gecko-dev/mfbt/Char16.h
Mike Hommey 672db6ba31 Bug 1189967 - Avoid including <string> from Char16.h. r=nfroyd
Since Char16.h is included everywhere, and MSVC 2015 uses the char16ptr_t trick
it contains, we include <string> everywhere, but that has the side effect of
breaking the build in subtle ways. One way around this would be to avoid including
Char16.h in the first place, but that requires more work than I was ready to put
in. So instead, just avoid including <string> by removing the conversion operator
for std::wstring.
2015-08-23 22:20:33 +09:00

235 lines
6.7 KiB
C++

/* -*- 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 <cstdint>
/**
* 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;
}
/* 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 */