator long() const
  85   {
  86     return reinterpret_cast<intptr_t>(mPtr);
  87   }
  88   explicit operator unsigned long() const
  89   {
  90     return reinterpret_cast<uintptr_t>(mPtr);
  91   }
  92   explicit operator long long() const
  93   {
  94     return reinterpret_cast<intptr_t>(mPtr);
  95   }
  96   explicit operator unsigned long long() const
  97   {
  98     return reinterpret_cast<uintptr_t>(mPtr);
  99   }
 100
 101   /**
 102    * Some Windows API calls accept BYTE* but require that data actually be
 103    * WCHAR*.  Supporting this requires explicit operators to support the
 104    * requisite explicit casts.
 105    */
 106   explicit operator const char*() const
 107   {
 108     return reinterpret_cast<const char*>(mPtr);
 109   }
 110   explicit operator const unsigned char*() const
 111   {
 112     return reinterpret_cast<const unsigned char*>(mPtr);
 113   }
 114   explicit operator unsigned char*() const
 115   {
 116     return
 117       const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(mPtr));
 118   }
 119   explicit operator void*() const
 120   {
 121     return const_cast<char16_t*>(mPtr);
 122   }
 123
 124   /* Some operators used on pointers. */
 125   char16_t operator[](size_t aIndex) const
 126   {
 127     return mPtr[aIndex];
 128   }
 129   bool operator==(const char16ptr_t& aOther) const
 130   {
 131     return mPtr == aOther.mPtr;
 132   }
 133   bool operator==(decltype(nullptr)) const
 134   {
 135     return mPtr == nullptr;
 136   }
 137   bool operator!=(const char16ptr_t& aOther) const
 138   {
 139     return mPtr != aOther.mPtr;
 140   }
 141   bool operator!=(decltype(nullptr)) const
 142   {
 143     return mPtr != nullptr;
 144   }
 145   char16ptr_t operator+(int aValue) const
 146   {
 147     return char16ptr_t(mPtr + aValue);
 148   }
 149   char16ptr_t operator+(unsigned int aValue) const
 150   {
 151     return char16ptr_t(mPtr + aValue);
 152   }
 153   char16ptr_t operator+(long aValue) const
 154   {
 155     return char16ptr_t(mPtr + aValue);
 156   }
 157   char16ptr_t operator+(unsigned long aValue) const
 158   {
 159     return char16ptr_t(mPtr + aValue);
 160   }
 161   char16ptr_t operator+(long long aValue) const
 162   {
 163     return char16ptr_t(mPtr + aValue);
 164   }
 165   char16ptr_t operator+(unsigned long long aValue) const
 166   {
 167     return char16ptr_t(mPtr + aValue);
 168   }
 169   ptrdiff_t operator-(const char16ptr_t& aOther) const
 170   {
 171     return mPtr - aOther.mPtr;
 172   }
 173 };
 174
 175 inline decltype((char*)0-(char*)0)
 176 operator-(const char16_t* aX, const char16ptr_t aY)
 177 {
 178   return aX - static_cast<const char16_t*>(aY);
 179 }
 180
 181 #else
 182
 183 typedef const char16_t* char16ptr_t;
 184
 185 #endif
 186
 187 static_assert(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
 188 static_assert(char16_t(-1) > char16_t(0), "Is char16_t type unsigned?");
 189 static_assert(sizeof(u'A') == 2, "Is unicode char literal 16 bits?");
 190 static_assert(sizeof(u""[0]) == 2, "Is unicode string char 16 bits?");
 191
 192 #endif
 193
 194 #endif /* mozilla_Char16_h */