json: improve parsing and serializing of integers

Add support for parsing and serializing of following integer types:
'int8_t', 'uint8_t', 'int16_t', 'uint16_t' and 'uint32_t'.

The generic integer token JSON_TOK_INT and JSON_TOK_UINT, in combination
with the field size (set by JSON_OBJ_DESCR_PRIM) allows to parse different
integer types, for example:

struct foo {
  int64_t i64;
  uint32_t u32;
  int16_t i16;
  uint8_t u8;
};

struct json_obj_descr foo_descr[] = {
  JSON_OBJ_DESCR_PRIM(struct foo, i64, JSON_TOK_INT),
  JSON_OBJ_DESCR_PRIM(struct foo, u32, JSON_TOK_UINT),
  JSON_OBJ_DESCR_PRIM(struct foo, i16, JSON_TOK_INT),
  JSON_OBJ_DESCR_PRIM(struct foo, u8, JSON_TOK_UINT),
};

These tokens also support parsing and serializing enums:

enum unsigned_enum { UA=0, UB=1, UC=2 };
enum signed_enum { SA=-1, SB=0, SC=1 };

struct foo {
  enum unsigned_enum u;
  enum signed_enum s;
};

struct json_obj_descr foo_descr[] = {
  JSON_OBJ_DESCR_PRIM(struct foo, u, JSON_TOK_UINT),
  JSON_OBJ_DESCR_PRIM(struct foo, s, JSON_TOK_INT),
};

Signed-off-by: Christoph Winklhofer <[email protected]>

Author: cjwinklhofer

include/zephyr/data/json.h

@@ -47,6 +47,8 @@ enum json_tokens {
 	JSON_TOK_UINT64 = '6',
 	JSON_TOK_FLOAT_FP = '7',
 	JSON_TOK_DOUBLE_FP = '8',
+	JSON_TOK_INT = 'i',
+	JSON_TOK_UINT = 'u',
 	JSON_TOK_TRUE = 't',
 	JSON_TOK_FALSE = 'f',
 	JSON_TOK_NULL = 'n',
@@ -251,6 +253,19 @@ typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
 			.sub_descr_len = elem_descr_len_, \
 		}, \
 
+/**
+ * @internal @brief Helper macro to declare a field descriptor
+ *
+ * @param struct_ Struct packing the values
+ * @param field_name_ Field name in the struct
+ */
+#define Z_JSON_DESCR_FIELD(struct_, field_name_) \
+	{ \
+		.field = { \
+			.size = SIZEOF_FIELD(struct_, field_name_), \
+		}, \
+	}
+
 /**
  * @brief Helper macro to declare a descriptor for an array of primitives
  *
@@ -283,7 +298,8 @@ typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
 		.offset = offsetof(struct_, field_name_), \
 		.array = { \
 			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
-				elem_type_,), \
+				elem_type_, \
+				Z_JSON_DESCR_FIELD(struct_, field_name_[0])), \
 			.n_elements = (max_len_), \
 		}, \
 	}
@@ -514,8 +530,9 @@ typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
 		.type = JSON_TOK_ARRAY_START, \
 		.offset = offsetof(struct_, struct_field_name_), \
 		.array = { \
-			.element_descr = \
-				Z_JSON_ELEMENT_DESCR(struct_, len_field_, elem_type_,), \
+			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
+				elem_type_, \
+				Z_JSON_DESCR_FIELD(struct_, struct_field_name_[0])), \
 			.n_elements = (max_len_), \
 		}, \
 	}