LIBXO(3)               FreeBSD Library Functions Manual               LIBXO(3)

NAME
     xo_open_marker, xo_open_marker_h, xo_close_marker, xo_close_marker_h -
     prevent and allow closing of open constructs

LIBRARY
     Text, XML, JSON, and HTML Output Emission Library (libxo, -lxo)

SYNOPSIS
     #include <libxo/xo.h>

     xo_ssize_t
     xo_open_marker(const char *name);

     xo_ssize_t
     xo_open_marker_h(xo_handle_t *handle, const char *name);

     xo_ssize_t
     xo_close_marker(const char *name);

     xo_ssize_t
     xo_close_marker_h(xo_handle_t *handle, const char *name);

DESCRIPTION
     libxo represents hierarchy using two constructs: "containers" and
     "lists".  A marker can be used to affect how open constructs are closed,
     either by preventing their (implicit or explicit) closure or by forcing
     their closure.  While a marker is open, no other open constructs can be
     closed.  When a marker is closed, all constructs open since the marker
     was opened will be closed.  A marker is used to "freeze" any open
     constructs.  Calls to xo_close_*() functions that would normally close
     them will be ignored, effectively blocking their closure.  However when
     xo_close_marker() is called, any containers, lists, or leaf-lists open
     since the matching xo_open_marker() call will be close and the marker
     discarded.  Markers use names which are not user-visible, allowing the
     caller to choose appropriate internal names.  The marker has no value and
     is not emitted in any form.

     To open a marker, call xo_open_marker() or xo_open_marker_h().  The
     former uses the default handle and the latter accepts a specific handle.

     To close a marker, use the xo_close_marker() or xo_close_marker_h()
     functions.

     Each open call must have a matching close call.

     In this example, the xo_close_container() call on line [1] will be
     ignored, since the open marker "outer" will prevent close of any open
     constructs that precede it.  The xo_close_marker() call on line [2] will
     close the "system" container, since it was opened after the "outer"
     marker.
               Example:

                   xo_open_container("top");
                   xo_open_marker("outer");
                   xo_open_container("system");
                   xo_emit("{:host-name/%s%s%s", hostname,
                           domainname ? "." : "", domainname ?: "");
                   xo_close_container("top");   /* [1] */
                   xo_close_marker("outer");    /* [2] */
                   xo_close_container("top");

     In this example, the code whiffles through a list of fish, calling a
     function to emit details about each fish.  The marker "fish-guts" is used
     to ensure that any constructs opened by the function are closed properly.

               for (i = 0; fish[i]; i++) {
                   xo_open_instance("fish");
                   xo_open_marker("fish-guts");
                   dump_fish_details(i);
                   xo_close_marker("fish-guts");
               }

SEE ALSO
     xo_emit(3), libxo(3)

HISTORY
     The libxo library first appeared in FreeBSD 11.0.

AUTHORS
     libxo was written by Phil Shafer <phil@freebsd.org>.

FreeBSD 13.1-RELEASE-p6        January 22, 2015        FreeBSD 13.1-RELEASE-p6