Implement NFA construction for empty expression and literals

lib/construct.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include "construct.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+static void construct_literal(char literal, fsa_t *out)
+{
+	fsa_init(out);
+	const int id = fsa_add_state(out);
+	fsa_add_rule(out, id, out->initial, literal);
+	out->initial = id;
+}
+
+static void construct_term(const regex_term_t *term, fsa_t *out)
+{
+	switch (term->type) {
+	case REGEX_TERM_EMPTY:
+		fsa_init(out);
+		break;
+	case REGEX_TERM_LITERAL:
+		construct_literal(term->literal, out);
+		break;
+	case REGEX_TERM_SUBEXPR:
+		return;
+
+	case REGEX_TERM_WILDCARD:
+	case REGEX_TERM_CLASS:
+		assert(false);
+	}
+}
+
+static void construct_sequence(const regex_sequence_t *seq, fsa_t *out)
+{
+	construct_term(&seq->contents[0], out);
+}
+
+void construct(const regex_t *regex, fsa_t *out)
+{
+	construct_sequence(&regex->contents[0], out);
+}

lib/construct.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#ifndef CONSTRUCT_H
+#define CONSTRUCT_H
+
+#include "fsa.h"
+#include "regex.h"
+
+void construct(const regex_t *regex, fsa_t *out);
+
+#endif

scripts/build.sh

@@ -13,7 +13,9 @@ clang $CFLAGS -Ilib -c lib/parse.c -o build/parse.o
 clang $CFLAGS -Ilib -c lib/desugar.c -o build/desugar.o
 clang $CFLAGS -Ilib -c lib/regex.c -o build/regex.o
 clang $CFLAGS -Ilib -c lib/fsa.c -o build/fsa.o
-ar -crs build/lib.a build/parse.o build/desugar.o build/regex.o build/fsa.o
+clang $CFLAGS -Ilib -c lib/construct.c -o build/construct.o
+ar -crs build/lib.a build/parse.o build/desugar.o build/regex.o \
+   build/fsa.o build/construct.o
 
 # Build tests
 clang $CFLAGS -Itests -c tests/testing.c -o build/testing.o
@@ -23,3 +25,5 @@ clang $CFLAGS -Ilib -Itests -o build/desugar_tests \
 	  tests/desugar_tests.c build/testing.o build/lib.a
 clang $CFLAGS -Ilib -Itests -o build/fsa_tests \
 	  tests/fsa_tests.c build/testing.o build/lib.a
+clang $CFLAGS -Ilib -Itests -o build/construct_tests \
+	  tests/construct_tests.c build/testing.o build/lib.a

scripts/test.sh

@@ -7,5 +7,6 @@ fails=0
 build/parse_tests || fails=`expr $fails + 1`
 build/desugar_tests || fails=`expr $fails + 1`
 build/fsa_tests || fails=`expr $fails + 1`
+build/construct_tests || fails=`expr $fails + 1`
 
 if [ $fails -eq 0 ]; then echo Tests OK; fi

tests/construct_tests.c

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include "construct.h"
+#include "testing.h"
+
+static void test_empty_expression(void)
+{
+	regex_term_t *terms = malloc(1 * sizeof(regex_term_t));
+	terms[0].quantifier = REGEX_QUANTIFIER_NONE;
+	terms[0].type = REGEX_TERM_EMPTY;
+	regex_sequence_t *alternatives = malloc(1 * sizeof(regex_sequence_t));
+	alternatives[0].count = alternatives[0].capacity = 1;
+	alternatives[0].contents = terms;
+	const regex_t regex
+	    = { .count = 1, .capacity = 1, .contents = alternatives };
+
+	fsa_t fsa;
+	construct(&regex, &fsa);
+
+	ASSERT_EQ(1, fsa.count);
+	ASSERT_TRUE(fsa.states[fsa.initial].final);
+	ASSERT_EQ(0, fsa.states[fsa.initial].count);
+
+	regex_free(&regex);
+	fsa_free(&fsa);
+}
+
+static void test_literal_expression(void)
+{
+	regex_term_t *terms = malloc(1 * sizeof(regex_term_t));
+	terms[0].quantifier = REGEX_QUANTIFIER_NONE;
+	terms[0].type = REGEX_TERM_LITERAL;
+	terms[0].literal = 'a';
+	regex_sequence_t *alternatives = malloc(1 * sizeof(regex_sequence_t));
+	alternatives[0].count = alternatives[0].capacity = 1;
+	alternatives[0].contents = terms;
+	const regex_t regex
+	    = { .count = 1, .capacity = 1, .contents = alternatives };
+
+	fsa_t fsa;
+	construct(&regex, &fsa);
+
+	const fsa_state_t *initial = &fsa.states[fsa.initial];
+	ASSERT_EQ(2, fsa.count);
+	ASSERT_EQ(1, initial->count);
+	ASSERT_EQ('a', initial->rules[0].input);
+	ASSERT_TRUE(fsa.states[initial->rules[0].next].final);
+	ASSERT_EQ(0, fsa.states[initial->rules[0].next].count);
+
+	regex_free(&regex);
+	fsa_free(&fsa);
+}
+
+int main(void)
+{
+	TESTING_BEGIN();
+	test_empty_expression();
+	test_literal_expression();
+	return TESTING_END();
+}