1 // SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
3 * Simple streaming JSON writer
5 * This takes care of the annoying bits of JSON syntax like the commas
8 * Authors: Stephen Hemminger <stephen@networkplumber.org>
19 #include "json_writer.h"
22 FILE *out; /* output file */
23 unsigned depth; /* nesting */
24 bool pretty; /* optional whitepace */
25 char sep; /* either nul or comma */
28 /* indentation for pretty print */
29 static void jsonw_indent(json_writer_t *self)
32 for (i = 0; i < self->depth; ++i)
33 fputs(" ", self->out);
36 /* end current line and indent if pretty printing */
37 static void jsonw_eol(json_writer_t *self)
42 putc('\n', self->out);
46 /* If current object is not empty print a comma */
47 static void jsonw_eor(json_writer_t *self)
49 if (self->sep != '\0')
50 putc(self->sep, self->out);
55 /* Output JSON encoded string */
56 /* Handles C escapes, does not do Unicode */
57 static void jsonw_puts(json_writer_t *self, const char *str)
63 fputs("\\t", self->out);
66 fputs("\\n", self->out);
69 fputs("\\r", self->out);
72 fputs("\\f", self->out);
75 fputs("\\b", self->out);
78 fputs("\\n", self->out);
81 fputs("\\\"", self->out);
84 putc(*str, self->out);
89 /* Create a new JSON stream */
90 json_writer_t *jsonw_new(FILE *f)
92 json_writer_t *self = malloc(sizeof(*self));
102 /* End output to JSON stream */
103 void jsonw_destroy(json_writer_t **self_p)
105 json_writer_t *self = *self_p;
107 assert(self->depth == 0);
108 fputs("\n", self->out);
114 void jsonw_pretty(json_writer_t *self, bool on)
119 void jsonw_reset(json_writer_t *self)
121 assert(self->depth == 0);
126 static void jsonw_begin(json_writer_t *self, int c)
134 static void jsonw_end(json_writer_t *self, int c)
136 assert(self->depth > 0);
139 if (self->sep != '\0')
146 /* Add a JSON property name */
147 void jsonw_name(json_writer_t *self, const char *name)
152 jsonw_puts(self, name);
153 putc(':', self->out);
155 putc(' ', self->out);
158 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
161 putc('"', self->out);
162 vfprintf(self->out, fmt, ap);
163 putc('"', self->out);
166 void jsonw_printf(json_writer_t *self, const char *fmt, ...)
172 vfprintf(self->out, fmt, ap);
177 void jsonw_start_object(json_writer_t *self)
179 jsonw_begin(self, '{');
182 void jsonw_end_object(json_writer_t *self)
184 jsonw_end(self, '}');
187 void jsonw_start_array(json_writer_t *self)
189 jsonw_begin(self, '[');
192 void jsonw_end_array(json_writer_t *self)
194 jsonw_end(self, ']');
197 /* JSON value types */
198 void jsonw_string(json_writer_t *self, const char *value)
201 jsonw_puts(self, value);
204 void jsonw_bool(json_writer_t *self, bool val)
206 jsonw_printf(self, "%s", val ? "true" : "false");
209 void jsonw_null(json_writer_t *self)
211 jsonw_printf(self, "null");
214 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
216 jsonw_printf(self, fmt, num);
220 void jsonw_float(json_writer_t *self, double num)
222 jsonw_printf(self, "%g", num);
226 void jsonw_hu(json_writer_t *self, unsigned short num)
228 jsonw_printf(self, "%hu", num);
231 void jsonw_uint(json_writer_t *self, uint64_t num)
233 jsonw_printf(self, "%"PRIu64, num);
236 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
238 jsonw_printf(self, "%llu", num);
241 void jsonw_int(json_writer_t *self, int64_t num)
243 jsonw_printf(self, "%"PRId64, num);
246 /* Basic name/value objects */
247 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
249 jsonw_name(self, prop);
250 jsonw_string(self, val);
253 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
255 jsonw_name(self, prop);
256 jsonw_bool(self, val);
260 void jsonw_float_field(json_writer_t *self, const char *prop, double val)
262 jsonw_name(self, prop);
263 jsonw_float(self, val);
267 void jsonw_float_field_fmt(json_writer_t *self,
272 jsonw_name(self, prop);
273 jsonw_float_fmt(self, fmt, val);
276 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
278 jsonw_name(self, prop);
279 jsonw_uint(self, num);
282 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
284 jsonw_name(self, prop);
288 void jsonw_lluint_field(json_writer_t *self,
290 unsigned long long int num)
292 jsonw_name(self, prop);
293 jsonw_lluint(self, num);
296 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
298 jsonw_name(self, prop);
299 jsonw_int(self, num);
302 void jsonw_null_field(json_writer_t *self, const char *prop)
304 jsonw_name(self, prop);
309 int main(int argc, char **argv)
311 json_writer_t *wr = jsonw_new(stdout);
313 jsonw_start_object(wr);
314 jsonw_pretty(wr, true);
315 jsonw_name(wr, "Vyatta");
316 jsonw_start_object(wr);
317 jsonw_string_field(wr, "url", "http://vyatta.com");
318 jsonw_uint_field(wr, "downloads", 2000000ul);
319 jsonw_float_field(wr, "stock", 8.16);
321 jsonw_name(wr, "ARGV");
322 jsonw_start_array(wr);
324 jsonw_string(wr, *++argv);
327 jsonw_name(wr, "empty");
328 jsonw_start_array(wr);
331 jsonw_name(wr, "NIL");
332 jsonw_start_object(wr);
333 jsonw_end_object(wr);
335 jsonw_null_field(wr, "my_null");
337 jsonw_name(wr, "special chars");
338 jsonw_start_array(wr);
339 jsonw_string_field(wr, "slash", "/");
340 jsonw_string_field(wr, "newline", "\n");
341 jsonw_string_field(wr, "tab", "\t");
342 jsonw_string_field(wr, "ff", "\f");
343 jsonw_string_field(wr, "quote", "\"");
344 jsonw_string_field(wr, "tick", "\'");
345 jsonw_string_field(wr, "backslash", "\\");
348 jsonw_end_object(wr);
350 jsonw_end_object(wr);