lib: jsmn: add helper for allocating tokens

jsmn_parse can be called with a NULL buffer to determine the needed
allocation size beforehand. Most users will go on to dynamically
allocate that buffer, so add a helper that does just that and start
using it to simplify the json selftest.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20230921102426.1109289-2-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/jsmn.c b/lib/jsmn.c
index 9eeed790d9..3d2ada7b7f 100644
--- a/lib/jsmn.c
+++ b/lib/jsmn.c
@@ -370,6 +370,42 @@ JSMN_API void jsmn_init(jsmn_parser *parser) {
 	parser->toksuper = -1;
 }
 
+/**
+ * Parse JSON string and fill tokens into self-allocated buffer.
+ */
+JSMN_API jsmntok_t *jsmn_parse_alloc(const char *js, const size_t len,
+				     unsigned int *num_tokens)
+{
+
+	ssize_t token_count;
+	jsmn_parser parser;
+	jsmntok_t *tokens;
+	int ret;
+
+	jsmn_init(&parser);
+
+	/* Figure out how many tokens we need. */
+	ret = jsmn_parse(&parser, js, len, NULL, 0);
+	if (ret < 0)
+		return NULL;
+
+	token_count = ret;
+
+	tokens = kmalloc_array(token_count, sizeof(jsmntok_t), GFP_KERNEL);
+	if (!tokens)
+		return NULL;
+
+	jsmn_init(&parser);
+	ret = jsmn_parse(&parser, js, len, tokens, token_count);
+	if (ret < 0) {
+		free(tokens);
+		return NULL;
+	}
+
+	if (num_tokens)
+		*num_tokens = ret;
+	return tokens;
+}
 JSMN_API bool jsmn_eq(const char *val, const char *json, const jsmntok_t *token)
 {
 	size_t token_size = jsmn_token_size(token);