Is it possible to use overlapped I/O with an anonymous pipe? CreatePipe() does not have any way of specifying FILE_FLAG_OVERLAPPED, so I assume ReadFile() will block, even if I supply an OVERLAPPED-structure.
Here is an implementation for an anonymous pipe function with the possibility to specify FILE_FLAG_OVERLAPPED
:
/******************************************************************************\
* This is a part of the Microsoft Source Code Samples.
* Copyright 1995 - 1997 Microsoft Corporation.
* All rights reserved.
* This source code is only intended as a supplement to
* Microsoft Development Tools and/or WinHelp documentation.
* See these sources for detailed information regarding the
* Microsoft samples programs.
\******************************************************************************/
/*++
Copyright (c) 1997 Microsoft Corporation
Module Name:
pipeex.c
Abstract:
CreatePipe-like function that lets one or both handles be overlapped
Author:
Dave Hart Summer 1997
Revision History:
--*/
#include <windows.h>
#include <stdio.h>
static volatile long PipeSerialNumber;
BOOL
APIENTRY
MyCreatePipeEx(
OUT LPHANDLE lpReadPipe,
OUT LPHANDLE lpWritePipe,
IN LPSECURITY_ATTRIBUTES lpPipeAttributes,
IN DWORD nSize,
DWORD dwReadMode,
DWORD dwWriteMode
)
/*++
Routine Description:
The CreatePipeEx API is used to create an anonymous pipe I/O device.
Unlike CreatePipe FILE_FLAG_OVERLAPPED may be specified for one or
both handles.
Two handles to the device are created. One handle is opened for
reading and the other is opened for writing. These handles may be
used in subsequent calls to ReadFile and WriteFile to transmit data
through the pipe.
Arguments:
lpReadPipe - Returns a handle to the read side of the pipe. Data
may be read from the pipe by specifying this handle value in a
subsequent call to ReadFile.
lpWritePipe - Returns a handle to the write side of the pipe. Data
may be written to the pipe by specifying this handle value in a
subsequent call to WriteFile.
lpPipeAttributes - An optional parameter that may be used to specify
the attributes of the new pipe. If the parameter is not
specified, then the pipe is created without a security
descriptor, and the resulting handles are not inherited on
process creation. Otherwise, the optional security attributes
are used on the pipe, and the inherit handles flag effects both
pipe handles.
nSize - Supplies the requested buffer size for the pipe. This is
only a suggestion and is used by the operating system to
calculate an appropriate buffering mechanism. A value of zero
indicates that the system is to choose the default buffering
scheme.
Return Value:
TRUE - The operation was successful.
FALSE/NULL - The operation failed. Extended error status is available
using GetLastError.
--*/
{
HANDLE ReadPipeHandle, WritePipeHandle;
DWORD dwError;
UCHAR PipeNameBuffer[ MAX_PATH ];
//
// Only one valid OpenMode flag - FILE_FLAG_OVERLAPPED
//
if ((dwReadMode | dwWriteMode) & (~FILE_FLAG_OVERLAPPED)) {
SetLastError(ERROR_INVALID_PARAMETER);
return FALSE;
}
//
// Set the default timeout to 120 seconds
//
if (nSize == 0) {
nSize = 4096;
}
sprintf( PipeNameBuffer,
"\\\\.\\Pipe\\RemoteExeAnon.%08x.%08x",
GetCurrentProcessId(),
InterlockedIncrement(&PipeSerialNumber)
);
ReadPipeHandle = CreateNamedPipeA(
PipeNameBuffer,
PIPE_ACCESS_INBOUND | dwReadMode,
PIPE_TYPE_BYTE | PIPE_WAIT,
1, // Number of pipes
nSize, // Out buffer size
nSize, // In buffer size
120 * 1000, // Timeout in ms
lpPipeAttributes
);
if (! ReadPipeHandle) {
return FALSE;
}
WritePipeHandle = CreateFileA(
PipeNameBuffer,
GENERIC_WRITE,
0, // No sharing
lpPipeAttributes,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | dwWriteMode,
NULL // Template file
);
if (INVALID_HANDLE_VALUE == WritePipeHandle) {
dwError = GetLastError();
CloseHandle( ReadPipeHandle );
SetLastError(dwError);
return FALSE;
}
*lpReadPipe = ReadPipeHandle;
*lpWritePipe = WritePipeHandle;
return( TRUE );
}