libplugin: use jsonrpc_io logic for sync requests too.

It's a little overkill, but it's clear.

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

common/jsonrpc_io.c

@@ -5,6 +5,8 @@
 #include <ccan/tal/str/str.h>
 #include <common/jsonrpc_io.h>
 #include <common/utils.h>
+#include <errno.h>
+#include <unistd.h>
 
 #define READ_CHUNKSIZE 64
 
@@ -126,3 +128,24 @@ struct io_plan *jsonrpc_io_read_(struct io_conn *conn,
 			       &json_in->bytes_read,
 			       next, arg);
 }
+
+bool jsonrpc_sync_read(struct jsonrpc_io *json_in, int infd)
+{
+	int r;
+
+	/* Make sure there's more room */
+	membuf_prepare_space(&json_in->membuf, READ_CHUNKSIZE);
+
+	/* Try to read more. */
+	r = read(infd,
+		 membuf_space(&json_in->membuf),
+		 membuf_num_space(&json_in->membuf));
+	if (r < 0)
+		return false;
+	if (r == 0) {
+		errno = 0;
+		return false;
+	}
+	json_in->bytes_read = r;
+	return true;
+}

common/jsonrpc_io.h

@@ -43,6 +43,15 @@ struct io_plan *jsonrpc_io_read_(struct io_conn *conn,
 const char *jsonrpc_newly_read(struct jsonrpc_io *json_in,
 			       size_t *len);
 
+/**
+ * jsonrpc_sync_read: read from fd into buffer.
+ * @json_in: buffer to read into.
+ * @infd: file descriptort to read.
+ *
+ * Returns false on error or EOF; for EOF errno will be 0.
+ */
+bool jsonrpc_sync_read(struct jsonrpc_io *json_in, int infd);
+
 /**
  * jsonrpc_io_parse: try to parse more of the buffer.
  * @ctx: context to allocate error message off.