hook: add internal state alloc/free callbacks

Some hooks use opaque structs to keep internal state between callbacks.

Because hooks ran sequentially (jobs == 1) with one command per hook,
these internal states could be allocated on the stack for each hook run.

Next commits add the ability to run multiple commands for each hook, so
the states cannot be shared or stored on the stack anymore, especially
since down the line we will also enable parallel execution (jobs > 1).

Add alloc/free helpers for each hook, doing a "deep" alloc/init & free
of their internal opaque struct.

The alloc callback takes a context pointer, to initialize the struct at
at the time of resource acquisition.

These callbacks must always be provided together: no alloc without free
and no free without alloc, otherwise a BUG() is triggered.

Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/refs.c b/refs.c
index 1e2ac90018..e06a137c29 100644
--- a/refs.c
+++ b/refs.c
@@ -2511,24 +2511,38 @@ static int transaction_hook_feed_stdin(int hook_stdin_fd, void *pp_cb, void *pp_
 	return 0; /* no more input to feed */
 }
 
+static void *transaction_feed_cb_data_alloc(void *feed_pipe_ctx UNUSED)
+{
+	struct transaction_feed_cb_data *data = xmalloc(sizeof(*data));
+	strbuf_init(&data->buf, 0);
+	data->index = 0;
+	return data;
+}
+
+static void transaction_feed_cb_data_free(void *data)
+{
+	struct transaction_feed_cb_data *d = data;
+	if (!d)
+		return;
+	strbuf_release(&d->buf);
+	free(d);
+}
+
 static int run_transaction_hook(struct ref_transaction *transaction,
 				const char *state)
 {
 	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
-	struct transaction_feed_cb_data feed_ctx = { 0 };
 	int ret = 0;
 
 	strvec_push(&opt.args, state);
 
 	opt.feed_pipe = transaction_hook_feed_stdin;
 	opt.feed_pipe_ctx = transaction;
-	opt.feed_pipe_cb_data = &feed_ctx;
-
-	strbuf_init(&feed_ctx.buf, 0);
+	opt.feed_pipe_cb_data_alloc = transaction_feed_cb_data_alloc;
+	opt.feed_pipe_cb_data_free = transaction_feed_cb_data_free;
 
 	ret = run_hooks_opt(transaction->ref_store->repo, "reference-transaction", &opt);
 
-	strbuf_release(&feed_ctx.buf);
 	return ret;
 }