sendfile_defs_win.hpp

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/*
    restinio
*/

/*!
    Sendfile routine definitions (win implementation).

    @since v.0.4.3
*/

#pragma once

//eao197: this code has to be uncommented to check the default
//implementation of sendfile operation.
//#if defined(RESTINIO_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)
//#undef RESTINIO_ASIO_HAS_WINDOWS_OVERLAPPED_PTR
//#endif

#if defined(RESTINIO_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)

#include <cstdio>

namespace restinio
{

/** @name Aliases for sendfile operation.
 */
///@{
using file_descriptor_t = HANDLE;
using file_offset_t = std::uint64_t;
using file_size_t = std::uint64_t;
///@}

/** @name File operations.
 * @brief A minimal set of file operations.
 *
 * Incapsulates details of windows API for a set of file operations neccessary
 * for sendfile_t class implementation.
 */
///@{
//! Get file descriptor which stands for null.
[[nodiscard]]
inline file_descriptor_t null_file_descriptor(){ return INVALID_HANDLE_VALUE; }

//! Open file.
[[nodiscard]]
inline file_descriptor_t
open_file( const char * file_path )
{
    file_descriptor_t file_descriptor =
        // We don't support Unicode on Windows, so call Ansi-version of
        // CreateFile directly.
        ::CreateFileA(
            file_path,
            GENERIC_READ,
            FILE_SHARE_READ,
            0,
            OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
            0 );

    if( null_file_descriptor() == file_descriptor )
    {
        throw exception_t{
            fmt::format(
                    RESTINIO_FMT_FORMAT_STRING( "unable to openfile '{}': error({})" ),
                    file_path, GetLastError() )
        };
    }

    return file_descriptor;
}

/*!
 * @brief Version of %open_file that accepts std::filesystem::path.
 *
 * @attention
 * It uses std::filesystem::path::wstring() to get the file name and
 * calls CreateFileW. We assume that @a file_path contains a valid
 * file name constructed from a wide-char string or from utf-8 string
 * literal (as `const std::char8_t[N]` in C++20). Or @a file_path is
 * specified as a narrow string, but it can be automatically converted
 * to wide-string in the current code page.
 *
 * @since v.0.7.1
 */
[[nodiscard]]
inline file_descriptor_t
open_file( const std::filesystem::path & file_path )
{
    const auto wide_file_path = file_path.wstring();
    file_descriptor_t file_descriptor =
        // Use wide-char version of CreateFile.
        ::CreateFileW(
            wide_file_path.c_str(),
            GENERIC_READ,
            FILE_SHARE_READ,
            0,
            OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
            0 );

    if( null_file_descriptor() == file_descriptor )
    {
        //NOTE(eao197): I don't know a simple way to add `file_path` value into
        //error message (with respect to the fact that file_path can contain name
        //in Unicode, in UCS-2, but not in UTF-8).
        //Because of that the current version doesn't include file name in the
        //error description.
        throw exception_t{
            fmt::format(
                    RESTINIO_FMT_FORMAT_STRING(
                            "open_file(std::filesystem::path) "
                            "unable to openfile: error({})" ),
                    GetLastError() )
        };
    }

    return file_descriptor;
}


//! Get file meta.
template < typename META >
[[nodiscard]]
META
get_file_meta( file_descriptor_t fd )
{
    file_size_t fsize = 0;
    std::chrono::system_clock::time_point flastmodified;

    if( null_file_descriptor() != fd )
    {
        LARGE_INTEGER file_size;
        // Obtain file size:
        if( GetFileSizeEx( fd, &file_size ) )
        {
            fsize = static_cast< file_size_t >( file_size.QuadPart );
        }
        else
        {
            throw exception_t{
                fmt::format(
                        RESTINIO_FMT_FORMAT_STRING(
                            "unable to get file size: error code:{}" ),
                        GetLastError() )
            };
        }

        FILETIME ftWrite;
        if( GetFileTime( fd, NULL, NULL, &ftWrite ) )
        {
            // https://msdn.microsoft.com/en-us/library/windows/desktop/ms724284(v=vs.85).aspx

            // Microseconds between 1601-01-01 00:00:00 UTC and 1970-01-01 00:00:00 UTC
            constexpr std::uint64_t nanosec100_in_microsec = 10;
            constexpr std::uint64_t epoch_difference_in_microsec =
                11644473600ULL * 1000 *1000;

            // First convert 100-ns intervals to microseconds, then adjust for the
            // epoch difference
            ULARGE_INTEGER ull;
            ull.LowPart = ftWrite.dwLowDateTime;
            ull.HighPart = ftWrite.dwHighDateTime;

            flastmodified =
                std::chrono::system_clock::time_point{
                    std::chrono::microseconds(
                        ull.QuadPart / nanosec100_in_microsec - epoch_difference_in_microsec ) };
        }
        else
        {
            throw exception_t{
                fmt::format(
                    RESTINIO_FMT_FORMAT_STRING(
                        "unable to get file last modification: error code:{}" ),
                    GetLastError() )
            };
        }
    }

    return META{ fsize, flastmodified};
}

//! Close file by its descriptor.
inline void
close_file( file_descriptor_t fd )
{
    CloseHandle( fd );
}
///@}

} /* namespace restinio */

#else // #if defined(RESTINIO_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)

#include <restinio/sendfile_defs_default.hpp>

#endif // #if defined(RESTINIO_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)