include/o3tl/char16_t2wchar_t.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #pragma once
  11
  12 #include <sal/config.h>
  13
  14 #include <string_view>
  15
  16 namespace o3tl
  17 {
  18 #if defined _WIN32
  19 // Helpers for safe conversion between wchar_t and char16_t in MSVC
  20
  21 static_assert(sizeof(char16_t) == sizeof(wchar_t),
  22               "These helper functions are only applicable to implementations with 16-bit wchar_t");
  23
  24 // While other implementations define wchar_t as 32-bit integral value, and mostly use
  25 // char-based UTF-8 string APIs, in MSVC wchar_t is (non-conformant) 16-bit, and Unicode
  26 // support is implemented by Unicode-aware WinAPI functions taking UTF-16 LE strings,
  27 // and also stdlib functions taking those strings.
  28 //
  29 // In LibreOffice, internal string representation is also UTF-16 with system endianness
  30 // (sal_Unicode that is typedef for char16_t); so it is an important implementation concept
  31 // to treat internal strings as directly usable by WinAPI/stdlib functions and vice versa.
  32 // Also, it's important to use safe conversion between unrelated underlying C++ types
  33 // used for MSVC and LibreOffice string storage without plain reinterpret_cast that brings
  34 // risks of masking errors like casting char buffers to wchar_t/char16_t.
  35 //
  36 // Use these helpers for wchar_t (WSTR, WCHAR, OLESTR etc) to char16_t (sal_Unicode) string
  37 // conversions instead of reinterpret-cast in Windows-specific code.
  38 inline wchar_t* toW(char16_t* p) { return reinterpret_cast<wchar_t*>(p); }
  39 inline wchar_t const* toW(char16_t const* p) { return reinterpret_cast<wchar_t const*>(p); }
  40 inline char16_t* toU(wchar_t* p) { return reinterpret_cast<char16_t*>(p); }
  41 inline char16_t const* toU(wchar_t const* p) { return reinterpret_cast<char16_t const*>(p); }
  42
  43 inline std::u16string_view toU(std::wstring_view v) { return { toU(v.data()), v.size() }; }
  44 inline std::wstring_view toW(std::u16string_view v) { return { toW(v.data()), v.size() }; }
  45 #endif
  46 }
  47
  48 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */