Re: Rados and user-provided buffers

[Rutger ter Borg <rutger@terborg.net>]

On 2013-09-18 22:01, Sage Weil wrote:
>
> The read-into-existing-buffer is only wired up properly for the C
> interface.  For the C++ it isn't generally necessary: we allocate and read
> the data off the network,a nd pass the reference directly back to the user
> without making another copy.  The 2010 thread is about similarly avoiding
> such a copy for the C API.  We didn't contemplate the situation where you
> specifically want the bytes to go to a particular address via C++.  If
> that's what you need, the C++ API needs to be extended, or you can just
> use the C call for that case.
>
> sage
>

Hey Sage,

my particular use case is a pager that uses Rados as a backend. Striping 
of pages works identical to the striping mechanism of Ceph. Reads and 
writes of multiple pages may be combined into one aio_ call with one 
bufferlist. Pages are allocated by the pager.

AFAICT, the C call provides reading into a contiguous buffer, whereas I 
would like to read into a bufferlist. What would need to be done to add 
support for this in rados?

Thanks,

Rutger