FileUtilities.h

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#ifndef LLU_FILEUTILITIES_H
#define LLU_FILEUTILITIES_H
 
#include <codecvt>
#include <cstdio>
#include <fstream>
#include <ios>
#include <locale>
#include <memory>
#include <string>
 
namespace LLU {
    using FilePtr = std::unique_ptr<std::FILE, int (*)(std::FILE*)>;
 
    FilePtr claimFile(std::FILE* f);
 
    void validatePath(const std::string& fileName, std::ios::openmode mode);
 
    template<typename T>
    std::basic_string<T> fromUTF8toUTF16(const std::string& source) {
#ifdef _WIN32
        // On Windows with VS2017 only conversion to wchar_t is supported, so we have no choice here
        std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> convertor;
        if constexpr (!std::is_same_v<T, wchar_t>) {
            std::wstring tmp = convertor.from_bytes(source);
            return std::basic_string<T> { std::begin(tmp), std::end(tmp) };
        } else {
            return convertor.from_bytes(source);
        }
#else
        std::wstring_convert<std::codecvt_utf8_utf16<T>, T> convertor;
        return convertor.from_bytes(source);
#endif
    }
 
    template<typename T>
    std::string fromUTF16toUTF8(const std::basic_string<T>& source) {
#ifdef _WIN32
        // On Windows with VS2017 only conversion from wchar_t is supported, so we have no choice here
        std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> convertor;
        if constexpr (!std::is_same_v<T, wchar_t>) {
            return convertor.to_bytes(std::wstring { std::begin(source), std::end(source) });
        } else {
            return convertor.to_bytes(source);
        }
#else
        std::wstring_convert<std::codecvt_utf8_utf16<T>, T> convertor;
        return convertor.to_bytes(source);
#endif
    }
 
    template<typename T>
    std::basic_string<T> fromUTF8toUTF32(const std::string& source) {
#ifdef _WIN32
        // On Windows with VS2017 we always convert to uint32_t
        std::wstring_convert<std::codecvt_utf8<uint32_t>, uint32_t> convertor;
        if constexpr (!std::is_same_v<T, uint32_t>) {
            std::basic_string<uint32_t> tmp = convertor.from_bytes(source);
            return std::basic_string<T> { std::begin(tmp), std::end(tmp) };
        } else {
            return convertor.from_bytes(source);
        }
#else
        std::wstring_convert<std::codecvt_utf8<T>, T> convertor;
        return convertor.from_bytes(source);
#endif
    }
 
    template<typename T>
    std::string fromUTF32toUTF8(const std::basic_string<T>& source) {
#ifdef _WIN32
        // On Windows with VS2017 we always convert from uint32_t
        std::wstring_convert<std::codecvt_utf8<uint32_t>, uint32_t> convertor;
        if constexpr (!std::is_same_v<T, uint32_t>) {
            return convertor.to_bytes(std::basic_string<uint32_t> { std::begin(source), std::end(source) });
        } else {
            return convertor.to_bytes(source);
        }
#else
        std::wstring_convert<std::codecvt_utf8<T>, T> convertor;
        return convertor.to_bytes(source.data());
#endif
    }
 
    struct SharePolicy {
        virtual ~SharePolicy() = default;
 
        virtual int flag(std::ios::openmode /*mode*/) const;
    };
 
    struct AlwaysReadExclusiveWrite : SharePolicy {
        int flag(std::ios::openmode m) const override;
    };
 
    FilePtr openFile(const std::string& fileName, std::ios::openmode mode, const SharePolicy& shp = AlwaysReadExclusiveWrite {});
 
    std::fstream openFileStream(const std::string& fileName, std::ios::openmode mode, const SharePolicy& shp = AlwaysReadExclusiveWrite {});
} // namespace LLU
 
#endif    // LLU_FILEUTILITIES_H