numpy-discussion

[Numpy-discussion] Please test the SVN branch

[Travis O. <oli...@ie...>]

I made some fixes to the "asbuffer" code which let me feel better about 
exposing it in NumPy (where it is now named int_asbuffer).

This code takes a Python integer and a size and returns a buffer object 
that points to that memory.  A little test is performed by trying to 
read (and possibly write if a writeable buffer is requested) to the 
first and last elements of the buffer.  Any segfault is trapped and used 
to raise a Python error indicating you can't use that area of memory. 

It doesn't guarantee you won't shoot yourself, but it does make it more 
difficult to segfault Python.  Previously a simple int_asbuffer(3423423, 
5) would have segfaulted (unless by chance you the memory area 3423423 
happens to be owned by Python).

I have not tested the code on other platforms to make sure it works as 
expected, so please try and compiled it.

-Travis

Re: [Numpy-discussion] Please test the SVN branch

[Nils W. <nw...@ia...>]

Travis Oliphant wrote:
> I made some fixes to the "asbuffer" code which let me feel better about 
> exposing it in NumPy (where it is now named int_asbuffer).
>
> This code takes a Python integer and a size and returns a buffer object 
> that points to that memory.  A little test is performed by trying to 
> read (and possibly write if a writeable buffer is requested) to the 
> first and last elements of the buffer.  Any segfault is trapped and used 
> to raise a Python error indicating you can't use that area of memory. 
>
> It doesn't guarantee you won't shoot yourself, but it does make it more 
> difficult to segfault Python.  Previously a simple int_asbuffer(3423423, 
> 5) would have segfaulted (unless by chance you the memory area 3423423 
> happens to be owned by Python).
>
> I have not tested the code on other platforms to make sure it works as 
> expected, so please try and compiled it.
>
> -Travis
>
>
> -------------------------------------------------------------------------
> Using Tomcat but need to do more? Need to support web services, security?
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>   
Numpy version 1.0.dev3315
Scipy version 0.5.2.dev2254

Works fine here. All tests passed !
x86_64 x86_64 x86_64 GNU/Linux

Nils


 

Re: [Numpy-discussion] Please test the SVN branch

[Stefan v. d. W. <st...@su...>]

On Thu, Oct 12, 2006 at 12:38:51AM -0600, Travis Oliphant wrote:
>=20
> I made some fixes to the "asbuffer" code which let me feel better about=
=20
> exposing it in NumPy (where it is now named int_asbuffer).
>=20
> This code takes a Python integer and a size and returns a buffer object=
=20
> that points to that memory.  A little test is performed by trying to=20
> read (and possibly write if a writeable buffer is requested) to the=20
> first and last elements of the buffer.  Any segfault is trapped and use=
d=20
> to raise a Python error indicating you can't use that area of memory.=20
>=20
> It doesn't guarantee you won't shoot yourself, but it does make it more=
=20
> difficult to segfault Python.  Previously a simple int_asbuffer(3423423=
,=20
> 5) would have segfaulted (unless by chance you the memory area 3423423=20
> happens to be owned by Python).

Some argument checking and a docstring would be helpful.  I guessed
wrong the first time:

In [1]: x =3D N.array([1,2,3])

In [4]: y =3D N.int_asbuffer(x.size,x.__array_interface__['data'][0])

In [5]: y[0]

Segmentation fault

Out of curiosity, why does the following outputs differ:

In [39]: y =3D N.int_asbuffer(0L,x.size)
-------------------------------------------------------------------------=
--
exceptions.SystemError                               Traceback (most rece=
nt call last)

/home/stefan/<ipython console>=20

SystemError: error return without exception set

In [40]: y =3D N.int_asbuffer(1L,x.size)
-------------------------------------------------------------------------=
--
exceptions.ValueError                                Traceback (most rece=
nt call last)

/home/stefan/<ipython console>=20

ValueError: cannot use memory location as a buffer.

Thanks for your work on this.

Cheers
St=E9fan

Re: [Numpy-discussion] Please test the SVN branch

[Tim H. <tim...@ie...>]

Travis Oliphant wrote:
> I made some fixes to the "asbuffer" code which let me feel better about 
> exposing it in NumPy (where it is now named int_asbuffer).
>
> This code takes a Python integer and a size and returns a buffer object 
> that points to that memory.  A little test is performed by trying to 
> read (and possibly write if a writeable buffer is requested) to the 
> first and last elements of the buffer.  Any segfault is trapped and used 
> to raise a Python error indicating you can't use that area of memory. 
>
> It doesn't guarantee you won't shoot yourself, but it does make it more 
> difficult to segfault Python.  Previously a simple int_asbuffer(3423423, 
> 5) would have segfaulted (unless by chance you the memory area 3423423 
> happens to be owned by Python).
>
> I have not tested the code on other platforms to make sure it works as 
> expected, so please try and compiled it.
>   
FWIW, it compiles fine and passes all tests under Visual Studio and 
Python 2.4.3. I haven't tried to use it though.

-tim


> -Travis
>
>
> -------------------------------------------------------------------------
> Using Tomcat but need to do more? Need to support web services, security?
> Get stuff done quickly with pre-integrated technology to make your job easier
> Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
> http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> _______________________________________________
> Numpy-discussion mailing list
> Num...@li...
> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>
>
>   

Re: [Numpy-discussion] Please test the SVN branch

[Christopher B. <Chr...@no...>]

Travis Oliphant wrote:
> I made some fixes to the "asbuffer" code which let me feel better about 
> exposing it in NumPy (where it is now named int_asbuffer).
> 
> This code takes a Python integer and a size and returns a buffer object 
> that points to that memory.

If I understand this correctly, maybe it should be called something like:

int_asbuffer_pointer

or something with "pointer" in it.

I sure didn't expect that meaning from "asbuffer" or in-asbuffer"

Otherwise -- nice idea!

-Chris

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