CNV(9)                 FreeBSD Kernel Developer's Manual                CNV(9)

NAME
     cnvlist_get, cnvlist_take, cnvlist_free - API for managing name/value
     pairs by cookie.

LIBRARY
     Name/value pairs library (libnv, -lnv)

SYNOPSIS
     #include <sys/cnv.h>

     const char *
     cnvlist_name(const void *cookie);

     int
     cnvlist_type(const void *cookie);

     bool
     cnvlist_get_bool(const void *cookie);

     uint64_t
     cnvlist_get_number(const void *cookie);

     const char *
     cnvlist_get_string(const void *cookie);

     const nvlist_t *
     cnvlist_get_nvlist(const void *cookie);

     const void *
     cnvlist_get_binary(const void *cookie, size_t *sizep);

     const bool *
     cnvlist_get_bool_array(const void *cookie, size_t *nitemsp);

     const uint64_t *
     cnvlist_get_number_array(const void *cookie, size_t *nitemsp);

     const char * const *
     cnvlist_get_string_array(const void *cookie, size_t *nitemsp);

     const nvlist_t * const *
     cnvlist_get_nvlist_array(const void *cookie, size_t *nitemsp);

     int
     cnvlist_get_descriptor(const void *cookie);

     const int *
     cnvlist_get_descriptor_array(const void *cookie, size_t *nitemsp);

     bool
     cnvlist_take_bool(void *cookie);

     uint64_t
     cnvlist_take_number(void *cookie);

     const char *
     cnvlist_take_string(void *cookie);

     const nvlist_t *
     cnvlist_take_nvlist(void *cookie);

     const void *
     cnvlist_take_binary(void *cookie, size_t *sizep);

     const bool *
     cnvlist_take_bool_array(void *cookie, size_t *nitemsp);

     const uint64_t *
     cnvlist_take_number_array(void *cookie, size_t *nitemsp);

     const char * const *
     cnvlist_take_string_array(void *cookie, size_t *nitemsp);

     const nvlist_t * const *
     cnvlist_take_nvlist_array(void *cookie, size_t *nitemsp);

     int
     cnvlist_take_descriptor(void *cookie);

     const int *
     cnvlist_take_descriptor_array(void *cookie, size_t *nitemsp);

     void
     cnvlist_free_null(void *cookie);

     void
     cnvlist_free_bool(void *cookie);

     void
     cnvlist_free_number(void *cookie);

     void
     cnvlist_free_string(void *cookie);

     void
     cnvlist_free_nvlist(void *cookie);

     void
     cnvlist_free_descriptor(void *cookie);

     void
     cnvlist_free_binary(void *cookie);

     void
     cnvlist_free_bool_array(void *cookie);

     void
     cnvlist_free_number_array(void *cookie);

     void
     cnvlist_free_string_array(void *cookie);

     void
     cnvlist_free_nvlist_array(void *cookie);

     void
     cnvlist_free_descriptor_array(void *cookie);

DESCRIPTION
     The libnv library permits easy management of name/value pairs and can
     send and receive them over sockets.  For more information, also see
     nv(9).

     The concept of cookies is explained in nvlist_next(),
     nvlist_get_parent(), and nvlist_get_pararr() from nv(9).

     The cnvlist_name() function returns the name of an element associated
     with the given cookie.

     The cnvlist_type() function returns the type of an element associated
     with the given cookie.  Types which can be returned are described in
     nv(9).

     The cnvlist_get family of functions obtains the value associated with the
     given cookie.  Returned strings, nvlists, descriptors, binaries, or
     arrays must not be modified by the user, since they still belong to the
     nvlist.  The nvlist must not be in an error state.

     The cnvlist_take family of functions returns the value associated with
     the given cookie and removes the element from the nvlist.  When the value
     is a string, binary, or array value, the caller is responsible for
     freeing the returned memory with free(3).  When the value is an nvlist,
     the caller is responsible for destroying the returned nvlist with
     nvlist_destroy().  When the value is a descriptor, the caller is
     responsible for closing the returned descriptor with the close(2).

     The cnvlist_free family of functions removes an element of the supplied
     cookie and frees all resources.  If an element of the given cookie has
     the wrong type or does not exist, the program is aborted.

EXAMPLES
     The following example demonstrates how to deal with cnvlist API.

     int type;
     void *cookie, *scookie, *bcookie;
     nvlist_t *nvl;
     char *name;

     nvl = nvlist_create(0);
     nvlist_add_bool(nvl, "test", 1 == 2);
     nvlist_add_string(nvl, "test2", "cnvlist");
     cookie = NULL;

     while (nvlist_next(nvl, &type, &cookie) != NULL) {
             switch (type) {
             case NV_TYPE_BOOL:
                     printf("test: %d\n", cnvlist_get_bool(cookie));
                     bcookie = cookie;
                     break;
             case NV_TYPE_STRING:
                     printf("test2: %s\n", cnvlist_get_string(cookie));
                     scookie = cookie;
                     break;
             }
     }

     name = cnvlist_take_string(scookie);
     cnvlist_free_bool(bcookie);

     printf("test2: %s\n", name);
     free(name);

     printf("nvlist_empty = %d\n", nvlist_empty(nvl));
     nvlist_destroy(nvl);

     return (0);

SEE ALSO
     close(2), free(3), nv(9)

AUTHORS
     The cnv API was created during the Google Summer Of Code 2016 by Adam
     Starak.

FreeBSD 13.1-RELEASE-p6          June 18, 2018         FreeBSD 13.1-RELEASE-p6