procedure CopyTIdInt64(
    const ASource: Int64; 
    var VDest: TIdBytes; 
    const ADestIndex: Integer
);

CopyTIdInt64 is a procedure used to copy bytes in the Int64 value specified in ASource into the TIdBytes argument specified in VDest. 

ADestIndex indicates the initial byte position in VDest where copied byte values are stored. ADestIndex is a zero-based offset into the array of bytes. 

On the .Net platform, CopyTIdInt64 uses the GetBytes method from the System.BitConverter class in the FCL to access the byte values in ASource. The Copy method in the System.Array class from the FCL is called to perform actual copy operation. 

For all other platforms where the Borland RTL is implemented, the Move procedure from SysUtils.pas is called to copy values from ASource into VDest at the indicated position using the native size of the Int64 data type.

Copying bytes from an an Int64 value into TIdBytes. 

[Delphi]

  var
    ASrc: Int64;
    ADst: TIdBytes;

  ...

  ASrc := 123456;
  SetLength(ADst, 4);
  CopyTIdInt64(ASrc, ADst, 0);