json: add and use a json_strdup() helper.

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

common/json.c

@@ -35,6 +35,11 @@ bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str)
 	return strncmp(buffer + tok->start, str, tok->end - tok->start) == 0;
 }
 
+char *json_strdup(const tal_t *ctx, const char *buffer, const jsmntok_t *tok)
+{
+	return tal_strndup(ctx, buffer + tok->start, tok->end - tok->start);
+}
+
 bool json_to_u64(const char *buffer, const jsmntok_t *tok,
 		  uint64_t *num)
 {

common/json.h

@@ -23,6 +23,9 @@ int json_tok_len(const jsmntok_t *t);
 /* Is this a string equal to str? */
 bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str);
 
+/* Allocate a tal string copy */
+char *json_strdup(const tal_t *ctx, const char *buffer, const jsmntok_t *tok);
+
 /* Extract number from this (may be a string, or a number literal) */
 bool json_to_number(const char *buffer, const jsmntok_t *tok,
 		    unsigned int *num);

lightningd/connect_control.c

@@ -99,8 +99,7 @@ static void json_connect(struct command *cmd,
 		return;
 
 	/* Check for id@addrport form */
-	id_str = tal_strndup(cmd, buffer + idtok->start,
-			     idtok->end - idtok->start);
+	id_str = json_strdup(cmd, buffer, idtok);
 	atptr = strchr(id_str, '@');
 	if (atptr) {
 		int atidx = atptr - id_str;

lightningd/plugin.c

@@ -551,14 +551,12 @@ static bool plugin_opt_add(struct plugin *plugin, const char *buffer,
 			     buffer + nametok->start);
 	popt->value = NULL;
 	if (defaulttok) {
-		popt->value = tal_strndup(popt, buffer + defaulttok->start,
-					  defaulttok->end - defaulttok->start);
+		popt->value = json_strdup(popt, buffer, defaulttok);
 		popt->description = tal_fmt(
 		    popt, "%.*s (default: %s)", desctok->end - desctok->start,
 		    buffer + desctok->start, popt->value);
 	} else {
-		popt->description = tal_strndup(popt, buffer + desctok->start,
-						desctok->end - desctok->start);
+		popt->description = json_strdup(popt, buffer, desctok);
 	}
 
 	list_add_tail(&plugin->plugin_opts, &popt->list);
@@ -722,14 +720,10 @@ static bool plugin_rpcmethod_add(struct plugin *plugin,
 	}
 
 	cmd = notleak(tal(plugin, struct json_command));
-	cmd->name = tal_strndup(cmd, buffer + nametok->start,
-				nametok->end - nametok->start);
-	cmd->description = tal_strndup(cmd, buffer + desctok->start,
-				       desctok->end - desctok->start);
+	cmd->name = json_strdup(cmd, buffer, nametok);
+	cmd->description = json_strdup(cmd, buffer, desctok);
 	if (longdesctok)
-		cmd->verbose =
-		    tal_strndup(cmd, buffer + longdesctok->start,
-				longdesctok->end - longdesctok->start);
+		cmd->verbose = json_strdup(cmd, buffer, longdesctok);
 	else
 		cmd->verbose = cmd->description;