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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;
namespace System.IO
{
public partial class FileStream : Stream
{
private unsafe SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options)
{
Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(share);
int access =
((_access & FileAccess.Read) == FileAccess.Read ? GENERIC_READ : 0) |
((_access & FileAccess.Write) == FileAccess.Write ? GENERIC_WRITE : 0);
// Our Inheritable bit was stolen from Windows, but should be set in
// the security attributes class. Don't leave this bit set.
share &= ~FileShare.Inheritable;
// Must use a valid Win32 constant here...
if (mode == FileMode.Append)
mode = FileMode.OpenOrCreate;
Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS parameters = new Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS();
parameters.dwSize = (uint)sizeof(Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS);
parameters.dwFileFlags = (uint)options;
parameters.lpSecurityAttributes = &secAttrs;
using (DisableMediaInsertionPrompt.Create())
{
return ValidateFileHandle(Interop.Kernel32.CreateFile2(
lpFileName: _path,
dwDesiredAccess: access,
dwShareMode: share,
dwCreationDisposition: mode,
pCreateExParams: ref parameters));
}
}
private static bool GetDefaultIsAsync(SafeFileHandle handle) => handle.IsAsync ?? DefaultIsAsync;
private static unsafe bool? IsHandleSynchronous(SafeFileHandle handle, FileAccess access)
{
// Do NOT use this method on any type other than DISK. Reading or writing to a pipe may
// cause an app to block incorrectly, introducing a deadlock (depending on whether a write
// will wake up an already-blocked thread or this Win32FileStream's thread).
byte* bytes = stackalloc byte[1];
int numBytesReadWritten;
int r = -1;
// If the handle is a pipe, ReadFile will block until there
// has been a write on the other end. We'll just have to deal with it,
// For the read end of a pipe, you can mess up and
// accidentally read synchronously from an async pipe.
if ((access & FileAccess.Read) != 0)
{
r = Interop.Kernel32.ReadFile(handle, bytes, 0, out numBytesReadWritten, IntPtr.Zero);
}
else if ((access & FileAccess.Write) != 0)
{
r = Interop.Kernel32.WriteFile(handle, bytes, 0, out numBytesReadWritten, IntPtr.Zero);
}
if (r == 0)
{
int errorCode = Marshal.GetLastWin32Error();
switch (errorCode)
{
case Interop.Errors.ERROR_INVALID_PARAMETER:
return false;
case Interop.Errors.ERROR_INVALID_HANDLE:
throw Win32Marshal.GetExceptionForWin32Error(errorCode);
}
}
return true;
}
private static void VerifyHandleIsSync(SafeFileHandle handle, int fileType, FileAccess access)
{
// The technique here only really works for FILE_TYPE_DISK. FileMode is the right thing to check, but it currently
// isn't available in WinRT.
if (fileType == Interop.Kernel32.FileTypes.FILE_TYPE_DISK)
{
// If we can't check the handle, just assume it is ok.
if (!(IsHandleSynchronous(handle, access) ?? true))
throw new ArgumentException(SR.Arg_HandleNotSync, nameof(handle));
}
}
}
}
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