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2a0942be41
--HG-- extra : rebase_source : 668cd394806203ddfa34bd4f226335ff26c846b5
193 lines
5.6 KiB
C++
193 lines
5.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Implements a UTF-16 character type. */
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#ifndef mozilla_Char16_h
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#define mozilla_Char16_h
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#ifdef __cplusplus
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/*
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* C++11 introduces a char16_t type and support for UTF-16 string and character
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* literals. C++11's char16_t is a distinct builtin type. Technically, char16_t
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* is a 16-bit code unit of a Unicode code point, not a "character".
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*/
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#ifdef _MSC_VER
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/*
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* C++11 says char16_t is a distinct builtin type, but Windows's yvals.h
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* typedefs char16_t as an unsigned short. We would like to alias char16_t
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* to Windows's 16-bit wchar_t so we can declare UTF-16 literals as constant
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* expressions (and pass char16_t pointers to Windows APIs). We #define
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* _CHAR16T here in order to prevent yvals.h from overriding our char16_t
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* typedefs, which we set to wchar_t for C++ code.
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*
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* In addition, #defining _CHAR16T will prevent yvals.h from defining a
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* char32_t type, so we have to undo that damage here and provide our own,
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* which is identical to the yvals.h type.
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*/
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# define MOZ_UTF16_HELPER(s) L##s
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# define _CHAR16T
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typedef wchar_t char16_t;
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typedef unsigned int char32_t;
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#else
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/* C++11 has a builtin char16_t type. */
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# define MOZ_UTF16_HELPER(s) u##s
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/**
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* This macro is used to distinguish when char16_t would be a distinct
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* typedef from wchar_t.
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*/
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# define MOZ_CHAR16_IS_NOT_WCHAR
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# ifdef WIN32
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# define MOZ_USE_CHAR16_WRAPPER
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# endif
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#endif
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#ifdef MOZ_USE_CHAR16_WRAPPER
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# include <string>
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/**
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* Win32 API extensively uses wchar_t, which is represented by a separated
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* builtin type than char16_t per spec. It's not the case for MSVC, but GCC
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* follows the spec. We want to mix wchar_t and char16_t on Windows builds.
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* This class is supposed to make it easier. It stores char16_t const pointer,
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* but provides implicit casts for wchar_t as well. On other platforms, we
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* simply use |typedef const char16_t* char16ptr_t|. Here, we want to make
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* the class as similar to this typedef, including providing some casts that
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* are allowed by the typedef.
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*/
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class char16ptr_t
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{
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private:
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const char16_t* mPtr;
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static_assert(sizeof(char16_t) == sizeof(wchar_t),
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"char16_t and wchar_t sizes differ");
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public:
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char16ptr_t(const char16_t* aPtr) : mPtr(aPtr) {}
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char16ptr_t(const wchar_t* aPtr) :
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mPtr(reinterpret_cast<const char16_t*>(aPtr))
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{}
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/* Without this, nullptr assignment would be ambiguous. */
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constexpr char16ptr_t(decltype(nullptr)) : mPtr(nullptr) {}
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operator const char16_t*() const
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{
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return mPtr;
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}
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operator const wchar_t*() const
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{
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return reinterpret_cast<const wchar_t*>(mPtr);
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}
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operator const void*() const
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{
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return mPtr;
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}
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operator bool() const
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{
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return mPtr != nullptr;
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}
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operator std::wstring() const
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{
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return std::wstring(static_cast<const wchar_t*>(*this));
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}
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/* Explicit cast operators to allow things like (char16_t*)str. */
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explicit operator char16_t*() const
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{
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return const_cast<char16_t*>(mPtr);
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}
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explicit operator wchar_t*() const
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{
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return const_cast<wchar_t*>(static_cast<const wchar_t*>(*this));
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}
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/**
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* Some Windows API calls accept BYTE* but require that data actually be
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* WCHAR*. Supporting this requires explicit operators to support the
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* requisite explicit casts.
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*/
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explicit operator const char*() const
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{
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return reinterpret_cast<const char*>(mPtr);
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}
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explicit operator const unsigned char*() const
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{
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return reinterpret_cast<const unsigned char*>(mPtr);
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}
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explicit operator unsigned char*() const
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{
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return
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const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(mPtr));
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}
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explicit operator void*() const
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{
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return const_cast<char16_t*>(mPtr);
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}
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/* Some operators used on pointers. */
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char16_t operator[](size_t aIndex) const
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{
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return mPtr[aIndex];
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}
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bool operator==(const char16ptr_t& aOther) const
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{
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return mPtr == aOther.mPtr;
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}
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bool operator==(decltype(nullptr)) const
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{
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return mPtr == nullptr;
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}
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bool operator!=(const char16ptr_t& aOther) const
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{
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return mPtr != aOther.mPtr;
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}
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bool operator!=(decltype(nullptr)) const
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{
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return mPtr != nullptr;
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}
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char16ptr_t operator+(size_t aValue) const
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{
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return char16ptr_t(mPtr + aValue);
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}
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ptrdiff_t operator-(const char16ptr_t& aOther) const
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{
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return mPtr - aOther.mPtr;
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}
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};
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inline decltype((char*)0-(char*)0)
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operator-(const char16_t* aX, const char16ptr_t aY)
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{
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return aX - static_cast<const char16_t*>(aY);
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}
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#else
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typedef const char16_t* char16ptr_t;
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#endif
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/*
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* Macro arguments used in concatenation or stringification won't be expanded.
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* Therefore, in order for |MOZ_UTF16(FOO)| to work as expected (which is to
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* expand |FOO| before doing whatever |MOZ_UTF16| needs to do to it) a helper
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* macro, |MOZ_UTF16_HELPER| needs to be inserted in between to allow the macro
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* argument to expand. See "3.10.6 Separate Expansion of Macro Arguments" of the
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* CPP manual for a more accurate and precise explanation.
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*/
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#define MOZ_UTF16(s) MOZ_UTF16_HELPER(s)
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static_assert(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
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static_assert(char16_t(-1) > char16_t(0), "Is char16_t type unsigned?");
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static_assert(sizeof(MOZ_UTF16('A')) == 2, "Is char literal 16 bits?");
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static_assert(sizeof(MOZ_UTF16("")[0]) == 2, "Is string char 16 bits?");
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#endif
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#endif /* mozilla_Char16_h */
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