> 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.
[snip]
> diff --git a/hook.h b/hook.h
> index 8a7542610c..0ac83fa7ca 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
> {
> @@ -14,6 +15,12 @@ struct hook
> /* The literal command to run. */
> struct strbuf command;
> int from_hookdir;
> +
> + /*
> + * 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;
When would we need per-hook state? I see in patch 14 that you give each
running process little by little (in pp_buffer_stdin()), perhaps so that
each hook can make progress at roughly the same pace, but I don't think
we can expect all hooks to work the same, so I don't think it's worth
complicating the design for all that.
> };
>
> /*
> @@ -57,12 +64,24 @@ struct run_hooks_opt
>
> /* Path to file which should be piped to stdin for each hook */
> const char *path_to_stdin;
> + /* Pipe each string to stdin, separated by newlines */
> + struct string_list str_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).
> + */
> + feed_pipe_fn feed_pipe;
> + void *feed_pipe_ctx;
Instead of 3 fields, I think 2 suffice - the function and the data
(called "ctx" here). We can supply a function that treats the data as a
string_list.
