[PATCH v11 16/41] refs.c: add transaction.status and track OPEN/CLOSED/ERROR

[Ronnie Sahlberg <sahlberg@google.com>]

Track the status of a transaction in a new status field. Check the field for
sanity, i.e. that status must be OPEN when _commit/_create/_delete or
_update is called or else die(BUG:...)

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index 1c660e0..9992da4 100644
--- a/refs.c
+++ b/refs.c
@@ -3335,6 +3335,27 @@ struct ref_update {
 };
 
 /*
+ * Transaction states.
+ * OPEN:   The transaction is in a valid state and can accept new updates.
+ *         An OPEN transaction can be committed.
+ * CLOSED: If an open transaction is successfully committed the state will
+ *         change to CLOSED. No further changes can be made to a CLOSED
+ *         transaction.
+ *         CLOSED means that all updates have been successfully committed and
+ *         the only thing that remains is to free the completed transaction.
+ * ERROR:  The transaction has failed. No further updates are possible
+ *         and any calls except free will return an error.
+ *         An ERRORed transaction can not be committed.
+ *         An ERRORed transaction can be rolled back and discarded by calling
+ *         by calling transaction_free.
+ */
+enum ref_transaction_state {
+	REF_TRANSACTION_OPEN   = 0,
+	REF_TRANSACTION_CLOSED = 1,
+	REF_TRANSACTION_ERROR  = 2,
+};
+
+/*
  * Data structure for holding a reference transaction, which can
  * consist of checks and updates to multiple references, carried out
  * as atomically as possible.  This structure is opaque to callers.
@@ -3343,6 +3364,8 @@ struct ref_transaction {
 	struct ref_update **updates;
 	size_t alloc;
 	size_t nr;
+	enum ref_transaction_state state;
+	int status;
 };
 
 struct ref_transaction *ref_transaction_begin(struct strbuf *err)
@@ -3385,6 +3408,9 @@ int ref_transaction_update(struct ref_transaction *transaction,
 {
 	struct ref_update *update;
 
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		return -1;
+
 	if (have_old && !old_sha1)
 		die("BUG: have_old is true but old_sha1 is NULL");
 
@@ -3405,6 +3431,9 @@ int ref_transaction_create(struct ref_transaction *transaction,
 {
 	struct ref_update *update;
 
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		return -1;
+
 	if (!new_sha1 || is_null_sha1(new_sha1))
 		die("BUG: create ref with null new_sha1");
 
@@ -3425,6 +3454,9 @@ int ref_transaction_delete(struct ref_transaction *transaction,
 {
 	struct ref_update *update;
 
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		return -1;
+
 	if (have_old && !old_sha1)
 		die("BUG: have_old is true but old_sha1 is NULL");
 
@@ -3480,8 +3512,13 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	int n = transaction->nr;
 	struct ref_update **updates = transaction->updates;
 
-	if (!n)
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		return transaction->status;
+
+	if (!n) {
+		transaction->state = REF_TRANSACTION_CLOSED;
 		return 0;
+	}
 
 	/* Allocate work space */
 	delnames = xmalloc(sizeof(*delnames) * n);
@@ -3544,6 +3581,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	clear_loose_ref_cache(&ref_cache);
 
 cleanup:
+	transaction->state = ret ? REF_TRANSACTION_ERROR
+		: REF_TRANSACTION_CLOSED;
+
 	for (i = 0; i < n; i++)
 		if (updates[i]->lock)
 			unlock_ref(updates[i]->lock);
-- 
2.0.0.rc3.474.g0203784