[erlang-questions] mmap file to binary
Wed Jul 14 11:47:34 CEST 2010
Max Lapshin wrote:
> I have to do so:
> Mmap *mm;
> mm = (Mmap *)enif_alloc_resource(mmap_resource, sizeof(Mmap));
> mm->ptr = m;
> mm->size = (size_t)file_stat.st_size;
> m_bin = enif_make_resource_binary(env, mm, mm->ptr, mm->size);
> enif_release_resource(mm); % <---------
> return enif_make_tuple2(env, enif_make_atom(env, "ok"), m_bin);
> If I don't add enif_release_resource, it will never be garbage
> collected. Why I have to do so
That was a design choice. Ownership of resources are never transfered.
enif_allloc_resource gives you ("the NIF") ownership of the resource.
enif_make_resource and enif_make_resource_binary adds a new ownership
from the created Erlang term.
So, to really free a resource, both "the NIF" ownership has to be
released by calling enif_release_resource and all referring terms has to
be garbage collected.
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