Files: scheme/glt_kernel.c, scheme/glt_kernel.h
For accessing VRR
objects from Scheme, it is needed to create
Scheme objects for VRR
objects. We call these Scheme objects
proxies. Proxy data types are defined during kernel initialization, in the
function glt_kernel_init(). There are three types of proxies:
o, anchor and hanger proxies. From the user's point
of view there a is different division based on the object kinds – in
this division o proxies are in two categories: obj and
go proxies, but their implementation is the same. Proxies are
implemented using the GUILE's mechanism of smobs - small objects
with type information and one pointer. This pointer is used to store
a pointer on the target structure. So, having a proxy, it is simple to get
the VRR
structure (functions scm2o(), scm2anchor(),
scm2hanger()). We wanted not to have more different proxies for
one kernel structure, so we use a hash table to convert pointers to
kernel structures to their proxies (functions o2scm(),
anchor2scm(), hanger2scm()). If anyone wants a proxy to
a kernel structure, it is taken from the hash table or created (and put to
the hash table). A proxy increases the reference counter of the appropriate kernel
structure. If garbage collector finds a proxy as unusable, then
the reference is freed and the proxy is removed from the hash table.