freebsd-skq/share/man/man9/cnv.9

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.Dd June 18, 2018
.Dt CNV 9
.Os
.Sh NAME
.Nm cnvlist_get ,
.Nm cnvlist_take ,
.Nm cnvlist_free
.Nd "API for managing name/value pairs by cookie."
.Sh LIBRARY
.Lb libnv
.Sh SYNOPSIS
.In sys/cnv.h
.Ft const char *
.Fn cnvlist_name "const void *cookie"
.Ft int
.Fn cnvlist_type "const void *cookie"
.\"
.Ft bool
.Fn cnvlist_get_bool "const void *cookie"
.Ft uint64_t
.Fn cnvlist_get_number "const void *cookie"
.Ft "const char *"
.Fn cnvlist_get_string "const void *cookie"
.Ft "const nvlist_t *"
.Fn cnvlist_get_nvlist "const void *cookie"
.Ft "const void *"
.Fn cnvlist_get_binary "const void *cookie" "size_t *sizep"
.Ft "const bool *"
.Fn cnvlist_get_bool_array "const void *cookie" "size_t *nitemsp"
.Ft "const uint64_t *"
.Fn cnvlist_get_number_array "const void *cookie" "size_t *nitemsp"
.Ft "const char * const *"
.Fn cnvlist_get_string_array "const void *cookie" "size_t *nitemsp"
.Ft "const nvlist_t * const *"
.Fn cnvlist_get_nvlist_array "const void *cookie" "size_t *nitemsp"
.Ft int
.Fn cnvlist_get_descriptor "const void *cookie"
.Ft "const int *"
.Fn cnvlist_get_descriptor_array "const void *cookie" "size_t *nitemsp"
.\"
.Ft bool
.Fn cnvlist_take_bool "void *cookie"
.Ft uint64_t
.Fn cnvlist_take_number "void *cookie"
.Ft "const char *"
.Fn cnvlist_take_string "void *cookie"
.Ft "const nvlist_t *"
.Fn cnvlist_take_nvlist "void *cookie"
.Ft "const void *"
.Fn cnvlist_take_binary "void *cookie" "size_t *sizep"
.Ft "const bool *"
.Fn cnvlist_take_bool_array "void *cookie" "size_t *nitemsp"
.Ft "const uint64_t *"
.Fn cnvlist_take_number_array "void *cookie" "size_t *nitemsp"
.Ft "const char * const *"
.Fn cnvlist_take_string_array "void *cookie" "size_t *nitemsp"
.Ft "const nvlist_t * const *"
.Fn cnvlist_take_nvlist_array "void *cookie" "size_t *nitemsp"
.Ft int
.Fn cnvlist_take_descriptor "void *cookie"
.Ft "const int *"
.Fn cnvlist_take_descriptor_array "void *cookie" "size_t *nitemsp"
.\"
.Ft void
.Fn cnvlist_free_null "void *cookie"
.Ft void
.Fn cnvlist_free_bool "void *cookie"
.Ft void
.Fn cnvlist_free_number "void *cookie"
.Ft void
.Fn cnvlist_free_string "void *cookie"
.Ft void
.Fn cnvlist_free_nvlist "void *cookie"
.Ft void
.Fn cnvlist_free_descriptor "void *cookie"
.Ft void
.Fn cnvlist_free_binary "void *cookie"
.Ft void
.Fn cnvlist_free_bool_array "void *cookie"
.Ft void
.Fn cnvlist_free_number_array "void *cookie"
.Ft void
.Fn cnvlist_free_string_array "void *cookie"
.Ft void
.Fn cnvlist_free_nvlist_array "void *cookie"
.Ft void
.Fn cnvlist_free_descriptor_array "void *cookie"
.Sh DESCRIPTION
The
.Nm libnv
library permits easy management of name/value pairs and can send and receive
them over sockets.
For more information, also see
.Xr nv 9 .
.Pp
The concept of cookies is explained in
.Fn nvlist_next ,
.Fn nvlist_get_parent ,
and
.Fn nvlist_get_pararr
from
.Xr nv 9 .
.Pp
The
.Fn cnvlist_name
function returns the name of an element associated with the given cookie.
.Pp
The
.Fn cnvlist_type
function returns the type of an element associated with the given cookie.
Types which can be returned are described in
.Xr nv 9 .
.Pp
The
.Nm 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.
.Pp
The
.Nm 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
.Fn free 3 .
When the value is an nvlist, the caller is responsible for destroying the
returned nvlist with
.Fn nvlist_destroy .
When the value is a descriptor, the caller is responsible for closing the
returned descriptor with the
.Fn close 2 .
.Pp
The
.Nm 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.
.Sh EXAMPLE
The following example demonstrates how to deal with cnvlist API.
.Bd -literal
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);
.Ed
.Sh SEE ALSO
.Xr close 2 ,
.Xr free 3 ,
.Xr nv 9
.Sh AUTHORS
The
.Nm cnv
API was created during the Google Summer Of Code 2016 by
.An Adam Starak .