C# Discussion Boards - CodeProject

18-Jun-02 5:45

My latest place that I'm stuck...

I call a function using DllImport that returns a pointer to some memory. How do I now write it to a file? The Write method doesn't take a pointer.

Thanks guys!

----------------------------------------------------------------

IntPtr pOutputBuffer = IntPtr.Zero;
IntPtr pInputBuffer = bmData.Scan0;

int iResult = wsq_compress_raw( pInputBuffer, ..., ref pOutputBuffer, ... );

FileStream pStream = new FileStream( strPathName, FileMode.Create, FileAccess.Write );
BinaryWriter pWriter = new BinaryWriter( pStream );

pWriter.Write( pOutputBuffer, 0, iCompressFileSize ); // Error

pWriter.Close( );
pStream.Close( );

18-Jun-02 6:11

This should probably work:

unsafe
{
pWriter.Write((byte*)pOutputBuffer.ToPointer(),0,iCompressFileSize);
}

Zombies with Coffee, LLC18-Jun-02 6:23

18-Jun-02 6:23

Thanks! I was headed there a few times, but...

unsafe
{
pWriter.Write((byte*)pOutputBuffer.ToPointer(),0,iCompressFileSize);
}

Gives the error: cannot convert from a byte* to byte[]

unsafe
{
pWriter.Write((byte[])pOutputBuffer.ToPointer(),0,iCompressFileSize);
}

Gives the error: cannot convert type void* to byte[]

18-Jun-02 7:25

I'm sorry I have to keep stabbing in the dark but offhand I can't recreate an example to test. So here's the next attempt:

Marshal To the Rescue!!! (System.Runtime.InteropServices.Marshal)

byte[] ba = new byte[iCompressFileSize];
Marshal.Copy(pOutputBuffer,ba,0,iCompressFileSize);
pWriter.Write(ba,0,iCompressFileSize);

Zombies with Coffee, LLC18-Jun-02 9:14

18-Jun-02 9:14

Perfect!!! Nice job and thanks!

18-Jun-02 9:54

No Prob. I must say I am a little dissapointed in this solution though. Having to allocate and copy the data through another byte[] will slow down your app, especially if this is a non-trivial file you're trying to write.

I'm certain there has to be a way to marshal a memory location as a standard byte[]. After all, its perfectly legal to do this:

byte[] ba = new byte[100];
byte* pb = ba;
*pb = 1;

Zombies with Coffee, LLC18-Jun-02 10:30

18-Jun-02 10:30

I totally agree with you. The memory is already out there, all I need is a byte pointer to it.

But with the bounds checking in place, I don't see a good way of doing it.

howto: multi-languaged gui

Eric Gunnerson (msft)19-Jun-02 5:54

Eric Gunnerson (msft)

19-Jun-02 5:54

I can't think of any good way to do it, either.

It's trivial in C# to get a pointer to a managed piece of data as long as you fix the managed object, but in this case, you've got a pointer to an unmanaged piece of data.

Rüpel18-Jun-02 0:29

Rüpel

18-Jun-02 0:29

hi there,

i want my app to appear in different languages. the user may choose his prefered language in an options-dialog.

which way would YOU do that?
* define a seperate class, containung a string-member for each string-constant?
* some resource-thing (as it was with the string-tables in C++/MFC-times)
* is there something built-in in C# for that purpose?
* ...

what about the language-files (containing all the strings)? is xml overkill?

i'm currently in the phase of thinking about it, implementing comes later. my current favorite is as described - a class containing a string-member for each message initialized by an xml-file for each language. so when the user changes the language, the class just reads a different xml-file, rewrites all of its string-members and everything is redrawn/reassigned. but i'm not sure, if this is the best way...

so if anyone has some hints, i would be glad to read them...

Rose | [Rose]

:wq

Zombies with Coffee, LLC18-Jun-02 6:09

18-Jun-02 6:09

Have you seen the 'Language' property?

Go to your dialog, change the 'Language' to the desired locale, and then .NET handles it for you. Was one of the neatest features I've seen in the IDE yet.

Rüpel18-Jun-02 20:51

Rüpel

18-Jun-02 20:51

what's the use? it didn't changed anything (i thought at least the system-menu-entries (minimize, maximize, move, etc.) should have changed)

btw: this doesn't help with the menu and labels etc. because I assign the text-properties myself (or is there some hidden dictionary somewhere) Eek! | :eek:

- and when i want my application to appear in a completely different language, all texts have to be changed.

or am i getting something wrong... Unsure | :~

:wq

Zombies with Coffee, LLC19-Jun-02 3:55

19-Jun-02 3:55

No, it doesn't change anything. You need to change it.

Make a new dialog and put the text field 'Name:'
Now change the language to French and rename the field 'Nom:'

Now change the language back to English.

Cool, eh?