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
25struct 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 */
33static 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 */
41static 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 */
51static 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 */
61static 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 */
97json_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 */
111void 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
123void jsonw_pretty(json_writer_t *self, bool on)
124{
125	self->pretty = on;
126}
127
128/* Basic blocks */
129static 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
137static 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 */
150void 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
161static 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 */
172void jsonw_start_object(json_writer_t *self)
173{
174	jsonw_begin(self, '{');
175}
176
177void jsonw_end_object(json_writer_t *self)
178{
179	jsonw_end(self, '}');
180}
181
182void jsonw_start_array(json_writer_t *self)
183{
184	jsonw_begin(self, '[');
185}
186
187void jsonw_end_array(json_writer_t *self)
188{
189	jsonw_end(self, ']');
190}
191
192/* JSON value types */
193void jsonw_string(json_writer_t *self, const char *value)
194{
195	jsonw_eor(self);
196	jsonw_puts(self, value);
197}
198
199void jsonw_bool(json_writer_t *self, bool val)
200{
201	jsonw_printf(self, "%s", val ? "true" : "false");
202}
203
204#ifdef notused
205void jsonw_null(json_writer_t *self)
206{
207	jsonw_printf(self, "null");
208}
209
210void jsonw_float(json_writer_t *self, double num)
211{
212	jsonw_printf(self, "%g", num);
213}
214#endif
215
216void jsonw_uint(json_writer_t *self, uint64_t num)
217{
218	jsonw_printf(self, "%"PRIu64, num);
219}
220
221void jsonw_int(json_writer_t *self, int64_t num)
222{
223	jsonw_printf(self, "%"PRId64, num);
224}
225
226/* Basic name/value objects */
227void 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
233void 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
240void 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
247void 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
253void 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
260void 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
268int 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