MemoryMappedFil e Problem

[Martin Priebe]

Hi,

i tried to use MMF to communicate between 2 processes.
i want to transfer a bitmap between the 2 processes.

i created a mmf in my first process

public IntPtr CreateMMF(FileA ccess access, int size)

{

if (size < 0)

throw new ArgumentExcepti on("The size parameter should be a number greater
than Zero.");

IntPtr memoryFileHandl e = CreateFileMappi ng(0xFFFFFFFF, IntPtr.Zero,
(uint)access, 0, (uint)size, "MMF");

if (memoryFileHand le == IntPtr.Zero)

throw new Exception("Crea ting Shared Memory failed.");

return memoryFileHandl e;

}

i mapped it and write the graphic to it

IntPtr mappedViewHandl e = MapViewOfFile(m mfHandle, (uint)FILE_MAP_ WRITE, 0,
0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

Marshal.WriteIn tPtr(mappedView Handle, gfxScreenshot.G etHdc());

UnmapViewOfFile (mappedViewHand le);

CloseHandle((ui nt)mappedViewHa ndle);

my other process mapped the file but throw an exception "not enough memory"

IntPtr mappedFileHandl e = OpenFileMapping ((int)FileAcces s.ReadWrite, false,
"MMF");

if (mappedFileHand le == IntPtr.Zero)

throw new Exception("Open ing the Shared Memory for Read failed.");

//here the Exception is thrown

IntPtr mappedViewHandl e = MapViewOfFile(m appedFileHandle ,
(uint)FILE_MAP_ READ, 0, 0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

IntPtr windowHandle = Marshal.ReadInt Ptr(mappedViewH andle);

if (windowHandle == IntPtr.Zero)

throw new ArgumentExcepti on("Reading from the specified address in Shared
Memory failed.");

UnmapViewOfFile (mappedViewHand le);

CloseHandle((ui nt)mappedFileHa ndle);

return windowHandle;

CreateMappedFil e i use a size of 200000. (nearly 200 KB)

Pleayse help me.

greetings

Martin

[Martin Priebe]

my error occurs when i try to convert the handle from the mmf to a
GraphicObject

gfxScreenshot = Graphics.FromHd cInternal(picPo inter);

[Nicholas Paldino [.NET/C# MVP]]

Martin,

The problem here is with this line:

Marshal.WriteIn tPtr(mappedView Handle, gfxScreenshot.G etHdc());

You are writing only the handle to the pointer. That DC handle is not
going to be valid outside of the process that created it.

What you need to do is write all the bitmap data to the memory mapped
file, and then read it back out on the other side.

Curious, why aren't you using Remoting or WCF to do this for you? You
could have transferred your Bitmap using much simpler code. My suggestion,
use Named Pipes as the channel if you go this route.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Martin Priebe" <ma***********@ hermos.comwrote in message
news:OY******** ******@TK2MSFTN GP02.phx.gbl...

Hi,

i tried to use MMF to communicate between 2 processes.
i want to transfer a bitmap between the 2 processes.

i created a mmf in my first process

public IntPtr CreateMMF(FileA ccess access, int size)

{

if (size < 0)

throw new ArgumentExcepti on("The size parameter should be a number greater
than Zero.");

IntPtr memoryFileHandl e = CreateFileMappi ng(0xFFFFFFFF, IntPtr.Zero,
(uint)access, 0, (uint)size, "MMF");

if (memoryFileHand le == IntPtr.Zero)

throw new Exception("Crea ting Shared Memory failed.");

return memoryFileHandl e;

}

i mapped it and write the graphic to it

IntPtr mappedViewHandl e = MapViewOfFile(m mfHandle, (uint)FILE_MAP_ WRITE,
0, 0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

Marshal.WriteIn tPtr(mappedView Handle, gfxScreenshot.G etHdc());

UnmapViewOfFile (mappedViewHand le);

CloseHandle((ui nt)mappedViewHa ndle);

my other process mapped the file but throw an exception "not enough
memory"

IntPtr mappedFileHandl e = OpenFileMapping ((int)FileAcces s.ReadWrite,
false, "MMF");

if (mappedFileHand le == IntPtr.Zero)

throw new Exception("Open ing the Shared Memory for Read failed.");

//here the Exception is thrown

IntPtr mappedViewHandl e = MapViewOfFile(m appedFileHandle ,
(uint)FILE_MAP_ READ, 0, 0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

IntPtr windowHandle = Marshal.ReadInt Ptr(mappedViewH andle);

if (windowHandle == IntPtr.Zero)

throw new ArgumentExcepti on("Reading from the specified address in Shared
Memory failed.");

UnmapViewOfFile (mappedViewHand le);

CloseHandle((ui nt)mappedFileHa ndle);

return windowHandle;

CreateMappedFil e i use a size of 200000. (nearly 200 KB)

Pleayse help me.

greetings

Martin

[Martin Priebe]

Thx.
it works.
I write the byteArray to the mapped file.
(Remoting is not fast enough.)

greetings
Martin
"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard .caspershouse.c omschrieb
im Newsbeitrag news:%2******** ********@TK2MSF TNGP02.phx.gbl. ..

Martin,

The problem here is with this line:

Marshal.WriteIn tPtr(mappedView Handle, gfxScreenshot.G etHdc());

You are writing only the handle to the pointer. That DC handle is not
going to be valid outside of the process that created it.

What you need to do is write all the bitmap data to the memory mapped
file, and then read it back out on the other side.

Curious, why aren't you using Remoting or WCF to do this for you? You
could have transferred your Bitmap using much simpler code. My
suggestion, use Named Pipes as the channel if you go this route.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Martin Priebe" <ma***********@ hermos.comwrote in message
news:OY******** ******@TK2MSFTN GP02.phx.gbl...

>Hi,

i tried to use MMF to communicate between 2 processes.
i want to transfer a bitmap between the 2 processes.

i created a mmf in my first process

public IntPtr CreateMMF(FileA ccess access, int size)

{

if (size < 0)

throw new ArgumentExcepti on("The size parameter should be a number
greater than Zero.");

IntPtr memoryFileHandl e = CreateFileMappi ng(0xFFFFFFFF, IntPtr.Zero,
(uint)access , 0, (uint)size, "MMF");

if (memoryFileHand le == IntPtr.Zero)

throw new Exception("Crea ting Shared Memory failed.");

return memoryFileHandl e;

}

i mapped it and write the graphic to it

IntPtr mappedViewHandl e = MapViewOfFile(m mfHandle, (uint)FILE_MAP_ WRITE,
0, 0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

Marshal.WriteI ntPtr(mappedVie wHandle, gfxScreenshot.G etHdc());

UnmapViewOfFil e(mappedViewHan dle);

CloseHandle((u int)mappedViewH andle);

my other process mapped the file but throw an exception "not enough
memory"

IntPtr mappedFileHandl e = OpenFileMapping ((int)FileAcces s.ReadWrite,
false, "MMF");

if (mappedFileHand le == IntPtr.Zero)

throw new Exception("Open ing the Shared Memory for Read failed.");

//here the Exception is thrown

IntPtr mappedViewHandl e = MapViewOfFile(m appedFileHandle ,
(uint)FILE_MAP _READ, 0, 0, 0);

if (mappedViewHand le == IntPtr.Zero)

throw new Exception("Crea ting a view of Shared Memory failed.");

IntPtr windowHandle = Marshal.ReadInt Ptr(mappedViewH andle);

if (windowHandle == IntPtr.Zero)

throw new ArgumentExcepti on("Reading from the specified address in Shared
Memory failed.");

UnmapViewOfFil e(mappedViewHan dle);

CloseHandle((u int)mappedFileH andle);

return windowHandle;

CreateMappedFi le i use a size of 200000. (nearly 200 KB)

Pleayse help me.

greetings

Martin