onlineupdate/source/update/inc/mozilla/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 #if defined(_MSC_VER) && _MSC_VER < 1900
  21    /*
  22     * C++11 says char16_t is a distinct builtin type, but Windows's yvals.h
  23     * typedefs char16_t as an unsigned short prior to MSVC 2015, which
  24     * implemented C++11's distinct char16_t type. We would like to alias
  25     * char16_t to Windows's 16-bit wchar_t so we can declare UTF-16 literals as
  26     * constant expressions (and pass char16_t pointers to Windows APIs). We
  27     * #define _CHAR16T here in order to prevent yvals.h from overriding our
  28     * char16_t typedefs, which we set to wchar_t for C++ code.
  29     *
  30     * In addition, #defining _CHAR16T will prevent yvals.h from defining a
  31     * char32_t type, so we have to undo that damage here and provide our own,
  32     * which is identical to the yvals.h type.
  33     */
  34 #  define MOZ_UTF16_HELPER(s) L##s
  35 #  define _CHAR16T
  36 typedef wchar_t char16_t;
  37 typedef unsigned int char32_t;
  38 #else
  39    /* C++11 has a builtin char16_t type. */
  40 #  define MOZ_UTF16_HELPER(s) u##s
  41    /**
  42     * This macro is used to distinguish when char16_t would be a distinct
  43     * typedef from wchar_t.
  44     */
  45 #  define MOZ_CHAR16_IS_NOT_WCHAR
  46 #  ifdef WIN32
  47 #    define MOZ_USE_CHAR16_WRAPPER
  48 #  endif
  49 #endif
  50
  51 #ifdef MOZ_USE_CHAR16_WRAPPER
  52 # include <string>
  53   /**
  54    * Win32 API extensively uses wchar_t, which is represented by a separated
  55    * builtin type than char16_t per spec. It's not the case for MSVC prior to
  56    * MSVC 2015, but other compilers follow the spec. We want to mix wchar_t and
  57    * char16_t on Windows builds. This class is supposed to make it easier. It
  58    * stores char16_t const pointer, but provides implicit casts for wchar_t as
  59    * well. On other platforms, we simply use
  60    * |typedef const char16_t* char16ptr_t|. Here, we want to make the class as
  61    * similar to this typedef, including providing some casts that are allowed
  62    * by the typedef.
  63    */
  64 class char16ptr_t
  65 {
  66 private:
  67   const char16_t* mPtr;
  68   static_assert(sizeof(char16_t) == sizeof(wchar_t),
  69                 "char16_t and wchar_t sizes differ");
  70
  71 public:
  72   char16ptr_t(const char16_t* aPtr) : mPtr(aPtr) {}
  73   char16ptr_t(const wchar_t* aPtr) :
  74     mPtr(reinterpret_cast<const char16_t*>(aPtr))
  75   {}
  76
  77   /* Without this, nullptr assignment would be ambiguous. */
  78   constexpr char16ptr_t(decltype(nullptr)) : mPtr(nullptr) {}
  79
  80   operator const char16_t*() const
  81   {
  82     return mPtr;
  83   }
  84   operator const wchar_t*() const
  85   {
  86     return reinterpret_cast<const wchar_t*>(mPtr);
  87   }
  88   operator const void*() const
  89   {
  90     return mPtr;
  91   }
  92   operator bool() const
  93   {
  94     return mPtr != nullptr;
  95   }
  96   operator std::wstring() const
  97   {
  98     return std::wstring(static_cast<const wchar_t*>(*this));
  99   }
 100
 101   /* Explicit cast operators to allow things like (char16_t*)str. */
 102   explicit operator char16_t*() const
 103   {
 104     return const_cast<char16_t*>(mPtr);
 105   }
 106   explicit operator wchar_t*() const
 107   {
 108     return const_cast<wchar_t*>(static_cast<const wchar_t*>(*this));
 109   }
 110   explicit operator int() const
 111   {
 112     return reinterpret_cast<intptr_t>(mPtr);
 113   }
 114   explicit operator unsigned int() const
 115   {
 116     return reinterpret_cast<uintptr_t>(mPtr);
 117   }
 118   explicit operator long() const
 119   {
 120     return reinterpret_cast<intptr_t>(mPtr);
 121   }
 122   explicit operator unsigned long() const
 123   {
 124     return reinterpret_cast<uintptr_t>(mPtr);
 125   }
 126   explicit operator long long() const
 127   {
 128     return reinterpret_cast<intptr_t>(mPtr);
 129   }
 130   explicit operator unsigned long long() const
 131   {
 132     return reinterpret_cast<uintptr_t>(mPtr);
 133   }
 134
 135   /**
 136    * Some Windows API calls accept BYTE* but require that data actually be
 137    * WCHAR*.  Supporting this requires explicit operators to support the
 138    * requisite explicit casts.
 139    */
 140   explicit operator const char*() const
 141   {
 142     return reinterpret_cast<const char*>(mPtr);
 143   }
 144   explicit operator const unsigned char*() const
 145   {
 146     return reinterpret_cast<const unsigned char*>(mPtr);
 147   }
 148   explicit operator unsigned char*() const
 149   {
 150     return
 151       const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(mPtr));
 152   }
 153   explicit operator void*() const
 154   {
 155     return const_cast<char16_t*>(mPtr);
 156   }
 157
 158   /* Some operators used on pointers. */
 159   char16_t operator[](size_t aIndex) const
 160   {
 161     return mPtr[aIndex];
 162   }
 163   bool operator==(const char16ptr_t& aOther) const
 164   {
 165     return mPtr == aOther.mPtr;
 166   }
 167   bool operator==(decltype(nullptr)) const
 168   {
 169     return mPtr == nullptr;
 170   }
 171   bool operator!=(const char16ptr_t& aOther) const
 172   {
 173     return mPtr != aOther.mPtr;
 174   }
 175   bool operator!=(decltype(nullptr)) const
 176   {
 177     return mPtr != nullptr;
 178   }
 179   char16ptr_t operator+(int aValue) const
 180   {
 181     return char16ptr_t(mPtr + aValue);
 182   }
 183   char16ptr_t operator+(unsigned int aValue) const
 184   {
 185     return char16ptr_t(mPtr + aValue);
 186   }
 187   char16ptr_t operator+(long aValue) const
 188   {
 189     return char16ptr_t(mPtr + aValue);
 190   }
 191   char16ptr_t operator+(unsigned long aValue) const
 192   {
 193     return char16ptr_t(mPtr + aValue);
 194   }
 195   char16ptr_t operator+(long long aValue) const
 196   {
 197     return char16ptr_t(mPtr + aValue);
 198   }
 199   char16ptr_t operator+(unsigned long long aValue) const
 200   {
 201     return char16ptr_t(mPtr + aValue);
 202   }
 203   ptrdiff_t operator-(const char16ptr_t& aOther) const
 204   {
 205     return mPtr - aOther.mPtr;
 206   }
 207 };
 208
 209 inline decltype((char*)0-(char*)0)
 210 operator-(const char16_t* aX, const char16ptr_t aY)
 211 {
 212   return aX - static_cast<const char16_t*>(aY);
 213 }
 214
 215 #else
 216
 217 typedef const char16_t* char16ptr_t;
 218
 219 #endif
 220
 221 /*
 222  * Macro arguments used in concatenation or stringification won't be expanded.
 223  * Therefore, in order for |MOZ_UTF16(FOO)| to work as expected (which is to
 224  * expand |FOO| before doing whatever |MOZ_UTF16| needs to do to it) a helper
 225  * macro, |MOZ_UTF16_HELPER| needs to be inserted in between to allow the macro
 226  * argument to expand. See "3.10.6 Separate Expansion of Macro Arguments" of the
 227  * CPP manual for a more accurate and precise explanation.
 228  */
 229 #define MOZ_UTF16(s) MOZ_UTF16_HELPER(s)
 230
 231 static_assert(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
 232 static_assert(char16_t(-1) > char16_t(0), "Is char16_t type unsigned?");
 233 static_assert(sizeof(MOZ_UTF16('A')) == 2, "Is char literal 16 bits?");
 234 static_assert(sizeof(MOZ_UTF16("")[0]) == 2, "Is string char 16 bits?");
 235
 236 #endif
 237
 238 #endif /* mozilla_Char16_h */
 239