4 * (c) 2015 Martin Mares <mj@ucw.cz>
6 * This software may be freely distributed and used according to the terms
7 * of the GNU Lesser General Public License.
10 #ifndef _UCW_JSON_JSON_H
11 #define _UCW_JSON_JSON_H
13 #include <ucw/mempool.h>
14 #include <ucw/fastbuf.h>
16 #ifdef CONFIG_UCW_CLEAN_ABI
17 #define json_array_append ucw_json_array_append
18 #define json_delete ucw_json_delete
19 #define json_new ucw_json_new
20 #define json_new_array ucw_json_new_array
21 #define json_new_node ucw_json_new_node
22 #define json_new_number ucw_json_new_number
23 #define json_new_object ucw_json_new_object
24 #define json_next_token ucw_json_next_token
25 #define json_next_value ucw_json_next_value
26 #define json_number_to_int ucw_json_number_to_int
27 #define json_number_to_s64 ucw_json_number_to_s64
28 #define json_number_to_u64 ucw_json_number_to_u64
29 #define json_number_to_uint ucw_json_number_to_uint
30 #define json_object_get ucw_json_object_get
31 #define json_object_set ucw_json_object_set
32 #define json_parse ucw_json_parse
33 #define json_peek_token ucw_json_peek_token
34 #define json_pop ucw_json_pop
35 #define json_push ucw_json_push
36 #define json_reset ucw_json_reset
37 #define json_set_input ucw_json_set_input
38 #define json_set_output ucw_json_set_output
39 #define json_write ucw_json_write
40 #define json_write_value ucw_json_write_value
44 * === JSON library context
46 * The context structure remembers the whole state of the JSON
47 * library. All JSON values are allocated from a memory pool associated
48 * with the context. By default, their lifetime is the same as that
51 * Alternatively, you can mark the current state of the context
52 * with json_push() and return to the marked state later using
53 * json_pop(). All JSON values created between these two operations
54 * are released afterwards. See json_push() for details.
58 * The context is represented a pointer to this structure.
59 * The fields marked with [*] are publicly accessible, the rest is private.
64 struct mempool_state init_state;
67 struct fastbuf *in_fb;
68 uint in_line; // [*] Current line number
69 uint in_column; // [*] Current column number
70 bool in_eof; // End of file was encountered
71 struct json_node *next_token;
72 struct json_node *trivial_token;
76 struct fastbuf *out_fb;
78 uint format_options; // [*] Formatting options (a combination of JSON_FORMAT_xxx)
81 /** Creates a new JSON context. **/
82 struct json_context *json_new(void);
84 /** Deletes a JSON context, deallocating all memory associated with it. **/
85 void json_delete(struct json_context *js);
88 * Recycles a JSON context. All state is reset, allocated objects are freed.
89 * This is equivalent to mp_delete() followed by mp_new(), but it is faster
90 * and the address of the context is preserved.
92 void json_reset(struct json_context *js);
95 * Push the current state of the context onto state stack.
97 * Between json_push() and the associated json_pop(), only newly
98 * created JSON values can be modified. Older values can be only
99 * inspected, never modified. In particular, new values cannot be
100 * inserted to old arrays nor objects.
102 * If you are using json_peek_token(), the saved tokens cannot
103 * be carried over push/pop boundary.
105 void json_push(struct json_context *js);
108 * Create a copy of a string in JSON memory.
110 * For example, this is useful when you want to use a string of unknown
111 * lifetime as a key in json_object_set().
113 static inline const char *json_strdup(struct json_context *js, const char *str)
115 return mp_strdup(js->pool, str);
119 * Pop state of the context off state stack. All JSON values created
120 * since the state was saved by json_push() are released.
122 void json_pop(struct json_context *js);
127 * Each JSON value is represented by <<struct json_node,struct json_node>>,
128 * which is either an elementary value (null, boolean, number, string),
129 * or a container (array, object) pointing to other values.
131 * A value can belong to multiple containers simultaneously, so in general,
132 * the relationships between values need not form a tree, but a directed
135 * You are allowed to read contents of nodes directly, but construction
136 * and modification of nodes must be always performed using the appropriate
141 enum json_node_type {
149 // These are not real nodes, but raw tokens.
150 // They are not present in the tree of values, but you may see them
151 // if you call json_next_token() and friends.
161 /** Each value is represented by a single node. **/
163 enum json_node_type type;
164 union { // Data specific to individual value types
168 struct json_node **elements; // Arrays: Growing array of values
169 struct json_pair *pairs; // Objects: Growing array of pairs
173 /** Attributes of objects are stored as (key, value) pairs of this format. **/
176 struct json_node *value;
181 struct json_node *json_new_node(struct json_context *js, enum json_node_type type);
183 /** Creates a new null value. **/
184 static inline struct json_node *json_new_null(struct json_context *js UNUSED)
186 static const struct json_node static_null = { .type = JSON_NULL };
187 return (struct json_node *) &static_null;
190 /** Creates a new boolean value. **/
191 static inline struct json_node *json_new_bool(struct json_context *js UNUSED, bool value)
193 static const struct json_node static_bool[2] = {
194 [0] = { .type = JSON_BOOLEAN, .boolean = 0 },
195 [1] = { .type = JSON_BOOLEAN, .boolean = 1 },
197 return (struct json_node *) &static_bool[value];
200 /** Creates a new numeric value. The @value must be a finite number. **/
201 struct json_node *json_new_number(struct json_context *js, double value);
204 * Convert a numeric value to an `int`. Returns false if the value
205 * is not numeric or if it is too large for an int.
207 bool json_number_to_int(struct json_node *num, int *dest);
209 /** Same as above, but for `uint`. **/
210 bool json_number_to_uint(struct json_node *num, uint *dest);
212 /** Same as above, but for `s64`. **/
213 bool json_number_to_s64(struct json_node *num, s64 *dest);
215 /** Same as above, but for `u64`. **/
216 bool json_number_to_u64(struct json_node *num, u64 *dest);
219 * Creates a new string value. The @value is kept only as a reference.
221 * String values can contain an arbitrary UTF-8 string with no null
222 * characters. However, it is not recommended to use UTF-8 values outside
223 * the range of UniCode codepoints (0 to 0x10ffff).
225 static inline struct json_node *json_new_string_ref(struct json_context *js, const char *value)
227 struct json_node *n = json_new_node(js, JSON_STRING);
232 /** Creates a new string value, making a private copy of @value. **/
233 static inline struct json_node *json_new_string(struct json_context *js, const char *value)
235 return json_new_string_ref(js, mp_strdup(js->pool, value));
238 /** Creates a new array value with no elements. **/
239 struct json_node *json_new_array(struct json_context *js);
241 /** Appends a new element to the given array. **/
242 void json_array_append(struct json_node *array, struct json_node *elt);
244 /** Creates a new object value with no attributes. **/
245 struct json_node *json_new_object(struct json_context *js);
248 * Adds a new (@key, @value) pair to the given object. If @key is already
249 * present, the pair is replaced. If @value is NULL, no new pair is created
250 * and a pre-existing pair is deleted.
252 * The @key is referenced by the object, you must not free it during
253 * the lifetime of the object. When in doubt, use json_strdup().
255 void json_object_set(struct json_node *n, const char *key, struct json_node *value);
257 /** Returns the value associated with @key, or NULL if no such value exists. **/
258 struct json_node *json_object_get(struct json_node *n, const char *key);
263 * The simplest way to parse a complete JSON file is to call json_parse(),
264 * which returns a value tree representing the contents of the file.
266 * Alternatively, you can read the input token by token: call json_set_input()
267 * and then repeat json_next_token(). If you are parsing huge JSON files,
268 * you probably want to do json_push() first, then scan and process some
269 * tokens, and then json_pop().
271 * All parsing functions throw LibUCW exceptions of class `ucw.json.parse`
272 * upon errors. If you want to catch them, call the parser inside
276 /** Parses a JSON file from the given fastbuf stream. **/
277 struct json_node *json_parse(struct json_context *js, struct fastbuf *fb);
279 /** Selects the given fastbuf stream as parser input. **/
280 void json_set_input(struct json_context *js, struct fastbuf *in);
282 /** Reads the next token from the input. **/
283 struct json_node *json_next_token(struct json_context *js);
285 /** Reads the next token, but keeps it in the input. **/
286 struct json_node *json_peek_token(struct json_context *js);
288 /** Reads the next JSON value, including nested values. **/
289 struct json_node *json_next_value(struct json_context *js);
294 * JSON files can be produced by simply calling json_write().
296 * If you want to generate the output on the fly (for example if it is huge),
297 * call json_set_output() and then iterate json_write_value().
299 * By default, we produce a single-line compact representation,
300 * but you can choose differently by setting the appropriate
301 * `format_options` in the `json_context`.
304 /** Writes a JSON file to the given fastbuf stream, containing the JSON value @n. **/
305 void json_write(struct json_context *js, struct fastbuf *fb, struct json_node *n);
307 /** Selects the given fastbuf stream as output. **/
308 void json_set_output(struct json_context *js, struct fastbuf *fb);
310 /** Writes a single JSON value to the output stream. **/
311 void json_write_value(struct json_context *js, struct json_node *n);
313 /** Formatting options. The `format_options` field in the context is a bitwise OR of these flags. **/
314 enum json_format_option {
315 JSON_FORMAT_ESCAPE_NONASCII = 1, // Produce pure ASCII output by escaping all Unicode characters in strings
316 JSON_FORMAT_INDENT = 2, // Produce pretty indented output