From 690f95ff1f6deffd87ef8f34d5319bd06ba21658 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 23 Oct 2025 14:23:04 +1030
Subject: [PATCH] libplugin: use jsonrpc_io for reading replies to our async
 commands.

This will also be more efficient than doing memmove every time.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 plugins/libplugin.c | 96 ++++++++++++---------------------------------
 1 file changed, 25 insertions(+), 71 deletions(-)

diff --git a/plugins/libplugin.c b/plugins/libplugin.c
index 836e1768a..96b2fc632 100644
--- a/plugins/libplugin.c
+++ b/plugins/libplugin.c
@@ -11,6 +11,7 @@
 #include <common/json_filter.h>
 #include <common/json_param.h>
 #include <common/json_stream.h>
+#include <common/jsonrpc_io.h>
 #include <common/memleak.h>
 #include <common/plugin.h>
 #include <common/route.h>
@@ -98,10 +99,8 @@ struct plugin {
 	/* Asynchronous RPC interaction */
 	struct io_conn *io_rpc_conn;
 	struct list_head rpc_js_list;
-	char *rpc_buffer;
-	size_t rpc_used, rpc_len_read, rpc_read_offset;
-	jsmn_parser rpc_parser;
-	jsmntok_t *rpc_toks;
+	struct jsonrpc_io *jsonrpc_in;
+
 	/* Tracking async RPC requests */
 	STRMAP(struct out_req *) out_reqs;
 	u64 next_outreq_id;
@@ -1365,73 +1364,33 @@ static void rpc_conn_finished(struct io_conn *conn,
 	plugin_err(plugin, "Lost connection to the RPC socket.");
 }
 
-static bool rpc_read_response_one(struct plugin *plugin)
-{
-	const jsmntok_t *jrtok;
-	bool complete;
-
-	if (!json_parse_input(&plugin->rpc_parser, &plugin->rpc_toks,
-			      plugin->rpc_buffer + plugin->rpc_read_offset,
-			      plugin->rpc_used - plugin->rpc_read_offset,
-			      &complete)) {
-		plugin_err(plugin, "Failed to parse RPC JSON response '%.*s'",
-			   (int)(plugin->rpc_used - plugin->rpc_read_offset),
-			   plugin->rpc_buffer + plugin->rpc_read_offset);
-	}
-
-	if (!complete) {
-		/* We need more. */
-		goto compact;
-	}
-
-	/* Empty buffer? (eg. just whitespace). */
-	if (tal_count(plugin->rpc_toks) == 1) {
-		jsmn_init(&plugin->rpc_parser);
-		toks_reset(plugin->rpc_toks);
-		goto compact;
-	}
-
-	jrtok = json_get_member(plugin->rpc_buffer + plugin->rpc_read_offset,
-				plugin->rpc_toks, "jsonrpc");
-	if (!jrtok) {
-		plugin_err(plugin, "JSON-RPC message does not contain \"jsonrpc\" field: '%.*s'",
-			   (int)(plugin->rpc_used - plugin->rpc_read_offset),
-			   plugin->rpc_buffer + plugin->rpc_read_offset);
-	}
-
-	handle_rpc_reply(plugin, plugin->rpc_buffer + plugin->rpc_read_offset, plugin->rpc_toks);
-
-	/* Move this object out of the buffer */
-	plugin->rpc_read_offset += plugin->rpc_toks[0].end;
-	jsmn_init(&plugin->rpc_parser);
-	toks_reset(plugin->rpc_toks);
-	return true;
-
-compact:
-	memmove(plugin->rpc_buffer, plugin->rpc_buffer + plugin->rpc_read_offset,
-		plugin->rpc_used - plugin->rpc_read_offset);
-	plugin->rpc_used -= plugin->rpc_read_offset;
-	plugin->rpc_read_offset = 0;
-	return false;
-}
 
 static struct io_plan *rpc_conn_read_response(struct io_conn *conn,
 					      struct plugin *plugin)
 {
-	plugin->rpc_used += plugin->rpc_len_read;
-	if (plugin->rpc_used == tal_count(plugin->rpc_buffer))
-		tal_resize(&plugin->rpc_buffer, plugin->rpc_used * 2);
+	/* Gather an parse any new bytes */
+	for (;;) {
+		const jsmntok_t *toks;
+		const char *buf;
+		const char *err;
 
-	/* Read and process all messages from the connection */
-	while (rpc_read_response_one(plugin))
-		;
+		err = jsonrpc_io_parse(tmpctx,
+				       plugin->jsonrpc_in,
+				       &toks, &buf);
+		if (err)
+			plugin_err(plugin, "%s", err);
 
-	/* Read more, if there is. */
-	return io_read_partial(plugin->io_rpc_conn,
-			       plugin->rpc_buffer + plugin->rpc_used,
-			       tal_bytelen(plugin->rpc_buffer) - plugin->rpc_used,
-			       &plugin->rpc_len_read,
-			       rpc_conn_read_response, plugin);
+		if (!toks)
+			break;
+
+		handle_rpc_reply(plugin, buf, toks);
+		jsonrpc_io_parse_done(plugin->jsonrpc_in);
+	}
+
+	/* Read more */
+	return jsonrpc_io_read(conn, plugin->jsonrpc_in,
+			       rpc_conn_read_response,
+			       plugin);
 }
 
 static struct io_plan *rpc_conn_write_request(struct io_conn *conn,
@@ -2416,14 +2375,9 @@ static struct plugin *new_plugin(const tal_t *ctx,
 	jsmn_init(&p->parser);
 	p->toks = toks_alloc(p);
 	/* Async RPC */
-	p->rpc_buffer = tal_arr(p, char, 64);
+	p->jsonrpc_in = jsonrpc_io_new(p);
 	list_head_init(&p->rpc_js_list);
 	p->io_rpc_conn = NULL;
-	p->rpc_used = 0;
-	p->rpc_read_offset = 0;
-	p->rpc_len_read = 0;
-	jsmn_init(&p->rpc_parser);
-	p->rpc_toks = toks_alloc(p);
 	p->next_outreq_id = 0;
 	strmap_init(&p->out_reqs);
 	p->beglist = NULL;