string_converters.h

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/**
 
    @file      string_converters.h
    @author    Khrapov
    @date      24.11.2021
    @copyright © Nick Khrapov, 2021. All right reserved.
 
**/
#pragma once
 
#include <qx/containers/string/string.h>
#include <qx/containers/string/string_view.h>
#include <qx/internal/perf_scope.h>
 
#include <codecvt>
#include <locale>
 
#if QX_WIN
    #include <windows.h>
#endif
 
namespace qx
{
 
/**
    @brief  convert cstring to wstring
    @param  stringView - char string view
    @param  locale     - locale to use
    @retval            - wchar_t string
**/
inline wstring to_wstring(cstring_view stringView, const std::locale& locale = std::locale())
{
    QX_PERF_SCOPE();
 
    std::vector<wchar_t> buf(stringView.size());
    std::use_facet<std::ctype<wchar_t>>(locale).widen(
        stringView.data(),
        stringView.data() + stringView.size(),
        buf.data());
 
    return wstring(buf.data(), buf.size());
}
 
/**
    @brief  Convert wstring to wstring (stub)
    @param  stringView - wchar_t string view
    @param  locale     - locale to use
    @retval            - wchar_t string
**/
inline wstring to_wstring(wstring_view stringView, const std::locale& locale = std::locale())
{
    return stringView;
}
 
/**
    @brief   Convert wstring to cstring
    @details '?' is a default character
    @param   stringView - wchar_t string view
    @param   locale     - locale to use
    @retval             - char string
**/
inline cstring to_cstring(wstring_view stringView, const std::locale& locale = std::locale())
{
    QX_PERF_SCOPE();
 
    std::vector<char> buf(stringView.size());
    std::use_facet<std::ctype<wchar_t>>(locale)
        .narrow(stringView.data(), stringView.data() + stringView.size(), '?', buf.data());
    return cstring(buf.data(), buf.size());
}
 
/**
    @brief  Convert string to string (stub)
    @param  stringView - char string view
    @param  locale     - locale to use
    @retval            - char string
**/
inline cstring to_cstring(cstring_view stringView, const std::locale& locale = std::locale())
{
    return stringView;
}
 
/**
    @brief  Convert a char string to common string type
    @param  stringView - char string
    @param  locale     - locale to use
    @retval            - common string type
**/
inline string to_string(cstring_view stringView, const std::locale& locale = std::locale())
{
#ifdef QX_CONF_USE_CHAR
    return stringView;
#elif defined(QX_CONF_USE_WCHAR)
    return to_wstring(stringView, locale);
#endif
}
 
/**
    @brief  Convert a wchar_t string to common string type
    @param  stringView - wchar_t string
    @param  locale     - locale to use
    @retval            - common string type
**/
inline string to_string(wstring_view stringView, const std::locale& locale = std::locale())
{
#ifdef QX_CONF_USE_CHAR
    return to_cstring(stringView, locale);
#elif defined(QX_CONF_USE_WCHAR)
    return stringView;
#endif
}
 
/**
    @brief  Convert const char* representing UTF8 to wstring
    @param  pszUtf8 - UTF8 string
    @retval         - wstring value
**/
inline string utf8_to_string(cstring_view pszUtf8)
{
    QX_PERF_SCOPE();
 
#ifdef QX_CONF_USE_WCHAR
    #if QX_WIN
 
    // much faster on windows
    const int nLength = MultiByteToWideChar(CP_UTF8, 0, pszUtf8.data(), static_cast<int>(pszUtf8.size()), nullptr, 0);
    string    sRet(nLength, QX_TEXT('\n'));
    MultiByteToWideChar(CP_UTF8, 0, pszUtf8.data(), static_cast<int>(pszUtf8.size()), sRet.data(), nLength);
    return sRet;
 
    #else
 
    QX_PUSH_SUPPRESS_ALL_WARNINGS();
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
    return converter.from_bytes(pszUtf8.data(), pszUtf8.data() + pszUtf8.size());
    QX_POP_SUPPRESS_WARNINGS();
 
    #endif
#endif
}
 
} // namespace qx