3 ms·

As an OOP dev this kind of horrifies me, even though it works okay (though it's surely not thread-safe?) Nevertheless, even in C, I'd find it conceptually simp

As an OOP dev this kind of horrifies me, even though it works okay (though it's surely not thread-safe?) Nevertheless, even in C, I'd find it conceptually simpler to understand if the functions were written as pure functions, returning a tuple with (c, state) and passing the state back into the caller. Using non-idiomatic tricks and macros in this way is harder to read and understand.

wahern 8y ago
Here's a POSIX compliant portable getopt() routine I wrote which uses this style. Is this hard to read? Note that it's several times shorter than every other implementation I've ever seen, and if I do say so myself I think it's eminently readable. static int u_getopt_r(int argc, char *const argv[], const char *shortopts, struct u_getopt_r *K) { K->optarg = NULL; K->optopt = 0; GETOPT_ENTER; while (K->optind < argc) { K->cp = argv[K->optind]; if (!K->cp || *(K->cp) != '-' || !strcmp(K->cp, "-")) { break; } else if (!strcmp(K->cp, "--")) { K->optind++; break; } for (;;) { char *shortopt; if (!(K->optopt = *++K->cp)) { K->optind++; break; } else if (!(shortopt = strchr(shortopts, K->optopt))) { getopt_err(argc, argv, shortopts, K, "illegal option -- %c\n", K->optopt); GETOPT_YIELD('?'); } else if (shortopt[1] != ':') { GETOPT_YIELD(K->optopt); } else if (K->cp[1]) { K->optarg = &K->cp[1]; K->optind++; GETOPT_YIELD(K->optopt); break; } else if (K->optind + 1 < argc) { K->optarg = argv[K->optind + 1]; K->optind += 2; GETOPT_YIELD(K->optopt); break; } else { getopt_err(argc, argv, shortopts, K, "option requires an argument -- %c\n", K->optopt); K->optind++; GETOPT_YIELD((*shortopts == ':')? ':' : '?'); break; } } } GETOPT_LEAVE; return -1; } Here's macro magic, the complexity of which is more than made up for by the readability of the core code: #define GETOPT_ENTER \ do { \ static const int pc0 = __LINE__; \ switch (pc0 + K->pc) { \ case __LINE__: (void)0 #define GETOPT_SAVE_AND_DO(do_statement) \ do { \ K->pc = __LINE__ - pc0; \ do_statement; \ case __LINE__: (void)0; \ } while (0) #define GETOPT_YIELD(rv) \ GETOPT_SAVE_AND_DO(return (rv)) #define GETOPT_LEAVE \ GETOPT_SAVE_AND_DO(break); \ } \ } while (0)

wahern 8y ago

Here's a POSIX compliant portable getopt() routine I wrote which uses this style. Is this hard to read? Note that it's several times shorter than every other implementation I've ever seen, and if I do say so myself I think it's eminently readable. static int u_getopt_r(int argc, char *const argv[], const char *shortopts, struct u_getopt_r *K) { K->optarg = NULL; K->optopt = 0; GETOPT_ENTER; while (K->optind < argc) { K->cp = argv[K->optind]; if (!K->cp || *(K->cp) != '-' || !strcmp(K->cp, "-")) { break; } else if (!strcmp(K->cp, "--")) { K->optind++; break; } for (;;) { char *shortopt; if (!(K->optopt = *++K->cp)) { K->optind++; break; } else if (!(shortopt = strchr(shortopts, K->optopt))) { getopt_err(argc, argv, shortopts, K, "illegal option -- %c\n", K->optopt); GETOPT_YIELD('?'); } else if (shortopt[1] != ':') { GETOPT_YIELD(K->optopt); } else if (K->cp[1]) { K->optarg = &K->cp[1]; K->optind++; GETOPT_YIELD(K->optopt); break; } else if (K->optind + 1 < argc) { K->optarg = argv[K->optind + 1]; K->optind += 2; GETOPT_YIELD(K->optopt); break; } else { getopt_err(argc, argv, shortopts, K, "option requires an argument -- %c\n", K->optopt); K->optind++; GETOPT_YIELD((*shortopts == ':')? ':' : '?'); break; } } } GETOPT_LEAVE; return -1; } Here's macro magic, the complexity of which is more than made up for by the readability of the core code: #define GETOPT_ENTER \ do { \ static const int pc0 = __LINE__; \ switch (pc0 + K->pc) { \ case __LINE__: (void)0 #define GETOPT_SAVE_AND_DO(do_statement) \ do { \ K->pc = __LINE__ - pc0; \ do_statement; \ case __LINE__: (void)0; \ } while (0) #define GETOPT_YIELD(rv) \ GETOPT_SAVE_AND_DO(return (rv)) #define GETOPT_LEAVE \ GETOPT_SAVE_AND_DO(break); \ } \ } while (0)