How to copy array?

Question

Hello,

I have such a basic problem in Delphi,I can't solve it.

My Code:

Note:DataR is local in the methods below,but usually it's a class var.Just for the concept it's local.

class procedure TCelebrity.BeginRead(var input:Array of byte);
var DataR:Array of byte;
begin
  VirtualFree(@DataRead,High(DataRead),MEM_RELEASE);
  SetLength(DataR,Length(input));
  Move(input,DataR,Length(input));
end;

This compiles,but after Move() is executed DataR = nil.

Second try:

class procedure TCelebrity.BeginRead(var input:Array of byte);
var DataR:Array of byte;
begin
  VirtualFree(@DataRead,High(DataRead),MEM_RELEASE);
  SetLength(DataR,Length(input));
  DataR := Copy(input,0,Length(input));
end;

This doesn't compile at all.Error at the third line(DataR := Copy(input....) saying "Incompatible types".

Where's the problem? They are all Array of byte!

Answer 1

Why not use FOR?

SetLength(DataR,Length(input));
for i:=Low(input) to High(input) do
  DataR[i]:=input[i];

BTW: if you want to have arrays passing as parameter, you should declare them as a type, eg:

type
  TMyArray = array of byte;

and use TMyArray as parameters type.

Edit: I was notified about i lower value. In my original post it was for i:=0, but i:=Low(input) is safer and more pure.

Answer 2

Try:

class procedure TCelebrity.BeginRead(var input:Array of byte);
var DataR:Array of byte;
begin
  VirtualFree(@DataRead,High(DataRead),MEM_RELEASE);
  SetLength(DataR,Length(input));
  Move(input[0],DataR,Length(input));
end;

Answer 3

try this

type
  TByteDynArray = array of Byte;

function CopyData(const Input:array of Byte):TByteDynArray;
begin
  SetLength(Result, Length(Input));
  Move(input[0], Result[0], Length(Input));
end;