1// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
  2/*
  3 * Simple streaming JSON writer
  4 *
  5 * This takes care of the annoying bits of JSON syntax like the commas
  6 * after elements
  7 *
  8 * Authors:	Stephen Hemminger <stephen@networkplumber.org>
  9 */
 10
 11#include <stdio.h>
 12#include <stdbool.h>
 13#include <stdarg.h>
 14#include <assert.h>
 15#include <malloc.h>
 16#include <inttypes.h>
 17#include <stdint.h>
 18
 19#include "json_writer.h"
 20
 21struct json_writer {
 22	FILE		*out;	/* output file */
 23	unsigned	depth;  /* nesting */
 24	bool		pretty; /* optional whitepace */
 25	char		sep;	/* either nul or comma */
 26};
 27
 28/* indentation for pretty print */
 29static void jsonw_indent(json_writer_t *self)
 30{
 31	unsigned i;
 32	for (i = 0; i < self->depth; ++i)
 33		fputs("    ", self->out);
 34}
 35
 36/* end current line and indent if pretty printing */
 37static void jsonw_eol(json_writer_t *self)
 38{
 39	if (!self->pretty)
 40		return;
 41
 42	putc('\n', self->out);
 43	jsonw_indent(self);
 44}
 45
 46/* If current object is not empty print a comma */
 47static void jsonw_eor(json_writer_t *self)
 48{
 49	if (self->sep != '\0')
 50		putc(self->sep, self->out);
 51	self->sep = ',';
 52}
 53
 54
 55/* Output JSON encoded string */
 56/* Handles C escapes, does not do Unicode */
 57static void jsonw_puts(json_writer_t *self, const char *str)
 58{
 59	putc('"', self->out);
 60	for (; *str; ++str)
 61		switch (*str) {
 62		case '\t':
 63			fputs("\\t", self->out);
 64			break;
 65		case '\n':
 66			fputs("\\n", self->out);
 67			break;
 68		case '\r':
 69			fputs("\\r", self->out);
 70			break;
 71		case '\f':
 72			fputs("\\f", self->out);
 73			break;
 74		case '\b':
 75			fputs("\\b", self->out);
 76			break;
 77		case '\\':
 78			fputs("\\\\", self->out);
 79			break;
 80		case '"':
 81			fputs("\\\"", self->out);
 82			break;
 83		default:
 84			putc(*str, self->out);
 85		}
 86	putc('"', self->out);
 87}
 88
 89/* Create a new JSON stream */
 90json_writer_t *jsonw_new(FILE *f)
 91{
 92	json_writer_t *self = malloc(sizeof(*self));
 93	if (self) {
 94		self->out = f;
 95		self->depth = 0;
 96		self->pretty = false;
 97		self->sep = '\0';
 98	}
 99	return self;
100}
101
102/* End output to JSON stream */
103void jsonw_destroy(json_writer_t **self_p)
104{
105	json_writer_t *self = *self_p;
106
107	assert(self->depth == 0);
108	fputs("\n", self->out);
109	fflush(self->out);
110	free(self);
111	*self_p = NULL;
112}
113
114void jsonw_pretty(json_writer_t *self, bool on)
115{
116	self->pretty = on;
117}
118
119void jsonw_reset(json_writer_t *self)
120{
121	assert(self->depth == 0);
122	self->sep = '\0';
123}
124
125/* Basic blocks */
126static void jsonw_begin(json_writer_t *self, int c)
127{
128	jsonw_eor(self);
129	putc(c, self->out);
130	++self->depth;
131	self->sep = '\0';
132}
133
134static void jsonw_end(json_writer_t *self, int c)
135{
136	assert(self->depth > 0);
137
138	--self->depth;
139	if (self->sep != '\0')
140		jsonw_eol(self);
141	putc(c, self->out);
142	self->sep = ',';
143}
144
145
146/* Add a JSON property name */
147void jsonw_name(json_writer_t *self, const char *name)
148{
149	jsonw_eor(self);
150	jsonw_eol(self);
151	self->sep = '\0';
152	jsonw_puts(self, name);
153	putc(':', self->out);
154	if (self->pretty)
155		putc(' ', self->out);
156}
157
158void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
159{
160	jsonw_eor(self);
161	putc('"', self->out);
162	vfprintf(self->out, fmt, ap);
163	putc('"', self->out);
164}
165
166void jsonw_printf(json_writer_t *self, const char *fmt, ...)
167{
168	va_list ap;
169
170	va_start(ap, fmt);
171	jsonw_eor(self);
172	vfprintf(self->out, fmt, ap);
173	va_end(ap);
174}
175
176/* Collections */
177void jsonw_start_object(json_writer_t *self)
178{
179	jsonw_begin(self, '{');
180}
181
182void jsonw_end_object(json_writer_t *self)
183{
184	jsonw_end(self, '}');
185}
186
187void jsonw_start_array(json_writer_t *self)
188{
189	jsonw_begin(self, '[');
190}
191
192void jsonw_end_array(json_writer_t *self)
193{
194	jsonw_end(self, ']');
195}
196
197/* JSON value types */
198void jsonw_string(json_writer_t *self, const char *value)
199{
200	jsonw_eor(self);
201	jsonw_puts(self, value);
202}
203
204void jsonw_bool(json_writer_t *self, bool val)
205{
206	jsonw_printf(self, "%s", val ? "true" : "false");
207}
208
209void jsonw_null(json_writer_t *self)
210{
211	jsonw_printf(self, "null");
212}
213
214void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
215{
216	jsonw_printf(self, fmt, num);
217}
218
219#ifdef notused
220void jsonw_float(json_writer_t *self, double num)
221{
222	jsonw_printf(self, "%g", num);
223}
224#endif
225
226void jsonw_hu(json_writer_t *self, unsigned short num)
227{
228	jsonw_printf(self, "%hu", num);
229}
230
231void jsonw_uint(json_writer_t *self, uint64_t num)
232{
233	jsonw_printf(self, "%"PRIu64, num);
234}
235
236void jsonw_lluint(json_writer_t *self, unsigned long long int num)
237{
238	jsonw_printf(self, "%llu", num);
239}
240
241void jsonw_int(json_writer_t *self, int64_t num)
242{
243	jsonw_printf(self, "%"PRId64, num);
244}
245
246/* Basic name/value objects */
247void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
248{
249	jsonw_name(self, prop);
250	jsonw_string(self, val);
251}
252
253void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
254{
255	jsonw_name(self, prop);
256	jsonw_bool(self, val);
257}
258
259#ifdef notused
260void jsonw_float_field(json_writer_t *self, const char *prop, double val)
261{
262	jsonw_name(self, prop);
263	jsonw_float(self, val);
264}
265#endif
266
267void jsonw_float_field_fmt(json_writer_t *self,
268			   const char *prop,
269			   const char *fmt,
270			   double val)
271{
272	jsonw_name(self, prop);
273	jsonw_float_fmt(self, fmt, val);
274}
275
276void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
277{
278	jsonw_name(self, prop);
279	jsonw_uint(self, num);
280}
281
282void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
283{
284	jsonw_name(self, prop);
285	jsonw_hu(self, num);
286}
287
288void jsonw_lluint_field(json_writer_t *self,
289			const char *prop,
290			unsigned long long int num)
291{
292	jsonw_name(self, prop);
293	jsonw_lluint(self, num);
294}
295
296void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
297{
298	jsonw_name(self, prop);
299	jsonw_int(self, num);
300}
301
302void jsonw_null_field(json_writer_t *self, const char *prop)
303{
304	jsonw_name(self, prop);
305	jsonw_null(self);
306}
307
308#ifdef TEST
309int main(int argc, char **argv)
310{
311	json_writer_t *wr = jsonw_new(stdout);
312
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);
320
321	jsonw_name(wr, "ARGV");
322	jsonw_start_array(wr);
323	while (--argc)
324		jsonw_string(wr, *++argv);
325	jsonw_end_array(wr);
326
327	jsonw_name(wr, "empty");
328	jsonw_start_array(wr);
329	jsonw_end_array(wr);
330
331	jsonw_name(wr, "NIL");
332	jsonw_start_object(wr);
333	jsonw_end_object(wr);
334
335	jsonw_null_field(wr, "my_null");
336
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", "\\");
346	jsonw_end_array(wr);
347
348	jsonw_end_object(wr);
349
350	jsonw_end_object(wr);
351	jsonw_destroy(&wr);
352	return 0;
353}
354
355#endif