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    // Formatting library for C++ - optional OS-specific functionality
    //
    // Copyright (c) 2012 - 2016, Victor Zverovich
    // All rights reserved.
    //
    // For the license information refer to format.h.

    // Disable bogus MSVC warnings.
    #if !defined(_CRT_SECURE_NO_WARNINGS) && defined(_MSC_VER)
    #  define _CRT_SECURE_NO_WARNINGS
    #endif

    #include "fmt/os.h"

    #include <climits>

    #if FMT_USE_FCNTL
    #  include <sys/stat.h>
    #  include <sys/types.h>

    #  ifndef _WIN32
    #    include <unistd.h>
    #  else
    #    ifndef WIN32_LEAN_AND_MEAN
    #      define WIN32_LEAN_AND_MEAN
    #    endif
    #    include <io.h>

    #    ifndef S_IRUSR
    #      define S_IRUSR _S_IREAD
    #    endif
    #    ifndef S_IWUSR
    #      define S_IWUSR _S_IWRITE
    #    endif
    #    ifndef S_IRGRP
    #      define S_IRGRP 0
    #    endif
    #    ifndef S_IROTH
    #      define S_IROTH 0
    #    endif
    #  endif  // _WIN32
    #endif    // FMT_USE_FCNTL

    #ifdef _WIN32
    #  include <windows.h>
    #endif

    #ifdef fileno
    #  undef fileno
    #endif

    namespace {
    #ifdef _WIN32
    // Return type of read and write functions.
    using rwresult = int;

    // On Windows the count argument to read and write is unsigned, so convert
    // it from size_t preventing integer overflow.
    inline unsigned convert_rwcount(std::size_t count) {
      return count <= UINT_MAX ? static_cast<unsigned>(count) : UINT_MAX;
    }
    #elif FMT_USE_FCNTL
    // Return type of read and write functions.
    using rwresult = ssize_t;

    inline std::size_t convert_rwcount(std::size_t count) { return count; }
    #endif
    }  // namespace

    FMT_BEGIN_NAMESPACE

    #ifdef _WIN32
    detail::utf16_to_utf8::utf16_to_utf8(basic_string_view<wchar_t> s) {
      if (int error_code = convert(s)) {
        FMT_THROW(windows_error(error_code,
                                "cannot convert string from UTF-16 to UTF-8"));
      }
    }

    int detail::utf16_to_utf8::convert(basic_string_view<wchar_t> s) {
      if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
      int s_size = static_cast<int>(s.size());
      if (s_size == 0) {
        // WideCharToMultiByte does not support zero length, handle separately.
        buffer_.resize(1);
        buffer_[0] = 0;
        return 0;
      }

      int length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, nullptr, 0,
                                       nullptr, nullptr);
      if (length == 0) return GetLastError();
      buffer_.resize(length + 1);
      length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, &buffer_[0],
                                   length, nullptr, nullptr);
      if (length == 0) return GetLastError();
      buffer_[length] = 0;
      return 0;
    }

    namespace detail {

    class system_message {
      system_message(const system_message&) = delete;
      void operator=(const system_message&) = delete;

      unsigned long result_;
      wchar_t* message_;

      static bool is_whitespace(wchar_t c) FMT_NOEXCEPT {
        return c == L' ' || c == L'\n' || c == L'\r' || c == L'\t' || c == L'\0';
      }

     public:
      explicit system_message(unsigned long error_code)
          : result_(0), message_(nullptr) {
        result_ = FormatMessageW(
            FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
                FORMAT_MESSAGE_IGNORE_INSERTS,
            nullptr, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
            reinterpret_cast<wchar_t*>(&message_), 0, nullptr);
        if (result_ != 0) {
          while (result_ != 0 && is_whitespace(message_[result_ - 1])) {
            --result_;
          }
        }
      }
      ~system_message() { LocalFree(message_); }
      explicit operator bool() const FMT_NOEXCEPT { return result_ != 0; }
      operator basic_string_view<wchar_t>() const FMT_NOEXCEPT {
        return basic_string_view<wchar_t>(message_, result_);
      }
    };

    class utf8_system_category final : public std::error_category {
     public:
      const char* name() const FMT_NOEXCEPT override { return "system"; }
      std::string message(int error_code) const override {
        system_message msg(error_code);
        if (msg) {
          utf16_to_utf8 utf8_message;
          if (utf8_message.convert(msg) == ERROR_SUCCESS) {
            return utf8_message.str();
          }
        }
        return "unknown error";
      }
    };

    }  // namespace detail

    FMT_API const std::error_category& system_category() FMT_NOEXCEPT {
      static const detail::utf8_system_category category;
      return category;
    }

    std::system_error vwindows_error(int err_code, string_view format_str,
                                     format_args args) {
      auto ec = std::error_code(err_code, system_category());
      return std::system_error(ec, vformat(format_str, args));
    }

    void detail::format_windows_error(detail::buffer<char>& out, int error_code,
                                      const char* message) FMT_NOEXCEPT {
      FMT_TRY {
        system_message msg(error_code);
        if (msg) {
          utf16_to_utf8 utf8_message;
          if (utf8_message.convert(msg) == ERROR_SUCCESS) {
            format_to(buffer_appender<char>(out), "{}: {}", message, utf8_message);
            return;
          }
        }
      }
      FMT_CATCH(...) {}
      format_error_code(out, error_code, message);
    }

    void report_windows_error(int error_code, const char* message) FMT_NOEXCEPT {
      report_error(detail::format_windows_error, error_code, message);
    }
    #endif  // _WIN32

    buffered_file::~buffered_file() FMT_NOEXCEPT {
      if (file_ && FMT_SYSTEM(fclose(file_)) != 0)
        report_system_error(errno, "cannot close file");
    }

    buffered_file::buffered_file(cstring_view filename, cstring_view mode) {
      FMT_RETRY_VAL(file_, FMT_SYSTEM(fopen(filename.c_str(), mode.c_str())),
                    nullptr);
      if (!file_)
        FMT_THROW(system_error(errno, "cannot open file {}", filename.c_str()));
    }

    void buffered_file::close() {
      if (!file_) return;
      int result = FMT_SYSTEM(fclose(file_));
      file_ = nullptr;
      if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
    }

    // A macro used to prevent expansion of fileno on broken versions of MinGW.
    #define FMT_ARGS

    int buffered_file::fileno() const {
      int fd = FMT_POSIX_CALL(fileno FMT_ARGS(file_));
      if (fd == -1) FMT_THROW(system_error(errno, "cannot get file descriptor"));
      return fd;
    }

    #if FMT_USE_FCNTL
    file::file(cstring_view path, int oflag) {
    #  ifdef _WIN32
      using mode_t = int;
    #  endif
      mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
    #  if defined(_WIN32) && !defined(__MINGW32__)
      fd_ = -1;
      FMT_POSIX_CALL(sopen_s(&fd_, path.c_str(), oflag, _SH_DENYNO, mode));
    #  else
      FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, mode)));
    #  endif
      if (fd_ == -1)
        FMT_THROW(system_error(errno, "cannot open file {}", path.c_str()));
    }

    file::~file() FMT_NOEXCEPT {
      // Don't retry close in case of EINTR!
      // See http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
      if (fd_ != -1 && FMT_POSIX_CALL(close(fd_)) != 0)
        report_system_error(errno, "cannot close file");
    }

    void file::close() {
      if (fd_ == -1) return;
      // Don't retry close in case of EINTR!
      // See http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
      int result = FMT_POSIX_CALL(close(fd_));
      fd_ = -1;
      if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
    }

    long long file::size() const {
    #  ifdef _WIN32
      // Use GetFileSize instead of GetFileSizeEx for the case when _WIN32_WINNT
      // is less than 0x0500 as is the case with some default MinGW builds.
      // Both functions support large file sizes.
      DWORD size_upper = 0;
      HANDLE handle = reinterpret_cast<HANDLE>(_get_osfhandle(fd_));
      DWORD size_lower = FMT_SYSTEM(GetFileSize(handle, &size_upper));
      if (size_lower == INVALID_FILE_SIZE) {
        DWORD error = GetLastError();
        if (error != NO_ERROR)
          FMT_THROW(windows_error(GetLastError(), "cannot get file size"));
      }
      unsigned long long long_size = size_upper;
      return (long_size << sizeof(DWORD) * CHAR_BIT) | size_lower;
    #  else
      using Stat = struct stat;
      Stat file_stat = Stat();
      if (FMT_POSIX_CALL(fstat(fd_, &file_stat)) == -1)
        FMT_THROW(system_error(errno, "cannot get file attributes"));
      static_assert(sizeof(long long) >= sizeof(file_stat.st_size),
                    "return type of file::size is not large enough");
      return file_stat.st_size;
    #  endif
    }

    std::size_t file::read(void* buffer, std::size_t count) {
      rwresult result = 0;
      FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
      if (result < 0) FMT_THROW(system_error(errno, "cannot read from file"));
      return detail::to_unsigned(result);
    }

    std::size_t file::write(const void* buffer, std::size_t count) {
      rwresult result = 0;
      FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
      if (result < 0) FMT_THROW(system_error(errno, "cannot write to file"));
      return detail::to_unsigned(result);
    }

    file file::dup(int fd) {
      // Don't retry as dup doesn't return EINTR.
      // http://pubs.opengroup.org/onlinepubs/009695399/functions/dup.html
      int new_fd = FMT_POSIX_CALL(dup(fd));
      if (new_fd == -1)
        FMT_THROW(system_error(errno, "cannot duplicate file descriptor {}", fd));
      return file(new_fd);
    }

    void file::dup2(int fd) {
      int result = 0;
      FMT_RETRY(result, FMT_POSIX_CALL(dup2(fd_, fd)));
      if (result == -1) {
        FMT_THROW(system_error(errno, "cannot duplicate file descriptor {} to {}",
                               fd_, fd));
      }
    }

    void file::dup2(int fd, std::error_code& ec) FMT_NOEXCEPT {
      int result = 0;
      FMT_RETRY(result, FMT_POSIX_CALL(dup2(fd_, fd)));
      if (result == -1) ec = std::error_code(errno, std::generic_category());
    }

    void file::pipe(file& read_end, file& write_end) {
      // Close the descriptors first to make sure that assignments don't throw
      // and there are no leaks.
      read_end.close();
      write_end.close();
      int fds[2] = {};
    #  ifdef _WIN32
      // Make the default pipe capacity same as on Linux 2.6.11+.
      enum { DEFAULT_CAPACITY = 65536 };
      int result = FMT_POSIX_CALL(pipe(fds, DEFAULT_CAPACITY, _O_BINARY));
    #  else
      // Don't retry as the pipe function doesn't return EINTR.
      // http://pubs.opengroup.org/onlinepubs/009696799/functions/pipe.html
      int result = FMT_POSIX_CALL(pipe(fds));
    #  endif
      if (result != 0) FMT_THROW(system_error(errno, "cannot create pipe"));
      // The following assignments don't throw because read_fd and write_fd
      // are closed.
      read_end = file(fds[0]);
      write_end = file(fds[1]);
    }

    buffered_file file::fdopen(const char* mode) {
    // Don't retry as fdopen doesn't return EINTR.
    #  if defined(__MINGW32__) && defined(_POSIX_)
      FILE* f = ::fdopen(fd_, mode);
    #  else
      FILE* f = FMT_POSIX_CALL(fdopen(fd_, mode));
    #  endif
      if (!f)
        FMT_THROW(
            system_error(errno, "cannot associate stream with file descriptor"));
      buffered_file bf(f);
      fd_ = -1;
      return bf;
    }

    long getpagesize() {
    #  ifdef _WIN32
      SYSTEM_INFO si;
      GetSystemInfo(&si);
      return si.dwPageSize;
    #  else
      long size = FMT_POSIX_CALL(sysconf(_SC_PAGESIZE));
      if (size < 0) FMT_THROW(system_error(errno, "cannot get memory page size"));
      return size;
    #  endif
    }

    FMT_API void ostream::grow(size_t) {
      if (this->size() == this->capacity()) flush();
    }
    #endif  // FMT_USE_FCNTL
    FMT_END_NAMESPACE