libcruft-util/io_win32.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2014 Danny Robson <danny@nerdcruft.net>
 */

#include "io_win32.hpp"

#include "win32/except.hpp"
#include "win32/windows.hpp"
#include "debug/panic.hpp"

#include <winbase.h>

using cruft::detail::win32::mapped_file;


///////////////////////////////////////////////////////////////////////////////
static constexpr
DWORD
fflags_to_generic (int flags) {
    switch (flags) {
    case O_RDONLY:  return GENERIC_READ;
    case O_WRONLY:  return GENERIC_WRITE;
    case O_RDWR:    return GENERIC_READ | GENERIC_WRITE;
    }

    unreachable ();
}


//-----------------------------------------------------------------------------
static constexpr
DWORD
fflags_to_access (int fflags)
{
    switch (fflags) {
    case O_RDONLY:  return FILE_MAP_READ;
    case O_WRONLY:  return FILE_MAP_WRITE;
    case O_RDWR:    return FILE_MAP_WRITE;
    }

    unreachable ();
}


//-----------------------------------------------------------------------------
static constexpr
DWORD
mflags_to_protect (int mflags) {
    DWORD res = 0;

    if (mflags & PROT_READ)  res |= PAGE_READONLY;
    if (mflags & PROT_WRITE) res |= PAGE_READWRITE;
    if (mflags & PROT_EXEC)  res |= PAGE_EXECUTE;

    return res;
}


///////////////////////////////////////////////////////////////////////////////
mapped_file::mapped_file (::cruft::win32::file &&src,
                          int fflags,
                          int mflags):
    m_file (std::forward<::cruft::win32::file> (src)),
    m_data (nullptr, UnmapViewOfFile)
{
    // I would rather perform checks on filesize after mapping, but mapping
    // requires a check for empty files before we perform the mapping to
    // detect errors it throws in that specific situation.
    DWORD hi_size;
    DWORD lo_size = GetFileSize (m_file.native (), &hi_size);
    if (lo_size == INVALID_FILE_SIZE)
        ::cruft::win32::error::throw_code ();

    m_size = static_cast<uint64_t> (hi_size) << 32 | lo_size;

    m_mapping.reset (
        CreateFileMapping (
            m_file,
            nullptr,
            mflags_to_protect (mflags),
            0, 0,
            nullptr
        )
    );

    // Apparently Windows lacks the ability to map zero length files; fucking
    // hell. Try not to collapse, but instead bail with a null mapping and
    // pray the user doesn't do something stupid with the result.
    if (!m_mapping) {
        auto err = ::cruft::win32::error::last_code ();
        if (err == ERROR_FILE_INVALID && m_size == 0)
            return;

        ::cruft::win32::error::throw_code (err);
    }

    auto view = MapViewOfFile (
        m_mapping,
        fflags_to_access (fflags),
        0, 0,
        0
    );

    if (!view)
        ::cruft::win32::error::throw_code ();

    m_data.reset (
        static_cast<unsigned char*> (view)
    );
}


//-----------------------------------------------------------------------------
mapped_file::mapped_file (
    std::filesystem::path const &path,
    int fflags,
    int mflags
)
: mapped_file (
    ::cruft::win32::file (
        path,
        fflags_to_generic (fflags),
        fflags == O_RDONLY ? FILE_SHARE_READ : 0,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN
    ),
    fflags,
    mflags
)
{ ; }


//-----------------------------------------------------------------------------
mapped_file::mapped_file (cruft::posix::fd const &src,
                          int fflags,
                          int mflags):
    mapped_file (cruft::win32::file (src.dup ()),
                 fflags,
                 mflags)
{ };


static BOOL noop (LPCVOID) { return TRUE; }

//-----------------------------------------------------------------------------
mapped_file::mapped_file (mapped_file &&rhs) noexcept
    : m_data (nullptr, noop)
{
    std::swap (m_file,    rhs.m_file);
    std::swap (m_mapping, rhs.m_mapping);
    std::swap (m_data,    rhs.m_data);
    std::swap (m_size,    rhs.m_size);
}


///////////////////////////////////////////////////////////////////////////////
size_t
mapped_file::size (void) const
{
    return m_size;
}


//-----------------------------------------------------------------------------
bool
mapped_file::empty (void) const
{
    return size () == 0;
}


//-----------------------------------------------------------------------------
const uint8_t*
mapped_file::data (void) const &
{
    return m_data.get ();
}


//-----------------------------------------------------------------------------
uint8_t*
mapped_file::data (void) &
{
    return m_data.get ();
}


//-----------------------------------------------------------------------------
uint8_t*
mapped_file::begin (void) &
{
    return data ();
}


//-----------------------------------------------------------------------------
uint8_t*
mapped_file::end (void) &
{
    return data () + size ();
}


//-----------------------------------------------------------------------------
const uint8_t*
mapped_file::begin (void) const &
{
    return cbegin ();
}


//-----------------------------------------------------------------------------
const uint8_t*
mapped_file::end (void) const &
{
    return cend ();
}


//-----------------------------------------------------------------------------
const uint8_t*
mapped_file::cbegin (void) const &
{
    return data ();
}


//-----------------------------------------------------------------------------
const uint8_t*
mapped_file::cend (void) const &
{
    return data () + size ();
}