Define regex_t data structure and write build script

lib/regex.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include "regex.h"
+
+#include <stdlib.h>
+
+static void class_free(class_t *c)
+{
+	if (NULL != c->contents)
+		free(c->contents);
+}
+
+static void sequence_free(sequence_t *s)
+{
+	if (NULL != s->contents) {
+		for (int i = 0; i < s->len; ++i) {
+			switch (s->contents[i].type) {
+			case TERM_TYPE_CLASS:
+				class_free(&s->contents[i].class);
+				break;
+			case TERM_TYPE_REGEX:
+				regex_free_children(&s->contents[i].regex);
+				break;
+			case TERM_TYPE_WILDCARD:
+			case TERM_TYPE_LITERAL:
+				break;
+			}
+		}
+		free(s->contents);
+	}
+}
+
+void regex_free_children(regex_t *r)
+{
+	sequence_free(&r->sequence);
+	if (NULL != r->alternative) {
+		regex_free_children(r->alternative);
+		free(r->alternative);
+	}
+}