From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-07-18T22:19:59+09:00
Subject: Re: Bitwise Shift Porting from PHP

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On Mon, 18 Jul 2005, Dan Fitzpatrick wrote:

> I am trying to port the OLE Reader from PHP to read Excel files on any=20
> platform. I am stuck on the following function:
>
> function GetInt4d($data, $pos) {
>  return ord($data[$pos]) | (ord($data[$pos+1]) << 8) | \
>  (ord($data[$pos+2]) << 16) | (ord($data[$pos+3]) << 24);
> }
>
> My ruby version is:
>
> def get_int_4_d(data, pos)
>  (data[pos]) | ((data[pos+1]) << 8) | \
>  ((data[pos+2]) << 16) | ((data[pos+3]) << 24)
> end
>
> It works in some cases but in the example xls file I am using, when=20
> data[pos,0] is the character =FE, the function returns -2 in PHP and 4294=
967294=20
> in Ruby.
>
> Thanks for your help.

your php function should have been named

   GetSignedInt

and your ruby function should be named

   get_unsigned_int_4_d

remember, 2 ** 32 =3D> 4294967296.  for larger numbers your php function wr=
aps
and yields negative numbers - dunno if it's supposed to.  you should look a=
t
String#unpack.  assuming you want to unpack a signed int in lsb order from
data starting at pos your method would become

   def get_int_4_d(data, pos)
     data[pos,4].unpack('i').first
   end

although you should be sure to understand little/big endian issues with reg=
ard
to your data and these functions.

hth.

-a
--=20
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D

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