Re: Is there any convenient CopyMemory function in Phobos?

[annonimous]

See you need copy only if     if (pEmfRecord->iType ==
EMR_RECTANGLE).
You can cast it and check it, else you perform with old
parameters.

Something like this

       if (pEmfRecord->iType == EMR_RECTANGLE)
       {
          pEmfr->iType = EMR_ELLIPSE ;

          PlayEnhMetaFileRecord (hdc, pHandleTable, pEmfr,
iHandles) ;

          free (pEmfr) ;
      }
      else
           PlayEnhMetaFileRecord (hdc, pHandleTable, pEmfRecord,
iHandles) ;

On Monday, 13 June 2011 at 23:31:56 UTC, Andrej Mitrovic wrote:

Apparently in the Windows API there's a whole lot of byte-copying going around.

Here's an example:

int CALLBACK EnhMetaFileProc (HDC hdc, HANDLETABLE * pHandleTable,

                              CONST ENHMETARECORD * pEmfRecord,
                              int iHandles, LPARAM pData)
{
     ENHMETARECORD * pEmfr ;

     pEmfr = (ENHMETARECORD *) malloc (pEmfRecord->nSize) ;

     CopyMemory (pEmfr, pEmfRecord, pEmfRecord->nSize) ;

     if (pEmfr->iType == EMR_RECTANGLE)
          pEmfr->iType = EMR_ELLIPSE ;

PlayEnhMetaFileRecord (hdc, pHandleTable, pEmfr, iHandles) ;

     free (pEmfr) ;

     return TRUE ;
}

The nSize field specifies the byte size of the structure pointed to by pEmfRecord. The reason copying is required is because of this code:

     if (pEmfr->iType == EMR_RECTANGLE)
          pEmfr->iType = EMR_ELLIPSE ;

pEmfRecord itself is const, so new memory has to be allocated first and then the memory from pEmfRecord is copied there, and then the iType field is changed. A simple pointer dereference won't copy all the bytes, since this is one of those variable-length structure types

you often see in C code.

In D I've used the slice trick to assign a byte range of data from one

memory location to another:
extern (Windows)
int EnhMetaFileProc(HDC hdc, HANDLETABLE* pHandleTable,
                    const ENHMETARECORD* pEmfRecord,
                    int iHandles, LPARAM pData)
{
    ENHMETARECORD* pEmfr;
    immutable newlength = pEmfRecord.nSize;

    pEmfr = cast(ENHMETARECORD*)GC.malloc(newlength);

(cast(ubyte*)pEmfr)[0..newlength] = (cast(ubyte*)pEmfRecord)[0..newlength];

    if (pEmfr.iType == EMR_RECTANGLE)
        pEmfr.iType = EMR_ELLIPSE;

    PlayEnhMetaFileRecord(hdc, pHandleTable, pEmfr, iHandles);

    GC.free(pEmfr);
    return TRUE;
}

That's quite ugly.. Is there a Phobos/Druntime and maybe

platform-independent function that can do byte-memory copies in a

simple way? Something like this is what I need:
CopyBytes(dest, src, bytecount);

Btw, CopyMemory is a WinAPI specific function, but I can't even link

to it (it's actually an alias to RtlCopyMemory, but it's not in
kernel32.lib for some reason even though MSDN says it is).