[18/27] hook: provide stdin by string_list or callback

Commit Message

Ævar Arnfjörð Bjarmason June 17, 2021, 10:22 a.m. UTC

From: Emily Shaffer <[e-mail]>

In cases where a hook requires only a small amount of information via
stdin, it should be simple for users to provide a string_list alone. But
in more complicated cases where the stdin is too large to hold in
memory, let's instead provide a callback the users can populate line
after line.

Signed-off-by: Emily Shaffer <[e-mail]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[e-mail]>
---
 hook.c | 32 +++++++++++++++++++++++++++++++-
 hook.h | 27 +++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

Patch

diff --git a/hook.c b/hook.c
index a012c3d458..c4df787f13 100644
--- a/hook.c
+++ b/hook.c
@@ -77,6 +77,29 @@  void run_hooks_opt_clear(struct run_hooks_opt *o)
 	strvec_clear(&o->args);
 }
 
+int pipe_from_string_list(struct strbuf *pipe, void *pp_cb, void *pp_task_cb)
+{
+	int *item_idx;
+	struct hook *ctx = pp_task_cb;
+	struct hook_cb_data *hook_cb = pp_cb;
+	struct string_list *to_pipe = hook_cb->options->feed_pipe_ctx;
+
+	/* Bootstrap the state manager if necessary. */
+	if (!ctx->feed_pipe_cb_data) {
+		ctx->feed_pipe_cb_data = xmalloc(sizeof(unsigned int));
+		*(int*)ctx->feed_pipe_cb_data = 0;
+	}
+
+	item_idx = ctx->feed_pipe_cb_data;
+
+	if (*item_idx < to_pipe->nr) {
+		strbuf_addf(pipe, "%s\n", to_pipe->items[*item_idx].string);
+		(*item_idx)++;
+		return 0;
+	}
+	return 1;
+}
+
 static int pick_next_hook(struct child_process *cp,
 			  struct strbuf *out,
 			  void *pp_cb,
@@ -90,6 +113,10 @@  static int pick_next_hook(struct child_process *cp,
 	if (hook_cb->options->path_to_stdin) {
 		cp->no_stdin = 0;
 		cp->in = xopen(hook_cb->options->path_to_stdin, O_RDONLY);
+	} else if (hook_cb->options->feed_pipe) {
+		/* ask for start_command() to make a pipe for us */
+		cp->in = -1;
+		cp->no_stdin = 0;
 	} else {
 		cp->no_stdin = 1;
 	}
@@ -164,7 +191,7 @@  int run_found_hooks(const char *hook_name, const char *hook_path,
 	run_processes_parallel_tr2(options->jobs,
 				   pick_next_hook,
 				   notify_start_failure,
-				   NULL,
+				   options->feed_pipe,
 				   notify_hook_finished,
 				   &cb_data,
 				   "hook",
@@ -182,6 +209,9 @@  int run_hooks(const char *hook_name, struct run_hooks_opt *options)
 	if (!options)
 		BUG("a struct run_hooks_opt must be provided to run_hooks");
 
+	if (options->path_to_stdin && options->feed_pipe)
+		BUG("choose only one method to populate stdin");
+
 	hook_path = find_hook(hook_name);
 
 	/*
diff --git a/hook.h b/hook.h
index c4ac054ee3..b78a8e4805 100644
--- a/hook.h
+++ b/hook.h
@@ -19,6 +19,12 @@  int hook_exists(const char *hookname);
 struct hook {
 	/* The path to the hook */
 	const char *hook_path;
+
+	/*
+	 * Use this to keep state for your feed_pipe_fn if you are using
+	 * run_hooks_opt.feed_pipe. Otherwise, do not touch it.
+	 */
+	void *feed_pipe_cb_data;
 };
 
 struct run_hooks_opt
@@ -47,6 +53,19 @@  struct run_hooks_opt
 
 	/* Path to file which should be piped to stdin for each hook */
 	const char *path_to_stdin;
+
+	/*
+	 * Callback and state pointer to ask for more content to pipe to stdin.
+	 * Will be called repeatedly, for each hook. See
+	 * hook.c:pipe_from_stdin() for an example. Keep per-hook state in
+	 * hook.feed_pipe_cb_data (per process). Keep initialization context in
+	 * feed_pipe_ctx (shared by all processes).
+	 *
+	 * See 'pipe_from_string_list()' for info about how to specify a
+	 * string_list as the stdin input instead of writing your own handler.
+	 */
+	feed_pipe_fn feed_pipe;
+	void *feed_pipe_ctx;
 };
 
 #define RUN_HOOKS_OPT_INIT { \
@@ -55,6 +74,14 @@  struct run_hooks_opt
 	.args = STRVEC_INIT, \
 }
 
+/*
+ * To specify a 'struct string_list', set 'run_hooks_opt.feed_pipe_ctx' to the
+ * string_list and set 'run_hooks_opt.feed_pipe' to 'pipe_from_string_list()'.
+ * This will pipe each string in the list to stdin, separated by newlines.  (Do
+ * not inject your own newlines.)
+ */
+int pipe_from_string_list(struct strbuf *pipe, void *pp_cb, void *pp_task_cb);
+
 struct hook_cb_data {
 	/* rc reflects the cumulative failure state */
 	int rc;