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Stringstream to clipboard with memcpy?

LsDefect (61)
Hi. I'm trying to, as the title suggests, copy the contents of a stringstream to the clip board. Here's what I have:

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stringstream ss;

ss << "Example string";

HANDLE h;
h = GlobalAlloc(GMEM_FIXED, sizeof(ss.str().c_str()));

memcpy(h, ss.str().c_str(), sizeof(ss.str().c_str()));

OpenClipboard(NULL);
EmptyClipboard();
SetClipboardData(CF_TEXT, h);
CloseClipboard();


The first four characters come out right and the rest is garbage.
Cubbi (4774)
it's ss.str().size(), not sizeof.
Last edited on
LsDefect (61)
Ty sir.
cire (8284)
You're suprised that sizeof(const char*) isn't the length of your string?

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#include <sstream>
#include <cstring>
#include <cstdlib>

#include <Windows.h>

using std::stringstream ;

bool PasteToClipboard(const std::string& text)
{
    bool succeeded = false ;

    if ( HANDLE clipdata = GlobalAlloc(GMEM_FIXED, text.length()+1) )
    {
        std::memcpy(clipdata, text.data(), text.length()+1) ;

        if ( OpenClipboard(NULL) )
        {
            if ( EmptyClipboard() && SetClipboardData(CF_TEXT, clipdata) )
              succeeded = true ;  

            CloseClipboard() ;
        }

        if ( !succeeded )
            GlobalFree(clipdata) ;
    }

    return succeeded ;
}

int main()
{
    stringstream ss;

    ss << "Example string";

    return PasteToClipboard(ss.str()) ? EXIT_SUCCESS : EXIT_FAILURE ;
}
andywestken (4094)
Note that the MSDN entry on the SetClipboardData function states:

If the hMem parameter identifies a memory object, the object must have been allocated using the function with the GMEM_MOVEABLE flag.

Rather than the GMEM_FIXED you are using. See the following article for further information (including the need to unlock the memory before closing the Clipboard)

SetClipboardData function
http://msdn.microsoft.com/en-us/library/windows/desktop/ms649051%28v=vs.85%29.aspx

And as used in this examples on this page

Using the Clipboard
http://msdn.microsoft.com/en-us/library/windows/desktop/ms649016%28v=vs.85%29.aspx

Andy
Last edited on
cire (8284)
I swear I verified GMEM_FIXED was correct. Maybe the Alzheimer's is kicking in.

At any rate, corrected code:

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#include <sstream>
#include <cstring>
#include <cstdlib>

#include <Windows.h>

bool PasteToClipboard(const std::string& text)
{
    bool succeeded = false ;

    if ( HANDLE clipdata = GlobalAlloc(GMEM_MOVEABLE, text.length()+1) )
    {
        if ( auto clipdataptr = GlobalLock(clipdata) )
        {
            std::memcpy(clipdataptr, text.data(), text.length()+1) ;
            GlobalUnlock(clipdata) ;

            if ( OpenClipboard(NULL) )
            {
                if ( EmptyClipboard() && SetClipboardData(CF_TEXT, clipdata) )
                  succeeded = true ;  

                CloseClipboard() ;
            }
        }

        if ( !succeeded )
            GlobalFree(clipdata) ;
    }

    return succeeded ;
}

int main()
{
    std::stringstream ss;

    ss << "Example string";

    return PasteToClipboard(ss.str()) ? EXIT_SUCCESS : EXIT_FAILURE ;
}
andywestken (4094)
Hmmm...

I have found this Microsoft example which is using GEM_FIXED... it's part of the MFC documentation. As it disagrees with the entry for the SetClipboardData function, I am suspicious of it.

Clipboard: Using the Windows Clipboard
http://msdn.microsoft.com/en-gb/library/vstudio/80db3kax%28v=vs.100%29.aspx

Andy
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