text: // Copyright (c) 2017-2020 The shitecoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <fs.h>
  
  #ifndef WIN32
  #include <cstring>
  #include <fcntl.h>
  #include <string>
  #include <sys/file.h>
  #include <sys/utsname.h>
  #include <unistd.h>
  #else
  #ifndef NOMINMAX
  #define NOMINMAX
  #endif
  #include <codecvt>
  #include <windows.h>
  #endif
  
  namespace fsbridge {
  
  FILE *fopen(const fs::path& p, const char *mode)
  {
  #ifndef WIN32
      return ::fopen(p.string().c_str(), mode);
  #else
      std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>,wchar_t> utf8_cvt;
      return ::_wfopen(p.wstring().c_str(), utf8_cvt.from_bytes(mode).c_str());
  #endif
  }
  
  #ifndef WIN32
  
  static std::string GetErrorReason()
  {
      return std::strerror(errno);
  }
  
  FileLock::FileLock(const fs::path& file)
  {
      fd = open(file.string().c_str(), O_RDWR);
      if (fd == -1) {
          reason = GetErrorReason();
      }
  }
  
  FileLock::~FileLock()
  {
      if (fd != -1) {
          close(fd);
      }
  }
  
  static bool IsWSL()
  {
      struct utsname uname_data;
      return uname(&uname_data) == 0 && std::string(uname_data.version).find("Microsoft") != std::string::npos;
  }
  
  bool FileLock::TryLock()
  {
      if (fd == -1) {
          return false;
      }
  
      // Exclusive file locking is broken on WSL using fcntl (issue #18622)
      // This workaround can be removed once the bug on WSL is fixed
      static const bool is_wsl = IsWSL();
      if (is_wsl) {
          if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
              reason = GetErrorReason();
              return false;
          }
      } else {
          struct flock lock;
          lock.l_type = F_WRLCK;
          lock.l_whence = SEEK_SET;
          lock.l_start = 0;
          lock.l_len = 0;
          if (fcntl(fd, F_SETLK, &lock) == -1) {
              reason = GetErrorReason();
              return false;
          }
      }
  
      return true;
  }
  #else
  
  static std::string GetErrorReason() {
      wchar_t* err;
      FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
          nullptr, GetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), reinterpret_cast<WCHAR*>(&err), 0, nullptr);
      std::wstring err_str(err);
      LocalFree(err);
      return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>>().to_bytes(err_str);
  }
  
  FileLock::FileLock(const fs::path& file)
  {
      hFile = CreateFileW(file.wstring().c_str(),  GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
          nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
      if (hFile == INVALID_HANDLE_VALUE) {
          reason = GetErrorReason();
      }
  }
  
  FileLock::~FileLock()
  {
      if (hFile != INVALID_HANDLE_VALUE) {
          CloseHandle(hFile);
      }
  }
  
  bool FileLock::TryLock()
  {
      if (hFile == INVALID_HANDLE_VALUE) {
          return false;
      }
      _OVERLAPPED overlapped = {0};
      if (!LockFileEx(hFile, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0, std::numeric_limits<DWORD>::max(), std::numeric_limits<DWORD>::max(), &overlapped)) {
          reason = GetErrorReason();
          return false;
      }
      return true;
  }
  #endif
  
  std::string get_filesystem_error_message(const fs::filesystem_error& e)
  {
  #ifndef WIN32
      return e.what();
  #else
      // Convert from Multi Byte to utf-16
      std::string mb_string(e.what());
      int size = MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(), nullptr, 0);
  
      std::wstring utf16_string(size, L'\0');
      MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(), &*utf16_string.begin(), size);
      // Convert from utf-16 to utf-8
      return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>().to_bytes(utf16_string);
  #endif
  }
  
  #ifdef WIN32
  #ifdef __GLIBCXX__
  
  // reference: https://github.com/gcc-mirror/gcc/blob/gcc-7_3_0-release/libstdc%2B%2B-v3/include/std/fstream#L270
  
  static std::string openmodeToStr(std::ios_base::openmode mode)
  {
      switch (mode & ~std::ios_base::ate) {
      case std::ios_base::out:
      case std::ios_base::out | std::ios_base::trunc:
          return "w";
      case std::ios_base::out | std::ios_base::app:
      case std::ios_base::app:
          return "a";
      case std::ios_base::in:
          return "r";
      case std::ios_base::in | std::ios_base::out:
          return "r+";
      case std::ios_base::in | std::ios_base::out | std::ios_base::trunc:
          return "w+";
      case std::ios_base::in | std::ios_base::out | std::ios_base::app:
      case std::ios_base::in | std::ios_base::app:
          return "a+";
      case std::ios_base::out | std::ios_base::binary:
      case std::ios_base::out | std::ios_base::trunc | std::ios_base::binary:
          return "wb";
      case std::ios_base::out | std::ios_base::app | std::ios_base::binary:
      case std::ios_base::app | std::ios_base::binary:
          return "ab";
      case std::ios_base::in | std::ios_base::binary:
          return "rb";
      case std::ios_base::in | std::ios_base::out | std::ios_base::binary:
          return "r+b";
      case std::ios_base::in | std::ios_base::out | std::ios_base::trunc | std::ios_base::binary:
          return "w+b";
      case std::ios_base::in | std::ios_base::out | std::ios_base::app | std::ios_base::binary:
      case std::ios_base::in | std::ios_base::app | std::ios_base::binary:
          return "a+b";
      default:
          return std::string();
      }
  }
  
  void ifstream::open(const fs::path& p, std::ios_base::openmode mode)
  {
      close();
      mode |= std::ios_base::in;
      m_file = fsbridge::fopen(p, openmodeToStr(mode).c_str());
      if (m_file == nullptr) {
          return;
      }
      m_filebuf = __gnu_cxx::stdio_filebuf<char>(m_file, mode);
      rdbuf(&m_filebuf);
      if (mode & std::ios_base::ate) {
          seekg(0, std::ios_base::end);
      }
  }
  
  void ifstream::close()
  {
      if (m_file != nullptr) {
          m_filebuf.close();
          fclose(m_file);
      }
      m_file = nullptr;
  }
  
  void ofstream::open(const fs::path& p, std::ios_base::openmode mode)
  {
      close();
      mode |= std::ios_base::out;
      m_file = fsbridge::fopen(p, openmodeToStr(mode).c_str());
      if (m_file == nullptr) {
          return;
      }
      m_filebuf = __gnu_cxx::stdio_filebuf<char>(m_file, mode);
      rdbuf(&m_filebuf);
      if (mode & std::ios_base::ate) {
          seekp(0, std::ios_base::end);
      }
  }
  
  void ofstream::close()
  {
      if (m_file != nullptr) {
          m_filebuf.close();
          fclose(m_file);
      }
      m_file = nullptr;
  }
  #else // __GLIBCXX__
  
  static_assert(sizeof(*fs::path().BOOST_FILESYSTEM_C_STR) == sizeof(wchar_t),
      "Warning: This build is using boost::filesystem ofstream and ifstream "
      "implementations which will fail to open paths containing multibyte "
      "characters. You should delete this static_assert to ignore this warning, "
      "or switch to a different C++ standard library like the Microsoft C++ "
      "Standard Library (where boost uses non-standard extensions to construct "
      "stream objects with wide filenames), or the GNU libstdc++ library (where "
      "a more complicated workaround has been implemented above).");
  
  #endif // __GLIBCXX__
  #endif // WIN32
  
  } // fsbridge
  