tools/bpf/bpftool/json_writer.c

   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 <[email protected]>
   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