diff options
Diffstat (limited to 'main.l')
| -rw-r--r-- | main.l | 171 |
1 files changed, 171 insertions, 0 deletions
@@ -0,0 +1,171 @@ +%{ +#include <err.h> +#include <getopt.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#define YY_USER_ACTION ECHO; + +const char empty_field[] = "argument to the -p option contains an empty field"; +const char invalid_char[] = "argument to the -p option must be a " + "comma-seperated list of positive integers"; +const char final_comma[] = "argument to the -p option contains trailing comma"; + +const char *argv0; +unsigned pos; +struct { + unsigned *ps; + size_t len; +} positions; + +static void usage(void); +static void append_positions(char *s); +static int ucmp(const void *, const void *); +static unsigned atou(const char *); +static bool print_ordinal(void); +%} + +%option nodefault noinput nounput + +%% + +[0-9]*(1[0-9]|[04-9]) { pos++; if (print_ordinal()) fputs("th", stdout); } +[0-9]*1 { pos++; if (print_ordinal()) fputs("st", stdout); } +[0-9]*2 { pos++; if (print_ordinal()) fputs("nd", stdout); } +[0-9]*3 { pos++; if (print_ordinal()) fputs("rd", stdout); } + +\n { pos = 0; } +[^0-9\n]+ ; + +%% + +void +usage(void) +{ + fprintf(stderr, "Usage: %s [-p indicies ...] [file ...]\n", argv0); + exit(EXIT_FAILURE); +} + +int +main(int argc, char **argv) +{ + int opt, rv; + struct option longopts[] = { + {"positions", required_argument, 0, 'p'}, + { NULL, 0, 0, 0 } + }; + + argv0 = argv[0]; + rv = EXIT_SUCCESS; + + while ((opt = getopt_long(argc, argv, "p:", longopts, NULL)) != -1) { + switch (opt) { + case 'p': + append_positions(optarg); + break; + default: + usage(); + } + } + + argc -= optind; + argv += optind; + + if (argc == 0) + yylex(); + for (int i = 0; i < argc; i++) { + if (strcmp(argv[i], "-") == 0) + yyin = stdin; + else if ((yyin = fopen(argv[i], "r")) == NULL) { + warn("fopen: %s", argv[i]); + rv = EXIT_FAILURE; + continue; + } + yylex(); + if (yyin != stdin) + fclose(yyin); + } + + return rv; +} + +void +append_positions(char *raw) +{ + bool comma = true; + const char *s; + + if (positions.ps != NULL) { + warnx("the -p option should only be provided once"); + usage(); + } + + for (s = raw, positions.len++; *s; s++) { + switch (*s) { + case ',': + if (comma) + errx(EXIT_FAILURE, empty_field); + comma = true; + positions.len++; + break; + case '0': case '1': case '2': case '3': case '4': + case '5': case '6': case '7': case '8': case '9': + comma = false; + break; + default: + errx(EXIT_FAILURE, invalid_char); + } + } + + if (comma == true) + errx(EXIT_FAILURE, final_comma); + + if ((positions.ps = malloc(sizeof(unsigned *) * positions.len)) == NULL) + err(EXIT_FAILURE, "malloc"); + + /* Iterate over each position, parse it, and sort the results. It’s + safe to use strtok() and atou() here since the input string has been + pre-validated. */ + s = strtok(raw, ","); + for (size_t i = 0; s != NULL; i++) { + positions.ps[i] = atou(s); + s = strtok(NULL, ","); + } + qsort(positions.ps, positions.len, sizeof(unsigned), ucmp); +} + +int +ucmp(const void *a, const void *b) +{ + unsigned a_ = *(unsigned *)a, + b_ = *(unsigned *)b; + return a_ > b_ ? 1 : b_ < a_ ? -1 : 0; +} + +unsigned +atou(const char *s) +{ + unsigned n = 0; + for (; *s; s++) + n = n * 10 + *s - '0'; + return n; +} + +bool +print_ordinal(void) +{ + /* Basic binary search */ + for (size_t l = 0, r = positions.len - 1, m; l <= r;) { + m = l + (r - l) / 2; + if (positions.ps[m] == pos) + return true; + if (positions.ps[m] > pos) + r = m - 1; + else + l = m + 1; + } + + return false; +} |