diff --git a/src/descriptor.c b/src/descriptor.c
index 49df56d..2f5c9e3 100644
--- a/src/descriptor.c
+++ b/src/descriptor.c
@@ -48,6 +48,8 @@
 
 #define C_ARRAY_SIZE(array) (sizeof (array) / sizeof *(array))
 
+static dc_status_t dc_descriptor_iterator_next (dc_iterator_t *iterator, void *item);
+
 struct dc_descriptor_t {
 	const char *vendor;
 	const char *product;
@@ -55,6 +57,17 @@ struct dc_descriptor_t {
 	unsigned int model;
 };
 
+typedef struct dc_descriptor_iterator_t {
+	dc_iterator_t base;
+	size_t current;
+} dc_descriptor_iterator_t;
+
+static const dc_iterator_vtable_t dc_descriptor_iterator_vtable = {
+	sizeof(dc_descriptor_iterator_t),
+	dc_descriptor_iterator_next,
+	NULL,
+};
+
 /*
  * The model numbers in the table are the actual model numbers reported by the
  * device. For devices where there is no model number available (or known), an
@@ -331,19 +344,6 @@ static const dc_descriptor_t g_descriptors[] = {
 	{"Cochran", "EMC-20H",      DC_FAMILY_COCHRAN_COMMANDER, 5},
 };
 
-typedef struct dc_descriptor_iterator_t {
-	dc_iterator_t base;
-	size_t current;
-} dc_descriptor_iterator_t;
-
-static dc_status_t dc_descriptor_iterator_next (dc_iterator_t *iterator, void *item);
-static dc_status_t dc_descriptor_iterator_free (dc_iterator_t *iterator);
-
-static const dc_iterator_vtable_t dc_descriptor_iterator_vtable = {
-	dc_descriptor_iterator_free,
-	dc_descriptor_iterator_next
-};
-
 dc_status_t
 dc_descriptor_iterator (dc_iterator_t **out)
 {
@@ -352,11 +352,10 @@ dc_descriptor_iterator (dc_iterator_t **out)
 	if (out == NULL)
 		return DC_STATUS_INVALIDARGS;
 
-	iterator = (dc_descriptor_iterator_t *) malloc (sizeof (dc_descriptor_iterator_t));
+	iterator = (dc_descriptor_iterator_t *) dc_iterator_allocate (NULL, &dc_descriptor_iterator_vtable);
 	if (iterator == NULL)
 		return DC_STATUS_NOMEMORY;
 
-	iterator->base.vtable = &dc_descriptor_iterator_vtable;
 	iterator->current = 0;
 
 	*out = (dc_iterator_t *) iterator;
@@ -364,14 +363,6 @@ dc_descriptor_iterator (dc_iterator_t **out)
 	return DC_STATUS_SUCCESS;
 }
 
-static dc_status_t
-dc_descriptor_iterator_free (dc_iterator_t *iterator)
-{
-	free (iterator);
-
-	return DC_STATUS_SUCCESS;
-}
-
 static dc_status_t
 dc_descriptor_iterator_next (dc_iterator_t *abstract, void *out)
 {
diff --git a/src/iterator-private.h b/src/iterator-private.h
index 105d40f..0cc1bfe 100644
--- a/src/iterator-private.h
+++ b/src/iterator-private.h
@@ -22,6 +22,7 @@
 #ifndef DC_ITERATOR_PRIVATE_H
 #define DC_ITERATOR_PRIVATE_H
 
+#include <libdivecomputer/context.h>
 #include <libdivecomputer/iterator.h>
 
 #ifdef __cplusplus
@@ -32,13 +33,24 @@ typedef struct dc_iterator_vtable_t dc_iterator_vtable_t;
 
 struct dc_iterator_t {
 	const dc_iterator_vtable_t *vtable;
+	dc_context_t *context;
 };
 
 struct dc_iterator_vtable_t {
-	dc_status_t (*free) (dc_iterator_t *iterator);
+	size_t size;
 	dc_status_t (*next) (dc_iterator_t *iterator, void *item);
+	dc_status_t (*free) (dc_iterator_t *iterator);
 };
 
+dc_iterator_t *
+dc_iterator_allocate (dc_context_t *context, const dc_iterator_vtable_t *vtable);
+
+void
+dc_iterator_deallocate (dc_iterator_t *iterator);
+
+int
+dc_iterator_isinstance (dc_iterator_t *iterator, const dc_iterator_vtable_t *vtable);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/iterator.c b/src/iterator.c
index 100f85a..83ad070 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -21,16 +21,51 @@
 
 #include <stddef.h>
 #include <stdlib.h>
+#include <assert.h>
 
+#include "context-private.h"
 #include "iterator-private.h"
 
+dc_iterator_t *
+dc_iterator_allocate (dc_context_t *context, const dc_iterator_vtable_t *vtable)
+{
+	dc_iterator_t *iterator = NULL;
+
+	assert(vtable != NULL);
+	assert(vtable->size >= sizeof(dc_iterator_t));
+
+	// Allocate memory.
+	iterator = (dc_iterator_t *) malloc (vtable->size);
+	if (iterator == NULL) {
+		ERROR (context, "Failed to allocate memory.");
+		return iterator;
+	}
+
+	iterator->vtable = vtable;
+	iterator->context = context;
+
+	return iterator;
+}
+
+void
+dc_iterator_deallocate (dc_iterator_t *iterator)
+{
+	free (iterator);
+}
+
+int
+dc_iterator_isinstance (dc_iterator_t *iterator, const dc_iterator_vtable_t *vtable)
+{
+	if (iterator == NULL)
+		return 0;
+
+	return iterator->vtable == vtable;
+}
+
 dc_status_t
 dc_iterator_next (dc_iterator_t *iterator, void *item)
 {
-	if (iterator == NULL)
-		return DC_STATUS_UNSUPPORTED;
-
-	if (iterator->vtable->next == NULL)
+	if (iterator == NULL || iterator->vtable->next == NULL)
 		return DC_STATUS_UNSUPPORTED;
 
 	if (item == NULL)
@@ -42,11 +77,16 @@ dc_iterator_next (dc_iterator_t *iterator, void *item)
 dc_status_t
 dc_iterator_free (dc_iterator_t *iterator)
 {
+	dc_status_t status = DC_STATUS_SUCCESS;
+
 	if (iterator == NULL)
 		return DC_STATUS_SUCCESS;
 
-	if (iterator->vtable->free == NULL)
-		return DC_STATUS_UNSUPPORTED;
+	if (iterator->vtable->free) {
+		status = iterator->vtable->free (iterator);
+	}
 
-	return iterator->vtable->free (iterator);
+	dc_iterator_deallocate (iterator);
+
+	return status;
 }