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 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 */
jsonw_new(FILE * f)93 json_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 */
jsonw_destroy(json_writer_t ** self_p)106 void 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
jsonw_pretty(json_writer_t * self,bool on)117 void jsonw_pretty(json_writer_t *self, bool on)
118 {
119 self->pretty = on;
120 }
121
jsonw_reset(json_writer_t * self)122 void jsonw_reset(json_writer_t *self)
123 {
124 assert(self->depth == 0);
125 self->sep = '\0';
126 }
127
128 /* Basic blocks */
jsonw_begin(json_writer_t * self,int c)129 static 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
jsonw_end(json_writer_t * self,int c)137 static 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 */
jsonw_name(json_writer_t * self,const char * name)150 void 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
jsonw_vprintf_enquote(json_writer_t * self,const char * fmt,va_list ap)161 void 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
jsonw_printf(json_writer_t * self,const char * fmt,...)169 void 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 */
jsonw_start_object(json_writer_t * self)180 void jsonw_start_object(json_writer_t *self)
181 {
182 jsonw_begin(self, '{');
183 }
184
jsonw_end_object(json_writer_t * self)185 void jsonw_end_object(json_writer_t *self)
186 {
187 jsonw_end(self, '}');
188 }
189
jsonw_start_array(json_writer_t * self)190 void jsonw_start_array(json_writer_t *self)
191 {
192 jsonw_begin(self, '[');
193 }
194
jsonw_end_array(json_writer_t * self)195 void jsonw_end_array(json_writer_t *self)
196 {
197 jsonw_end(self, ']');
198 }
199
200 /* JSON value types */
jsonw_string(json_writer_t * self,const char * value)201 void jsonw_string(json_writer_t *self, const char *value)
202 {
203 jsonw_eor(self);
204 jsonw_puts(self, value);
205 }
206
jsonw_bool(json_writer_t * self,bool val)207 void jsonw_bool(json_writer_t *self, bool val)
208 {
209 jsonw_printf(self, "%s", val ? "true" : "false");
210 }
211
jsonw_null(json_writer_t * self)212 void jsonw_null(json_writer_t *self)
213 {
214 jsonw_printf(self, "null");
215 }
216
jsonw_float_fmt(json_writer_t * self,const char * fmt,double num)217 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
218 {
219 jsonw_printf(self, fmt, num);
220 }
221
222 #ifdef notused
jsonw_float(json_writer_t * self,double num)223 void jsonw_float(json_writer_t *self, double num)
224 {
225 jsonw_printf(self, "%g", num);
226 }
227 #endif
228
jsonw_hu(json_writer_t * self,unsigned short num)229 void jsonw_hu(json_writer_t *self, unsigned short num)
230 {
231 jsonw_printf(self, "%hu", num);
232 }
233
jsonw_uint(json_writer_t * self,uint64_t num)234 void jsonw_uint(json_writer_t *self, uint64_t num)
235 {
236 jsonw_printf(self, "%"PRIu64, num);
237 }
238
jsonw_lluint(json_writer_t * self,unsigned long long int num)239 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
240 {
241 jsonw_printf(self, "%llu", num);
242 }
243
jsonw_int(json_writer_t * self,int64_t num)244 void jsonw_int(json_writer_t *self, int64_t num)
245 {
246 jsonw_printf(self, "%"PRId64, num);
247 }
248
249 /* Basic name/value objects */
jsonw_string_field(json_writer_t * self,const char * prop,const char * val)250 void 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
jsonw_bool_field(json_writer_t * self,const char * prop,bool val)256 void 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
jsonw_float_field(json_writer_t * self,const char * prop,double val)263 void 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
jsonw_float_field_fmt(json_writer_t * self,const char * prop,const char * fmt,double val)270 void 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
jsonw_uint_field(json_writer_t * self,const char * prop,uint64_t num)279 void 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
jsonw_hu_field(json_writer_t * self,const char * prop,unsigned short num)285 void 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
jsonw_lluint_field(json_writer_t * self,const char * prop,unsigned long long int num)291 void 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
jsonw_int_field(json_writer_t * self,const char * prop,int64_t num)299 void 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
jsonw_null_field(json_writer_t * self,const char * prop)305 void 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
main(int argc,char ** argv)312 int 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
359