@Kou, we removed that bit, so Buffer::mutable_data is always inline now. @Saul, you will want to create a C wrapper for arrow::Buffer so you can manage memory lifetime from C. Depending on the kind of Buffer you have, it may not be as simple as calling free(...) on its internal data.
- Wes On Tue, Mar 27, 2018 at 10:31 AM, Kouhei Sutou <k...@clear-code.com> wrote: > Hi, > > It may be wrong but you may need to add -DNDEBUG flag to C > compiler. > > > Thanks, > -- > kou > > In <CANapY_LzahViR9e7e90H=wq3j0tnbZJe1Vm=j7=vvyqawnc...@mail.gmail.com> > "Re: Using Plasma with xnd" on Tue, 27 Mar 2018 13:41:49 +0000, > Saul Shanabrook <s.shanabr...@gmail.com> wrote: > >> Ah, I see I can use garrow_buffer_get_mutable_data from c_glib. >> >> On Tue, Mar 27, 2018 at 9:29 AM Saul Shanabrook <s.shanabr...@gmail.com> >> wrote: >> >>> I am in the process of changing over my C wrapper to work with Arrow >>> 0.9.0. One change is that the plasma APIs now use arrow::Buffer instead of >>> of raw pointers, in Create and Get. >>> >>> In my C wrapper for Create, I need to get the mutable data pointer from >>> the arrow::Buffer, after it is created. Here is my current implementation: >>> https://github.com/plures/pxnd/blob/84e9403ef3811e0893e12076455d7cbc49c39358/libplasma/plasma.cc#L56-L75 >>> I do something similar to the Python wrapper around plasma: >>> https://github.com/apache/arrow/blob/f9f8320339692d4134d1ef42c32cb7c8d547593e/python/pyarrow/plasma.pyx#L300-L307 >>> >>> >>> However, this fails to link, I think because the mutable_data method is >>> defined in the class and so is inline. So it doesn't show up in the >>> libarrow.dylib/libarrow.a archive. Let me know if I am missing something >>> obvious, this is just my hypothesis for why it isn't working. >>> >>> Is there a way for a third party library to get the pointer to the data >>> from a arrow::Buffer? >>> >>> On Wed, Mar 7, 2018 at 10:59 AM Wes McKinney <wesmck...@gmail.com> wrote: >>> >>>> Where are you going to make Plasma requests, in Python or in C? >>>> >>>> * If in Python, use the buffer protocol to access the memory in C >>>> https://docs.python.org/3/c-api/buffer.html#bufferobjects >>>> * If in C, then I would suggest adding extern "C" APIs directly in >>>> libplasma.so so you can connect to the Plasma store and make requests >>>> directly in C. >>>> >>>> I want to make 100% sure that you need to interact with the Plasma >>>> client in C before I send you down that path. Here's an example of a C >>>> API embedded in an otherwise C++ library >>>> https://github.com/wesm/feather/blob/master/cpp/src/feather/feather-c.h. >>>> >>>> - Wes >>>> >>>> On Wed, Mar 7, 2018 at 10:53 AM, Saul Shanabrook <s.shanabr...@gmail.com> >>>> wrote: >>>> > Hey Wes, >>>> > >>>> > Since all our logic for writing and reading the data is written in C, we >>>> > need to be get access to the memory in C as well. I think it makes sense >>>> > then for me to work on creating a C++ wrapper around Plasma that exports >>>> > what is necessary in C. Should that be in Arrow GLib? >>>> > >>>> > Best, >>>> > Saul >>>> > >>>> > On Tue, Mar 6, 2018 at 11:49 PM Wes McKinney <wesmck...@gmail.com> >>>> wrote: >>>> > >>>> >> hi Saul -- I think the easiest solution here is the buffer/memoryview >>>> >> protocol. You won't have to touch the Cython or C++ API from pyarrow >>>> >> if you do this. >>>> >> >>>> >> You can interact with a Buffer object like any other Python object >>>> >> implementing the buffer protocol. See numpy.frombuffer as an example >>>> >> of a function that interacts with such objects. I would suggest adding >>>> >> a method to xnd method for this. >>>> >> >>>> >> If you need to interact with Plasma from C then things will be more >>>> >> complicated -- Robert or Philipp should be able to advise in this >>>> >> case. >>>> >> >>>> >> - Wes >>>> >> >>>> >> On Tue, Mar 6, 2018 at 4:55 PM, Saul Shanabrook < >>>> s.shanabr...@gmail.com> >>>> >> wrote: >>>> >> > Hey Wes, >>>> >> > >>>> >> > I don't have much experience doing C + Python + Cython development, >>>> so I >>>> >> am >>>> >> > probably missing something obvious, but reading the Cython docs, >>>> >> > < >>>> >> >>>> https://cython.readthedocs.io/en/latest/src/userguide/external_C_code.html#public-declarations >>>> >> > >>>> >> > it >>>> >> > seems like I can only access types marked as public from C code. >>>> When I >>>> >> > compile arrow locally, I do get some C++ headers for the plasma code, >>>> >> but I >>>> >> > don't think I can use them from C code either. >>>> >> > >>>> >> > Best, >>>> >> > Saul >>>> >> > >>>> >> > >>>> >> > >>>> >> > On Tue, Mar 6, 2018 at 3:12 PM Wes McKinney <wesmck...@gmail.com> >>>> wrote: >>>> >> > >>>> >> >> hi Saul, >>>> >> >> >>>> >> >> Are you able to use the buffer/memoryview protocol? Instances of >>>> >> >> pyarrow.Buffer, like PlasmaBuffer, support this >>>> >> >> >>>> >> >> >>>> >> >>>> https://github.com/apache/arrow/blob/master/python/pyarrow/plasma.pyx#L182 >>>> >> >> >>>> >> >> - Wes >>>> >> >> >>>> >> >> On Tue, Mar 6, 2018 at 3:09 PM, Saul Shanabrook < >>>> s.shanabr...@gmail.com >>>> >> > >>>> >> >> wrote: >>>> >> >> > I am trying to use the Plasma store to back xnd objects. Xnd ( >>>> >> >> > https://xnd.readthedocs.io/en/latest/xnd/index.html) is a >>>> container >>>> >> >> library >>>> >> >> > in C that has Python bindings. I would like to get a pointer to >>>> the >>>> >> >> > allocated memory after creating or get an object in Plasma. I see >>>> that >>>> >> >> this >>>> >> >> > is supported in the C++ API ( >>>> >> >> > >>>> >> >> >>>> >> >>>> https://arrow.apache.org/docs/cpp/classplasma_1_1_plasma_client.html#ac18ab9cc792c620a97a3dcb165e0ecd7 >>>> >> >> ) >>>> >> >> > but not in the python API (as far as I can tell). Is it possible >>>> to >>>> >> use >>>> >> >> the >>>> >> >> > C++ Plasma API from a C project? If not, would it make sense to >>>> expose >>>> >> >> > pointer access on the Python API using capsules >>>> >> >> > https://docs.python.org/3.6/c-api/capsule.html >>>> >> >> > <https://docs.python.org/3.6/c-api/capsule.html#capsules>? >>>> >> >> >>>> >> >>>> >>>
