From bdba362695bd5ee97fca685839a9e90e1e788ecb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <stefan.bruens@rwth-aachen.de>
Date: Fri, 22 Apr 2016 23:15:54 +0200
Subject: [PATCH] analog: Add equality check for sr_rational

---
 include/libsigrok/proto.h |  1 +
 src/analog.c              | 79 +++++++++++++++++++++++++++++++++++++++
 tests/analog.c            | 30 +++++++++++++++
 3 files changed, 110 insertions(+)

diff --git a/include/libsigrok/proto.h b/include/libsigrok/proto.h
index f2dc8d49..0dd594ed 100644
--- a/include/libsigrok/proto.h
+++ b/include/libsigrok/proto.h
@@ -33,6 +33,7 @@ SR_API int sr_analog_to_float(const struct sr_datafeed_analog *analog,
 SR_API int sr_analog_unit_to_string(const struct sr_datafeed_analog *analog,
 		char **result);
 SR_API void sr_rational_set(struct sr_rational *r, int64_t p, uint64_t q);
+SR_API int sr_rational_eq(const struct sr_rational *a, const struct sr_rational *b);
 
 /*--- backend.c -------------------------------------------------------------*/
 
diff --git a/src/analog.c b/src/analog.c
index da1560cd..a04844d6 100644
--- a/src/analog.c
+++ b/src/analog.c
@@ -354,4 +354,83 @@ SR_API void sr_rational_set(struct sr_rational *r, int64_t p, uint64_t q)
 	r->q = q;
 }
 
+#ifndef HAVE___INT128_T
+struct sr_int128_t {
+	int64_t high;
+	uint64_t low;
+};
+
+struct sr_uint128_t {
+	uint64_t high;
+	uint64_t low;
+};
+
+static void mult_int64(struct sr_int128_t *res, const int64_t a,
+	const int64_t b)
+{
+	uint64_t t1, t2, t3, t4;
+
+	t1 = (UINT32_MAX & a) * (UINT32_MAX & b);
+	t2 = (UINT32_MAX & a) * (b >> 32);
+	t3 = (a >> 32) * (UINT32_MAX & b);
+	t4 = (a >> 32) * (b >> 32);
+
+	res->low = t1 + (t2 << 32) + (t3 << 32);
+	res->high = (t1 >> 32) + (uint64_t)((uint32_t)(t2)) + (uint64_t)((uint32_t)(t3));
+	res->high >>= 32;
+	res->high += ((int64_t)t2 >> 32) + ((int64_t)t3 >> 32) + t4;
+}
+
+static void mult_uint64(struct sr_uint128_t *res, const uint64_t a,
+	const uint64_t b)
+{
+	uint64_t t1, t2, t3, t4;
+
+	// (x1 + x2) * (y1 + y2) = x1*y1 + x1*y2 + x2*y1 + x2*y2
+	t1 = (UINT32_MAX & a) * (UINT32_MAX & b);
+	t2 = (UINT32_MAX & a) * (b >> 32);
+	t3 = (a >> 32) * (UINT32_MAX & b);
+	t4 = (a >> 32) * (b >> 32);
+
+	res->low = t1 + (t2 << 32) + (t3 << 32);
+	res->high = (t1 >> 32) + (uint64_t)((uint32_t)(t2)) + (uint64_t)((uint32_t)(t3));
+	res->high >>= 32;
+	res->high += ((int64_t)t2 >> 32) + ((int64_t)t3 >> 32) + t4;
+}
+#endif
+
+/**
+ * Compare two sr_rational for equality
+ *
+ * @param[in] a First value
+ * @param[in] b Second value
+ *
+ * The values are compared for numerical equality, i.e. 2/10 == 1/5
+ *
+ * @retval 1 if both values are equal
+ * @retval 0 otherwise
+ *
+ * @since 0.5.0
+ */
+SR_API int sr_rational_eq(const struct sr_rational *a, const struct sr_rational *b)
+{
+#ifdef HAVE___INT128_T
+	__int128_t m1, m2;
+
+	/* p1/q1 = p2/q2  <=>  p1*q2 = p2*q1 */
+	m1 = ((__int128_t)(b->p)) * ((__uint128_t)a->q);
+	m2 = ((__int128_t)(a->p)) * ((__uint128_t)b->q);
+
+	return (m1 == m2);
+
+#else
+	struct sr_int128_t m1, m2;
+
+	mult_int64(&m1, a->q, b->p);
+	mult_int64(&m2, a->p, b->q);
+
+	return (m1.high == m2.high) && (m1.low == m2.low);
+#endif
+}
+
 /** @} */
diff --git a/tests/analog.c b/tests/analog.c
index 13eb107c..64e355eb 100644
--- a/tests/analog.c
+++ b/tests/analog.c
@@ -196,6 +196,35 @@ START_TEST(test_set_rational_null)
 }
 END_TEST
 
+START_TEST(test_cmp_rational)
+{
+	const struct sr_rational r[] = { { 1, 1 },
+		{ 2, 2 },
+		{ 1000, 1000 },
+		{ INT64_MAX, INT64_MAX },
+		{ 1, 4 },
+		{ 2, 8 },
+		{ INT64_MAX, UINT64_MAX },
+		{ INT64_MIN, UINT64_MAX },
+	};
+
+	fail_unless(sr_rational_eq(&r[0], &r[0]) == 1);
+	fail_unless(sr_rational_eq(&r[0], &r[1]) == 1);
+	fail_unless(sr_rational_eq(&r[1], &r[2]) == 1);
+	fail_unless(sr_rational_eq(&r[2], &r[3]) == 1);
+	fail_unless(sr_rational_eq(&r[3], &r[3]) == 1);
+
+	fail_unless(sr_rational_eq(&r[4], &r[4]) == 1);
+	fail_unless(sr_rational_eq(&r[4], &r[5]) == 1);
+	fail_unless(sr_rational_eq(&r[5], &r[5]) == 1);
+
+	fail_unless(sr_rational_eq(&r[6], &r[6]) == 1);
+	fail_unless(sr_rational_eq(&r[7], &r[7]) == 1);
+
+	fail_unless(sr_rational_eq(&r[1], &r[4]) == 0);
+}
+END_TEST
+
 Suite *suite_analog(void)
 {
 	Suite *s;
@@ -210,6 +239,7 @@ Suite *suite_analog(void)
 	tcase_add_test(tc, test_analog_unit_to_string_null);
 	tcase_add_test(tc, test_set_rational);
 	tcase_add_test(tc, test_set_rational_null);
+	tcase_add_test(tc, test_cmp_rational);
 	suite_add_tcase(s, tc);
 
 	return s;