rbd admin: add initial basic types

Adds types to work with the ceph cluster (the admin type) and a type
to work with the "level spec" - which is unfortunately not well
described in the ceph docs, but I think I worked it out well enough
by reading the ceph sources.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

rbd/admin/admin.go

@@ -0,0 +1,51 @@
+// +build !nautilus
+
+package admin
+
+import (
+	"fmt"
+
+	ccom "github.com/ceph/go-ceph/common/commands"
+)
+
+// RBDAdmin is used to administrate rbd volumes and pools.
+type RBDAdmin struct {
+	conn ccom.RadosCommander
+}
+
+// NewFromConn creates an new management object from a preexisting
+// rados connection. The existing connection can be rados.Conn or any
+// type implementing the RadosCommander interface.
+func NewFromConn(conn ccom.RadosCommander) *RBDAdmin {
+	return &RBDAdmin{conn}
+}
+
+// LevelSpec values are used to identify RBD objects wherever Ceph APIs
+// require a levelspec to select an image, pool, or namespace.
+type LevelSpec struct {
+	spec string
+}
+
+// NewLevelSpec is used to construct a LevelSpec given a pool and
+// optional namespace and image names.
+func NewLevelSpec(pool, namespace, image string) LevelSpec {
+	var s string
+	if image != "" && namespace != "" {
+		s = fmt.Sprintf("%s/%s/%s", pool, namespace, image)
+	} else if image != "" {
+		s = fmt.Sprintf("%s/%s", pool, image)
+	} else if namespace != "" {
+		s = fmt.Sprintf("%s/%s/", pool, namespace)
+	} else {
+		s = fmt.Sprintf("%s/", pool)
+	}
+	return LevelSpec{s}
+}
+
+// NewRawLevelSpec returns a LevelSpec directly based on the spec string
+// argument without constructing it from component values. This should only be
+// used if NewLevelSpec can not create the levelspec value you want to pass to
+// ceph.
+func NewRawLevelSpec(spec string) LevelSpec {
+	return LevelSpec{spec}
+}