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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 } 116 117 void jsonw_pretty(json_writer_t *self, bool on) 118 { 119 self->pretty = on; 120 } 121 122 void jsonw_reset(json_writer_t *self) 123 { 124 assert(self->depth == 0); 125 self->sep = '\0'; 126 } 127 128 /* Basic blocks */ 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 } 136 137 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 */ 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 } 160 161 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap) 162 { 163 jsonw_eor(self); 164 putc('"', self->out); 165 vfprintf(self->out, fmt, ap); 166 putc('"', self->out); 167 } 168 169 void jsonw_printf(json_writer_t *self, const char *fmt, ...) 170 { 171 va_list ap; 172 173 va_start(ap, fmt); 174 jsonw_eor(self); 175 vfprintf(self->out, fmt, ap); 176 va_end(ap); 177 } 178 179 /* Collections */ 180 void jsonw_start_object(json_writer_t *self) 181 { 182 jsonw_begin(self, '{'); 183 } 184 185 void jsonw_end_object(json_writer_t *self) 186 { 187 jsonw_end(self, '}'); 188 } 189 190 void jsonw_start_array(json_writer_t *self) 191 { 192 jsonw_begin(self, '['); 193 } 194 195 void jsonw_end_array(json_writer_t *self) 196 { 197 jsonw_end(self, ']'); 198 } 199 200 /* JSON value types */ 201 void jsonw_string(json_writer_t *self, const char *value) 202 { 203 jsonw_eor(self); 204 jsonw_puts(self, value); 205 } 206 207 void jsonw_bool(json_writer_t *self, bool val) 208 { 209 jsonw_printf(self, "%s", val ? "true" : "false"); 210 } 211 212 void jsonw_null(json_writer_t *self) 213 { 214 jsonw_printf(self, "null"); 215 } 216 217 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num) 218 { 219 jsonw_printf(self, fmt, num); 220 } 221 222 #ifdef notused 223 void jsonw_float(json_writer_t *self, double num) 224 { 225 jsonw_printf(self, "%g", num); 226 } 227 #endif 228 229 void jsonw_hu(json_writer_t *self, unsigned short num) 230 { 231 jsonw_printf(self, "%hu", num); 232 } 233 234 void jsonw_uint(json_writer_t *self, uint64_t num) 235 { 236 jsonw_printf(self, "%"PRIu64, num); 237 } 238 239 void jsonw_lluint(json_writer_t *self, unsigned long long int num) 240 { 241 jsonw_printf(self, "%llu", num); 242 } 243 244 void jsonw_int(json_writer_t *self, int64_t num) 245 { 246 jsonw_printf(self, "%"PRId64, num); 247 } 248 249 /* Basic name/value objects */ 250 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val) 251 { 252 jsonw_name(self, prop); 253 jsonw_string(self, val); 254 } 255 256 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val) 257 { 258 jsonw_name(self, prop); 259 jsonw_bool(self, val); 260 } 261 262 #ifdef notused 263 void jsonw_float_field(json_writer_t *self, const char *prop, double val) 264 { 265 jsonw_name(self, prop); 266 jsonw_float(self, val); 267 } 268 #endif 269 270 void jsonw_float_field_fmt(json_writer_t *self, 271 const char *prop, 272 const char *fmt, 273 double val) 274 { 275 jsonw_name(self, prop); 276 jsonw_float_fmt(self, fmt, val); 277 } 278 279 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num) 280 { 281 jsonw_name(self, prop); 282 jsonw_uint(self, num); 283 } 284 285 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num) 286 { 287 jsonw_name(self, prop); 288 jsonw_hu(self, num); 289 } 290 291 void jsonw_lluint_field(json_writer_t *self, 292 const char *prop, 293 unsigned long long int num) 294 { 295 jsonw_name(self, prop); 296 jsonw_lluint(self, num); 297 } 298 299 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num) 300 { 301 jsonw_name(self, prop); 302 jsonw_int(self, num); 303 } 304 305 void jsonw_null_field(json_writer_t *self, const char *prop) 306 { 307 jsonw_name(self, prop); 308 jsonw_null(self); 309 } 310 311 #ifdef TEST 312 int main(int argc, char **argv) 313 { 314 json_writer_t *wr = jsonw_new(stdout); 315 316 jsonw_start_object(wr); 317 jsonw_pretty(wr, true); 318 jsonw_name(wr, "Vyatta"); 319 jsonw_start_object(wr); 320 jsonw_string_field(wr, "url", "http://vyatta.com"); 321 jsonw_uint_field(wr, "downloads", 2000000ul); 322 jsonw_float_field(wr, "stock", 8.16); 323 324 jsonw_name(wr, "ARGV"); 325 jsonw_start_array(wr); 326 while (--argc) 327 jsonw_string(wr, *++argv); 328 jsonw_end_array(wr); 329 330 jsonw_name(wr, "empty"); 331 jsonw_start_array(wr); 332 jsonw_end_array(wr); 333 334 jsonw_name(wr, "NIL"); 335 jsonw_start_object(wr); 336 jsonw_end_object(wr); 337 338 jsonw_null_field(wr, "my_null"); 339 340 jsonw_name(wr, "special chars"); 341 jsonw_start_array(wr); 342 jsonw_string_field(wr, "slash", "/"); 343 jsonw_string_field(wr, "newline", "\n"); 344 jsonw_string_field(wr, "tab", "\t"); 345 jsonw_string_field(wr, "ff", "\f"); 346 jsonw_string_field(wr, "quote", "\""); 347 jsonw_string_field(wr, "tick", "\'"); 348 jsonw_string_field(wr, "backslash", "\\"); 349 jsonw_end_array(wr); 350 351 jsonw_end_object(wr); 352 353 jsonw_end_object(wr); 354 jsonw_destroy(&wr); 355 return 0; 356 } 357 358 #endif 359