Re: Extending Lua for multiple light userdata types
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- Subject: Re: Extending Lua for multiple light userdata types
- From: Dirk Laurie <dirk.laurie@...>
- Date: 2012年11月13日 17:42:36 +0200
2012年11月13日 Rena <hyperhacker@gmail.com>:
> Recently I was thinking about how you might add a 64-bit integer type to Lua.
This is only a pressing question if you need IEEE floats and 64-bit integers
in the same program, otherwise you can build Lua with 64-bit integers
as your `number`.
But apart from that, the generalization you propose, of
> more "primitive" types, that function like light userdata. Each
> type having its own metatable and data size (up to 8 bytes?).
is interesting. The gap between "each object has its own
metatable" and "each type has one metatable" is a wide one when
"type" is a pointer to a C-defined data type.
I have an application with several userdata types. At present I use
the following technique to create them:
1. Make Lua allocate the storage as a newuserdata.
2. Initialize it, including the allocation of a metatable.
3. Push it back on the stack as a lightuserdata.
4. Store it in the registry index using the lightuserdata as a key.
5. Return it to Lua.
All the objects contain pointers to other objects in their structure.
To access these, I call a member function that does this:
1. Push the pointer from the data structure on the stack as a lightuserdata.
2. Retrieve the userdata from the registry.
3. Return it to Lua.