plugin: Setup read and write connection to talk to the plugin

Mostly copied from bitcoind.c

contrib/helloworld-plugin/main.py

@@ -46,7 +46,6 @@ methods = {
     'ping': json_ping,
 }
 
-
 partial = ""
 for l in sys.stdin:
     partial += l

lightningd/plugin.c

@@ -1,5 +1,6 @@
 #include "lightningd/plugin.h"
 
+#include <ccan/io/io.h>
 #include <ccan/list/list.h>
 #include <ccan/pipecmd/pipecmd.h>
 #include <ccan/tal/str/str.h>
@@ -10,12 +11,27 @@ struct plugin {
 	int stdin, stdout;
 	pid_t pid;
 	char *cmd;
+	struct io_conn *stdin_conn, *stdout_conn;
+	bool stop;
+
+	/* Stuff we read */
+	char *buffer;
+	size_t used, len_read;
+
+	/* Stuff we write */
+	struct list_head output;
+	const char *outbuf;
 };
 
 struct plugins {
 	struct plugin *plugins;
 };
 
+struct json_output {
+	struct list_node list;
+	const char *json;
+};
+
 struct plugins *plugins_new(const tal_t *ctx){
 	struct plugins *p;
 	p = tal(ctx, struct plugins);
@@ -32,13 +48,123 @@ void plugin_register(struct plugins *plugins, const char* path TAKES)
 	p->cmd = tal_strdup(p, path);
 }
 
+/**
+ * Try to parse a complete message from the plugin's buffer.
+ *
+ * Internally calls the handler if it was able to fully parse a JSON message,
+ * and returns true in that case.
+ */
+static bool plugin_read_json_one(struct plugin *plugin)
+{
+	jsmntok_t *toks;
+	bool valid;
+	toks = json_parse_input(plugin->buffer, plugin->used, &valid);
+	if (!toks) {
+		if (!valid) {
+			/* FIXME (cdecker) Print error and kill the plugin */
+			return io_close(plugin->stdout_conn);
+		}
+		/* We need more. */
+		return false;
+	}
+
+	/* Empty buffer? (eg. just whitespace). */
+	if (tal_count(toks) == 1) {
+		plugin->used = 0;
+		return false;
+	}
+
+	/* FIXME(cdecker) Call dispatch to handle this message. */
+
+	/* Move this object out of the buffer */
+	memmove(plugin->buffer, plugin->buffer + toks[0].end,
+		tal_count(plugin->buffer) - toks[0].end);
+	plugin->used -= toks[0].end;
+	tal_free(toks);
+	return true;
+}
+
+static struct io_plan *plugin_read_json(struct io_conn *conn UNUSED,
+					struct plugin *plugin)
+{
+	bool success;
+	plugin->used += plugin->len_read;
+	if (plugin->used == tal_count(plugin->buffer))
+		tal_resize(&plugin->buffer, plugin->used * 2);
+
+	/* Read and process all messages from the connection */
+	do {
+		success = plugin_read_json_one(plugin);
+	} while (success);
+
+	/* Now read more from the connection */
+	return io_read_partial(plugin->stdout_conn,
+			       plugin->buffer + plugin->used,
+			       tal_count(plugin->buffer) - plugin->used,
+			       &plugin->len_read, plugin_read_json, plugin);
+}
+
+static struct io_plan *plugin_write_json(struct io_conn *conn UNUSED,
+					 struct plugin *plugin)
+{
+	struct json_output *out;
+	out = list_pop(&plugin->output, struct json_output, list);
+	if (!out) {
+		if (plugin->stop) {
+			return io_close(conn);
+		} else {
+			return io_out_wait(plugin->stdin_conn, plugin,
+					   plugin_write_json, plugin);
+		}
+	}
+
+	/* We have a message we'd like to send */
+	plugin->outbuf = tal_steal(plugin, out->json);
+	tal_free(out);
+	return io_write(conn, plugin->outbuf, strlen(plugin->outbuf),
+			plugin_write_json, plugin);
+}
+
+static struct io_plan *plugin_conn_init(struct io_conn *conn,
+					struct plugin *plugin)
+{
+	plugin->stop = false;
+	if (plugin->stdout == io_conn_fd(conn)) {
+		/* We read from their stdout */
+		plugin->stdout_conn = conn;
+		return io_read_partial(plugin->stdout_conn, plugin->buffer,
+				       tal_bytelen(plugin->buffer),
+				       &plugin->len_read, plugin_read_json,
+				       plugin);
+	} else {
+		/* We write to their stdin */
+		plugin->stdin_conn = conn;
+		/* We don't have anything queued yet, wait for notification */
+		return io_wait(plugin->stdin_conn, plugin, plugin_write_json,
+			       plugin);
+	}
+}
+
 void plugins_init(struct plugins *plugins)
 {
 	struct plugin *p;
+	char **cmd;
 	/* Spawn the plugin processes before entering the io_loop */
 	for (size_t i=0; i<tal_count(plugins->plugins); i++) {
 		p = &plugins->plugins[i];
-		p->pid = pipecmd(&p->stdout, &p->stdin, NULL, p->cmd);
+		cmd = tal_arr(p, char *, 2);
+		cmd[0] = p->cmd;
+		cmd[1] = NULL;
+		p->pid = pipecmdarr(&p->stdout, &p->stdin, NULL, cmd);
+
+		list_head_init(&p->output);
+		p->buffer = tal_arr(p, char, 64);
+		p->used = 0;
+
+		/* Create two connections, one read-only on top of p->stdin, and one
+		 * write-only on p->stdout */
+		io_new_conn(p, p->stdout, plugin_conn_init, p);
+		io_new_conn(p, p->stdin, plugin_conn_init, p);
 	}
 }