Implement star construction

lib/construct.c

@@ -17,6 +17,53 @@ static void construct_literal(char literal, fsa_t *out)
 	out->initial = id;
 }
 
+static void star_fsa(fsa_t *fsa)
+{
+	// If the initial state is already the final state then nothing
+	// needs to be done.
+	if (0 == fsa->initial)
+		return;
+
+	// Copy inital state's rules to final state.
+	fsa_state_t *final = &fsa->states[0];
+	const fsa_state_t *initial = &fsa->states[fsa->initial];
+	if (final->capacity < final->count + initial->count) {
+		do
+			final->capacity *= 2;
+		while (final->capacity < final->count + initial->count);
+		final->rules
+		    = realloc(final->rules, final->capacity * sizeof(fsa_rule_t));
+		assert(final->rules);
+	}
+	const int copy_size = initial->count * sizeof(fsa_rule_t);
+	memcpy(&final->rules[final->count], initial->rules, copy_size);
+	final->count += initial->count;
+
+	// Move states that come after initial state if there are any.
+	if (fsa->count - 1 > fsa->initial) {
+		const int count = fsa->count - fsa->initial - 1;
+		fsa_state_t *start = &fsa->states[fsa->initial];
+		memmove(start, start + 1, count * sizeof(fsa_state_t));
+	}
+
+	// Retarget all states' rules.
+	for (int i = 0; i < fsa->count - 1; ++i) {
+		for (int j = 0; j < fsa->states[i].count; ++j) {
+			if (fsa->states[i].rules[j].next == fsa->initial)
+				fsa->states[i].rules[j].next = 0;
+			else if (fsa->states[i].rules[j].next > fsa->initial)
+				// All states after the initial state have been moved
+				// down by one position.
+				--fsa->states[i].rules[j].next;
+		}
+	}
+
+	--fsa->count;
+	fsa->initial = 0;
+
+	free(initial->rules);
+}
+
 static void construct_term(const regex_term_t *term, fsa_t *out)
 {
 	switch (term->type) {
@@ -28,10 +75,22 @@ static void construct_term(const regex_term_t *term, fsa_t *out)
 		break;
 	case REGEX_TERM_SUBEXPR:
 		return;
-
 	case REGEX_TERM_WILDCARD:
 	case REGEX_TERM_CLASS:
 		assert(false);
+		break;
+	}
+
+	switch (term->quantifier) {
+	case REGEX_QUANTIFIER_NONE:
+		break;
+	case REGEX_QUANTIFIER_STAR:
+		star_fsa(out);
+		break;
+	case REGEX_QUANTIFIER_PLUS:
+	case REGEX_QUANTIFIER_QMARK:
+		assert(false);
+		break;
 	}
 
 	assert(out->states[0].final);