Re: what exactly happens with string casts?
- From: Dimiter 'malkia' Stanev <malkia@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Wed, 16 May 2012 00:18:09 -0700
My understanding is this:
On 5/15/2012 10:19 PM, William Adams wrote:
I can do this:
str = ffi.cast("char *", "Any old string")
This ffi string would live as long as "str" itself lives.
For example
do
local str = ffi.cast( "char *", "Any old string" )
end
-- here it might be gone
And that's a quick and dirty way to get a pointer to a string. Or to be more
precise, a pointer on a bit of memory that has some characters in it.
Does anyone know about the lifetime semantics of that string? Also, does this
make a copy of the string, or is the 'str' variable now pointing at the in
memory representation of the string. I'm assumig the former but I'm not sure.
Second, I can do this:
buff = ffi.new("char[256]")
This would create an ffi object that is array of 256 characters, all zero
buff[255]=0
I guess then this would not have an effect.
luastring = ffi.string(buff)
Most likely just an empty string, returned in luastring
now, I have a lua string, which has been interned?, and the buff has been
copied?
It's interned, as much as luastring = "" is interned. The buff was
"copied" but actually zero bytes were copied from there. But most likely
the buff[0] was accessed.
These are just some assumptions I need some clarification on.
-- William
===============================
- Shaping clay is easier than digging it out of the ground.
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