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 */
jsonw_indent(json_writer_t * self)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 */
jsonw_eol(json_writer_t * self)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 */
jsonw_eor(json_writer_t * self)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 */
jsonw_puts(json_writer_t * self,const char * str)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("\\n", 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 */
jsonw_new(FILE * f)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 */
jsonw_destroy(json_writer_t ** self_p)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
jsonw_pretty(json_writer_t * self,bool on)114 void jsonw_pretty(json_writer_t *self, bool on)
115 {
116 self->pretty = on;
117 }
118
119 /* Basic blocks */
jsonw_begin(json_writer_t * self,int c)120 static void jsonw_begin(json_writer_t *self, int c)
121 {
122 jsonw_eor(self);
123 putc(c, self->out);
124 ++self->depth;
125 self->sep = '\0';
126 }
127
jsonw_end(json_writer_t * self,int c)128 static void jsonw_end(json_writer_t *self, int c)
129 {
130 assert(self->depth > 0);
131
132 --self->depth;
133 if (self->sep != '\0')
134 jsonw_eol(self);
135 putc(c, self->out);
136 self->sep = ',';
137 }
138
139
140 /* Add a JSON property name */
jsonw_name(json_writer_t * self,const char * name)141 void jsonw_name(json_writer_t *self, const char *name)
142 {
143 jsonw_eor(self);
144 jsonw_eol(self);
145 self->sep = '\0';
146 jsonw_puts(self, name);
147 putc(':', self->out);
148 if (self->pretty)
149 putc(' ', self->out);
150 }
151
jsonw_vprintf_enquote(json_writer_t * self,const char * fmt,va_list ap)152 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
153 {
154 jsonw_eor(self);
155 putc('"', self->out);
156 vfprintf(self->out, fmt, ap);
157 putc('"', self->out);
158 }
159
jsonw_printf(json_writer_t * self,const char * fmt,...)160 void jsonw_printf(json_writer_t *self, const char *fmt, ...)
161 {
162 va_list ap;
163
164 va_start(ap, fmt);
165 jsonw_eor(self);
166 vfprintf(self->out, fmt, ap);
167 va_end(ap);
168 }
169
170 /* Collections */
jsonw_start_object(json_writer_t * self)171 void jsonw_start_object(json_writer_t *self)
172 {
173 jsonw_begin(self, '{');
174 }
175
jsonw_end_object(json_writer_t * self)176 void jsonw_end_object(json_writer_t *self)
177 {
178 jsonw_end(self, '}');
179 }
180
jsonw_start_array(json_writer_t * self)181 void jsonw_start_array(json_writer_t *self)
182 {
183 jsonw_begin(self, '[');
184 }
185
jsonw_end_array(json_writer_t * self)186 void jsonw_end_array(json_writer_t *self)
187 {
188 jsonw_end(self, ']');
189 }
190
191 /* JSON value types */
jsonw_string(json_writer_t * self,const char * value)192 void jsonw_string(json_writer_t *self, const char *value)
193 {
194 jsonw_eor(self);
195 jsonw_puts(self, value);
196 }
197
jsonw_bool(json_writer_t * self,bool val)198 void jsonw_bool(json_writer_t *self, bool val)
199 {
200 jsonw_printf(self, "%s", val ? "true" : "false");
201 }
202
jsonw_null(json_writer_t * self)203 void jsonw_null(json_writer_t *self)
204 {
205 jsonw_printf(self, "null");
206 }
207
jsonw_float_fmt(json_writer_t * self,const char * fmt,double num)208 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
209 {
210 jsonw_printf(self, fmt, num);
211 }
212
213 #ifdef notused
jsonw_float(json_writer_t * self,double num)214 void jsonw_float(json_writer_t *self, double num)
215 {
216 jsonw_printf(self, "%g", num);
217 }
218 #endif
219
jsonw_hu(json_writer_t * self,unsigned short num)220 void jsonw_hu(json_writer_t *self, unsigned short num)
221 {
222 jsonw_printf(self, "%hu", num);
223 }
224
jsonw_uint(json_writer_t * self,uint64_t num)225 void jsonw_uint(json_writer_t *self, uint64_t num)
226 {
227 jsonw_printf(self, "%"PRIu64, num);
228 }
229
jsonw_lluint(json_writer_t * self,unsigned long long int num)230 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
231 {
232 jsonw_printf(self, "%llu", num);
233 }
234
jsonw_int(json_writer_t * self,int64_t num)235 void jsonw_int(json_writer_t *self, int64_t num)
236 {
237 jsonw_printf(self, "%"PRId64, num);
238 }
239
240 /* Basic name/value objects */
jsonw_string_field(json_writer_t * self,const char * prop,const char * val)241 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
242 {
243 jsonw_name(self, prop);
244 jsonw_string(self, val);
245 }
246
jsonw_bool_field(json_writer_t * self,const char * prop,bool val)247 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
248 {
249 jsonw_name(self, prop);
250 jsonw_bool(self, val);
251 }
252
253 #ifdef notused
jsonw_float_field(json_writer_t * self,const char * prop,double val)254 void jsonw_float_field(json_writer_t *self, const char *prop, double val)
255 {
256 jsonw_name(self, prop);
257 jsonw_float(self, val);
258 }
259 #endif
260
jsonw_float_field_fmt(json_writer_t * self,const char * prop,const char * fmt,double val)261 void jsonw_float_field_fmt(json_writer_t *self,
262 const char *prop,
263 const char *fmt,
264 double val)
265 {
266 jsonw_name(self, prop);
267 jsonw_float_fmt(self, fmt, val);
268 }
269
jsonw_uint_field(json_writer_t * self,const char * prop,uint64_t num)270 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
271 {
272 jsonw_name(self, prop);
273 jsonw_uint(self, num);
274 }
275
jsonw_hu_field(json_writer_t * self,const char * prop,unsigned short num)276 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
277 {
278 jsonw_name(self, prop);
279 jsonw_hu(self, num);
280 }
281
jsonw_lluint_field(json_writer_t * self,const char * prop,unsigned long long int num)282 void jsonw_lluint_field(json_writer_t *self,
283 const char *prop,
284 unsigned long long int num)
285 {
286 jsonw_name(self, prop);
287 jsonw_lluint(self, num);
288 }
289
jsonw_int_field(json_writer_t * self,const char * prop,int64_t num)290 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
291 {
292 jsonw_name(self, prop);
293 jsonw_int(self, num);
294 }
295
jsonw_null_field(json_writer_t * self,const char * prop)296 void jsonw_null_field(json_writer_t *self, const char *prop)
297 {
298 jsonw_name(self, prop);
299 jsonw_null(self);
300 }
301
302 #ifdef TEST
main(int argc,char ** argv)303 int main(int argc, char **argv)
304 {
305 json_writer_t *wr = jsonw_new(stdout);
306
307 jsonw_start_object(wr);
308 jsonw_pretty(wr, true);
309 jsonw_name(wr, "Vyatta");
310 jsonw_start_object(wr);
311 jsonw_string_field(wr, "url", "http://vyatta.com");
312 jsonw_uint_field(wr, "downloads", 2000000ul);
313 jsonw_float_field(wr, "stock", 8.16);
314
315 jsonw_name(wr, "ARGV");
316 jsonw_start_array(wr);
317 while (--argc)
318 jsonw_string(wr, *++argv);
319 jsonw_end_array(wr);
320
321 jsonw_name(wr, "empty");
322 jsonw_start_array(wr);
323 jsonw_end_array(wr);
324
325 jsonw_name(wr, "NIL");
326 jsonw_start_object(wr);
327 jsonw_end_object(wr);
328
329 jsonw_null_field(wr, "my_null");
330
331 jsonw_name(wr, "special chars");
332 jsonw_start_array(wr);
333 jsonw_string_field(wr, "slash", "/");
334 jsonw_string_field(wr, "newline", "\n");
335 jsonw_string_field(wr, "tab", "\t");
336 jsonw_string_field(wr, "ff", "\f");
337 jsonw_string_field(wr, "quote", "\"");
338 jsonw_string_field(wr, "tick", "\'");
339 jsonw_string_field(wr, "backslash", "\\");
340 jsonw_end_array(wr);
341
342 jsonw_end_object(wr);
343
344 jsonw_end_object(wr);
345 jsonw_destroy(&wr);
346 return 0;
347 }
348
349 #endif
350