十六进制数相加校验和计算程序

{-------------------------------------------------------------------------------
  过程名:    16进制数相加效验和程序
  作者:      陈新光
  日期:      2008.07.24
  参数:      AStr: string; AIndex: Integer(从第几个字符开始计算)
  返回值:    string
-------------------------------------------------------------------------------}
function GetCheckStr(AStr: string; AIndex: Integer): string;
var
  newstr1,he,oldstr:string;
  tj:boolean;
  i:integer;
begin
   i:=1;
   he:='';
   tj:=true;
  oldstr:=copy(AStr,AIndex,length(AStr)-AIndex+1);
  while tj=true do
    begin
      newstr1:=copy(oldstr,i,2);
      oldstr:=copy(oldstr,i+2,length(oldstr)-2);
      //开始计算校验和并给he变量
      if he='' then
        begin
          he:=inttohex(strtointdef('$'+newstr1,16)+ strtointdef('$'+'00',16),2);
          he:=rightstr(he,2);
        end
      else
        begin
          he:=inttohex(strtointdef('$'+newstr1,16)+ strtointdef('$'+he,16),2);
          he:=rightstr(he,2);
        end;
      if  length(oldstr) =0 then tj:=false;
    end;
  Result:= AStr+he;
end;