1 files changed, 136 insertions, 0 deletions
diff --git a/config.c b/config.c
new file mode 100644
index 0000000..ce1bd25
--- /dev/null
+++ b/config.c
@@ -0,0 +1,136 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define WS "\t "
+
+static const char *path;
+static FILE *file;
+static size_t num;
+static char *line;
+static size_t cap;
+
+static int clean(int opt) {
+	if (file) fclose(file);
+	free(line);
+	line = NULL;
+	cap = 0;
+	return opt;
+}
+
+int getopt_config(
+	int argc, char *const *argv,
+	const char *optstring, const struct option *longopts, int *longindex
+) {
+	static int opt;
+	if (opt >= 0) {
+		opt = getopt_long(argc, argv, optstring, longopts, longindex);
+	}
+	if (opt >= 0) return opt;
+
+	for (;;) {
+		if (!file) {
+			if (optind < argc) {
+				num = 0;
+				path = argv[optind++];
+				file = fopen(path, "r");
+				if (!file) {
+					warn("%s", path);
+					return clean('?');
+				}
+			} else {
+				return clean(-1);
+			}
+		}
+
+		for (;;) {
+			ssize_t llen = getline(&line, &cap, file);
+			if (ferror(file)) {
+				warn("%s", path);
+				return clean('?');
+			}
+			if (llen <= 0) break;
+			if (line[llen - 1] == '\n') line[llen - 1] = '\0';
+			num++;
+
+			char *name = line + strspn(line, WS);
+			size_t len = strcspn(name, WS "=");
+			if (!name[0] || name[0] == '#') continue;
+
+			const struct option *option;
+			for (option = longopts; option->name; ++option) {
+				if (strlen(option->name) != len) continue;
+				if (!strncmp(option->name, name, len)) break;
+			}
+			if (!option->name) {
+				warnx(
+					"%s:%zu: unrecognized option `%.*s'",
+					path, num, (int)len, name
+				);
+				return clean('?');
+			}
+
+			char *equal = &name[len] + strspn(&name[len], WS);
+			if (*equal && *equal != '=') {
+				warnx(
+					"%s:%zu: option `%s' missing equals sign",
+					path, num, option->name
+				);
+				return clean('?');
+			}
+			if (option->has_arg == no_argument && *equal) {
+				warnx(
+					"%s:%zu: option `%s' doesn't allow an argument",
+					path, num, option->name
+				);
+				return clean('?');
+			}
+			if (option->has_arg == required_argument && !*equal) {
+				warnx(
+					"%s:%zu: option `%s' requires an argument",
+					path, num, option->name
+				);
+				return clean(':');
+			}
+
+			optarg = NULL;
+			if (*equal) {
+				char *arg = &equal[1] + strspn(&equal[1], WS);
+				optarg = strdup(arg);
+				if (!optarg) {
+					warn("getopt_config");
+					return clean('?');
+				}
+			}
+
+			if (longindex) *longindex = option - longopts;
+			if (option->flag) {
+				*option->flag = option->val;
+				return 0;
+			} else {
+				return option->val;
+			}
+		}
+
+		fclose(file);
+		file = NULL;
+	}
+}