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
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