On 4/19/20 4:14 PM, Richard W.M. Jones wrote:
This extends the vector library with an insert function. It is more
expensive than appending, but this does not affect existing code using
vector and can be used in new places without making those uses more
expensive.
We use this function in nbdkit-extentlist-filter, nbdkit-eval-plugin
and the sparse library.
This is refactoring, so should not affect functionality at all.
However during the rewrite of eval it revealed a fencepost error in
the loop iterating over method_scripts which is fixed here.
---
common/sparse/Makefile.am | 1 +
common/utils/vector.h | 24 +++++--
common/sparse/sparse.c | 50 +++++++-------
plugins/eval/eval.c | 49 ++++++--------
filters/extentlist/extentlist.c | 113 ++++++++++++++++----------------
TODO | 5 +-
6 files changed, 119 insertions(+), 123 deletions(-)
+++ b/plugins/eval/eval.c
@@ -104,21 +106,12 @@ compare_script (const void *methodvp, const void *entryvp)
static int
insert_method_script (const char *method, char *script)
{
- struct method_script *newp;
- size_t i;
int r;
+ size_t i;
+ struct method_script new_entry = { .method = method, .script = script };
- newp = realloc (method_scripts,
- sizeof (struct method_script) * (nr_method_scripts + 1));
- if (newp == NULL) {
- nbdkit_error ("insert_method_script: realloc: %m");
- return -1;
- }
- nr_method_scripts++;
- method_scripts = newp;
The old code appended the new element first, then
-
- for (i = 0; i < nr_method_scripts-1; ++i) {
- r = compare_script (method, &method_scripts[i]);
iterated on the previously-existing elements to see if re-sorting was
needed.
+ for (i = 0; i < method_scripts.size; ++i) {
+ r = compare_script (method, &method_scripts.ptr[i]);
The new code does not increase the list size until first finding where
to insert. I see why you called this a fencepost error, as comparing
just the pre-/post-patch 'for' lines looks like you fixed an off-by-one
error, but with the additional context of when the list counter was
incremented, I don't think it is actually a bug fix, so the commit
message had me hunting for something not there.
At any rate, the series looks good.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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