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("\\\\", self->out); 79 break; 80 case '"': 81 fputs("\\\"", self->out); 82 break; 83 default: 84 putc(*str, self->out); 85 } 86 putc('"', self->out); 87 } 88 89 /* Create a new JSON stream */ 90 json_writer_t *jsonw_new(FILE *f) 91 { 92 json_writer_t *self = malloc(sizeof(*self)); 93 if (self) { 94 self->out = f; 95 self->depth = 0; 96 self->pretty = false; 97 self->sep = '\0'; 98 } 99 return self; 100 } 101 102 /* End output to JSON stream */ 103 void jsonw_destroy(json_writer_t **self_p) 104 { 105 json_writer_t *self = *self_p; 106 107 assert(self->depth == 0); 108 fputs("\n", self->out); 109 fflush(self->out); 110 free(self); 111 *self_p = NULL; 112 } 113 114 void jsonw_pretty(json_writer_t *self, bool on) 115 { 116 self->pretty = on; 117 } 118 119 void jsonw_reset(json_writer_t *self) 120 { 121 assert(self->depth == 0); 122 self->sep = '\0'; 123 } 124 125 /* Basic blocks */ 126 static void jsonw_begin(json_writer_t *self, int c) 127 { 128 jsonw_eor(self); 129 putc(c, self->out); 130 ++self->depth; 131 self->sep = '\0'; 132 } 133 134 static void jsonw_end(json_writer_t *self, int c) 135 { 136 assert(self->depth > 0); 137 138 --self->depth; 139 if (self->sep != '\0') 140 jsonw_eol(self); 141 putc(c, self->out); 142 self->sep = ','; 143 } 144 145 146 /* Add a JSON property name */ 147 void jsonw_name(json_writer_t *self, const char *name) 148 { 149 jsonw_eor(self); 150 jsonw_eol(self); 151 self->sep = '\0'; 152 jsonw_puts(self, name); 153 putc(':', self->out); 154 if (self->pretty) 155 putc(' ', self->out); 156 } 157 158 void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap) 159 { 160 jsonw_eor(self); 161 putc('"', self->out); 162 vfprintf(self->out, fmt, ap); 163 putc('"', self->out); 164 } 165 166 void jsonw_printf(json_writer_t *self, const char *fmt, ...) 167 { 168 va_list ap; 169 170 va_start(ap, fmt); 171 jsonw_eor(self); 172 vfprintf(self->out, fmt, ap); 173 va_end(ap); 174 } 175 176 /* Collections */ 177 void jsonw_start_object(json_writer_t *self) 178 { 179 jsonw_begin(self, '{'); 180 } 181 182 void jsonw_end_object(json_writer_t *self) 183 { 184 jsonw_end(self, '}'); 185 } 186 187 void jsonw_start_array(json_writer_t *self) 188 { 189 jsonw_begin(self, '['); 190 } 191 192 void jsonw_end_array(json_writer_t *self) 193 { 194 jsonw_end(self, ']'); 195 } 196 197 /* JSON value types */ 198 void jsonw_string(json_writer_t *self, const char *value) 199 { 200 jsonw_eor(self); 201 jsonw_puts(self, value); 202 } 203 204 void jsonw_bool(json_writer_t *self, bool val) 205 { 206 jsonw_printf(self, "%s", val ? "true" : "false"); 207 } 208 209 void jsonw_null(json_writer_t *self) 210 { 211 jsonw_printf(self, "null"); 212 } 213 214 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num) 215 { 216 jsonw_printf(self, fmt, num); 217 } 218 219 #ifdef notused 220 void jsonw_float(json_writer_t *self, double num) 221 { 222 jsonw_printf(self, "%g", num); 223 } 224 #endif 225 226 void jsonw_hu(json_writer_t *self, unsigned short num) 227 { 228 jsonw_printf(self, "%hu", num); 229 } 230 231 void jsonw_uint(json_writer_t *self, uint64_t num) 232 { 233 jsonw_printf(self, "%"PRIu64, num); 234 } 235 236 void jsonw_lluint(json_writer_t *self, unsigned long long int num) 237 { 238 jsonw_printf(self, "%llu", num); 239 } 240 241 void jsonw_int(json_writer_t *self, int64_t num) 242 { 243 jsonw_printf(self, "%"PRId64, num); 244 } 245 246 /* Basic name/value objects */ 247 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val) 248 { 249 jsonw_name(self, prop); 250 jsonw_string(self, val); 251 } 252 253 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val) 254 { 255 jsonw_name(self, prop); 256 jsonw_bool(self, val); 257 } 258 259 #ifdef notused 260 void jsonw_float_field(json_writer_t *self, const char *prop, double val) 261 { 262 jsonw_name(self, prop); 263 jsonw_float(self, val); 264 } 265 #endif 266 267 void jsonw_float_field_fmt(json_writer_t *self, 268 const char *prop, 269 const char *fmt, 270 double val) 271 { 272 jsonw_name(self, prop); 273 jsonw_float_fmt(self, fmt, val); 274 } 275 276 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num) 277 { 278 jsonw_name(self, prop); 279 jsonw_uint(self, num); 280 } 281 282 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num) 283 { 284 jsonw_name(self, prop); 285 jsonw_hu(self, num); 286 } 287 288 void jsonw_lluint_field(json_writer_t *self, 289 const char *prop, 290 unsigned long long int num) 291 { 292 jsonw_name(self, prop); 293 jsonw_lluint(self, num); 294 } 295 296 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num) 297 { 298 jsonw_name(self, prop); 299 jsonw_int(self, num); 300 } 301 302 void jsonw_null_field(json_writer_t *self, const char *prop) 303 { 304 jsonw_name(self, prop); 305 jsonw_null(self); 306 } 307 308 #ifdef TEST 309 int main(int argc, char **argv) 310 { 311 json_writer_t *wr = jsonw_new(stdout); 312 313 jsonw_start_object(wr); 314 jsonw_pretty(wr, true); 315 jsonw_name(wr, "Vyatta"); 316 jsonw_start_object(wr); 317 jsonw_string_field(wr, "url", "http://vyatta.com"); 318 jsonw_uint_field(wr, "downloads", 2000000ul); 319 jsonw_float_field(wr, "stock", 8.16); 320 321 jsonw_name(wr, "ARGV"); 322 jsonw_start_array(wr); 323 while (--argc) 324 jsonw_string(wr, *++argv); 325 jsonw_end_array(wr); 326 327 jsonw_name(wr, "empty"); 328 jsonw_start_array(wr); 329 jsonw_end_array(wr); 330 331 jsonw_name(wr, "NIL"); 332 jsonw_start_object(wr); 333 jsonw_end_object(wr); 334 335 jsonw_null_field(wr, "my_null"); 336 337 jsonw_name(wr, "special chars"); 338 jsonw_start_array(wr); 339 jsonw_string_field(wr, "slash", "/"); 340 jsonw_string_field(wr, "newline", "\n"); 341 jsonw_string_field(wr, "tab", "\t"); 342 jsonw_string_field(wr, "ff", "\f"); 343 jsonw_string_field(wr, "quote", "\""); 344 jsonw_string_field(wr, "tick", "\'"); 345 jsonw_string_field(wr, "backslash", "\\"); 346 jsonw_end_array(wr); 347 348 jsonw_end_object(wr); 349 350 jsonw_end_object(wr); 351 jsonw_destroy(&wr); 352 return 0; 353 } 354 355 #endif 356