python: support 'with' statement for objects

The python 'with' statement allows for correct resource tracking,
where the allocated resource will be freed at the end of the statement.
This is helpful for 'host', 'subsystem', and 'controller' objects
which we might want to clean up (and clear out the internal tree).
The nice thing here is that we can do an automatic controller
disconnect, and don't have to worry about leaving stale connections
or objects around.

Signed-off-by: Hannes Reinecke <[email protected]>

Author: hreinecke

libnvme/nvme.i

@@ -496,6 +496,12 @@ struct nvme_ns {
 	~nvme_root() {
 		nvme_free_tree($self);
 	}
+	struct nvme_root* __enter__() {
+		return $self;
+	}
+	struct nvme_root* __exit__(PyObject *type, PyObject *value, PyObject *traceback) {
+		return $self;
+	}
 	void log_level(const char *level) {
 		int log_level = DEFAULT_LOGLEVEL;
 		if (!strcmp(level, "debug")) log_level = LOG_DEBUG;
@@ -559,6 +565,12 @@ struct nvme_ns {
 	~nvme_host() {
 		nvme_free_host($self);
 	}
+	struct nvme_host* __enter__() {
+		return $self;
+	}
+	struct nvme_host* __exit__(PyObject *type, PyObject *value, PyObject *traceback) {
+		return $self;
+	}
 	%feature("autodoc", SET_SYMNAME_DOCSTRING) set_symname;
 	void set_symname(const char *hostsymname) {
 		nvme_host_set_hostsymname($self, hostsymname);
@@ -599,6 +611,12 @@ struct nvme_ns {
 	~nvme_subsystem() {
 		nvme_free_subsystem($self);
 	}
+	struct nvme_subsystem* __enter__() {
+		return $self;
+	}
+	struct nvme_subsystem* __exit__(PyObject *type, PyObject *value, PyObject *traceback) {
+		return $self;
+	}
 	PyObject *__str__() {
 		return PyUnicode_FromFormat("nvme.subsystem(%s,%s)", STR_OR_NONE($self->name), STR_OR_NONE($self->subsysnqn));
 	}
@@ -664,6 +682,14 @@ struct nvme_ns {
 	~nvme_ctrl() {
 		nvme_free_ctrl($self);
 	}
+	struct nvme_ctrl* __enter__() {
+		return $self;
+	}
+	struct nvme_ctrl* __exit__(PyObject *type, PyObject *value, PyObject *traceback) {
+		if (nvme_ctrl_get_name($self))
+			nvme_disconnect_ctrl($self);
+		return $self;
+	}
 
 	%pythoncode %{
 	def discovery_ctrl_set(self, discovery: bool):
@@ -962,6 +988,12 @@ struct nvme_ns {
 	~nvme_ns() {
 		nvme_free_ns($self);
 	}
+	struct nvme_ns* __enter__() {
+		return $self;
+	}
+	struct nvme_ns* __exit__(PyObject *type, PyObject *value, PyObject *traceback) {
+		return $self;
+	}
 	PyObject *__str__() {
 		return PyUnicode_FromFormat("nvme.ns(%u)", $self->nsid);
 	}