Re: How to convert to-be-closed variable to normal one in runtime?
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- Subject: Re: How to convert to-be-closed variable to normal one in runtime?
- From: Andrew Gierth <andrew@...>
- Date: 2020年7月21日 15:52:15 +0100
>>>>> "Mimmo" == Mimmo Mane <pocomane_7a@pocomane.com> writes:
Mimmo> Normally, you can declosify just overriding the __close()
Mimmo> metamethod, but here it is impossible without affecting the
Mimmo> other files. You can still use the proxy trick suggested by
Mimmo> Andrew
Incidentally, I forgot to mention the main reason for the proxy, which
is to be able to _return_ the value.
e.g.
function f1(fn)
local fc <close>, f, err, errno = auto_close(io.open(fn,"r"))
--[[ check for errors ]]
--[[ do stuff with f, that might throw an error ]]
-- if successful, return the file to the caller
return fc:release()
end
function f2()
local fc <close>, f = auto_close(f1("filename"))
--[[ do stuff ]]
end
This does leave a small window for error in the auto_close call itself,
but I believe with the C implementation and with no intervention from
hooks, the only likely failure is an "out of memory" on allocating the
new proxy object.
--
Andrew.