[PATCH v9 14/37] hook: provide stdin by string_list or callback

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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 provide a callback the users can populate line after line
with instead.

Signed-off-by: Emily Shaffer <emilyshaffer@xxxxxxxxxx>
---
 hook.c | 38 ++++++++++++++++++++++++++++++++++++--
 hook.h | 28 ++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/hook.c b/hook.c
index 1fa7976583..8aa0d4fdf2 100644
--- a/hook.c
+++ b/hook.c
@@ -7,8 +7,10 @@
 
 void free_hook(struct hook *ptr)
 {
-	if (ptr)
+	if (ptr) {
 		strbuf_release(&ptr->command);
+		free(ptr->feed_pipe_cb_data);
+	}
 	free(ptr);
 }
 
@@ -38,6 +40,7 @@ static void append_or_move_hook(struct list_head *head, const char *command)
 		strbuf_init(&to_add->command, 0);
 		strbuf_addstr(&to_add->command, command);
 		to_add->from_hookdir = 0;
+		to_add->feed_pipe_cb_data = NULL;
 	}
 
 	/* re-set the scope so we show where an override was specified */
@@ -257,6 +260,8 @@ void run_hooks_opt_init_sync(struct run_hooks_opt *o)
 	o->run_hookdir = configured_hookdir_opt();
 	o->jobs = 1;
 	o->dir = NULL;
+	o->feed_pipe = NULL;
+	o->feed_pipe_ctx = NULL;
 }
 
 void run_hooks_opt_init_async(struct run_hooks_opt *o)
@@ -290,6 +295,28 @@ 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 string_list *to_pipe = ((struct hook_cb_data*)pp_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,
@@ -305,6 +332,10 @@ 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;
 	}
@@ -383,6 +414,9 @@ int run_hooks(const char *hookname, 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");
+
 	to_run = hook_list(hookname);
 
 	list_for_each_safe(pos, tmp, to_run) {
@@ -402,7 +436,7 @@ int run_hooks(const char *hookname, struct run_hooks_opt *options)
 	run_processes_parallel_tr2(options->jobs,
 				   pick_next_hook,
 				   notify_start_failure,
-				   NULL,
+				   options->feed_pipe,
 				   notify_hook_finished,
 				   &cb_data,
 				   "hook",
diff --git a/hook.h b/hook.h
index 218b9e1721..aba62d4112 100644
--- a/hook.h
+++ b/hook.h
@@ -2,6 +2,7 @@
 #include "list.h"
 #include "strbuf.h"
 #include "strvec.h"
+#include "run-command.h"
 
 struct hook {
 	struct list_head list;
@@ -13,6 +14,12 @@ struct hook {
 	/* The literal command to run. */
 	struct strbuf command;
 	unsigned from_hookdir : 1;
+
+	/*
+	 * 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;
 };
 
 /*
@@ -58,14 +65,35 @@ 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;
 
 	/* Number of threads to parallelize across */
 	int jobs;
 
 	/* Path to initial working directory for subprocess */
 	const char *dir;
+
 };
 
+/*
+ * 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);
+
 /*
  * Callback provided to feed_pipe_fn and consume_sideband_fn.
  */
-- 
2.31.1.818.g46aad6cb9e-goog




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