windows/io.cpp

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/*
* This program source code file is part of KiCad, a free EDA CAD application.
*
* Copyright The KiCad Developers, see AUTHORS.txt for contributors.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
 
#include <kiplatform/io.h>
 
#include <wx/string.h>
#include <wx/wxcrt.h>
#include <wx/filename.h>
 
#include <cstdio>
#include <io.h>
#include <stdexcept>
#include <string>
#include <vector>
#include <windows.h>
#include <shlwapi.h>
#include <winternl.h>
 
// NtQueryDirectoryFile-based directory enumeration for fast file listing.
// This approach is based on git-for-windows fscache implementation:
// https://github.com/git-for-windows/git/blob/main/compat/win32/fscache.c
// Copyright (C) Johannes Schindelin and the Git for Windows project
// Licensed under GPL v2.
//
// FILE_FULL_DIR_INFORMATION is documented in the Windows Driver Kit but not the SDK.
 
#if !defined( __MINGW32__ )     // already defined in the included mingw header <winternl.h>
                                // So do not redefine it on mingw
typedef struct _FILE_FULL_DIR_INFORMATION
{
    ULONG         NextEntryOffset;
    ULONG         FileIndex;
    LARGE_INTEGER CreationTime;
    LARGE_INTEGER LastAccessTime;
    LARGE_INTEGER LastWriteTime;
    LARGE_INTEGER ChangeTime;
    LARGE_INTEGER EndOfFile;
    LARGE_INTEGER AllocationSize;
    ULONG         FileAttributes;
    ULONG         FileNameLength;
    ULONG         EaSize;
    WCHAR         FileName[1];
} FILE_FULL_DIR_INFORMATION, *PFILE_FULL_DIR_INFORMATION;
#endif
 
typedef NTSTATUS( NTAPI* PFN_NtQueryDirectoryFile )( HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
                                                     PIO_STATUS_BLOCK, PVOID, ULONG,
                                                     FILE_INFORMATION_CLASS, BOOLEAN,
                                                     PUNICODE_STRING, BOOLEAN );
 
#define FileFullDirectoryInformation ( (FILE_INFORMATION_CLASS) 2 )
 
// Define USE_MSYS2_FALlBACK if the code for _MSC_VER does not compile on msys2
//#define  USE_MSYS2_FALLBACK
 
FILE* KIPLATFORM::IO::SeqFOpen( const wxString& aPath, const wxString& aMode )
{
#if defined( _MSC_VER ) || !defined( USE_MSYS2_FALLBACK )
    // We need to use the win32 api to setup a file handle with sequential scan flagged
    // and pass it up the chain to create a normal FILE stream
    HANDLE hFile = INVALID_HANDLE_VALUE;
    hFile = CreateFileW( aPath.wc_str(),
                         GENERIC_READ,
                         FILE_SHARE_READ,
                         NULL,
                         OPEN_EXISTING,
                         FILE_FLAG_SEQUENTIAL_SCAN,
                         NULL );
 
    if (hFile == INVALID_HANDLE_VALUE)
    {
        return NULL;
    }
 
    int fd = _open_osfhandle( reinterpret_cast<intptr_t>( hFile ), 0 );
 
    if( fd == -1 )
    {
        // close the handle manually as the ownership didnt transfer
        CloseHandle( hFile );
        return NULL;
    }
 
    FILE* fp = _fdopen( fd, aMode.c_str() );
 
    if( !fp )
    {
        // close the file descriptor manually as the ownership didnt transfer
        _close( fd );
    }
 
    return fp;
#else
    // Fallback for MSYS2
    return wxFopen( aPath, aMode );
#endif
}
 
bool KIPLATFORM::IO::DuplicatePermissions( const wxString &aSrc, const wxString &aDest )
{
    // Only copy the DACL. Copying OWNER/GROUP would require SE_RESTORE_NAME when the
    // target is owned by a different principal (common for files under ProgramData or
    // on network shares), turning ACL preservation into a hard failure. The temp file
    // is created by the current user, so leaving owner as the current user is correct.
    const SECURITY_INFORMATION secInfo = DACL_SECURITY_INFORMATION;
 
    // Size-probe call: required buffer size is returned via dwSize. By API contract this
    // call fails with ERROR_INSUFFICIENT_BUFFER; the previous implementation wrapped it
    // in an if() and therefore never executed the body, silently returning false on every
    // save and surfacing as "Cannot copy permissions" once atomic save made the failure
    // fatal.
    DWORD dwSize = 0;
    GetFileSecurityW( aSrc.wc_str(), secInfo, nullptr, 0, &dwSize );
 
    if( dwSize == 0 || GetLastError() != ERROR_INSUFFICIENT_BUFFER )
        return false;
 
    std::vector<BYTE> sdBuffer( dwSize );
    PSECURITY_DESCRIPTOR pSD = static_cast<PSECURITY_DESCRIPTOR>( sdBuffer.data() );
 
    return GetFileSecurityW( aSrc.wc_str(), secInfo, pSD, dwSize, &dwSize )
           && SetFileSecurityW( aDest.wc_str(), secInfo, pSD );
}
 
bool KIPLATFORM::IO::MakeWriteable( const wxString& aFilePath )
{
    DWORD attrs = GetFileAttributesW( aFilePath.wc_str() );
 
    if( attrs == INVALID_FILE_ATTRIBUTES )
        return false;
 
    // Remove read-only and hidden attributes if present. Both of these can prevent file
    // operations on Windows. Hidden files in particular can cause issues when files are
    // synced via cloud services like OneDrive.
    DWORD attrsToRemove = FILE_ATTRIBUTE_READONLY | FILE_ATTRIBUTE_HIDDEN;
 
    if( attrs & attrsToRemove )
    {
        attrs &= ~attrsToRemove;
        return SetFileAttributesW( aFilePath.wc_str(), attrs ) != 0;
    }
 
    return true;
}
 
KIPLATFORM::IO::TARGET_ATTRS KIPLATFORM::IO::CaptureTargetAttributes( const wxString& aPath )
{
    TARGET_ATTRS snapshot;
    DWORD        attrs = GetFileAttributesW( aPath.wc_str() );
 
    if( attrs == INVALID_FILE_ATTRIBUTES )
        return snapshot;
 
    // Only preserve bits that SetFileSecurity (used by DuplicatePermissions) does not
    // carry across a rename. Other attributes on the new file come from the temp's
    // default creation attrs and should not be overwritten here.
    snapshot.value    = static_cast<std::uint32_t>( attrs )
                        & ( FILE_ATTRIBUTE_READONLY | FILE_ATTRIBUTE_HIDDEN );
    snapshot.captured = true;
    return snapshot;
}
 
 
bool KIPLATFORM::IO::ApplyTargetAttributes( const wxString& aPath, const TARGET_ATTRS& aAttrs )
{
    if( !aAttrs.captured )
        return true;
 
    DWORD current = GetFileAttributesW( aPath.wc_str() );
 
    if( current == INVALID_FILE_ATTRIBUTES )
        return false;
 
    DWORD merged = current | static_cast<DWORD>( aAttrs.value );
 
    if( merged == current )
        return true;
 
    return SetFileAttributesW( aPath.wc_str(), merged ) != 0;
}
 
 
FILE* KIPLATFORM::IO::OpenUniqueSiblingTempFile( const wxString& aTargetPath,
                                                 const wxString& aMode, wxString* aTempPathOut,
                                                 wxString* aError )
{
    // Exclusive-create closes the TOCTOU window: if another process pre-created a file
    // at the candidate path, CreateFileW with CREATE_NEW fails and we retry.
    for( unsigned attempt = 0; attempt < 32; ++attempt )
    {
        wxString candidate = MakeSiblingTempPath( aTargetPath );
        HANDLE h = CreateFileW( candidate.wc_str(), GENERIC_WRITE, 0, nullptr, CREATE_NEW,
                                FILE_ATTRIBUTE_NORMAL, nullptr );
 
        if( h != INVALID_HANDLE_VALUE )
        {
            int fd = _open_osfhandle( reinterpret_cast<intptr_t>( h ), _O_WRONLY | _O_BINARY );
 
            if( fd < 0 )
            {
                CloseHandle( h );
                DeleteFileW( candidate.wc_str() );
 
                if( aError )
                {
                    *aError = wxString::Format( wxT( "_open_osfhandle failed for '%s'" ),
                                                candidate );
                }
 
                return nullptr;
            }
 
            FILE* fp = _wfdopen( fd, aMode.wc_str() );
 
            if( !fp )
            {
                _close( fd ); // also closes the HANDLE
                DeleteFileW( candidate.wc_str() );
 
                if( aError )
                    *aError = wxString::Format( wxT( "_wfdopen failed for '%s'" ), candidate );
 
                return nullptr;
            }
 
            if( aTempPathOut )
                *aTempPathOut = candidate;
 
            return fp;
        }
 
        DWORD err = GetLastError();
 
        if( err != ERROR_FILE_EXISTS && err != ERROR_ALREADY_EXISTS )
        {
            if( aError )
                *aError = wxString::Format( wxT( "CreateFile failed for '%s' (Win32 %lu)" ),
                                            candidate, err );
 
            return nullptr;
        }
    }
 
    if( aError )
        *aError = wxT( "Exhausted temp-file retry budget" );
 
    return nullptr;
}
 
 
wxString KIPLATFORM::IO::ResolveSymlinkTarget( const wxString& aPath )
{
    // Windows reparse points are semantically richer than POSIX symlinks (junctions,
    // mount points, symlinks). The pre-atomic save code used wxFopen which opened
    // through symlinks; MoveFileExW with MOVEFILE_REPLACE_EXISTING also follows
    // reparse points for the target, so no pre-resolution is needed here.
    return aPath;
}
 
 
bool KIPLATFORM::IO::IsFileHidden( const wxString& aFileName )
{
    const DWORD attributes = GetFileAttributesW( aFileName.fn_str() );
 
    return attributes != INVALID_FILE_ATTRIBUTES
           && ( attributes & FILE_ATTRIBUTE_HIDDEN ) != 0;
}
 
 
void KIPLATFORM::IO::LongPathAdjustment( wxFileName& aFilename )
{
    // dont shortcut this for shorter lengths as there are uses like directory
    // paths that exceed the path length when you start traversing their subdirectories
    // so we want to start with the long path prefix all the time
 
    if( aFilename.GetVolume().Length() == 1 )
        // assume single letter == drive volume
        aFilename.SetVolume( "\\\\?\\" + aFilename.GetVolume() + ":" );
    else if( aFilename.GetVolume().Length() > 1
            && aFilename.GetVolume().StartsWith( wxT( "\\\\" ) )
            && !aFilename.GetVolume().StartsWith( wxT( "\\\\?" ) ) )
        // unc path aka network share, wx returns with \\ already
        // so skip the first slash and combine with the prefix
        // which in the case of UNCs is actually \\?\UNC<server><share>
        // where UNC is literally the text UNC
        aFilename.SetVolume( "\\\\?\\UNC" + aFilename.GetVolume().Mid( 1 ) );
    else if( aFilename.GetVolume().StartsWith( wxT( "\\\\?" ) )
             && aFilename.GetDirs().size() >= 2
             && aFilename.GetDirs()[0] == "UNC" )
    {
        // wxWidgets can parse \\?\UNC<server> into a mess
        // UNC gets stored into a directory
        // volume gets reduced to just \\?
        // so we need to repair it
        aFilename.SetVolume( "\\\\?\\UNC\\" + aFilename.GetDirs()[1] );
        aFilename.RemoveDir( 0 );
        aFilename.RemoveDir( 0 );
    }
}
 
 
long long KIPLATFORM::IO::TimestampDir( const wxString& aDirPath, const wxString& aFilespec )
{
    long long timestamp = 0;
 
    // Use NtQueryDirectoryFile for fast directory enumeration (same approach as git-for-windows).
    // This retrieves multiple directory entries per syscall into a large buffer, reducing
    // kernel transitions compared to FindFirstFile/FindNextFile.
    static PFN_NtQueryDirectoryFile pNtQueryDirectoryFile = nullptr;
 
    if( !pNtQueryDirectoryFile )
    {
        HMODULE ntdll = GetModuleHandleW( L"ntdll.dll" );
 
        if( ntdll )
        {
            pNtQueryDirectoryFile =
                    (PFN_NtQueryDirectoryFile) GetProcAddress( ntdll, "NtQueryDirectoryFile" );
        }
    }
 
    if( !pNtQueryDirectoryFile )
        return timestamp;
 
    std::wstring dirPath( aDirPath.t_str() );
 
    if( !dirPath.empty() && dirPath.back() != L'\\' )
        dirPath += L'\\';
 
    // Prefix with \\?\ for long path support, handling UNC paths specially
    std::wstring ntPath;
 
    if( dirPath.size() >= 2 && dirPath[0] == L'\\' && dirPath[1] == L'\\' )
    {
        if( dirPath.size() >= 4 && dirPath[2] == L'?' && dirPath[3] == L'\\' )
        {
            // Already has \\?\ prefix
            ntPath = dirPath;
        }
        else
        {
            // UNC path: \\server\share -> \\?\UNC\server\share
            ntPath = L"\\\\?\\UNC\\" + dirPath.substr( 2 );
        }
    }
    else
    {
        // Local path: C:\foo -> \\?\C:\foo
        ntPath = L"\\\\?\\" + dirPath;
    }
 
    HANDLE hDir = CreateFileW( ntPath.c_str(), FILE_LIST_DIRECTORY,
                               FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr,
                               OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, nullptr );
 
    if( hDir == INVALID_HANDLE_VALUE )
        return timestamp;
 
    std::wstring pattern( aFilespec.t_str() );
 
    // 64KB buffer for directory entries (same size as git-for-windows)
    alignas( sizeof( LONGLONG ) ) char buffer[64 * 1024];
 
    IO_STATUS_BLOCK iosb;
    NTSTATUS        status;
    bool            firstQuery = true;
 
    for( ;; )
    {
        status = pNtQueryDirectoryFile( hDir, nullptr, nullptr, nullptr, &iosb, buffer,
                                        sizeof( buffer ), FileFullDirectoryInformation, FALSE,
                                        nullptr, firstQuery ? TRUE : FALSE );
        firstQuery = false;
 
        if( status != 0 )
            break;
 
        PFILE_FULL_DIR_INFORMATION dirInfo = (PFILE_FULL_DIR_INFORMATION) buffer;
 
        for( ;; )
        {
            // Extract null-terminated filename
            std::wstring fileName( dirInfo->FileName, dirInfo->FileNameLength / sizeof( WCHAR ) );
 
            // Skip directories and match against pattern
            if( !( dirInfo->FileAttributes & FILE_ATTRIBUTE_DIRECTORY )
                && PathMatchSpecW( fileName.c_str(), pattern.c_str() ) )
            {
                // Shift right by 13 (~0.8ms resolution) to avoid overflow when summing many files
                timestamp += dirInfo->LastWriteTime.QuadPart >> 13;
                timestamp += dirInfo->EndOfFile.LowPart;
            }
 
            if( dirInfo->NextEntryOffset == 0 )
                break;
 
            dirInfo = (PFILE_FULL_DIR_INFORMATION) ( (char*) dirInfo + dirInfo->NextEntryOffset );
        }
    }
 
    CloseHandle( hDir );
 
    return timestamp;
}
 
 
bool KIPLATFORM::IO::FlushToDisk( FILE* aFp )
{
    if( !aFp )
        return false;
 
    if( std::fflush( aFp ) != 0 )
        return false;
 
    int fd = _fileno( aFp );
 
    if( fd < 0 )
        return false;
 
    HANDLE h = reinterpret_cast<HANDLE>( _get_osfhandle( fd ) );
 
    if( h == INVALID_HANDLE_VALUE )
        return false;
 
    return FlushFileBuffers( h ) != 0;
}
 
 
bool KIPLATFORM::IO::FlushDirectory( const wxString& aDirPath )
{
    // NTFS metadata journaling commits rename operations durably on its own, so there is
    // no equivalent of POSIX dir-fsync. Report success unconditionally.
    (void) aDirPath;
    return true;
}
 
 
bool KIPLATFORM::IO::AtomicRename( const wxString& aSrc, const wxString& aDst, wxString* aError )
{
    // Try MoveFileEx first. MOVEFILE_WRITE_THROUGH ensures the rename is committed before
    // return, so a power loss after success does not lose the replacement. MOVEFILE_REPLACE_EXISTING
    // allows overwriting the destination (the caller has already verified this is the intent).
    // A brief retry loop absorbs transient antivirus / indexer / cloud-sync locks that would
    // otherwise surface as ERROR_SHARING_VIOLATION or ERROR_ACCESS_DENIED.
    DWORD lastError = 0;
 
    for( int attempt = 0; attempt < 10; ++attempt )
    {
        if( MoveFileExW( aSrc.wc_str(), aDst.wc_str(),
                         MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH ) )
            return true;
 
        lastError = GetLastError();
 
        if( lastError != ERROR_SHARING_VIOLATION && lastError != ERROR_ACCESS_DENIED
            && lastError != ERROR_LOCK_VIOLATION )
            break;
 
        Sleep( 50 );
    }
 
    // Fall back to ReplaceFileW, which handles some share-mode cases MoveFileEx cannot
    // (for instance when the destination is open for reading with FILE_SHARE_DELETE).
    if( ReplaceFileW( aDst.wc_str(), aSrc.wc_str(), nullptr, REPLACEFILE_WRITE_THROUGH, nullptr,
                      nullptr ) )
        return true;
 
    DWORD fallbackError = GetLastError();
 
    if( aError )
    {
        wchar_t* msg = nullptr;
        FormatMessageW( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM
                            | FORMAT_MESSAGE_IGNORE_INSERTS,
                        nullptr, fallbackError ? fallbackError : lastError,
                        MAKELANGID( LANG_NEUTRAL, SUBLANG_DEFAULT ), reinterpret_cast<LPWSTR>( &msg ),
                        0, nullptr );
 
        if( msg )
        {
            *aError = wxString( msg );
            LocalFree( msg );
        }
        else
        {
            *aError = wxString::Format( wxT( "Win32 error %lu" ), fallbackError ? fallbackError
                                                                                : lastError );
        }
    }
 
    return false;
}
 
 
KIPLATFORM::IO::MAPPED_FILE::MAPPED_FILE( const wxString& aFileName )
{
    m_fileHandle = CreateFileW( aFileName.wc_str(), GENERIC_READ, FILE_SHARE_READ,
                                nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr );
 
    if( m_fileHandle == INVALID_HANDLE_VALUE )
    {
        m_fileHandle = nullptr;
        throw std::runtime_error( std::string( "Cannot open file: " )
                                  + aFileName.ToStdString() );
    }
 
    LARGE_INTEGER fileSize;
 
    if( !GetFileSizeEx( m_fileHandle, &fileSize ) )
    {
        CloseHandle( m_fileHandle );
        m_fileHandle = nullptr;
        throw std::runtime_error( std::string( "Cannot determine file size: " )
                                  + aFileName.ToStdString() );
    }
 
    m_size = static_cast<size_t>( fileSize.QuadPart );
 
    if( m_size == 0 )
    {
        CloseHandle( m_fileHandle );
        m_fileHandle = nullptr;
        return;
    }
 
    m_mapHandle = CreateFileMappingW( m_fileHandle, nullptr, PAGE_READONLY, 0, 0, nullptr );
 
    if( !m_mapHandle )
    {
        CloseHandle( m_fileHandle );
        m_fileHandle = nullptr;
        readIntoBuffer( aFileName );
        return;
    }
 
    void* ptr = MapViewOfFile( m_mapHandle, FILE_MAP_READ, 0, 0, 0 );
 
    if( !ptr )
    {
        CloseHandle( m_mapHandle );
        m_mapHandle = nullptr;
        CloseHandle( m_fileHandle );
        m_fileHandle = nullptr;
        readIntoBuffer( aFileName );
        return;
    }
 
    m_data = static_cast<const uint8_t*>( ptr );
}
 
 
KIPLATFORM::IO::MAPPED_FILE::~MAPPED_FILE()
{
    if( m_data && m_mapHandle )
        UnmapViewOfFile( m_data );
 
    if( m_mapHandle )
        CloseHandle( m_mapHandle );
 
    if( m_fileHandle )
        CloseHandle( m_fileHandle );
}
 
 
 
// Past any content, so reading a held lock's owner still works; SQLite's PENDING_BYTE offset
static constexpr DWORD LOCK_BYTE_OFFSET = 0x40000000;
 
 
KIPLATFORM::IO::FILE_LOCK::STATE KIPLATFORM::IO::FILE_LOCK::Acquire( const wxString& aPath,
                                                                     bool& aCreated )
{
    Release();
 
    // FILE_SHARE_DELETE lets the owner remove the lock file while we still hold it open
    auto openFile = [&]( DWORD aAccess, DWORD aDisposition )
    {
        return CreateFileW( aPath.wc_str(), aAccess,
                            FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr,
                            aDisposition, FILE_ATTRIBUTE_NORMAL, nullptr );
    };
 
    HANDLE handle = openFile( GENERIC_READ | GENERIC_WRITE, CREATE_NEW );
 
    aCreated = handle != INVALID_HANDLE_VALUE;
 
    if( !aCreated )
        handle = openFile( GENERIC_READ | GENERIC_WRITE, OPEN_EXISTING );
 
    if( handle == INVALID_HANDLE_VALUE )
    {
        // Fall back to read-only so we can still report the lock owner
        handle = openFile( GENERIC_READ, OPEN_EXISTING );
 
        if( handle != INVALID_HANDLE_VALUE )
        {
            m_handle = handle;
            m_state = STATE::UNSUPPORTED;
        }
 
        return m_state;
    }
 
    m_handle = handle;
 
    OVERLAPPED overlapped = {};
    overlapped.Offset = LOCK_BYTE_OFFSET;
 
    if( LockFileEx( handle, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0,
                    &overlapped ) )
    {
        m_state = STATE::HELD;
    }
    else if( GetLastError() == ERROR_LOCK_VIOLATION || GetLastError() == ERROR_IO_PENDING )
    {
        m_state = STATE::BUSY;
    }
    else
    {
        m_state = STATE::UNSUPPORTED;
    }
 
    return m_state;
}
 
 
bool KIPLATFORM::IO::FILE_LOCK::OpenForInspect( const wxString& aPath, bool& aHeldByAnother )
{
    Release();
 
    aHeldByAnother = false;
 
    HANDLE handle = CreateFileW( aPath.wc_str(), GENERIC_READ,
                                 FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr,
                                 OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr );
 
    if( handle == INVALID_HANDLE_VALUE )
        return false;
 
    m_handle = handle;
 
    OVERLAPPED overlapped = {};
    overlapped.Offset = LOCK_BYTE_OFFSET;
 
    // Briefly take the lock to test for a holder, then release; m_state stays NONE
    if( LockFileEx( handle, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0,
                    &overlapped ) )
    {
        UnlockFileEx( handle, 0, 1, 0, &overlapped );
    }
    else if( GetLastError() == ERROR_LOCK_VIOLATION || GetLastError() == ERROR_IO_PENDING )
    {
        aHeldByAnother = true;
    }
 
    return true;
}
 
 
bool KIPLATFORM::IO::FILE_LOCK::IsOpen() const
{
    return m_handle != nullptr;
}
 
 
bool KIPLATFORM::IO::FILE_LOCK::ReadAll( std::string& aContents ) const
{
    if( !IsOpen() )
        return false;
 
    LARGE_INTEGER zero = {};
 
    if( !SetFilePointerEx( m_handle, zero, nullptr, FILE_BEGIN ) )
        return false;
 
    aContents.clear();
 
    char  buffer[4096];
    DWORD read = 0;
 
    while( ReadFile( m_handle, buffer, sizeof( buffer ), &read, nullptr ) && read > 0 )
        aContents.append( buffer, read );
 
    return true;
}
 
 
bool KIPLATFORM::IO::FILE_LOCK::Rewrite( const std::string& aContents )
{
    if( !IsOpen() )
        return false;
 
    LARGE_INTEGER zero = {};
 
    if( !SetFilePointerEx( m_handle, zero, nullptr, FILE_BEGIN ) || !SetEndOfFile( m_handle ) )
        return false;
 
    DWORD written = 0;
 
    if( !WriteFile( m_handle, aContents.data(), static_cast<DWORD>( aContents.size() ), &written,
                    nullptr ) )
    {
        return false;
    }
 
    return written == aContents.size();
}
 
 
void KIPLATFORM::IO::FILE_LOCK::Release()
{
    if( IsOpen() )
    {
        // Closing the handle releases the lock, same as process death would
        CloseHandle( m_handle );
        m_handle = nullptr;
    }
 
    m_state = STATE::NONE;
}