#778: Make FileHandle Subclassable
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Reporter: whiteknight | Owner:
Type: RFC | Status: new
Priority: normal | Milestone:
Component: none | Version: 1.3.0
Severity: medium | Keywords: io oo pmc
Lang: | Patch:
Platform: |
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There were some other related tickets (I can't find them now) about this,
so sorry if I am duplicating anything.
FileHandles are not current subclassable in PIR because they have ATTRs
that are not usable from PIR (char*, PIOOFF_T, etc). In order for a PMC
like FileHandle to be properly subclassable, every one of it's ATTRs must
be an INTVAL, FLOATVAL, STRING* or PMC*. Otherwise, the subclass will
throw an exception if we try to access an ATTR that is not one of these
from the parent type.
I want to make two changes to FileHandle (in addition to the cleanups I am
working on in the io_cleanups branch right now) to make this possible:
1) Create a new IOBuffer PMC type to take care of buffering. FileHandle
will then delegate it's buffering needs to a PMC of this type. The benefit
here is that we can use this same buffering functionality from other IO
PMC types (sockets, pipes, etc).
2) Convert the ATTRs file_pos and last_pos from type PIOOFF_T into type
INTVAL. This may be a lossy transition but it's worth noting that almost
every use of these two ATTRs, outside the IO API, are converted to INTVAL
already.
#2 of course is a little sketchy, so I would be happy to hear about
alternate ideas to fix this issue. Shortly after getting these ATTRs fixed
(if not immediately thereafter) we should be able to properly subclass
FileHandles.
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Ticket URL: <https://trac.parrot.org/parrot/ticket/778>
Parrot <https://trac.parrot.org/parrot/>
Parrot Development
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