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>

3 files changed, 46 insertions, 29 deletions

diff --git a/include/jsmn.h b/include/jsmn.h
index 2dd1d5ffc0..62197c2593 100644
--- a/include/jsmn.h
+++ b/include/jsmn.h
@@ -84,6 +84,12 @@ JSMN_API void jsmn_init(jsmn_parser *parser);
 JSMN_API int jsmn_parse(jsmn_parser *parser, const char *js, const size_t len,
 			jsmntok_t *tokens, const unsigned int num_tokens);
 
+/**
+ * Like jsmn_parse, but allocates tokens dynamically.
+ */
+JSMN_API jsmntok_t *jsmn_parse_alloc(const char *js, const size_t len,
+				     unsigned int *num_tokens);
+
 static inline int jsmn_token_size(const jsmntok_t *token)
 {
 	return token->end - token->start;
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);
diff --git a/test/self/json.c b/test/self/json.c
index 54323cf435..d3088f1b75 100644
--- a/test/self/json.c
+++ b/test/self/json.c
@@ -75,45 +75,20 @@ static const char json[] =
 
 static void test_json(void)
 {
-	ssize_t token_count;
 	const jsmntok_t *token;
 	jsmntok_t *tokens;
-	jsmn_parser parser;
 	char *string;
-	int ret;
 
 	total_tests++;
 
-	jsmn_init(&parser);
-
 	/* Figure out how many tokens we need. */
-	ret = jsmn_parse(&parser, json, sizeof(json), NULL, 0);
-	if (ret < 0) {
-		printf("failed to determine number of tokens: %d\n", ret);
+	tokens = jsmn_parse_alloc(json, sizeof(json), NULL);
+	if (!tokens) {
+		printf("failed to parse JSON\n");
 		failed_tests++;
 		return;
 	}
 
-	token_count = ret;
-
-	/* `token_count` is strictly less than `length` which is strictly less
-	 * than CONFIG_SYS_EEPROM_SIZE (or 8K), so we should never overflow an
-	 * int here.
-	 */
-	tokens = kmalloc_array(token_count, sizeof(jsmntok_t), GFP_KERNEL);
-	if (WARN_ON(!tokens))
-		return;
-
-	total_tests++;
-
-	jsmn_init(&parser);
-	ret = jsmn_parse(&parser, json, sizeof(json), tokens, token_count);
-	if (ret < 0) {
-		printf("failed to parse JSON with tokens: %d\n", ret);
-		failed_tests++;
-		goto out;
-	}
-
 	json_expect(json, tokens, JP("null"), JSMN_PRIMITIVE, "null");
 	json_expect(json, tokens, JP("number"), JSMN_PRIMITIVE, "0x42");
 	json_expect(json, tokens, JP("object"), JSMN_OBJECT, NULL);
@@ -131,7 +106,7 @@ static void test_json(void)
 
 	string = jsmn_strcpy(JP("string"), json, tokens);
 	if (WARN_ON(!string))
-		return;
+		goto out;
 
 	total_tests++;
 	if (strcmp(string, "Hello World\n")) {