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Message-ID: <19e0530f0507151133516c52b7@mail.gmail.com>
Date: Fri, 15 Jul 2005 14:33:58 -0400
From: Davanum Srinivas <davanum@gmail.com>
Reply-To: dims@apache.org
To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
Subject: Re: UnboundedFifoBuffer - serialization bug + fix
In-Reply-To: 
 <ADD3F72CEE4D4945967DB6A9B23B9B4B04866837@exnjmb16.nam.nsroot.net>
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References: <ADD3F72CEE4D4945967DB6A9B23B9B4B04866837@exnjmb16.nam.nsroot.net>

Applied to SVN. thanks.

-- dims

On 7/15/05, Knych, Thomas [IT] <thomas.knych@citigroup.com> wrote:
> Dims -
>=20
> The patch should be:
>=20
> private void readObject(ObjectInputStream in) throws IOException, ClassNo=
tFoundException {
>         in.defaultReadObject();
>         int size =3D in.readInt();
> -       buffer =3D new Object[size];
> +       buffer =3D new Object[size + 1];
>         for (int i =3D 0; i < size; i++) {
>                 buffer[i] =3D in.readObject();
>         }
>         head =3D 0;
>         tail =3D size;
> }
>=20
>=20
>=20
> Setting tail =3D size - 1; just caused another bug (ie you couldn't get t=
he last element in the buffer). This is because tail is supposed to point t=
o the next unused cell in the buffer array. By creating the buffer to be si=
ze + 1, tail will be set to a valid cell within buffer that is empty (but t=
he cell before it has an element in it), and the class works properly.
>=20
> Thanks,
>=20
> -TK
>=20
>=20
> -----Original Message-----
> From: Davanum Srinivas [mailto:davanum@gmail.com]
> Sent: Thursday, July 14, 2005 8:26 AM
> To: Jakarta Commons Developers List
> Cc: Knych, Thomas [IT]; *GT GFI ALF Development
> Subject: Re: UnboundedFifoBuffer - serialization bug + fix
>=20
>=20
> Jordan,
>=20
> So the patch is the one-liner in previous email? ("tail =3D size - 1;"?)
>=20
> -- dims
>=20
> On 7/13/05, Krey, Jordan [IT] <jordan.krey@citigroup.com> wrote:
> > Commons Collections-
> >
> > Correction.
> >
> > 116     /***
> > 117      * Read the buffer in using a custom routine.
> > 118      *
> > 119      * @param in  the input stream
> > 120      * @throws IOException
> > 121      * @throws ClassNotFoundException
> > 122      */
> > 123     private void readObject(ObjectInputStream in) throws IOExceptio=
n, ClassNotFoundException {
> > 124         in.defaultReadObject();
> > 125         int size =3D in.readInt();
> > 126         buffer =3D new Object[size + 1];     <-- must be size + 1 i=
n order to satisfy the condition of Iterator.hasNext()
> > 127         for (int i =3D 0; i < size; i++) {
> > 128             buffer[i] =3D in.readObject();
> > 129         }
> > 130         head =3D 0;
> > 131         tail =3D size;
> > 132     }
> >
> > For example, previously, if size =3D=3D 1 and the object was read in.  =
The next iteration would fail at the increment() and hasNext() methods:
> > 246     private int increment(int index) {
> > 247         index++;
> > 248         if (index >=3D buffer.length) {       <-- buffer length =3D=
=3D 1
> > 249             index =3D 0;                              <-- index now=
 set back to 0
> > 250         }
> > 251         return index;
> > 252     }
> >
> > 279             public boolean hasNext() {
> > 280                 return index !=3D tail;       <-- index =3D=3D 0, t=
ail =3D=3D 1
> > 281
> > 282             }
> >
> > Now:
> > 246     private int increment(int index) {
> > 247         index++;
> > 248         if (index >=3D buffer.length) {       <-- buffer length =3D=
=3D 2
> > 249             index =3D 0;
> > 250         }
> > 251         return index;                               <-- index =3D=
=3D 1
> > 252     }
> >
> > 279             public boolean hasNext() {
> > 280                 return index !=3D tail;       <-- index =3D=3D 1, t=
ail =3D=3D 1
> > 281
> > 282             }
> >
> > -Jordan & Citigroup Analytics Dev team
> >
> >
> > -----Original Message-----
> > From: Knych, Thomas [IT]
> > Sent: Wednesday, July 13, 2005 10:15 AM
> > To: 'commons-dev@jakarta.apache.org'
> > Cc: *GT GFI ALF Development
> > Subject: UnboundedFifoBuffer - serialization bug + fix
> >
> >
> > Commons Collections-
> >
> > We recently found a bug in the serialization of UnboundedFifoBuffer. Ap=
parently when the object is serialized and then read back in the tail varia=
ble is set to size; it should actually be set to size - 1 because otherwise=
 the tail element will be beyond the bounds of the internal array. Among ot=
her things this will cause the iterator to infinitely loop.
> >
> >
> > Attached is our own local patch...
> >
> > Thanks!
> >
> > -TK & Citigroup Analytics Dev team
> >
> >
> >
> >
> > --- /home/tk53899/tmp/commons-colls/commons-collections-3.1/src/java/or=
g/apache/commons/collections/buffer/UnboundedFifoBuffer.java   2005-07-13 1=
0:08:12.000000000 -0400
> > +++ org/apache/commons/collections/buffer/UnboundedFifoBuffer.java     =
 2005-07-13 10:01:56.000000000 -0400
> > @@ -50,7 +50,7 @@
> >   * This class is Serializable from Commons Collections 3.1.
> >   *
> >   * @since Commons Collections 3.0 (previously in main package v2.1)
> > - * @version $Revision: 1.9 $ $Date: 2004/06/01 22:57:18 $
> > + * @version $Revision: 1.1.2.1 $ $Date: 2005/07/13 14:01:56 $
> >   *
> >   * @author Avalon
> >   * @author Federico Barbieri
> > @@ -128,7 +128,7 @@
> >              buffer[i] =3D in.readObject();
> >          }
> >          head =3D 0;
> > -        tail =3D size;
> > +        tail =3D size - 1;
> >      }
> >
> >      //----------------------------------------------------------------=
-------
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: commons-dev-unsubscribe@jakarta.apache.org
> > For additional commands, e-mail: commons-dev-help@jakarta.apache.org
> >
> >
>=20
>=20
> --
> Davanum Srinivas -http://blogs.cocoondev.org/dims/
>=20
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: commons-dev-unsubscribe@jakarta.apache.org
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>=20
>=20


--=20
Davanum Srinivas -http://blogs.cocoondev.org/dims/

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