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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* Implements a UTF-16 character type. */
#ifndef mozilla_Char16_h
#define mozilla_Char16_h
#ifdef __cplusplus
/*
* C++11 introduces a char16_t type and support for UTF-16 string and character
* literals. C++11's char16_t is a distinct builtin type. Technically, char16_t
* is a 16-bit code unit of a Unicode code point, not a "character".
*/
#if defined(_MSC_VER) && _MSC_VER < 1900
/*
* C++11 says char16_t is a distinct builtin type, but Windows's yvals.h
* typedefs char16_t as an unsigned short prior to MSVC 2015, which
* implemented C++11's distinct char16_t type. We would like to alias
* char16_t to Windows's 16-bit wchar_t so we can declare UTF-16 literals as
* constant expressions (and pass char16_t pointers to Windows APIs). We
* #define _CHAR16T here in order to prevent yvals.h from overriding our
* char16_t typedefs, which we set to wchar_t for C++ code.
*
* In addition, #defining _CHAR16T will prevent yvals.h from defining a
* char32_t type, so we have to undo that damage here and provide our own,
* which is identical to the yvals.h type.
*/
# define MOZ_UTF16_HELPER(s) L##s
# define _CHAR16T
typedef wchar_t char16_t;
typedef unsigned int char32_t;
#else
/* C++11 has a builtin char16_t type. */
# define MOZ_UTF16_HELPER(s) u##s
/**
* This macro is used to distinguish when char16_t would be a distinct
* typedef from wchar_t.
*/
# define MOZ_CHAR16_IS_NOT_WCHAR
# ifdef WIN32
# define MOZ_USE_CHAR16_WRAPPER
# endif
#endif
#ifdef MOZ_USE_CHAR16_WRAPPER
# include <string>
/**
* Win32 API extensively uses wchar_t, which is represented by a separated
* builtin type than char16_t per spec. It's not the case for MSVC prior to
* MSVC 2015, but other compilers follow the spec. We want to mix wchar_t and
* char16_t on Windows builds. This class is supposed to make it easier. It
* stores char16_t const pointer, but provides implicit casts for wchar_t as
* well. On other platforms, we simply use
* |typedef const char16_t* char16ptr_t|. Here, we want to make the class as
* similar to this typedef, including providing some casts that are allowed
* by the typedef.
*/
class char16ptr_t
{
private:
const char16_t* mPtr;
static_assert(sizeof(char16_t) == sizeof(wchar_t),
"char16_t and wchar_t sizes differ");
public:
char16ptr_t(const char16_t* aPtr) : mPtr(aPtr) {}
char16ptr_t(const wchar_t* aPtr) :
mPtr(reinterpret_cast<const char16_t*>(aPtr))
{}
/* Without this, nullptr assignment would be ambiguous. */
constexpr char16ptr_t(decltype(nullptr)) : mPtr(nullptr) {}
operator const char16_t*() const
{
return mPtr;
}
operator const wchar_t*() const
{
return reinterpret_cast<const wchar_t*>(mPtr);
}
operator const void*() const
{
return mPtr;
}
operator bool() const
{
return mPtr != nullptr;
}
operator std::wstring() const
{
return std::wstring(static_cast<const wchar_t*>(*this));
}
/* Explicit cast operators to allow things like (char16_t*)str. */
explicit operator char16_t*() const
{
return const_cast<char16_t*>(mPtr);
}
explicit operator wchar_t*() const
{
return const_cast<wchar_t*>(static_cast<const wchar_t*>(*this));
}
explicit operator int() const
{
return reinterpret_cast<intptr_t>(mPtr);
}
explicit operator unsigned int() const
{
return reinterpret_cast<uintptr_t>(mPtr);
}
explicit operator long() const
{
return reinterpret_cast<intptr_t>(mPtr);
}
explicit operator unsigned long() const
{
return reinterpret_cast<uintptr_t>(mPtr);
}
explicit operator long long() const
{
return reinterpret_cast<intptr_t>(mPtr);
}
explicit operator unsigned long long() const
{
return reinterpret_cast<uintptr_t>(mPtr);
}
/**
* Some Windows API calls accept BYTE* but require that data actually be
* WCHAR*. Supporting this requires explicit operators to support the
* requisite explicit casts.
*/
explicit operator const char*() const
{
return reinterpret_cast<const char*>(mPtr);
}
explicit operator const unsigned char*() const
{
return reinterpret_cast<const unsigned char*>(mPtr);
}
explicit operator unsigned char*() const
{
return
const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(mPtr));
}
explicit operator void*() const
{
return const_cast<char16_t*>(mPtr);
}
/* Some operators used on pointers. */
char16_t operator[](size_t aIndex) const
{
return mPtr[aIndex];
}
bool operator==(const char16ptr_t& aOther) const
{
return mPtr == aOther.mPtr;
}
bool operator==(decltype(nullptr)) const
{
return mPtr == nullptr;
}
bool operator!=(const char16ptr_t& aOther) const
{
return mPtr != aOther.mPtr;
}
bool operator!=(decltype(nullptr)) const
{
return mPtr != nullptr;
}
char16ptr_t operator+(int aValue) const
{
return char16ptr_t(mPtr + aValue);
}
char16ptr_t operator+(unsigned int aValue) const
{
return char16ptr_t(mPtr + aValue);
}
char16ptr_t operator+(long aValue) const
{
return char16ptr_t(mPtr + aValue);
}
char16ptr_t operator+(unsigned long aValue) const
{
return char16ptr_t(mPtr + aValue);
}
char16ptr_t operator+(long long aValue) const
{
return char16ptr_t(mPtr + aValue);
}
char16ptr_t operator+(unsigned long long aValue) const
{
return char16ptr_t(mPtr + aValue);
}
ptrdiff_t operator-(const char16ptr_t& aOther) const
{
return mPtr - aOther.mPtr;
}
};
inline decltype((char*)0-(char*)0)
operator-(const char16_t* aX, const char16ptr_t aY)
{
return aX - static_cast<const char16_t*>(aY);
}
#else
typedef const char16_t* char16ptr_t;
#endif
/*
* Macro arguments used in concatenation or stringification won't be expanded.
* Therefore, in order for |MOZ_UTF16(FOO)| to work as expected (which is to
* expand |FOO| before doing whatever |MOZ_UTF16| needs to do to it) a helper
* macro, |MOZ_UTF16_HELPER| needs to be inserted in between to allow the macro
* argument to expand. See "3.10.6 Separate Expansion of Macro Arguments" of the
* CPP manual for a more accurate and precise explanation.
*/
#define MOZ_UTF16(s) MOZ_UTF16_HELPER(s)
static_assert(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
static_assert(char16_t(-1) > char16_t(0), "Is char16_t type unsigned?");
static_assert(sizeof(MOZ_UTF16('A')) == 2, "Is char literal 16 bits?");
static_assert(sizeof(MOZ_UTF16("")[0]) == 2, "Is string char 16 bits?");
#endif
#endif /* mozilla_Char16_h */
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