1 /*
2 * Simple streaming JSON writer
3 *
4 * This takes care of the annoying bits of JSON syntax like the commas
5 * after elements
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 *
12 * Authors: Stephen Hemminger <stephen@networkplumber.org>
13 */
14
15 #include <stdio.h>
16 #include <stdbool.h>
17 #include <stdarg.h>
18 #include <assert.h>
19 #include <malloc.h>
20 #include <inttypes.h>
21 #include <stdint.h>
22
23 #include "json_writer.h"
24
25 struct json_writer {
26 FILE *out; /* output file */
27 unsigned depth; /* nesting */
28 bool pretty; /* optional whitepace */
29 char sep; /* either nul or comma */
30 };
31
32 /* indentation for pretty print */
jsonw_indent(json_writer_t * self)33 static void jsonw_indent(json_writer_t *self)
34 {
35 unsigned i;
36 for (i = 0; i < self->depth; ++i)
37 fputs(" ", self->out);
38 }
39
40 /* end current line and indent if pretty printing */
jsonw_eol(json_writer_t * self)41 static void jsonw_eol(json_writer_t *self)
42 {
43 if (!self->pretty)
44 return;
45
46 putc('\n', self->out);
47 jsonw_indent(self);
48 }
49
50 /* If current object is not empty print a comma */
jsonw_eor(json_writer_t * self)51 static void jsonw_eor(json_writer_t *self)
52 {
53 if (self->sep != '\0')
54 putc(self->sep, self->out);
55 self->sep = ',';
56 }
57
58
59 /* Output JSON encoded string */
60 /* Handles C escapes, does not do Unicode */
jsonw_puts(json_writer_t * self,const char * str)61 static void jsonw_puts(json_writer_t *self, const char *str)
62 {
63 putc('"', self->out);
64 for (; *str; ++str)
65 switch (*str) {
66 case '\t':
67 fputs("\\t", self->out);
68 break;
69 case '\n':
70 fputs("\\n", self->out);
71 break;
72 case '\r':
73 fputs("\\r", self->out);
74 break;
75 case '\f':
76 fputs("\\f", self->out);
77 break;
78 case '\b':
79 fputs("\\b", self->out);
80 break;
81 case '\\':
82 fputs("\\n", self->out);
83 break;
84 case '"':
85 fputs("\\\"", self->out);
86 break;
87 case '\'':
88 fputs("\\\'", self->out);
89 break;
90 default:
91 putc(*str, self->out);
92 }
93 putc('"', self->out);
94 }
95
96 /* Create a new JSON stream */
jsonw_new(FILE * f)97 json_writer_t *jsonw_new(FILE *f)
98 {
99 json_writer_t *self = malloc(sizeof(*self));
100 if (self) {
101 self->out = f;
102 self->depth = 0;
103 self->pretty = false;
104 self->sep = '\0';
105 }
106 return self;
107 }
108
109 /* End output to JSON stream */
jsonw_destroy(json_writer_t ** self_p)110 void jsonw_destroy(json_writer_t **self_p)
111 {
112 json_writer_t *self = *self_p;
113
114 assert(self->depth == 0);
115 fputs("\n", self->out);
116 fflush(self->out);
117 free(self);
118 *self_p = NULL;
119 }
120
jsonw_pretty(json_writer_t * self,bool on)121 void jsonw_pretty(json_writer_t *self, bool on)
122 {
123 self->pretty = on;
124 }
125
126 /* Basic blocks */
jsonw_begin(json_writer_t * self,int c)127 static void jsonw_begin(json_writer_t *self, int c)
128 {
129 jsonw_eor(self);
130 putc(c, self->out);
131 ++self->depth;
132 self->sep = '\0';
133 }
134
jsonw_end(json_writer_t * self,int c)135 static void jsonw_end(json_writer_t *self, int c)
136 {
137 assert(self->depth > 0);
138
139 --self->depth;
140 if (self->sep != '\0')
141 jsonw_eol(self);
142 putc(c, self->out);
143 self->sep = ',';
144 }
145
146
147 /* Add a JSON property name */
jsonw_name(json_writer_t * self,const char * name)148 void jsonw_name(json_writer_t *self, const char *name)
149 {
150 jsonw_eor(self);
151 jsonw_eol(self);
152 self->sep = '\0';
153 jsonw_puts(self, name);
154 putc(':', self->out);
155 if (self->pretty)
156 putc(' ', self->out);
157 }
158
jsonw_vprintf_enquote(json_writer_t * self,const char * fmt,va_list ap)159 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
160 {
161 jsonw_eor(self);
162 putc('"', self->out);
163 vfprintf(self->out, fmt, ap);
164 putc('"', self->out);
165 }
166
jsonw_printf(json_writer_t * self,const char * fmt,...)167 void jsonw_printf(json_writer_t *self, const char *fmt, ...)
168 {
169 va_list ap;
170
171 va_start(ap, fmt);
172 jsonw_eor(self);
173 vfprintf(self->out, fmt, ap);
174 va_end(ap);
175 }
176
177 /* Collections */
jsonw_start_object(json_writer_t * self)178 void jsonw_start_object(json_writer_t *self)
179 {
180 jsonw_begin(self, '{');
181 }
182
jsonw_end_object(json_writer_t * self)183 void jsonw_end_object(json_writer_t *self)
184 {
185 jsonw_end(self, '}');
186 }
187
jsonw_start_array(json_writer_t * self)188 void jsonw_start_array(json_writer_t *self)
189 {
190 jsonw_begin(self, '[');
191 }
192
jsonw_end_array(json_writer_t * self)193 void jsonw_end_array(json_writer_t *self)
194 {
195 jsonw_end(self, ']');
196 }
197
198 /* JSON value types */
jsonw_string(json_writer_t * self,const char * value)199 void jsonw_string(json_writer_t *self, const char *value)
200 {
201 jsonw_eor(self);
202 jsonw_puts(self, value);
203 }
204
jsonw_bool(json_writer_t * self,bool val)205 void jsonw_bool(json_writer_t *self, bool val)
206 {
207 jsonw_printf(self, "%s", val ? "true" : "false");
208 }
209
jsonw_null(json_writer_t * self)210 void jsonw_null(json_writer_t *self)
211 {
212 jsonw_printf(self, "null");
213 }
214
jsonw_float_fmt(json_writer_t * self,const char * fmt,double num)215 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
216 {
217 jsonw_printf(self, fmt, num);
218 }
219
220 #ifdef notused
jsonw_float(json_writer_t * self,double num)221 void jsonw_float(json_writer_t *self, double num)
222 {
223 jsonw_printf(self, "%g", num);
224 }
225 #endif
226
jsonw_hu(json_writer_t * self,unsigned short num)227 void jsonw_hu(json_writer_t *self, unsigned short num)
228 {
229 jsonw_printf(self, "%hu", num);
230 }
231
jsonw_uint(json_writer_t * self,uint64_t num)232 void jsonw_uint(json_writer_t *self, uint64_t num)
233 {
234 jsonw_printf(self, "%"PRIu64, num);
235 }
236
jsonw_lluint(json_writer_t * self,unsigned long long int num)237 void jsonw_lluint(json_writer_t *self, unsigned long long int num)
238 {
239 jsonw_printf(self, "%llu", num);
240 }
241
jsonw_int(json_writer_t * self,int64_t num)242 void jsonw_int(json_writer_t *self, int64_t num)
243 {
244 jsonw_printf(self, "%"PRId64, num);
245 }
246
247 /* Basic name/value objects */
jsonw_string_field(json_writer_t * self,const char * prop,const char * val)248 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
249 {
250 jsonw_name(self, prop);
251 jsonw_string(self, val);
252 }
253
jsonw_bool_field(json_writer_t * self,const char * prop,bool val)254 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
255 {
256 jsonw_name(self, prop);
257 jsonw_bool(self, val);
258 }
259
260 #ifdef notused
jsonw_float_field(json_writer_t * self,const char * prop,double val)261 void jsonw_float_field(json_writer_t *self, const char *prop, double val)
262 {
263 jsonw_name(self, prop);
264 jsonw_float(self, val);
265 }
266 #endif
267
jsonw_float_field_fmt(json_writer_t * self,const char * prop,const char * fmt,double val)268 void jsonw_float_field_fmt(json_writer_t *self,
269 const char *prop,
270 const char *fmt,
271 double val)
272 {
273 jsonw_name(self, prop);
274 jsonw_float_fmt(self, fmt, val);
275 }
276
jsonw_uint_field(json_writer_t * self,const char * prop,uint64_t num)277 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
278 {
279 jsonw_name(self, prop);
280 jsonw_uint(self, num);
281 }
282
jsonw_hu_field(json_writer_t * self,const char * prop,unsigned short num)283 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
284 {
285 jsonw_name(self, prop);
286 jsonw_hu(self, num);
287 }
288
jsonw_lluint_field(json_writer_t * self,const char * prop,unsigned long long int num)289 void jsonw_lluint_field(json_writer_t *self,
290 const char *prop,
291 unsigned long long int num)
292 {
293 jsonw_name(self, prop);
294 jsonw_lluint(self, num);
295 }
296
jsonw_int_field(json_writer_t * self,const char * prop,int64_t num)297 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
298 {
299 jsonw_name(self, prop);
300 jsonw_int(self, num);
301 }
302
jsonw_null_field(json_writer_t * self,const char * prop)303 void jsonw_null_field(json_writer_t *self, const char *prop)
304 {
305 jsonw_name(self, prop);
306 jsonw_null(self);
307 }
308
309 #ifdef TEST
main(int argc,char ** argv)310 int main(int argc, char **argv)
311 {
312 json_writer_t *wr = jsonw_new(stdout);
313
314 jsonw_start_object(wr);
315 jsonw_pretty(wr, true);
316 jsonw_name(wr, "Vyatta");
317 jsonw_start_object(wr);
318 jsonw_string_field(wr, "url", "http://vyatta.com");
319 jsonw_uint_field(wr, "downloads", 2000000ul);
320 jsonw_float_field(wr, "stock", 8.16);
321
322 jsonw_name(wr, "ARGV");
323 jsonw_start_array(wr);
324 while (--argc)
325 jsonw_string(wr, *++argv);
326 jsonw_end_array(wr);
327
328 jsonw_name(wr, "empty");
329 jsonw_start_array(wr);
330 jsonw_end_array(wr);
331
332 jsonw_name(wr, "NIL");
333 jsonw_start_object(wr);
334 jsonw_end_object(wr);
335
336 jsonw_null_field(wr, "my_null");
337
338 jsonw_name(wr, "special chars");
339 jsonw_start_array(wr);
340 jsonw_string_field(wr, "slash", "/");
341 jsonw_string_field(wr, "newline", "\n");
342 jsonw_string_field(wr, "tab", "\t");
343 jsonw_string_field(wr, "ff", "\f");
344 jsonw_string_field(wr, "quote", "\"");
345 jsonw_string_field(wr, "tick", "\'");
346 jsonw_string_field(wr, "backslash", "\\");
347 jsonw_end_array(wr);
348
349 jsonw_end_object(wr);
350
351 jsonw_end_object(wr);
352 jsonw_destroy(&wr);
353 return 0;
354 }
355
356 #endif
357
