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https://issues.apache.org/jira/browse/ARROW-3662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16670185#comment-16670185
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Dimitri Vorona edited comment on ARROW-3662 at 10/31/18 2:39 PM:
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I was under the impression that on some platforms we used SEEK_END/Tell trick
to get the size, but it's apparently not true. We do however call seek on the
fd in some cases, (io-util.cc:372 => io-util.cc:218) and I'm not sure about
the reason here. I hesitate considering a seek operation to be const, even if
it effectively doesn't move the head. If it isn't a convern, I can of course
change all GetSize methods.
was (Author: alendit):
I was on some platforms we used SEEK_END/Tell trick to get the size, but it's
apparently not true. We do however call seek on the fd in some cases,
(io-util.cc:372 => io-util.cc:218) and I'm not sure about the reason here. I
hesitate considering a seek operation to be const, even if it effectively
doesn't move the head. If it isn't a convern, I can of course change all
GetSize methods.
> [C++] Add a const overload to MemoryMappedFile::GetSize
> -------------------------------------------------------
>
> Key: ARROW-3662
> URL: https://issues.apache.org/jira/browse/ARROW-3662
> Project: Apache Arrow
> Issue Type: New Feature
> Affects Versions: 0.11.1
> Reporter: Dimitri Vorona
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 20m
> Remaining Estimate: 0h
>
>
> While GetSize in general is not a const function, it can be on a
> MemoryMappedFile. I propose to add a const override directly to the
> MemoryMappedFile.
> Alternatively we could add a const version on the RandomAccessFile level
> which would fail, if a const size getting (e.g. without a seek) isn't
> possible, but it seems to me to be a potential source of hard-to-debug bugs
> and spurious failures. At would at least require a careful analysis of the
> platform support of different size getting options.
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