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