Define FSA data structure

lib/fsa.c

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include "fsa.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+#define FSA_START_CAPACITY 16
+#define STATE_START_CAPACITY 16
+
+void fsa_init(fsa_t *fsa)
+{
+	fsa->count = 0;
+	fsa->capacity = FSA_START_CAPACITY;
+	fsa->states = malloc(fsa->capacity * sizeof(fsa_state_t));
+	assert(NULL != fsa->states);
+
+	fsa->initial = fsa_add_state(fsa);
+	fsa->states[fsa->initial].final = true;
+}
+
+void fsa_free(const fsa_t *fsa)
+{
+	for (int i = 0; i < fsa->count; ++i)
+		free(fsa->states[i].rules);
+	free(fsa->states);
+}
+
+int fsa_add_state(fsa_t *fsa)
+{
+	if (fsa->count >= fsa->capacity) {
+		fsa->capacity *= 2;
+		fsa->states = realloc(fsa->states, fsa->capacity);
+		assert(NULL != fsa->states);
+	}
+
+	fsa_state_t *state = &fsa->states[fsa->count];
+	state->final = false;
+	state->count = 0;
+	state->capacity = STATE_START_CAPACITY;
+	state->rules = malloc(state->capacity * sizeof(fsa_rule_t));
+	assert(state->rules);
+
+	return fsa->count++;
+}
+
+void fsa_add_rule(fsa_t *fsa, int from, int to, int input)
+{
+	assert(fsa->count > from);
+	assert(fsa->count > to);
+	assert(input < ALPHABET_SIZE);
+
+	fsa_state_t *state = &fsa->states[from];
+	if (state->count >= state->capacity) {
+		state->capacity *= 2;
+		state->rules = realloc(state->rules, state->capacity);
+		assert(NULL != state->rules);
+	}
+
+	fsa_rule_t *rule = &state->rules[state->count];
+	rule->input = input;
+	rule->next = to;
+	++state->count;
+}

lib/fsa.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#ifndef FSA_H
+#define FSA_H
+
+#include <stdbool.h>
+
+#define CHAR_COUNT 256
+#define ALPHABET_SIZE (CHAR_COUNT + 1)
+
+// Use one more than any valid char to represent empty string
+#define EPSILON CHAR_COUNT
+
+typedef struct {
+	int input, next;
+} fsa_rule_t;
+
+typedef struct {
+	bool final;
+	int count, capacity;
+	fsa_rule_t *rules;
+} fsa_state_t;
+
+typedef struct {
+	int count, capacity, initial;
+	fsa_state_t *states;
+} fsa_t;
+
+void fsa_init(fsa_t *fsa);
+void fsa_free(const fsa_t *fsa);
+
+int fsa_add_state(fsa_t *fsa);
+void fsa_add_rule(fsa_t *fsa, int from, int to, int input);
+
+#endif