refs.c: add transaction.status and track OPEN/CLOSED

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

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index 9cb79081b5b7edcb0d40cf6f689e6f6d61606f53..cc6305630c2ee6ef6802cf5aa479caf729640387 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -3386,6 +3386,21 @@ struct ref_update {
        const char refname[FLEX_ARRAY];
 };
 
+/*
+ * Transaction states.
+ * OPEN:   The transaction is in a valid state and can accept new updates.
+ *         An OPEN transaction can be committed.
+ * CLOSED: A closed transaction is no longer active and no other operations
+ *         than free can be used on it in this state.
+ *         A transaction can either become closed by successfully committing
+ *         an active transaction or if there is a failure while building
+ *         the transaction thus rendering it failed/inactive.
+ */
+enum ref_transaction_state {
+       REF_TRANSACTION_OPEN   = 0,
+       REF_TRANSACTION_CLOSED = 1
+};
+
 /*
  * Data structure for holding a reference transaction, which can
  * consist of checks and updates to multiple references, carried out
@@ -3395,6 +3410,7 @@ struct ref_transaction {
        struct ref_update **updates;
        size_t alloc;
        size_t nr;
+       enum ref_transaction_state state;
 };
 
 struct ref_transaction *ref_transaction_begin(struct strbuf *err)
@@ -3437,6 +3453,9 @@ int ref_transaction_update(struct ref_transaction *transaction,
 {
        struct ref_update *update;
 
+       if (transaction->state != REF_TRANSACTION_OPEN)
+               die("BUG: update called for transaction that is not open");
+
        if (have_old && !old_sha1)
                die("BUG: have_old is true but old_sha1 is NULL");
 
@@ -3457,6 +3476,9 @@ int ref_transaction_create(struct ref_transaction *transaction,
 {
        struct ref_update *update;
 
+       if (transaction->state != REF_TRANSACTION_OPEN)
+               die("BUG: create called for transaction that is not open");
+
        if (!new_sha1 || is_null_sha1(new_sha1))
                die("BUG: create ref with null new_sha1");
 
@@ -3477,6 +3499,9 @@ int ref_transaction_delete(struct ref_transaction *transaction,
 {
        struct ref_update *update;
 
+       if (transaction->state != REF_TRANSACTION_OPEN)
+               die("BUG: delete called for transaction that is not open");
+
        if (have_old && !old_sha1)
                die("BUG: have_old is true but old_sha1 is NULL");
 
@@ -3532,8 +3557,13 @@ 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)
+               die("BUG: commit called for transaction that is not open");
+
+       if (!n) {
+               transaction->state = REF_TRANSACTION_CLOSED;
                return 0;
+       }
 
        /* Allocate work space */
        delnames = xmalloc(sizeof(*delnames) * n);
@@ -3595,6 +3625,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        clear_loose_ref_cache(&ref_cache);
 
 cleanup:
+       transaction->state = REF_TRANSACTION_CLOSED;
+
        for (i = 0; i < n; i++)
                if (updates[i]->lock)
                        unlock_ref(updates[i]->lock);