From 73f61e13d752fd0946df435e29ff431ab0097a6a Mon Sep 17 00:00:00 2001
From: Anna Schumaker <Anna@OcarinaProject.net>
Date: Sat, 7 Nov 2015 11:20:19 -0500
Subject: [PATCH] core/set: Add function for finding set intersections

Finding an inline intersection is really easy using iterators, so I
wrote this function to modify one of the set rather than returning a new
one.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>
---
 core/set.c         | 15 ++++++++++++++
 include/core/set.h |  2 ++
 tests/core/set.c   | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)
 create mode 100644 core/set.c

diff --git a/core/set.c b/core/set.c
new file mode 100644
index 00000000..9557c528
--- /dev/null
+++ b/core/set.c
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2015 (c) Anna Schumaker.
+ */
+
+#include <core/set.h>
+
+void set_inline_intersect(const struct set *lhs, struct set *rhs)
+{
+	struct set_iter it_rhs;
+
+	set_for_each(rhs, &it_rhs) {
+		if (!set_has(lhs, it_rhs.it_val))
+			g_hash_table_iter_remove(&it_rhs.it_iter);
+	}
+}
diff --git a/include/core/set.h b/include/core/set.h
index 5746affa..496e9f88 100644
--- a/include/core/set.h
+++ b/include/core/set.h
@@ -49,6 +49,8 @@ static inline unsigned int set_size(struct set *set)
 	return g_hash_table_size(set->s_set);
 }
 
+/* Remove values from set2 that are not also in set1. */
+void set_inline_intersect(const struct set *, struct set *);
 
 
 static inline bool set_iter_next(struct set_iter *it)
diff --git a/tests/core/set.c b/tests/core/set.c
index 52d97142..96bba1bc 100644
--- a/tests/core/set.c
+++ b/tests/core/set.c
@@ -40,6 +40,56 @@ void test_set()
 	set_deinit(&set);
 }
 
+void test_intersection()
+{
+	struct set set1 = SET_INIT();
+	struct set set2 = SET_INIT();
+	unsigned int i;
+
+	/* Test intersection between two empty sets. */
+	set_inline_intersect(&set1, &set2);
+	test_equal(set_size(&set1), 0);
+	test_equal(set_size(&set2), 0);
+
+
+	/* Add values 5 - 14 to set2, but keep set1 empty. */
+	for (i = 5; i < 15; i++)
+		set_insert(&set2, i);
+	set_inline_intersect(&set1, &set2);
+	test_equal(set_size(&set1), 0);
+	test_equal(set_size(&set2), 0);
+
+
+	/* Add values 0 - 9 to set1, but keep set2 empty. */
+	for (i = 0; i < 10; i++)
+		set_insert(&set1, i);
+	set_inline_intersect(&set1, &set2);
+	test_equal(set_size(&set1), 10);
+	test_equal(set_size(&set2), 0);
+
+
+	/* Add values 5 - 14 back into set2. */
+	for (i = 5; i < 15; i++)
+		set_insert(&set2, i);
+	set_inline_intersect(&set1, &set2);
+	test_equal(set_size(&set1), 10);
+	test_equal(set_size(&set2), 5);
+
+
+	/* Set1 should now contain values 5 - 9. */
+	for (i = 0; i < 15; i++) {
+		if (i >= 5 && i < 10) {
+			test_loop_equal(set_has(&set2, i), (bool)true, i);
+		} else {
+			test_loop_equal(set_has(&set2, i), (bool)false, i);
+		}
+	} test_loop_passed();
+
+	set_deinit(&set1);
+	set_deinit(&set2);
+}
+
 DECLARE_UNIT_TESTS(
 	UNIT_TEST("Set", test_set),
+	UNIT_TEST("Set Intersection", test_intersection),
 );