python: fix iterators failing on empty lists

The python bindings implement hosts(), subsystems(),
controllers(), and namespaces() as iterators. However,
these iterators all fail on empty lists.

This hopefully fixes this issue.

Signed-off-by: Martin Belanger <[email protected]>

Author: Martin Belanger

libnvme/nvme.i

@@ -411,6 +411,17 @@ PyObject *hostid_from_file();
 #include "fabrics.h"
 #define STR_OR_NONE(str) (!(str) ? "None" : str)
 
+struct nvme_host * nvme_first_host(struct nvme_root * r);
+struct nvme_host * nvme_next_host(struct nvme_root * r, struct nvme_host * h);
+struct nvme_subsystem * nvme_first_subsystem(struct nvme_host * h);
+struct nvme_subsystem * nvme_next_subsystem(struct nvme_host * h, struct nvme_subsystem * s);
+struct nvme_ctrl * nvme_subsystem_first_ctrl(struct nvme_subsystem * s);
+struct nvme_ctrl * nvme_subsystem_next_ctrl(struct nvme_subsystem * s, struct nvme_ctrl * c);
+struct nvme_ns * nvme_subsystem_first_ns(struct nvme_subsystem * s);
+struct nvme_ns * nvme_subsystem_next_ns(struct nvme_subsystem * s, struct nvme_ns * n);
+struct nvme_ns * nvme_ctrl_first_ns(struct nvme_ctrl * c);
+struct nvme_ns * nvme_ctrl_next_ns(struct nvme_ctrl * c, struct nvme_ns * n);
+
 struct nvme_root {
 	%immutable config_file;
 	%immutable application;
@@ -560,9 +571,14 @@ struct nvme_ns {
 		else if (!strcmp(level, "emerg")) log_level = LOG_EMERG;
 		nvme_init_logging($self, log_level, false, false);
 	}
-	struct nvme_host *hosts() {
-		return nvme_first_host($self);
-	}
+	%pythoncode %{
+	def hosts(self):
+	    """Iterator over all host objects"""
+	    h = nvme_first_host(self)
+	    while h:
+	        yield h
+	        h = nvme_next_host(self, h)
+	%}
 	void refresh_topology() {
 		nvme_refresh_topology($self);
 	}
@@ -636,9 +652,14 @@ struct nvme_ns {
 		};
 		return ret;
 	}
-	struct nvme_subsystem* subsystems() {
-		return nvme_first_subsystem($self);
-	}
+	%pythoncode %{
+	def subsystems(self):
+	    """Iterator over all subsystem objects"""
+	    s = nvme_first_subsystem(self)
+	    while s:
+	        yield s
+	        s = nvme_next_subsystem(self, s)
+	%}
 }
 
 %{
@@ -708,12 +729,22 @@ struct nvme_ns {
 		};
 		return ret;
 	}
-	struct nvme_ctrl *controllers() {
-		return nvme_subsystem_first_ctrl($self);
-	}
-	struct nvme_ns *namespaces() {
-		return nvme_subsystem_first_ns($self);
-	}
+	%pythoncode %{
+	def controllers(self):
+	    """Iterator over all controller objects"""
+	    c = nvme_subsystem_first_ctrl(self)
+	    while c:
+	        yield c
+	        c = nvme_subsystem_next_ctrl(self, c)
+	%}
+	%pythoncode %{
+	def namespaces(self):
+	    """Iterator over all namespace objects"""
+	    ns = nvme_subsystem_first_ns(self)
+	    while ns:
+	        yield ns
+	        ns = nvme_subsystem_next_ns(self, ns)
+	%}
 	%immutable name;
 	const char *name;
 	%immutable host;
@@ -924,9 +955,14 @@ struct nvme_ns {
 		};
 		return ret;
 	}
-	struct nvme_ns* namespaces() {
-		return nvme_ctrl_first_ns($self);
-	}
+	%pythoncode %{
+	def namespaces(self):
+	    """Iterator over all namespace objects"""
+	    ns = nvme_ctrl_first_ns(self)
+	    while ns:
+	        yield ns
+	        ns = nvme_ctrl_next_ns(self, ns)
+	%}
 }
 
 %{

libnvme/tests/gc.py

@@ -12,9 +12,6 @@
 host = nvme.host(root)
 print(f'host: {host}')
 
-subsystem = host.subsystems()
-print(f'subsystem: {subsystem}')
-
 ctrls = []
 for i in range(10):
     ctrl = nvme.ctrl(
@@ -25,8 +22,10 @@
     ctrls.append(ctrl)
     print(f'ctrl {i}: {ctrl}')
 
-ns = subsystem.namespaces() if subsystem is not None else None
-print(f'ns: {ns}')
+for s in host.subsystems():
+    print(f'subsystem: {s}')
+    for ns in s.namespaces():
+        print(f'ns: {ns}')
 
 # Deleting objects in the following order would create a segmentation
 # fault if it weren't for the %pythonappend in nvme.i. This test is to