2009/12/22 Thomas E Enebo <tom.enebo@gmail.com>:

> I have been wondering about the Struct API myself.   It seems like it
> should support a simple explicit memory management API ala:
>
> class MyFFIStruct < FFI::Struct ....
>
> MyFFIStruct.new do |struct_instance|
>   some_ffi_call struct_instance
>   # Do other stuff....
> end
> # I know the block has disposed of my allocated struct

It does support this indirectly via MemoryPointer.new
e.g.
  MemoryPointer.new(MyFFIStruct.size) do |p|
    s = MyFFIStruct.new(p)
    some_ffi_call s
    # do other stuff
  end

An alternative is to use FFI::Buffer as the backing memory - on JRuby,
that is jvm-heap memory, which is copied in/out of a temporary native
memory area (usually on the stack) when passed to a native function.
For small structs, especially ones that are passed to a native
function just once, this can be up to 10x faster than the alloc/free
cycle of a MemoryPointer backed Struct.