Delphi 十六进制，十进制，字符串之间的类型转换

//内存数据(字符串或者内存指针)转化为十六进制字符串
//'111'==>>'31313131'
//E5 8D 40 00 45 72 72 6F==>>'E58D40004572726F'
function StrToHex(Value: PAnsiChar; Len: Integer): AnsiString;
var
  I: Integer;
begin
  Result := '';
  for I := 0 to Len - 1 do
    Result := Result + IntToHex(Ord(Value[I]), 2);
end;

//十六进制数的字符串转化为整形 '004543C4'==>>4539332
function HexToInt(Hex: AnsiString): Integer;
var
  I, Res: Integer;
  ch: AnsiChar;
begin
  Res := 0;
  for I := 0 to Length(Hex) - 1 do
  begin
    ch := Hex[I + 1];
    if (ch >= '0') and (ch <= '9') then
      Res := Res * 16 + Ord(ch) - Ord('0')
    else if (ch >= 'A') and (ch <= 'F') then
      Res := Res * 16 + Ord(ch) - Ord('A') + 10
    else if (ch >= 'a') and (ch <= 'f') then
      Res := Res * 16 + Ord(ch) - Ord('a') + 10
    else raise Exception.Create('Error: not a Hex String');
  end;
  Result := Res;
end;

//十六进制字符串转化为对应的字符 '31313131'==>>'111'
function HexToStr(Value: AnsiString): AnsiString;
var
  I: Integer;
begin
  Result := '';
  for I := 1 to Length(Value) do
  begin
    if ((I mod 2) = 1) then
      Result := Result + AnsiChar(HexToInt(Copy(Value, I, 2)));
  end;
end;