plugin/libplugin: API for C plugins.

Doesn't do logging yet.

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

plugins/libplugin.h

@@ -0,0 +1,94 @@
+/* Helper library for C plugins. */
+#ifndef LIGHTNING_PLUGINS_LIBPLUGIN_H
+#define LIGHTNING_PLUGINS_LIBPLUGIN_H
+#include "config.h"
+
+#include <common/json.h>
+#include <common/json_command.h>
+#include <common/json_helpers.h>
+#include <common/jsonrpc_errors.h>
+#include <common/param.h>
+
+struct command;
+struct plugin_conn;
+
+/* Create an array of these, one for each command you support. */
+struct plugin_command {
+	const char *name;
+	const char *description;
+	const char *long_description;
+	struct command_result *(*handle)(struct command *cmd,
+					 const char *buf,
+					 const jsmntok_t *params);
+};
+
+/* Return this iff the param() call failed in your handler. */
+struct command_result *command_param_failed(void);
+
+/* Call this on fatal error. */
+void NORETURN plugin_err(const char *fmt, ...);
+
+/* This command is finished, here's a detailed error. data can be NULL. */
+struct command_result *WARN_UNUSED_RESULT
+command_done_err(struct command *cmd,
+		 int code,
+		 const char *errmsg,
+		 const char *data);
+
+/* This command is finished, here's the success msg. */
+struct command_result *WARN_UNUSED_RESULT
+command_success(struct command *cmd, const char *result);
+
+/* Synchronous helper to send command and extract single field from
+ * response; can only be used in init callback. */
+const char *rpc_delve(const tal_t *ctx,
+		      const char *method, const char *params,
+		      struct plugin_conn *rpc, const char *guide);
+
+/* Async rpc request.  For convenience, and single ' are turned into ". */
+PRINTF_FMT(6,7) struct command_result *
+send_outreq_(struct command *cmd,
+	     const char *method,
+	     struct command_result *(*cb)(struct command *command,
+					  const char *buf,
+					  const jsmntok_t *result,
+					  void *arg),
+	     struct command_result *(*errcb)(struct command *command,
+					     const char *buf,
+					     const jsmntok_t *result,
+					     void *arg),
+	     void *arg,
+	     const char *paramfmt_single_ticks, ...);
+
+#define send_outreq(cmd, method, cb, errcb, arg, ...)			\
+	send_outreq_((cmd), (method),					\
+		     typesafe_cb_preargs(struct command_result *, void *, \
+					 (cb), (arg),			\
+					 struct command *command,	\
+					 const char *buf,		\
+					 const jsmntok_t *result),	\
+		     typesafe_cb_preargs(struct command_result *, void *, \
+					 (errcb), (arg),		\
+					 struct command *command,	\
+					 const char *buf,		\
+					 const jsmntok_t *result),	\
+		     (arg), __VA_ARGS__)
+
+/* Callback to just forward error and close request. */
+struct command_result *forward_error(struct command *cmd,
+				     const char *buf,
+				     const jsmntok_t *error,
+				     void *arg);
+
+/* Callback to just forward result and close request. */
+struct command_result *forward_result(struct command *cmd,
+				      const char *buf,
+				      const jsmntok_t *result,
+				      void *arg);
+
+/* The main plugin runner. */
+void NORETURN plugin_main(char *argv[],
+			  void (*init)(struct plugin_conn *rpc),
+			  const struct plugin_command *commands,
+			  size_t num_commands);
+#endif /* LIGHTNING_PLUGINS_LIBPLUGIN_H */