Support sequences in construct()

lib/construct.c

@@ -7,6 +7,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <string.h>
 
 static void construct_literal(char literal, fsa_t *out)
 {
@@ -34,9 +35,48 @@ static void construct_term(const regex_term_t *term, fsa_t *out)
 	}
 }
 
+static void concat_fsas(fsa_t *base, const fsa_t *other)
+{
+	const int new_count = base->count + other->count - 1;
+	if (base->capacity < new_count) {
+		do
+			base->capacity *= 2;
+		while (base->capacity < new_count);
+		base->states = realloc(base->states, base->capacity);
+		assert(base->states);
+	}
+
+	const int copy_size = (other->count - 1) * sizeof(fsa_state_t);
+	memcpy(&base->states[base->count], &other->states[1], copy_size);
+
+	const int id_offset = base->count - 1;
+	for (int i = base->count; i < new_count; ++i) {
+		fsa_state_t *state = &base->states[i];
+		for (int j = 0; j < state->count; ++j) {
+			if (0 == state->rules[j].next)
+				state->rules[j].next = base->initial;
+			else
+				state->rules[j].next += id_offset;
+		}
+	}
+
+	base->count = new_count;
+	base->initial = other->initial + id_offset;
+
+	free(other->states[0].rules);
+	free(other->states);
+}
+
 static void construct_sequence(const regex_sequence_t *seq, fsa_t *out)
 {
-	construct_term(&seq->contents[0], out);
+	assert(seq->count > 0);
+
+	fsa_t term_fsa;
+	construct_term(&seq->contents[seq->count - 1], out);
+	for (int i = seq->count - 2; i >= 0; --i) {
+		construct_term(&seq->contents[i], &term_fsa);
+		concat_fsas(out, &term_fsa);
+	}
 }
 
 void construct(const regex_t *regex, fsa_t *out)