However this does not implement can_cache, since that is not a simple
boolean.
---
plugins/python/nbdkit-python-plugin.pod | 14 +++++++++-
plugins/python/python.c | 34 +++++++++++++++++++++++++
2 files changed, 47 insertions(+), 1 deletion(-)
diff --git a/plugins/python/nbdkit-python-plugin.pod
b/plugins/python/nbdkit-python-plugin.pod
index 0fd4dcb..ee58cd7 100644
--- a/plugins/python/nbdkit-python-plugin.pod
+++ b/plugins/python/nbdkit-python-plugin.pod
@@ -293,6 +293,19 @@ because there is nothing to optimize if
S<C<flags & nbdkit.FLAG_MAY_TRIM>> is false), use
S<C<nbdkit.set_error (errno.EOPNOTSUPP)>>.
+=item C<cache>
+
+(Optional)
+
+ def cache(h, count, offset, flags):
+ # no return value
+
+The body of your C<cache> function should prefetch data in the
+indicated range.
+
+If the cache operation fails, your function should throw an exception,
+optionally using C<nbdkit.set_error> first.
+
=back
=head2 Missing callbacks
@@ -321,7 +334,6 @@ C<can_zero>,
C<can_fast_zero>,
C<can_extents>,
C<can_multi_conn>,
-C<cache>,
C<extents>.
These are not yet supported.
diff --git a/plugins/python/python.c b/plugins/python/python.c
index 9445343..6d5a0b7 100644
--- a/plugins/python/python.c
+++ b/plugins/python/python.c
@@ -683,6 +683,39 @@ py_zero (void *handle, uint32_t count, uint64_t offset, uint32_t
flags)
return -1;
}
+static int
+py_cache (void *handle, uint32_t count, uint64_t offset, uint32_t flags)
+{
+ PyObject *obj = handle;
+ PyObject *fn;
+ PyObject *r;
+
+ if (callback_defined ("cache", &fn)) {
+ PyErr_Clear ();
+
+ switch (py_api_version) {
+ case 1:
+ nbdkit_error ("%s can only be called when using api_version >= 2",
+ "cache");
+ return -1;
+ case 2:
+ r = PyObject_CallFunction (fn, "OiLI", obj, count, offset, flags, NULL);
+ break;
+ default: abort ();
+ }
+ Py_DECREF (fn);
+ if (check_python_failure ("cache") == -1)
+ return -1;
+ Py_DECREF (r);
+ }
+ else {
+ nbdkit_error ("%s not implemented", "cache");
+ return -1;
+ }
+
+ return 0;
+}
+
static int
boolean_callback (void *handle, const char *can_fn, const char *plain_fn)
{
@@ -768,6 +801,7 @@ static struct nbdkit_plugin plugin = {
.flush = py_flush,
.trim = py_trim,
.zero = py_zero,
+ .cache = py_cache,
};
NBDKIT_REGISTER_PLUGIN (plugin)
--
2.23.0