June 13, 2011 Is there any convenient CopyMemory function in Phobos? | ||||
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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). |
July 05, 2013 Re: Is there any convenient CopyMemory function in Phobos? | ||||
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Posted in reply to Andrej Mitrovic | 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).
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