Build out the API for dealing with a bunch of reference checks and
changes within a transaction. Define an opaque ref_transaction type
that is managed entirely within refs.c. Introduce functions for
beginning a transaction, adding updates to a transaction, and
committing/rolling back a transaction.
This API will soon replace update_refs().
Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
---
refs.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
refs.h | 65 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 164 insertions(+)
diff --git a/refs.c b/refs.c
index 1305eb1..f0b5764 100644
--- a/refs.c
+++ b/refs.c
@@ -3267,6 +3267,96 @@ static int update_ref_write(const char *action, const char *refname,
return 0;
}
+/*
+ * 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.
+ */
+struct ref_transaction {
+ struct ref_update **updates;
+ size_t alloc;
+ size_t nr;
+};
+
+struct ref_transaction *ref_transaction_begin(void)
+{
+ return xcalloc(1, sizeof(struct ref_transaction));
+}
+
+static void ref_transaction_free(struct ref_transaction *transaction)
+{
+ int i;
+
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+
+ free((char *)update->ref_name);
+ free(update);
+ }
+
+ free(transaction->updates);
+ free(transaction);
+}
+
+void ref_transaction_rollback(struct ref_transaction *transaction)
+{
+ ref_transaction_free(transaction);
+}
+
+static struct ref_update *add_update(struct ref_transaction *transaction,
+ const char *refname)
+{
+ struct ref_update *update = xcalloc(1, sizeof(*update));
+
+ update->ref_name = xstrdup(refname);
+ ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
+ transaction->updates[transaction->nr++] = update;
+ return update;
+}
+
+void ref_transaction_update(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *new_sha1, unsigned char *old_sha1,
+ int flags, int have_old)
+{
+ struct ref_update *update = add_update(transaction, refname);
+
+ hashcpy(update->new_sha1, new_sha1);
+ update->flags = flags;
+ update->have_old = have_old;
+ if (have_old)
+ hashcpy(update->old_sha1, old_sha1);
+}
+
+void ref_transaction_create(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *new_sha1,
+ int flags)
+{
+ struct ref_update *update = add_update(transaction, refname);
+
+ assert(!is_null_sha1(new_sha1));
+ hashcpy(update->new_sha1, new_sha1);
+ hashclr(update->old_sha1);
+ update->flags = flags;
+ update->have_old = 1;
+}
+
+void ref_transaction_delete(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *old_sha1,
+ int flags, int have_old)
+{
+ struct ref_update *update = add_update(transaction, refname);
+
+ update->flags = flags;
+ update->have_old = have_old;
+ if (have_old) {
+ assert(!is_null_sha1(old_sha1));
+ hashcpy(update->old_sha1, old_sha1);
+ }
+}
+
int update_ref(const char *action, const char *refname,
const unsigned char *sha1, const unsigned char *oldval,
int flags, enum action_on_err onerr)
@@ -3378,6 +3468,15 @@ cleanup:
return ret;
}
+int ref_transaction_commit(struct ref_transaction *transaction,
+ const char *msg, enum action_on_err onerr)
+{
+ int ret = update_refs(msg, transaction->updates, transaction->nr,
+ onerr);
+ ref_transaction_free(transaction);
+ return ret;
+}
+
char *shorten_unambiguous_ref(const char *refname, int strict)
{
int i;
diff --git a/refs.h b/refs.h
index 08e60ac..0518dd5 100644
--- a/refs.h
+++ b/refs.h
@@ -24,6 +24,8 @@ struct ref_update {
int have_old; /* 1 if old_sha1 is valid, 0 otherwise */
};
+struct ref_transaction;
+
/*
* Bit values set in the flags argument passed to each_ref_fn():
*/
@@ -220,6 +222,69 @@ enum action_on_err {
UPDATE_REFS_QUIET_ON_ERR
};
+/*
+ * Begin a reference transaction. The reference transaction must
+ * eventually be commited using ref_transaction_commit() or rolled
+ * back using ref_transaction_rollback().
+ */
+struct ref_transaction *ref_transaction_begin(void);
+
+/*
+ * Roll back a ref_transaction and free all associated data.
+ */
+void ref_transaction_rollback(struct ref_transaction *transaction);
+
+
+/*
+ * The following functions add a reference check or update to a
+ * ref_transaction. In all of them, refname is the name of the
+ * reference to be affected. The functions make internal copies of
+ * refname, so the caller retains ownership of the parameter. flags
+ * can be REF_NODEREF; it is passed to update_ref_lock().
+ */
+
+
+/*
+ * Add a reference update to transaction. new_sha1 is the value that
+ * the reference should have after the update, or zeros if it should
+ * be deleted. If have_old is true, then old_sha1 holds the value
+ * that the reference should have had before the update, or zeros if
+ * it must not have existed beforehand.
+ */
+void ref_transaction_update(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *new_sha1, unsigned char *old_sha1,
+ int flags, int have_old);
+
+/*
+ * Add a reference creation to transaction. new_sha1 is the value
+ * that the reference should have after the update; it must not be the
+ * null SHA-1. It is verified that the reference does not exist
+ * already.
+ */
+void ref_transaction_create(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *new_sha1,
+ int flags);
+
+/*
+ * Add a reference deletion to transaction. If have_old is true, then
+ * old_sha1 holds the value that the reference should have had before
+ * the update (which must not be the null SHA-1).
+ */
+void ref_transaction_delete(struct ref_transaction *transaction,
+ const char *refname,
+ unsigned char *old_sha1,
+ int flags, int have_old);
+
+/*
+ * Commit all of the changes that have been queued in transaction, as
+ * atomically as possible. Return a nonzero value if there is a
+ * problem. The ref_transaction is freed by this function.
+ */
+int ref_transaction_commit(struct ref_transaction *transaction,
+ const char *msg, enum action_on_err onerr);
+
/** Lock a ref and then write its file */
int update_ref(const char *action, const char *refname,
const unsigned char *sha1, const unsigned char *oldval,
--
1.9.1
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