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 fputs("\\\'", self->out);
87 putc(*str, self->out);
92 /* Create a new JSON stream */
93 json_writer_t *jsonw_new(FILE *f)
95 json_writer_t *self = malloc(sizeof(*self));
105 /* End output to JSON stream */
106 void jsonw_destroy(json_writer_t **self_p)
108 json_writer_t *self = *self_p;
110 assert(self->depth == 0);
111 fputs("\n", self->out);
117 void jsonw_pretty(json_writer_t *self, bool on)
123 static void jsonw_begin(json_writer_t *self, int c)
131 static void jsonw_end(json_writer_t *self, int c)
133 assert(self->depth > 0);
136 if (self->sep != '\0')
143 /* Add a JSON property name */
144 void jsonw_name(json_writer_t *self, const char *name)
149 jsonw_puts(self, name);
150 putc(':', self->out);
152 putc(' ', self->out);
155 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
158 putc('"', self->out);
159 vfprintf(self->out, fmt, ap);
160 putc('"', self->out);
163 void jsonw_printf(json_writer_t *self, const char *fmt, ...)
169 vfprintf(self->out, fmt, ap);
174 void jsonw_start_object(json_writer_t *self)
176 jsonw_begin(self, '{');
179 void jsonw_end_object(json_writer_t *self)
181 jsonw_end(self, '}');
184 void jsonw_start_array(json_writer_t *self)
186 jsonw_begin(self, '[');
189 void jsonw_end_array(json_writer_t *self)
191 jsonw_end(self, ']');
194 /* JSON value types */
195 void jsonw_string(json_writer_t *self, const char *value)
198 jsonw_puts(self, value);
201 void jsonw_bool(json_writer_t *self, bool val)
203 jsonw_printf(self, "%s", val ? "true" : "false");
206 void jsonw_null(json_writer_t *self)
208 jsonw_printf(self, "null");
211 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
213 jsonw_printf(self, fmt, num);
217 void jsonw_float(json_writer_t *self, double num)
219 jsonw_printf(self, "%g", num);
223 void jsonw_hu(json_writer_t *self, unsigned short num)
225 jsonw_printf(self, "%hu", num);
228 void jsonw_uint(json_writer_t *self, uint64_t num)
230 jsonw_printf(self, "%"PRIu64, num);
233 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
235 jsonw_printf(self, "%llu", num);
238 void jsonw_int(json_writer_t *self, int64_t num)
240 jsonw_printf(self, "%"PRId64, num);
243 /* Basic name/value objects */
244 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
246 jsonw_name(self, prop);
247 jsonw_string(self, val);
250 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
252 jsonw_name(self, prop);
253 jsonw_bool(self, val);
257 void jsonw_float_field(json_writer_t *self, const char *prop, double val)
259 jsonw_name(self, prop);
260 jsonw_float(self, val);
264 void jsonw_float_field_fmt(json_writer_t *self,
269 jsonw_name(self, prop);
270 jsonw_float_fmt(self, fmt, val);
273 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
275 jsonw_name(self, prop);
276 jsonw_uint(self, num);
279 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
281 jsonw_name(self, prop);
285 void jsonw_lluint_field(json_writer_t *self,
287 unsigned long long int num)
289 jsonw_name(self, prop);
290 jsonw_lluint(self, num);
293 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
295 jsonw_name(self, prop);
296 jsonw_int(self, num);
299 void jsonw_null_field(json_writer_t *self, const char *prop)
301 jsonw_name(self, prop);
306 int main(int argc, char **argv)
308 json_writer_t *wr = jsonw_new(stdout);
310 jsonw_start_object(wr);
311 jsonw_pretty(wr, true);
312 jsonw_name(wr, "Vyatta");
313 jsonw_start_object(wr);
314 jsonw_string_field(wr, "url", "http://vyatta.com");
315 jsonw_uint_field(wr, "downloads", 2000000ul);
316 jsonw_float_field(wr, "stock", 8.16);
318 jsonw_name(wr, "ARGV");
319 jsonw_start_array(wr);
321 jsonw_string(wr, *++argv);
324 jsonw_name(wr, "empty");
325 jsonw_start_array(wr);
328 jsonw_name(wr, "NIL");
329 jsonw_start_object(wr);
330 jsonw_end_object(wr);
332 jsonw_null_field(wr, "my_null");
334 jsonw_name(wr, "special chars");
335 jsonw_start_array(wr);
336 jsonw_string_field(wr, "slash", "/");
337 jsonw_string_field(wr, "newline", "\n");
338 jsonw_string_field(wr, "tab", "\t");
339 jsonw_string_field(wr, "ff", "\f");
340 jsonw_string_field(wr, "quote", "\"");
341 jsonw_string_field(wr, "tick", "\'");
342 jsonw_string_field(wr, "backslash", "\\");
345 jsonw_end_object(wr);
347 jsonw_end_object(wr);