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An XFN link is a special form of reference that contains a composite name, the link name, and that may be bound to an atomic name in an XFN
context. Because the link name is a composite name, it may span multiple namespaces.
Normal resolution of names in context operations always follows XFN links. If the first composite name component of the link name is the atomic name ".", the link name is resolved relative to the
same context in which the link is bound, otherwise, the link name is resolved relative to the XFN Initial Context of the client. The link name may itself cause resolution to pass through other XFN links.
This gives rise to the possibility of a cycle of links whose resolution could not terminate normally. As a simple means to avoid such non-terminating resolutions, implementations may define limits on
the number of XFN links that may be resolved in any single operation invoked by the caller.
These are the interfaces:
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#include <xfn/xfn.h>
FN_ref_t *fn_ref_create_link(const FN_composite_name_t *link_name);
int fn_ref_is_link(const FN_ref_t *ref);
FN_composite_name_t *fn_ref_link_name( const FN_ref_t *link_ref);
FN_ref_t *fn_ctx_lookup_link(FN_ctx_t *ctx, const FN_composite_name_t *name,
FN_status_t *status);
unsigned int fn_status_link_code(const FN_status_t *stat);
const FN_composite_name_t *fn_status_link_remaining_name(
const FN_status_t *stat);
const FN_composite_name_t *fn_status_link_resolved_name(
const FN_status_t *stat);
const FN_ref_t *fn_status_link_resolved_ref( const FN_status_t *stat);
int fn_status_set_link_code(FN_status_t *stat,
unsigned int code);
int fn_status_set_link_remaining_name(FN_status_t *stat,
const FN_composite_name_t *name);
int fn_status_set_link_resolved_name(FN_status_t *stat,
const FN_composite_name_t *name);
int fn_status_set_link_resolved_ref(FN_status_t *stat,
const FN_ref_t *ref);
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Links are bound to names using the normal fn_ctx_bind() and unbound using the normal fn_ctx_unbind() operation. The operation fn_ref_create_link()
is provided for constructing a link reference from a composite name. Since normal resolution always follows links, a separate operation, fn_ctx_lookup_link() is provided to lookup the
link itself.
In the case that an error occurred while resolving an XFN link, the status object set by the operation contains additional information about that error and sets the corresponding link status fields
using fn_status_set_link_code(), fn_status_set_link_remaining_name(), fn_status_set_link_resolved_name() and fn_status_set_link_resolved_ref(). The link status fields can be retrieved using fn_status_link_code(), fn_status_link_remaining_name(), fn_status_link_resolved_name()
and fn_status_link_resolved_ref().
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