rbd: add wrapper for rbd_namespace_list() function.

Added wrapper for rbd_namespace_list() function which returns the names of all the namespaces
present for a given IOContext.

Signed-off-by: Mudit Agarwal muagarwa@redhat.com

rbd/namespace_nautilus.go

@@ -1,7 +1,7 @@
 // +build !luminous,!mimic
 //
 // Ceph Nautilus is the first release that includes rbd_namespace_create(),
-// rbd_namespace_remove(), rbd_namespace_exists().
+// rbd_namespace_remove(), rbd_namespace_exists() and rbd_namespace_list().
 
 package rbd
 
@@ -13,8 +13,10 @@ package rbd
 import "C"
 
 import (
+	"bytes"
 	"unsafe"
 
+	"github.com/ceph/go-ceph/internal/retry"
 	"github.com/ceph/go-ceph/rados"
 )
 
@@ -72,3 +74,38 @@ func NamespaceExists(ioctx *rados.IOContext, namespaceName string) (bool, error)
 	ret := C.rbd_namespace_exists(cephIoctx(ioctx), cNamespaceName, &exists)
 	return bool(exists), getErrorIfNegative(ret)
 }
+
+// NamespaceList returns a slice containing the names of existing rbd namespaces.
+//
+// Implements:
+//  int rbd_namespace_list(rados_ioctx_t io, char *namespace_names, size_t *size);
+func NamespaceList(ioctx *rados.IOContext) (names []string, err error) {
+	if ioctx == nil {
+		return nil, ErrNoIOContext
+	}
+	var (
+		buf   []byte
+		cSize C.size_t
+	)
+	retry.WithSizes(4096, 262144, func(size int) retry.Hint {
+		cSize = C.size_t(size)
+		buf = make([]byte, cSize)
+		ret := C.rbd_namespace_list(cephIoctx(ioctx),
+			(*C.char)(unsafe.Pointer(&buf[0])),
+			&cSize)
+		err = getErrorIfNegative(ret)
+		return retry.Size(int(cSize)).If(err == errRange)
+	})
+
+	if err != nil {
+		return nil, err
+	}
+	tmpList := bytes.Split(buf[:cSize-1], []byte{0})
+	for _, s := range tmpList {
+		if len(s) > 0 {
+			name := C.GoString((*C.char)(unsafe.Pointer(&s[0])))
+			names = append(names, name)
+		}
+	}
+	return names, nil
+}

rbd/namespace_nautilus_test.go

@@ -42,6 +42,10 @@ func TestNamespace(t *testing.T) {
 		assert.Error(t, err)
 		_, err = NamespaceExists(ioctx, "")
 		assert.Error(t, err)
+
+		// NamespaceList.
+		_, err = NamespaceList(nil)
+		assert.Error(t, err)
 	})
 
 	t.Run("CreateNamespace", func(t *testing.T) {
@@ -73,4 +77,32 @@ func TestNamespace(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, val, false)
 	})
+
+	t.Run("NamespaceList", func(t *testing.T) {
+		var (
+			name1 = "name1"
+			name2 = "name2"
+			name3 = "name3"
+		)
+		err := NamespaceCreate(ioctx, name1)
+		assert.NoError(t, err)
+		err = NamespaceCreate(ioctx, name2)
+		assert.NoError(t, err)
+		err = NamespaceCreate(ioctx, name3)
+		assert.NoError(t, err)
+		defer func() {
+			assert.NoError(t, NamespaceRemove(ioctx, name1))
+			assert.NoError(t, NamespaceRemove(ioctx, name2))
+			assert.NoError(t, NamespaceRemove(ioctx, name3))
+		}()
+
+		eval, err := NamespaceExists(ioctx, name1)
+		assert.NoError(t, err)
+		assert.Equal(t, eval, true)
+		nList, err := NamespaceList(ioctx)
+		assert.NoError(t, err)
+		assert.Contains(t, nList, name1)
+		assert.Contains(t, nList, name2)
+		assert.Contains(t, nList, name3)
+	})
 }