tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
21struct 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 */
29static 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 */
37static 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 */
47static 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 */
57static 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 */
93json_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 */
106void 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
117void jsonw_pretty(json_writer_t *self, bool on)
118{
119 self->pretty = on;
120}
121
122/* Basic blocks */
123static 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
131static 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 */
144void 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
155void 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
163void 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 */
174void jsonw_start_object(json_writer_t *self)
175{
176 jsonw_begin(self, '{');
177}
178
179void jsonw_end_object(json_writer_t *self)
180{
181 jsonw_end(self, '}');
182}
183
184void jsonw_start_array(json_writer_t *self)
185{
186 jsonw_begin(self, '[');
187}
188
189void jsonw_end_array(json_writer_t *self)
190{
191 jsonw_end(self, ']');
192}
193
194/* JSON value types */
195void jsonw_string(json_writer_t *self, const char *value)
196{
197 jsonw_eor(self);
198 jsonw_puts(self, value);
199}
200
201void jsonw_bool(json_writer_t *self, bool val)
202{
203 jsonw_printf(self, "%s", val ? "true" : "false");
204}
205
206void jsonw_null(json_writer_t *self)
207{
208 jsonw_printf(self, "null");
209}
210
211void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
212{
213 jsonw_printf(self, fmt, num);
214}
215
216#ifdef notused
217void jsonw_float(json_writer_t *self, double num)
218{
219 jsonw_printf(self, "%g", num);
220}
221#endif
222
223void jsonw_hu(json_writer_t *self, unsigned short num)
224{
225 jsonw_printf(self, "%hu", num);
226}
227
228void jsonw_uint(json_writer_t *self, uint64_t num)
229{
230 jsonw_printf(self, "%"PRIu64, num);
231}
232
233void jsonw_lluint(json_writer_t *self, unsigned long long int num)
234{
235 jsonw_printf(self, "%llu", num);
236}
237
238void jsonw_int(json_writer_t *self, int64_t num)
239{
240 jsonw_printf(self, "%"PRId64, num);
241}
242
243/* Basic name/value objects */
244void 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
250void 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
257void 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
264void 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
273void 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
279void 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
285void 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
293void 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
299void 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
306int 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