amyinorbit / parser.c

A very basic recursive-descent parser that can lex and pare words, integers, real numbers, and that's it

parser.c

A very basic recursive-descent parser that can lex and pare words, integers, real numbers, and that's it. Exciting!

Why?

Because I've written the same parser code about 20 times by now for various data formats that all use the same basic primitives, and got tired of it. So now it's up here, I can reuse it, and you can too!

How

1. Drop parser.h and parser.c in your project;
2. Optionally, you may want to define PARSE_ASSERT(expr), PARSE_CALLOC(n, size), and PARSE_FREE(ptr) to use your own functions.
3. Profit!

Detailed Usage

The following example parses a GPS SEM almanac file:

gps_alm_t alm;

// Initialise the parser
parser_t parser = {};
parse_init(&parser, src, len);

// Do the actual parsing
alm->num_sv = parse_int(parser);
parse_text(parser, NULL, 0); // We just ignore the almanac name
alm->week = parse_int(parser);
alm->epoch = parse_int(parser);

for(int i = 0; i < alm->num_sv; ++i) {
  alm->sv[i].prn = parse_int(parser);
  alm->sv[i].svn = parse_int(parser);
  alm->sv[i].ura = parse_int(parser);
  
  alm->sv[i].ecc = parse_float(parser);
  alm->sv[i].inc = DEG2RAD(55) + M_PI * parse_float(parser);
  alm->sv[i].raan_dot = M_PI * parse_float(parser);
  alm->sv[i].sma = pow(parse_float(parser), 2);
  alm->sv[i].raan = M_PI * parse_float(parser);
  alm->sv[i].arg_p = M_PI * parse_float(parser);
  alm->sv[i].ma = M_PI * parse_float(parser);
  
  alm->sv[i].clk[0] = parse_float(parser);
  alm->sv[i].clk[1] = parse_float(parser);
  
  alm->sv[i].healthy = (parse_int(parser) == 0);
  (void)parse_int(parser); // SV conf
}

// Report errors if needed, and clean up.
if(parser.error) {
  fprintf(stderr, "parse error: %s\n", parser.error);
}
parse_fini(&parser);