1 // SPDX-License-Identifier: (GPL-2.0-only 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 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License 10 * as published by the Free Software Foundation; either version 11 * 2 of the License, or (at your option) any later version. 12 * 13 * Authors: Stephen Hemminger <stephen@networkplumber.org> 14 */ 15 16 #include <stdio.h> 17 #include <stdbool.h> 18 #include <stdarg.h> 19 #include <assert.h> 20 #include <malloc.h> 21 #include <inttypes.h> 22 #include <stdint.h> 23 #include <linux/compiler.h> 24 25 #include "json_writer.h" 26 27 struct json_writer { 28 FILE *out; /* output file */ 29 unsigned depth; /* nesting */ 30 bool pretty; /* optional whitepace */ 31 char sep; /* either nul or comma */ 32 }; 33 34 /* indentation for pretty print */ 35 static void jsonw_indent(json_writer_t *self) 36 { 37 unsigned i; 38 for (i = 0; i < self->depth; ++i) 39 fputs(" ", self->out); 40 } 41 42 /* end current line and indent if pretty printing */ 43 static void jsonw_eol(json_writer_t *self) 44 { 45 if (!self->pretty) 46 return; 47 48 putc('\n', self->out); 49 jsonw_indent(self); 50 } 51 52 /* If current object is not empty print a comma */ 53 static void jsonw_eor(json_writer_t *self) 54 { 55 if (self->sep != '\0') 56 putc(self->sep, self->out); 57 self->sep = ','; 58 } 59 60 61 /* Output JSON encoded string */ 62 /* Handles C escapes, does not do Unicode */ 63 static void jsonw_puts(json_writer_t *self, const char *str) 64 { 65 putc('"', self->out); 66 for (; *str; ++str) 67 switch (*str) { 68 case '\t': 69 fputs("\\t", self->out); 70 break; 71 case '\n': 72 fputs("\\n", self->out); 73 break; 74 case '\r': 75 fputs("\\r", self->out); 76 break; 77 case '\f': 78 fputs("\\f", self->out); 79 break; 80 case '\b': 81 fputs("\\b", self->out); 82 break; 83 case '\\': 84 fputs("\\n", self->out); 85 break; 86 case '"': 87 fputs("\\\"", self->out); 88 break; 89 case '\'': 90 fputs("\\\'", self->out); 91 break; 92 default: 93 putc(*str, self->out); 94 } 95 putc('"', self->out); 96 } 97 98 /* Create a new JSON stream */ 99 json_writer_t *jsonw_new(FILE *f) 100 { 101 json_writer_t *self = malloc(sizeof(*self)); 102 if (self) { 103 self->out = f; 104 self->depth = 0; 105 self->pretty = false; 106 self->sep = '\0'; 107 } 108 return self; 109 } 110 111 /* End output to JSON stream */ 112 void jsonw_destroy(json_writer_t **self_p) 113 { 114 json_writer_t *self = *self_p; 115 116 assert(self->depth == 0); 117 fputs("\n", self->out); 118 fflush(self->out); 119 free(self); 120 *self_p = NULL; 121 } 122 123 void jsonw_pretty(json_writer_t *self, bool on) 124 { 125 self->pretty = on; 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 __printf(2, 0) 162 jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap) 163 { 164 jsonw_eor(self); 165 putc('"', self->out); 166 vfprintf(self->out, fmt, ap); 167 putc('"', self->out); 168 } 169 170 void __printf(2, 3) jsonw_printf(json_writer_t *self, const char *fmt, ...) 171 { 172 va_list ap; 173 174 va_start(ap, fmt); 175 jsonw_eor(self); 176 vfprintf(self->out, fmt, ap); 177 va_end(ap); 178 } 179 180 /* Collections */ 181 void jsonw_start_object(json_writer_t *self) 182 { 183 jsonw_begin(self, '{'); 184 } 185 186 void jsonw_end_object(json_writer_t *self) 187 { 188 jsonw_end(self, '}'); 189 } 190 191 void jsonw_start_array(json_writer_t *self) 192 { 193 jsonw_begin(self, '['); 194 } 195 196 void jsonw_end_array(json_writer_t *self) 197 { 198 jsonw_end(self, ']'); 199 } 200 201 /* JSON value types */ 202 void jsonw_string(json_writer_t *self, const char *value) 203 { 204 jsonw_eor(self); 205 jsonw_puts(self, value); 206 } 207 208 void jsonw_bool(json_writer_t *self, bool val) 209 { 210 jsonw_printf(self, "%s", val ? "true" : "false"); 211 } 212 213 void jsonw_null(json_writer_t *self) 214 { 215 jsonw_printf(self, "null"); 216 } 217 218 void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num) 219 { 220 jsonw_printf(self, fmt, num); 221 } 222 223 #ifdef notused 224 void jsonw_float(json_writer_t *self, double num) 225 { 226 jsonw_printf(self, "%g", num); 227 } 228 #endif 229 230 void jsonw_hu(json_writer_t *self, unsigned short num) 231 { 232 jsonw_printf(self, "%hu", num); 233 } 234 235 void jsonw_uint(json_writer_t *self, uint64_t num) 236 { 237 jsonw_printf(self, "%"PRIu64, num); 238 } 239 240 void jsonw_lluint(json_writer_t *self, unsigned long long int num) 241 { 242 jsonw_printf(self, "%llu", num); 243 } 244 245 void jsonw_int(json_writer_t *self, int64_t num) 246 { 247 jsonw_printf(self, "%"PRId64, num); 248 } 249 250 /* Basic name/value objects */ 251 void jsonw_string_field(json_writer_t *self, const char *prop, const char *val) 252 { 253 jsonw_name(self, prop); 254 jsonw_string(self, val); 255 } 256 257 void jsonw_bool_field(json_writer_t *self, const char *prop, bool val) 258 { 259 jsonw_name(self, prop); 260 jsonw_bool(self, val); 261 } 262 263 #ifdef notused 264 void jsonw_float_field(json_writer_t *self, const char *prop, double val) 265 { 266 jsonw_name(self, prop); 267 jsonw_float(self, val); 268 } 269 #endif 270 271 void jsonw_float_field_fmt(json_writer_t *self, 272 const char *prop, 273 const char *fmt, 274 double val) 275 { 276 jsonw_name(self, prop); 277 jsonw_float_fmt(self, fmt, val); 278 } 279 280 void jsonw_uint_field(json_writer_t *self, const char *prop, uint64_t num) 281 { 282 jsonw_name(self, prop); 283 jsonw_uint(self, num); 284 } 285 286 void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num) 287 { 288 jsonw_name(self, prop); 289 jsonw_hu(self, num); 290 } 291 292 void jsonw_lluint_field(json_writer_t *self, 293 const char *prop, 294 unsigned long long int num) 295 { 296 jsonw_name(self, prop); 297 jsonw_lluint(self, num); 298 } 299 300 void jsonw_int_field(json_writer_t *self, const char *prop, int64_t num) 301 { 302 jsonw_name(self, prop); 303 jsonw_int(self, num); 304 } 305 306 void jsonw_null_field(json_writer_t *self, const char *prop) 307 { 308 jsonw_name(self, prop); 309 jsonw_null(self); 310 } 311 312 #ifdef TEST 313 int main(int argc, char **argv) 314 { 315 json_writer_t *wr = jsonw_new(stdout); 316 317 jsonw_start_object(wr); 318 jsonw_pretty(wr, true); 319 jsonw_name(wr, "Vyatta"); 320 jsonw_start_object(wr); 321 jsonw_string_field(wr, "url", "http://vyatta.com"); 322 jsonw_uint_field(wr, "downloads", 2000000ul); 323 jsonw_float_field(wr, "stock", 8.16); 324 325 jsonw_name(wr, "ARGV"); 326 jsonw_start_array(wr); 327 while (--argc) 328 jsonw_string(wr, *++argv); 329 jsonw_end_array(wr); 330 331 jsonw_name(wr, "empty"); 332 jsonw_start_array(wr); 333 jsonw_end_array(wr); 334 335 jsonw_name(wr, "NIL"); 336 jsonw_start_object(wr); 337 jsonw_end_object(wr); 338 339 jsonw_null_field(wr, "my_null"); 340 341 jsonw_name(wr, "special chars"); 342 jsonw_start_array(wr); 343 jsonw_string_field(wr, "slash", "/"); 344 jsonw_string_field(wr, "newline", "\n"); 345 jsonw_string_field(wr, "tab", "\t"); 346 jsonw_string_field(wr, "ff", "\f"); 347 jsonw_string_field(wr, "quote", "\""); 348 jsonw_string_field(wr, "tick", "\'"); 349 jsonw_string_field(wr, "backslash", "\\"); 350 jsonw_end_array(wr); 351 352 jsonw_end_object(wr); 353 354 jsonw_end_object(wr); 355 jsonw_destroy(&wr); 356 return 0; 357 } 358 359 #endif 360