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("\\n", self->out);
 79			break;
 80		case '"':
 81			fputs("\\\"", self->out);
 82			break;
 83		case '\'':
 84			fputs("\\\'", self->out);
 85			break;
 86		default:
 87			putc(*str, self->out);
 88		}
 89	putc('"', self->out);
 90}
 91
 92/* Create a new JSON stream */
 93json_writer_t *jsonw_new(FILE *f)
 94{
 95	json_writer_t *self = malloc(sizeof(*self));
 96	if (self) {
 97		self->out = f;
 98		self->depth = 0;
 99		self->pretty = false;
100		self->sep = '\0';
101	}
102	return self;
103}
104
105/* End output to JSON stream */
106void jsonw_destroy(json_writer_t **self_p)
107{
108	json_writer_t *self = *self_p;
109
110	assert(self->depth == 0);
111	fputs("\n", self->out);
112	fflush(self->out);
113	free(self);
114	*self_p = NULL;
115}
116
117void jsonw_pretty(json_writer_t *self, bool on)
118{
119	self->pretty = on;
120}
121
122/* Basic blocks */
123static void jsonw_begin(json_writer_t *self, int c)
124{
125	jsonw_eor(self);
126	putc(c, self->out);
127	++self->depth;
128	self->sep = '\0';
129}
130
131static void jsonw_end(json_writer_t *self, int c)
132{
133	assert(self->depth > 0);
134
135	--self->depth;
136	if (self->sep != '\0')
137		jsonw_eol(self);
138	putc(c, self->out);
139	self->sep = ',';
140}
141
142
143/* Add a JSON property name */
144void jsonw_name(json_writer_t *self, const char *name)
145{
146	jsonw_eor(self);
147	jsonw_eol(self);
148	self->sep = '\0';
149	jsonw_puts(self, name);
150	putc(':', self->out);
151	if (self->pretty)
152		putc(' ', self->out);
153}
154
155void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
156{
157	jsonw_eor(self);
158	putc('"', self->out);
159	vfprintf(self->out, fmt, ap);
160	putc('"', self->out);
161}
162
163void jsonw_printf(json_writer_t *self, const char *fmt, ...)
164{
165	va_list ap;
166
167	va_start(ap, fmt);
168	jsonw_eor(self);
169	vfprintf(self->out, fmt, ap);
170	va_end(ap);
171}
172
173/* Collections */
174void jsonw_start_object(json_writer_t *self)
175{
176	jsonw_begin(self, '{');
177}
178
179void jsonw_end_object(json_writer_t *self)
180{
181	jsonw_end(self, '}');
182}
183
184void jsonw_start_array(json_writer_t *self)
185{
186	jsonw_begin(self, '[');
187}
188
189void jsonw_end_array(json_writer_t *self)
190{
191	jsonw_end(self, ']');
192}
193
194/* JSON value types */
195void jsonw_string(json_writer_t *self, const char *value)
196{
197	jsonw_eor(self);
198	jsonw_puts(self, value);
199}
200
201void jsonw_bool(json_writer_t *self, bool val)
202{
203	jsonw_printf(self, "%s", val ? "true" : "false");
204}
205
206void jsonw_null(json_writer_t *self)
207{
208	jsonw_printf(self, "null");
209}
210
211void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
212{
213	jsonw_printf(self, fmt, num);
214}
215
216#ifdef notused
217void jsonw_float(json_writer_t *self, double num)
218{
219	jsonw_printf(self, "%g", num);
220}
221#endif
222
223void jsonw_hu(json_writer_t *self, unsigned short num)
224{
225	jsonw_printf(self, "%hu", num);
226}
227
228void jsonw_uint(json_writer_t *self, uint64_t num)
229{
230	jsonw_printf(self, "%"PRIu64, num);
231}
232
233void jsonw_lluint(json_writer_t *self, unsigned long long int num)
234{
235	jsonw_printf(self, "%llu", num);
236}
237
238void jsonw_int(json_writer_t *self, int64_t num)
239{
240	jsonw_printf(self, "%"PRId64, num);
241}
242
243/* Basic name/value objects */
244void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
245{
246	jsonw_name(self, prop);
247	jsonw_string(self, val);
248}
249
250void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
251{
252	jsonw_name(self, prop);
253	jsonw_bool(self, val);
254}
255
256#ifdef notused
257void jsonw_float_field(json_writer_t *self, const char *prop, double val)
258{
259	jsonw_name(self, prop);
260	jsonw_float(self, val);
261}
262#endif
263
264void jsonw_float_field_fmt(json_writer_t *self,
265			   const char *prop,
266			   const char *fmt,
267			   double val)
268{
269	jsonw_name(self, prop);
270	jsonw_float_fmt(self, fmt, val);
271}
272
273void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
274{
275	jsonw_name(self, prop);
276	jsonw_uint(self, num);
277}
278
279void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
280{
281	jsonw_name(self, prop);
282	jsonw_hu(self, num);
283}
284
285void jsonw_lluint_field(json_writer_t *self,
286			const char *prop,
287			unsigned long long int num)
288{
289	jsonw_name(self, prop);
290	jsonw_lluint(self, num);
291}
292
293void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
294{
295	jsonw_name(self, prop);
296	jsonw_int(self, num);
297}
298
299void jsonw_null_field(json_writer_t *self, const char *prop)
300{
301	jsonw_name(self, prop);
302	jsonw_null(self);
303}
304
305#ifdef TEST
306int main(int argc, char **argv)
307{
308	json_writer_t *wr = jsonw_new(stdout);
309
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);
317
318	jsonw_name(wr, "ARGV");
319	jsonw_start_array(wr);
320	while (--argc)
321		jsonw_string(wr, *++argv);
322	jsonw_end_array(wr);
323
324	jsonw_name(wr, "empty");
325	jsonw_start_array(wr);
326	jsonw_end_array(wr);
327
328	jsonw_name(wr, "NIL");
329	jsonw_start_object(wr);
330	jsonw_end_object(wr);
331
332	jsonw_null_field(wr, "my_null");
333
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", "\\");
343	jsonw_end_array(wr);
344
345	jsonw_end_object(wr);
346
347	jsonw_end_object(wr);
348	jsonw_destroy(&wr);
349	return 0;
350}
351
352#endif