lightningd/subdaemon: routines to create daemons and get request/response.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/subdaemon.h

@@ -0,0 +1,83 @@
+#ifndef LIGHTNING_LIGHTNINGD_SUBDAEMON_H
+#define LIGHTNING_LIGHTNINGD_SUBDAEMON_H
+#include "config.h"
+#include <ccan/endian/endian.h>
+#include <ccan/list/list.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+
+struct io_conn;
+
+/* One of our subdaemons. */
+struct subdaemon {
+	/* Name, like John, or "lightningd_hsm" */
+	const char *name;
+	/* The Big Cheese. */
+	struct lightningd *ld;
+	/* pid, for waiting for status when it dies. */
+	int pid;
+	/* Connection for status (read, then write) */
+	struct io_conn *status_conn;
+	/* Connection for requests if any (write, then read) */
+	struct io_conn *req_conn;
+
+	/* For logging */
+	struct log *log;
+
+	const char *(*statusname)(int status);
+	const char *(*reqname)(int req);
+	void (*finished)(struct subdaemon *sd, int status);
+
+	/* Buffer for input. */
+	u8 *status_in;
+
+	/* Status handler puts last status msg here. */
+	u8 *last_status;
+
+	/* Requests queue up here. */
+	struct list_head reqs;
+};
+
+/**
+ * new_subdaemon - create a new subdaemon.
+ * @ctx: context to allocate from
+ * @ld: global state
+ * @name: basename of daemon
+ * @statusname: function to get name from status messages
+ * @reqname: function to get name from request messages, or NULL if no requests.
+ * @finished: function to call when it's finished (with exit status).
+ * @...: the fds to hand as fd 3, 4... terminated with -1.
+ *
+ * You should free it from finished().
+ */
+struct subdaemon *new_subdaemon(const tal_t *ctx,
+				struct lightningd *ld,
+				const char *name,
+				const char *(*statusname)(int status),
+				const char *(*reqname)(int req),
+				void (*finished)(struct subdaemon *, int), ...);
+
+/**
+ * subdaemon_req - add a request to the subdaemon.
+ * @sd: subdaemon to request
+ * @msg_out: request message (can be take, can be NULL for fd passing only)
+ * @fd_out: if >=0 fd to pass at the end of the message (closed after)
+ * @fd_in: if not NULL, where to put fd read in at end of reply.
+ * @reqcb: callback when reply comes in
+ * @reqcb_data: final arg to hand to @reqcb
+ *
+ * The subdaemon must take requests.
+ */
+#define subdaemon_req(sd, msg_out, fd_out, fd_in, reqcb, reqcb_data)	\
+	subdaemon_req_((sd), (msg_out), (fd_out), (fd_in),		\
+		       typesafe_cb_preargs(void, void *,		\
+					   (reqcb), (reqcb_data),	\
+					   struct subdaemon *,		\
+					   const u8 *),			\
+		       (reqcb_data))
+void subdaemon_req_(struct subdaemon *sd,
+		    const u8 *msg_out,
+		    int fd_out, int *fd_in,
+		    void (*reqcb)(struct subdaemon *, const u8 *, void *),
+		    void *reqcb_data);
+#endif /* LIGHTNING_LIGHTNINGD_SUBDAEMON_H */