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json: Add top-level array decoding support

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The library supports encoding JSON objects and arrays as well as
parsing JSON objects. Introduce a new function json_arr_parse() adding
support for parsing top-level JSON arrays.

Signed-off-by: Markus Fuchs <markus.fuchs@ch.sauter-bc.com>
This commit is contained in:
Markus Fuchs 2021-10-29 17:32:37 +02:00 • committed by Christopher Friedt
commit c6bc548b73
2 changed files with 70 additions and 1 deletions
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37
include/data/json.h
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@ -528,7 +528,7 @@ typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
}
/**
* @brief Parses the JSON-encoded object pointer to by @a json, with
* @brief Parses the JSON-encoded object pointed to by @a json, with
* size @a len, according to the descriptor pointed to by @a descr.
* Values are stored in a struct pointed to by @a val. Set up the
* descriptor like this:
@ -561,6 +561,41 @@ int json_obj_parse(char *json, size_t len,
const struct json_obj_descr *descr, size_t descr_len,
void *val);
/**
* @brief Parses the JSON-encoded array pointed to by @a json, with
* size @a len, according to the descriptor pointed to by @a descr.
* Values are stored in a struct pointed to by @a val. Set up the
* descriptor like this:
*
* struct s { int foo; char *bar; }
* struct json_obj_descr descr[] = {
* JSON_OBJ_DESCR_PRIM(struct s, foo, JSON_TOK_NUMBER),
* JSON_OBJ_DESCR_PRIM(struct s, bar, JSON_TOK_STRING),
* };
* struct a { struct s baz[10]; size_t count; }
* struct json_obj_descr array[] = {
* JSON_OBJ_DESCR_OBJ_ARRAY(struct a, baz, 10, count,
* descr, ARRAY_SIZE(descr)),
* };
*
* Since this parser is designed for machine-to-machine communications, some
* liberties were taken to simplify the design:
* (1) strings are not unescaped (but only valid escape sequences are
* accepted);
* (2) no UTF-8 validation is performed; and
* (3) only integer numbers are supported (no strtod() in the minimal libc).
*
* @param json Pointer to JSON-encoded array to be parsed
* @param len Length of JSON-encoded array
* @param descr Pointer to the descriptor array
* @param val Pointer to the struct to hold the decoded values
*
* @return 0 if array has been successfully parsed. A negative value
* indicates an error (as defined on errno.h).
*/
int json_arr_parse(char *json, size_t len,
const struct json_obj_descr *descr, void *val);
/**
* @brief Escapes the string so it can be used to encode JSON objects
*