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 
21 struct 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 */
29 static 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 */
37 static 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 */
47 static 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 */
57 static 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 */
90 json_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 */
103 void 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 
114 void jsonw_pretty(json_writer_t *self, bool on)
115 {
116 	self->pretty = on;
117 }
118 
119 void jsonw_reset(json_writer_t *self)
120 {
121 	assert(self->depth == 0);
122 	self->sep = '\0';
123 }
124 
125 /* Basic blocks */
126 static 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 
134 static 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 */
147 void 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 
158 void 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 
166 void 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 */
177 void jsonw_start_object(json_writer_t *self)
178 {
179 	jsonw_begin(self, '{');
180 }
181 
182 void jsonw_end_object(json_writer_t *self)
183 {
184 	jsonw_end(self, '}');
185 }
186 
187 void jsonw_start_array(json_writer_t *self)
188 {
189 	jsonw_begin(self, '[');
190 }
191 
192 void jsonw_end_array(json_writer_t *self)
193 {
194 	jsonw_end(self, ']');
195 }
196 
197 /* JSON value types */
198 void jsonw_string(json_writer_t *self, const char *value)
199 {
200 	jsonw_eor(self);
201 	jsonw_puts(self, value);
202 }
203 
204 void jsonw_bool(json_writer_t *self, bool val)
205 {
206 	jsonw_printf(self, "%s", val ? "true" : "false");
207 }
208 
209 void jsonw_null(json_writer_t *self)
210 {
211 	jsonw_printf(self, "null");
212 }
213 
214 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
215 {
216 	jsonw_printf(self, fmt, num);
217 }
218 
219 #ifdef notused
220 void jsonw_float(json_writer_t *self, double num)
221 {
222 	jsonw_printf(self, "%g", num);
223 }
224 #endif
225 
226 void jsonw_hu(json_writer_t *self, unsigned short num)
227 {
228 	jsonw_printf(self, "%hu", num);
229 }
230 
231 void jsonw_uint(json_writer_t *self, uint64_t num)
232 {
233 	jsonw_printf(self, "%"PRIu64, num);
234 }
235 
236 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
237 {
238 	jsonw_printf(self, "%llu", num);
239 }
240 
241 void jsonw_int(json_writer_t *self, int64_t num)
242 {
243 	jsonw_printf(self, "%"PRId64, num);
244 }
245 
246 /* Basic name/value objects */
247 void 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 
253 void 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
260 void 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 
267 void 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 
276 void 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 
282 void 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 
288 void 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 
296 void 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 
302 void 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
309 int 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
356