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
122void jsonw_reset(json_writer_t *self)
123{
124	assert(self->depth == 0);
125	self->sep = '\0';
126}
127
128/* Basic blocks */
129static void jsonw_begin(json_writer_t *self, int c)
130{
131	jsonw_eor(self);
132	putc(c, self->out);
133	++self->depth;
134	self->sep = '\0';
135}
136
137static void jsonw_end(json_writer_t *self, int c)
138{
139	assert(self->depth > 0);
140
141	--self->depth;
142	if (self->sep != '\0')
143		jsonw_eol(self);
144	putc(c, self->out);
145	self->sep = ',';
146}
147
148
149/* Add a JSON property name */
150void jsonw_name(json_writer_t *self, const char *name)
151{
152	jsonw_eor(self);
153	jsonw_eol(self);
154	self->sep = '\0';
155	jsonw_puts(self, name);
156	putc(':', self->out);
157	if (self->pretty)
158		putc(' ', self->out);
159}
160
161void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
162{
163	jsonw_eor(self);
164	putc('"', self->out);
165	vfprintf(self->out, fmt, ap);
166	putc('"', self->out);
167}
168
169void jsonw_printf(json_writer_t *self, const char *fmt, ...)
170{
171	va_list ap;
172
173	va_start(ap, fmt);
174	jsonw_eor(self);
175	vfprintf(self->out, fmt, ap);
176	va_end(ap);
177}
178
179/* Collections */
180void jsonw_start_object(json_writer_t *self)
181{
182	jsonw_begin(self, '{');
183}
184
185void jsonw_end_object(json_writer_t *self)
186{
187	jsonw_end(self, '}');
188}
189
190void jsonw_start_array(json_writer_t *self)
191{
192	jsonw_begin(self, '[');
193}
194
195void jsonw_end_array(json_writer_t *self)
196{
197	jsonw_end(self, ']');
198}
199
200/* JSON value types */
201void jsonw_string(json_writer_t *self, const char *value)
202{
203	jsonw_eor(self);
204	jsonw_puts(self, value);
205}
206
207void jsonw_bool(json_writer_t *self, bool val)
208{
209	jsonw_printf(self, "%s", val ? "true" : "false");
210}
211
212void jsonw_null(json_writer_t *self)
213{
214	jsonw_printf(self, "null");
215}
216
217void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
218{
219	jsonw_printf(self, fmt, num);
220}
221
222#ifdef notused
223void jsonw_float(json_writer_t *self, double num)
224{
225	jsonw_printf(self, "%g", num);
226}
227#endif
228
229void jsonw_hu(json_writer_t *self, unsigned short num)
230{
231	jsonw_printf(self, "%hu", num);
232}
233
234void jsonw_uint(json_writer_t *self, uint64_t num)
235{
236	jsonw_printf(self, "%"PRIu64, num);
237}
238
239void jsonw_lluint(json_writer_t *self, unsigned long long int num)
240{
241	jsonw_printf(self, "%llu", num);
242}
243
244void jsonw_int(json_writer_t *self, int64_t num)
245{
246	jsonw_printf(self, "%"PRId64, num);
247}
248
249/* Basic name/value objects */
250void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
251{
252	jsonw_name(self, prop);
253	jsonw_string(self, val);
254}
255
256void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
257{
258	jsonw_name(self, prop);
259	jsonw_bool(self, val);
260}
261
262#ifdef notused
263void jsonw_float_field(json_writer_t *self, const char *prop, double val)
264{
265	jsonw_name(self, prop);
266	jsonw_float(self, val);
267}
268#endif
269
270void jsonw_float_field_fmt(json_writer_t *self,
271			   const char *prop,
272			   const char *fmt,
273			   double val)
274{
275	jsonw_name(self, prop);
276	jsonw_float_fmt(self, fmt, val);
277}
278
279void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
280{
281	jsonw_name(self, prop);
282	jsonw_uint(self, num);
283}
284
285void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
286{
287	jsonw_name(self, prop);
288	jsonw_hu(self, num);
289}
290
291void jsonw_lluint_field(json_writer_t *self,
292			const char *prop,
293			unsigned long long int num)
294{
295	jsonw_name(self, prop);
296	jsonw_lluint(self, num);
297}
298
299void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
300{
301	jsonw_name(self, prop);
302	jsonw_int(self, num);
303}
304
305void jsonw_null_field(json_writer_t *self, const char *prop)
306{
307	jsonw_name(self, prop);
308	jsonw_null(self);
309}
310
311#ifdef TEST
312int main(int argc, char **argv)
313{
314	json_writer_t *wr = jsonw_new(stdout);
315
316	jsonw_start_object(wr);
317	jsonw_pretty(wr, true);
318	jsonw_name(wr, "Vyatta");
319	jsonw_start_object(wr);
320	jsonw_string_field(wr, "url", "http://vyatta.com");
321	jsonw_uint_field(wr, "downloads", 2000000ul);
322	jsonw_float_field(wr, "stock", 8.16);
323
324	jsonw_name(wr, "ARGV");
325	jsonw_start_array(wr);
326	while (--argc)
327		jsonw_string(wr, *++argv);
328	jsonw_end_array(wr);
329
330	jsonw_name(wr, "empty");
331	jsonw_start_array(wr);
332	jsonw_end_array(wr);
333
334	jsonw_name(wr, "NIL");
335	jsonw_start_object(wr);
336	jsonw_end_object(wr);
337
338	jsonw_null_field(wr, "my_null");
339
340	jsonw_name(wr, "special chars");
341	jsonw_start_array(wr);
342	jsonw_string_field(wr, "slash", "/");
343	jsonw_string_field(wr, "newline", "\n");
344	jsonw_string_field(wr, "tab", "\t");
345	jsonw_string_field(wr, "ff", "\f");
346	jsonw_string_field(wr, "quote", "\"");
347	jsonw_string_field(wr, "tick", "\'");
348	jsonw_string_field(wr, "backslash", "\\");
349	jsonw_end_array(wr);
350
351	jsonw_end_object(wr);
352
353	jsonw_end_object(wr);
354	jsonw_destroy(&wr);
355	return 0;
356}
357
358#endif