CODEWITHSUNDEEP
delphimemorycopy
John
John

Reputation: 33

delphi CopyMemory from index

I am using Delphi 7. Could you tell me if there is or can be found somewhere a procedure which acts like: CopyMemory but I would be able to copy memory from the specific number of byte.

I need something with the following signature:

procedure CopyMemory(Destination: Pointer; Source: Pointer; Length: DWORD; fromByte: Integer);

I need this, because I have to send unsent bytes over tcpip and that's the reason why I have to extract unsent bytes stored in the memory.

I have looked in the source and I would need to rewrite a little asm section. I have not touched asm for years and I would rather stay with something reliable ..

Thanks!

Upvotes: 3

Views: 3108

Answers (4)

Arnaud Bouchez
Arnaud Bouchez

Reputation: 43053

You could use this:

procedure CopyMemory(Destination: Pointer; Source: Pointer; Length, fromByte: Integer);
begin
  move(PAnsiChar(Source)[frombyte],PAnsichar(Dest)[frombyte],Length-fromByte);
end;

And don't rewrite the moving part. Rely on the VCL version. Or use the FastCode version if you need.

Upvotes: 4

David Heffernan
David Heffernan

Reputation: 613422

procedure CopyMemory(Src, Dest: Pointer; Len: Cardinal; Offset: Integer);
var
  OffsetSrc: ^Byte;
begin
  OffsetSrc := Src;
  inc(OffsetSrc, Offset);
  Move(OffsetSrc^, Dest^, Len);
end;

But I think I'd probably prefer to do the pointer arithmetic outside a helper function.

Upvotes: 3

ain
ain

Reputation: 22759

You could still use CopyMemory, just use the address of the fist unsent byte as the source pointer.

Upvotes: 1

jpfollenius
jpfollenius

Reputation: 16620

Just pass the address of the first byte you want to copy. Make sure you adjust the length.

Pseudocode:

var
  Dest   : TBytes;
  Source : TBytes;
...
SetLength (Dest, Length (Source) - FromByte);
CopyMemory (@Dest[0], @Source[FromByte], Length (Source) - FromByte);

Upvotes: 0

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