Board code may not be interested in iterating fully over the JSON blob
and instead just wants to lookup a value at a specific JSONPath.
Add helpers to facilitate this.
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
include/jsmn.h | 57 +++++++++++++++++++++++++++++++++
lib/jsmn.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+)
diff --git a/include/jsmn.h b/include/jsmn.h
index 394ffc467487..8f6db8d534f4 100644
--- a/include/jsmn.h
+++ b/include/jsmn.h
@@ -84,6 +84,63 @@ 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);
+/** Returns `true` if `token` is a string and equal to `str`. */
+JSMN_API bool jsmn_str_eq(const char *str, const char *json, const jsmntok_t *token);
+
+/** Returns `true` if `token` is to `str`. */
+JSMN_API bool jsmn_eq(const char *val, const char *json, const jsmntok_t *token);
+
+/** Returns the token after the value at `tokens[0]`. */
+JSMN_API const jsmntok_t *jsmn_skip_value(const jsmntok_t *tokens);
+
+/**
+ * Returns a pointer to the value associated with `key` inside `json` starting
+ * at `tokens[0]`, which is expected to be an object, or returns `NULL` if `key`
+ * cannot be found.
+ */
+JSMN_API const jsmntok_t *jsmn_find_value(const char *key, const char *json,
+ const jsmntok_t *tokens);
+
+/**
+ * Locate the token at `path` inside `json` in a manner similar to JSONPath.
+ *
+ * Example:
+ * \code
+ * {
+ * "date": "...",
+ * "product": {
+ * "serial": "1234",
+ * }
+ * }
+ * \endcode
+ *
+ * To locate the serial number in the JSON object above, you would use the
+ * JSONPath expression "$.product.serial". The same thing can be accomplished
+ * with this call:
+ *
+ * \code
+ * const char *path[] = {"product", "serial", NULL};
+ * const jsmntok_t *token = jsmn_locate(path, json, tokens);
+ * \endcode
+ *
+ * \remark This function cannot search inside arrays.
+ *
+ * @param path Null-terminated list of path elements.
+ * @param json JSON string to search in.
+ * @param tokens Tokens for `json`.
+ *
+ * @return Pointer to the value token or `NULL` if the token could not be found.
+ */
+JSMN_API const jsmntok_t *jsmn_locate(const char *path[], const char *json,
+ const jsmntok_t *tokens);
+
+/**
+ * Similar to `jsmn_locate` but returns a copy of the value or `NULL` if the
+ * value does not exist or is not a string. The caller takes ownership of the
+ * pointer returned.
+ */
+JSMN_API char *jsmn_strcpy(const char *path[], const char *json, const jsmntok_t *tokens);
+
#ifdef __cplusplus
}
#endif
diff --git a/lib/jsmn.c b/lib/jsmn.c
index 3a68f89337fc..7bdcc90f2f4b 100644
--- a/lib/jsmn.c
+++ b/lib/jsmn.c
@@ -369,3 +369,89 @@ JSMN_API void jsmn_init(jsmn_parser *parser) {
parser->toknext = 0;
parser->toksuper = -1;
}
+
+JSMN_API bool jsmn_eq(const char *val, const char *json, const jsmntok_t *token)
+{
+ size_t token_size = token->end - token->start;
+ return strlen(val) == token_size
+ && strncmp(json + token->start, val, token_size) == 0;
+}
+
+JSMN_API bool jsmn_str_eq(const char *str, const char *json, const jsmntok_t *token)
+{
+ return token->type == JSMN_STRING && jsmn_eq(str, json, token);
+}
+
+JSMN_API const jsmntok_t *jsmn_skip_value(const jsmntok_t *tokens)
+{
+ int max_index = tokens[0].end;
+ do {
+ ++tokens;
+ } while (tokens[0].start < max_index);
+ return &tokens[0];
+}
+
+JSMN_API const jsmntok_t *jsmn_find_value(const char *key, const char *json,
+ const jsmntok_t *tokens)
+{
+ int items;
+ if (tokens[0].type != JSMN_OBJECT || tokens[0].size == 0)
+ return NULL;
+
+ items = tokens[0].size;
+ ++tokens;
+
+ do {
+ if (jsmn_str_eq(key, json, tokens))
+ return &tokens[1];
+ tokens = --items ? jsmn_skip_value(&tokens[1]) : NULL;
+ } while (tokens);
+
+ return NULL;
+}
+
+JSMN_API const jsmntok_t *jsmn_locate(const char *path[], const char *json,
+ const jsmntok_t *tokens)
+{
+ int i = 0;
+ while (path[i] != NULL) {
+ const jsmntok_t *value = jsmn_find_value(path[i], json, tokens);
+ if (!value)
+ return NULL;
+
+ switch (value->type) {
+ case JSMN_OBJECT:
+ case JSMN_ARRAY:
+ tokens = value;
+ ++i;
+ break;
+ case JSMN_UNDEFINED:
+ case JSMN_STRING:
+ case JSMN_PRIMITIVE:
+ return value;
+ }
+ }
+
+ return tokens;
+}
+
+JSMN_API char *jsmn_strcpy(const char *path[], const char *json,
+ const jsmntok_t *tokens)
+{
+ const jsmntok_t *node;
+ int value_size;
+ char *value;
+
+ node = jsmn_locate(path, json, tokens);
+ if (!node || node->type != JSMN_STRING)
+ return NULL;
+
+ value_size = node->end - node->start;
+ value = malloc(value_size + 1);
+ if (value) {
+ strncpy(value, json + node->start, value_size);
+ value[value_size] = '\0';
+ }
+
+ return value;
+}
--
2.30.2
