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 putc('{', self->out);
106 }
107 return self;
108 }
109
110 /* End output to JSON stream */
jsonw_destroy(json_writer_t ** self_p)111 void jsonw_destroy(json_writer_t **self_p)
112 {
113 json_writer_t *self = *self_p;
114
115 assert(self->depth == 0);
116 jsonw_eol(self);
117 fputs("}\n", self->out);
118 fflush(self->out);
119 free(self);
120 *self_p = NULL;
121 }
122
jsonw_pretty(json_writer_t * self,bool on)123 void jsonw_pretty(json_writer_t *self, bool on)
124 {
125 self->pretty = on;
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_printf(json_writer_t * self,const char * fmt,...)161 static void jsonw_printf(json_writer_t *self, const char *fmt, ...)
162 {
163 va_list ap;
164
165 va_start(ap, fmt);
166 jsonw_eor(self);
167 vfprintf(self->out, fmt, ap);
168 va_end(ap);
169 }
170
171 /* Collections */
jsonw_start_object(json_writer_t * self)172 void jsonw_start_object(json_writer_t *self)
173 {
174 jsonw_begin(self, '{');
175 }
176
jsonw_end_object(json_writer_t * self)177 void jsonw_end_object(json_writer_t *self)
178 {
179 jsonw_end(self, '}');
180 }
181
jsonw_start_array(json_writer_t * self)182 void jsonw_start_array(json_writer_t *self)
183 {
184 jsonw_begin(self, '[');
185 }
186
jsonw_end_array(json_writer_t * self)187 void jsonw_end_array(json_writer_t *self)
188 {
189 jsonw_end(self, ']');
190 }
191
192 /* JSON value types */
jsonw_string(json_writer_t * self,const char * value)193 void jsonw_string(json_writer_t *self, const char *value)
194 {
195 jsonw_eor(self);
196 jsonw_puts(self, value);
197 }
198
jsonw_bool(json_writer_t * self,bool val)199 void jsonw_bool(json_writer_t *self, bool val)
200 {
201 jsonw_printf(self, "%s", val ? "true" : "false");
202 }
203
204 #ifdef notused
jsonw_null(json_writer_t * self)205 void jsonw_null(json_writer_t *self)
206 {
207 jsonw_printf(self, "null");
208 }
209
jsonw_float(json_writer_t * self,double num)210 void jsonw_float(json_writer_t *self, double num)
211 {
212 jsonw_printf(self, "%g", num);
213 }
214 #endif
215
jsonw_uint(json_writer_t * self,uint64_t num)216 void jsonw_uint(json_writer_t *self, uint64_t num)
217 {
218 jsonw_printf(self, "%"PRIu64, num);
219 }
220
jsonw_int(json_writer_t * self,int64_t num)221 void jsonw_int(json_writer_t *self, int64_t num)
222 {
223 jsonw_printf(self, "%"PRId64, num);
224 }
225
226 /* Basic name/value objects */
jsonw_string_field(json_writer_t * self,const char * prop,const char * val)227 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
228 {
229 jsonw_name(self, prop);
230 jsonw_string(self, val);
231 }
232
jsonw_bool_field(json_writer_t * self,const char * prop,bool val)233 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
234 {
235 jsonw_name(self, prop);
236 jsonw_bool(self, val);
237 }
238
239 #ifdef notused
jsonw_float_field(json_writer_t * self,const char * prop,double val)240 void jsonw_float_field(json_writer_t *self, const char *prop, double val)
241 {
242 jsonw_name(self, prop);
243 jsonw_float(self, val);
244 }
245 #endif
246
jsonw_uint_field(json_writer_t * self,const char * prop,uint64_t num)247 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num)
248 {
249 jsonw_name(self, prop);
250 jsonw_uint(self, num);
251 }
252
jsonw_int_field(json_writer_t * self,const char * prop,int64_t num)253 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num)
254 {
255 jsonw_name(self, prop);
256 jsonw_int(self, num);
257 }
258
259 #ifdef notused
jsonw_null_field(json_writer_t * self,const char * prop)260 void jsonw_null_field(json_writer_t *self, const char *prop)
261 {
262 jsonw_name(self, prop);
263 jsonw_null(self);
264 }
265 #endif
266
267 #ifdef TEST
main(int argc,char ** argv)268 int main(int argc, char **argv)
269 {
270 json_writer_t *wr = jsonw_new(stdout);
271
272 jsonw_pretty(wr, true);
273 jsonw_name(wr, "Vyatta");
274 jsonw_start_object(wr);
275 jsonw_string_field(wr, "url", "http://vyatta.com");
276 jsonw_uint_field(wr, "downloads", 2000000ul);
277 jsonw_float_field(wr, "stock", 8.16);
278
279 jsonw_name(wr, "ARGV");
280 jsonw_start_array(wr);
281 while (--argc)
282 jsonw_string(wr, *++argv);
283 jsonw_end_array(wr);
284
285 jsonw_name(wr, "empty");
286 jsonw_start_array(wr);
287 jsonw_end_array(wr);
288
289 jsonw_name(wr, "NIL");
290 jsonw_start_object(wr);
291 jsonw_end_object(wr);
292
293 jsonw_null_field(wr, "my_null");
294
295 jsonw_name(wr, "special chars");
296 jsonw_start_array(wr);
297 jsonw_string_field(wr, "slash", "/");
298 jsonw_string_field(wr, "newline", "\n");
299 jsonw_string_field(wr, "tab", "\t");
300 jsonw_string_field(wr, "ff", "\f");
301 jsonw_string_field(wr, "quote", "\"");
302 jsonw_string_field(wr, "tick", "\'");
303 jsonw_string_field(wr, "backslash", "\\");
304 jsonw_end_array(wr);
305
306 jsonw_end_object(wr);
307
308 jsonw_destroy(&wr);
309 return 0;
310 }
311
312 #endif
313