Add signed arithmetics

Signed-off-by: Mattias Andrée <m@maandree.se>

1 files changed, 153 insertions, 0 deletions

diff --git a/libj2_ji_add_ji_to_j2i.c b/libj2_ji_add_ji_to_j2i.c
new file mode 100644
index 0000000..08bf2e1
--- /dev/null
+++ b/libj2_ji_add_ji_to_j2i.c
@@ -0,0 +1,153 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+extern inline void libj2_ji_add_ji_to_j2i(intmax_t a, intmax_t b, struct libj2_j2i *res);
+/* TODO Add man page */
+
+
+#else
+
+static intmax_t
+random_ji(void)
+{
+	size_t n = LIBJ2_JU_BIT - 1U;
+	intmax_t r = 0;
+	while (n--)
+		if (rand() < rand())
+			r |= (intmax_t)1 << n;
+	if (rand() < rand()) {
+		r = -r;
+#if INTMAX_MIN + 1 == -INTMAX_MAX
+		r -= 1;
+#endif
+	}
+	return r;
+}
+
+
+static void
+get_expected(intmax_t a, intmax_t b, uintmax_t *expected_high, uintmax_t *expected_low)
+{
+	uintmax_t pos, neg;
+	if (a >= 0 && b >= 0) {
+		*expected_high = 0;
+		*expected_low = (uintmax_t)a + (uintmax_t)b;
+	} else if (a <= 0 && b <= 0) {
+		*expected_high = UINTMAX_MAX;
+		*expected_low = (uintmax_t)a + (uintmax_t)b;
+	} else if (a < 0) {
+		pos = (uintmax_t)b;
+		neg = (uintmax_t)-(a + 1) + 1U;
+		goto pos_neg;
+	} else {
+		pos = (uintmax_t)a;
+		neg = (uintmax_t)-(b + 1) + 1U;
+	pos_neg:
+		if (pos >= neg)
+			*expected_high = 0;
+		else
+			*expected_high = UINTMAX_MAX;
+		*expected_low = pos - neg;
+	}
+}
+
+
+static void
+check(intmax_t a, intmax_t b)
+{
+	struct libj2_j2i r;
+	uintmax_t expected_high, expected_low;
+
+	get_expected(a, b, &expected_high, &expected_low);
+
+	r = (struct libj2_j2i){111, 222};
+	libj2_ji_add_ji_to_j2i(a, b, &r);
+	EXPECT(r.high == expected_high);
+	EXPECT(r.low == expected_low);
+
+#if INTMAX_MIN + 1 == -INTMAX_MAX
+	if (a == INTMAX_MIN || b == INTMAX_MIN)
+		return;
+#endif
+
+	r = (struct libj2_j2i){111, 222};
+	libj2_ji_add_ji_to_j2i(-a, -b, &r);
+	libj2_minus_j2i(&r);
+	EXPECT(r.high == expected_high);
+	EXPECT(r.low == expected_low);
+}
+
+
+static void
+check_manual(intmax_t a, intmax_t b, uintmax_t expected_high, uintmax_t expected_low)
+{
+	struct libj2_j2i r;
+
+	r = (struct libj2_j2i){111, 222};
+	libj2_ji_add_ji_to_j2i(a, b, &r);
+	EXPECT(r.high == expected_high);
+	EXPECT(r.low == expected_low);
+
+#if INTMAX_MIN + 1 == -INTMAX_MAX
+	if (a == INTMAX_MIN || b == INTMAX_MIN)
+		goto check;
+#endif
+
+	r = (struct libj2_j2i){111, 222};
+	libj2_ji_add_ji_to_j2i(-a, -b, &r);
+	libj2_minus_j2i(&r);
+	EXPECT(r.high == expected_high);
+	EXPECT(r.low == expected_low);
+
+check:
+	check(a, b);
+}
+
+
+int
+main(void)
+{
+	unsigned i;
+
+	srand((unsigned)time(NULL));
+
+	check_manual(0, 0, 0, 0);
+	check_manual(0, INTMAX_MAX, 0, (uintmax_t)INTMAX_MAX);
+	check_manual(INTMAX_MAX, 0, 0, (uintmax_t)INTMAX_MAX);
+	check_manual(INTMAX_MAX, 1, 0, UINTMAX_MAX ^ (UINTMAX_MAX >> 1));
+	check_manual(1, INTMAX_MAX, 0, UINTMAX_MAX ^ (UINTMAX_MAX >> 1));
+	check_manual(INTMAX_MAX, INTMAX_MAX, 0, (uintmax_t)INTMAX_MAX << 1);
+
+	check_manual(0, -INTMAX_MAX, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 1U);
+	check_manual(-INTMAX_MAX, 0, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 1U);
+	check_manual(INTMAX_MAX, -1, 0, (uintmax_t)INTMAX_MAX - 1U);
+	check_manual(-1, INTMAX_MAX, 0, (uintmax_t)INTMAX_MAX - 1U);
+	check_manual(-INTMAX_MAX, 1, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 2U);
+	check_manual(1, -INTMAX_MAX, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 2U);
+	check_manual(INTMAX_MAX, -INTMAX_MAX, 0, 0);
+
+#if INTMAX_MIN + 1 == -INTMAX_MAX
+	check_manual(0, INTMAX_MIN, UINTMAX_MAX, UINTMAX_MAX ^ (UINTMAX_MAX >> 1));
+	check_manual(INTMAX_MIN, 0, UINTMAX_MAX, UINTMAX_MAX ^ (UINTMAX_MAX >> 1));
+	check_manual(INTMAX_MIN, 1, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 1U);
+	check_manual(1, INTMAX_MIN, UINTMAX_MAX, (UINTMAX_MAX ^ (UINTMAX_MAX >> 1)) + 1U);
+	check_manual(INTMAX_MIN, INTMAX_MAX, UINTMAX_MAX, UINTMAX_MAX);
+	check_manual(INTMAX_MIN, -INTMAX_MAX, UINTMAX_MAX, 1);
+	check_manual(INTMAX_MIN, INTMAX_MIN, UINTMAX_MAX, 0);
+#endif
+
+	for (i = 0; i < 256; i++) {
+		check(0, random_ji());
+		check(1, random_ji());
+		check(random_ji(), 0);
+		check(random_ji(), 1);
+		check(random_ji(), random_ji());
+		check(random_ji(), INTMAX_MAX);
+		check(INTMAX_MAX, random_ji());
+	}
+
+	return 0;
+}
+
+#endif