Hi Wes,
Thanks for the quick reply! To be clear, the usage I'm working on needs to own
both the Open FileDescriptor and corresponding mapped memory. In other words
...
SAS component does both open() and mmap() which could be for READ or WRITE.
-> Calls low-level Parquet APIs to read an existing file or write a new one.
The open() and mmap() flags are guaranteed to be correct.
At some later point SAS component does an unmap() and close().
-Brian
On 3/14/19, 3:42 PM, "Wes McKinney" <wesmck...@gmail.com> wrote:
hi Brian,
This is mostly an Arrow platform question so I'm copying the Arrow mailing
list.
You can open a file using an existing file descriptor using
ReadableFile::Open
https://github.com/apache/arrow/blob/master/cpp/src/arrow/io/file.h#L145
The documentation for this function says:
"The file descriptor becomes owned by the ReadableFile, and will be
closed on Close() or destruction."
If you want to do the equivalent thing, but using memory mapping, I
think you'll need to add a corresponding API to MemoryMappedFile. This
is more perilous because of the API requirements of mmap -- you need
to pass the right flags and they may need to be the same flags that
were passed when opening the file descriptor, see
https://github.com/apache/arrow/blob/master/cpp/src/arrow/io/file.cc#L378
and
https://github.com/apache/arrow/blob/master/cpp/src/arrow/io/file.cc#L476
- Wes
On Thu, Mar 14, 2019 at 1:47 PM Brian Bowman <brian.bow...@sas.com> wrote:
>
> The ReadableFile class (arrow/io/file.cc) has utility methods where a
FileDescriptor is either passed in or returned, but I don’t see how this
surfaces through the API.
>
> Is there a way for application code to control the open lifetime of
mmap()’d Parquet files by passing an already open FileDescriptor to Parquet
low-level API open/close methods?
>
> Thanks,
>
> Brian
>
