Introduce cnvlist_name() and cnvlist_type() functions.

Those function can be used when we are iterating over nvlist to reduce
amount of extra variables we need to declare.

MFC after:	1 month

share/man/man9/cnv.9

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 27, 2016
+.Dd October 26, 2017
 .Dt CNV 9
 .Os
 .Sh NAME
@@ -37,6 +37,11 @@
 .Lb libnv
 .Sh SYNOPSIS
 .In sys/cnv.h
+.Ft const char *
+.Fn cnvlist_name "void *cookiep"
+.Ft int
+.Fn cnvlist_type "void *cookiep"
+.\"
 .Ft bool
 .Fn cnvlist_get_bool "void *cookiep"
 .Ft uint64_t
@@ -124,6 +129,16 @@ 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

sys/contrib/libnv/cnvlist.c

@@ -53,6 +53,20 @@ __FBSDID("$FreeBSD$");
 #include "nvlist_impl.h"
 #include "nvpair_impl.h"
 
+const char *
+cnvlist_name(void *cookiep)
+{
+
+	return (nvpair_name(cookiep));
+}
+
+int
+cnvlist_type(void *cookiep)
+{
+
+	return (nvpair_type(cookiep));
+}
+
 #define	CNVLIST_GET(ftype, type, NVTYPE)				\
 ftype									\
 cnvlist_get_##type(void *cookiep)					\

sys/sys/cnv.h

@@ -47,6 +47,12 @@ typedef struct nvlist nvlist_t;
 
 __BEGIN_DECLS
 
+/*
+ * Functions which returns information about the given cookie.
+ */
+const char	*cnvlist_name(void *cookiep);
+int		 cnvlist_type(void *cookiep);
+
 /*
  * The cnvlist_get functions returns value associated with the given cookie.
  * If it returns a pointer, the pointer represents internal buffer and should