Re: Strings and GC - was RE: Using full userdata as table index?
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- Subject: Re: Strings and GC - was RE: Using full userdata as table index?
- From: RLake@...
- Date: 2004年2月10日 15:28:04 -0500
Kevin Baca escribió:
> I had a similar issue where I wanted to index tables using an opaque
> C-generated id object.
> The id was encapsulated in a user data.
> Each call to getId() generated a new user data, so it was not possible
> to use it as an index. The solution was to convert the id to a unique
> string and use that as a key.
Wouldn't a better solution have been to generate the same userdata for
each id? Or alternatively, use a number or lightuserdata instead of
a character string?
> I discarded whole thing because of the number of strings that would be
> generated and because of my (possibly wrong) understanding that lua
> doesn't GC strings.
Lua garbage collects strings.
U:\>lua
Lua 5.0 Copyright (C) 1994-2003 Tecgraf, PUC-Rio
> =gcinfo()
17 29
> a = {}
> for i = 1, 5000 do
>> a[i] = string.rep("a", i)
>> end
> =gcinfo()
12474 13446
> a = nil
> =collectgarbage()
> =gcinfo()
34 68
-- However, there is some persistence
> =collectgarbage()
> =gcinfo()
25 50
> =collectgarbage()
> =gcinfo()
21 41
> =collectgarbage()
> =gcinfo()
18 36
> Would someone more knowledgeable than myself please clarify the
> string/GC issue?
Hope that reassured you a bit.