Re: [PATCH v3 17/19] refs.c: change update_ref to use a transaction

Thanks.

On Fri, Apr 25, 2014 at 4:28 PM, Michael Haggerty [off-list ref] wrote:

On 04/25/2014 06:14 PM, Ronnie Sahlberg wrote:

quoted

Change the update_ref helper function to use a ref transaction internally.

Signed-off-by: Ronnie Sahlberg <redacted>
---
 refs.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/refs.c b/refs.c
index 1557c3c..95df4a9 100644
--- a/refs.c
+++ b/refs.c

@@ -3397,11 +3397,26 @@ int update_ref(const char *action, const char *refname,
             const unsigned char *sha1, const unsigned char *oldval,
             int flags, enum action_on_err onerr)
 {
-     struct ref_lock *lock;
-     lock = update_ref_lock(refname, oldval, flags, NULL, onerr);
-     if (!lock)
+     struct ref_transaction *t;
+     char *err = NULL;
+
+     t = ref_transaction_begin();
+     if ((!t ||
+         ref_transaction_update(t, refname, sha1, oldval, flags,
+                                !!oldval)) ||
+         (ref_transaction_commit(t, action, &err) && !(t = NULL))) {

This is transient code to just show how ugly this pattern becomes when
ref_transaction_commit()
implicitly also frees the transaction.

Later patches toward the end of the series will replace this with
something nicer.
Currently in this patch series I pass a pointer to pointer for the
transaction to _commit()
but that is perhaps not optimal either.
I will try and see how it would look if _commit would not free the
transaction at all
and the caller would always have to call ref_transaction_free() explicitely.


I am thinking of something like this :

   t = ref_transaction_begin();
   if ((!t ||
       ref_transaction_update(t, ...)) ||
       ref_transaction_commit(t, ...)) {
          ...something...
   }
   ref_transaction_free(t);

You seem to have extra parentheses around the first || subexpression.

You also don't need the parentheses around the && expression because &&
binds more tightly than ||.

But using "!(t = NULL)" in the middle of a conditional expression is
pretty obscure.  I think you will change this in a later patch, so I
will defer my comments.

quoted

+          const char *str = "update_ref failed for ref '%s': %s";

Indentation error.

Fixed.

quoted

+
+             ref_transaction_rollback(t);
+             switch (onerr) {
+             case UPDATE_REFS_MSG_ON_ERR: error(str, refname, err); break;
+             case UPDATE_REFS_DIE_ON_ERR: die(str, refname, err); break;
+             case UPDATE_REFS_QUIET_ON_ERR: break;
+             free(err);
+             }
              return 1;
-     return update_ref_write(action, refname, sha1, lock, NULL, onerr);
+     }
+     return 0;
 }

 static int ref_update_compare(const void *r1, const void *r2)

--
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/