Hopefully less bad version of Evoral::RangeList::subtract,

with more tests.


git-svn-id: svn://localhost/ardour2/branches/3.0@12514 d708f5d6-7413-0410-9779-e7cbd77b26cf

libs/evoral/evoral/Range.hpp

@@ -139,7 +139,6 @@ public:
 		return _list.empty ();
 	}
 
-private:
 	void coalesce () {
 		if (!_dirty) {
 			return;
@@ -164,6 +163,8 @@ private:
 
 		_dirty = false;
 	}
+
+private:
 	
 	List _list;
 	bool _dirty;
@@ -178,37 +179,71 @@ struct RangeMove {
 	T         to;     ///< new start of the range
 };
 
+/** Subtract the ranges in `sub' from that in `range',
+ *  returning the result.
+ */
 template<typename T>
 RangeList<T> subtract (Range<T> range, RangeList<T> sub)
 {
+	/* Start with the input range */
 	RangeList<T> result;
+	result.add (range);
 
 	if (sub.empty ()) {
-		result.add (range);
 		return result;
 	}
-			
-	T x = range.from;
 
 	typename RangeList<T>::List s = sub.get ();
+
+	/* The basic idea here is to keep a list of the result ranges, and subtract
+	   the bits of `sub' from them one by one.
+	*/
 	
 	for (typename RangeList<T>::List::const_iterator i = s.begin(); i != s.end(); ++i) {
 
-		if (coverage (range.from, range.to, i->from, i->to) == OverlapNone) {
+		/* Here's where we'll put the new current result after subtracting *i from it */
-			continue;
+		RangeList<T> new_result;
+
+		typename RangeList<T>::List r = result.get ();
+
+		/* Work on all parts of the current result using this range *i */
+		for (typename RangeList<T>::List::const_iterator j = r.begin(); j != r.end(); ++j) {
+
+			switch (coverage (j->from, j->to, i->from, i->to)) {
+			case OverlapNone:
+				/* The thing we're subtracting does not overlap this bit of the result,
+				   so pass it through.
+				*/
+				new_result.add (*j);
+				break;
+			case OverlapInternal:
+				/* Internal overlap of the thing we're subtracting from this bit of the result,
+				   so we might end up with two bits left over.
+				*/
+				if (j->from < (i->from - 1)) {
+					new_result.add (Range<T> (j->from, i->from - 1));
+				}
+				if (j->to != i->to) {
+					new_result.add (Range<T> (i->to, j->to));
+				}
+				break;
+			case OverlapStart:
+				/* The bit we're subtracting overlaps the start of the bit of the result */
+				new_result.add (Range<T> (i->to, j->to - 1));
+				break;
+			case OverlapEnd:
+				/* The bit we're subtracting overlaps the end of the bit of the result */
+				new_result.add (Range<T> (j->from, i->from - 1));
+				break;
+			case OverlapExternal:
+				/* total overlap of the bit we're subtracting with the result bit, so the
+				   result bit is completely removed; do nothing */
+				break;
+			}
 		}
 
-		Range<T> clamped (std::max (range.from, i->from), std::min (range.to, i->to));
+		new_result.coalesce ();
-		
+		result = new_result;
-		if (clamped.from != x) {
-			result.add (Range<T> (x, clamped.from - 1));
-		}
-		
-		x = clamped.to;
-	}
-
-	if (s.back().to < range.to) {
-		result.add (Range<T> (x, range.to));
 	}
 
 	return result;

libs/evoral/test/RangeTest.cpp

@@ -1,5 +1,6 @@
 #include "RangeTest.hpp"
 #include "evoral/Range.hpp"
+#include <stdlib.h>
 
 CPPUNIT_TEST_SUITE_REGISTRATION (RangeTest);
 
@@ -24,6 +25,7 @@ RangeTest::coalesceTest ()
 	CPPUNIT_ASSERT_EQUAL (8, i->to);
 }
 
+/* Basic subtraction of a few smaller ranges from a larger one */
 void
 RangeTest::subtractTest1 ()
 {
@@ -51,6 +53,7 @@ RangeTest::subtractTest1 ()
 	CPPUNIT_ASSERT_EQUAL (10, i->to);
 }
 
+/* Test subtraction of a range B from a range A, where A and B do not overlap */
 void
 RangeTest::subtractTest2 ()
 {
@@ -69,6 +72,7 @@ RangeTest::subtractTest2 ()
 	CPPUNIT_ASSERT_EQUAL (10, i->to);
 }
 
+/* Test subtraction of B from A, where B entirely overlaps A */
 void
 RangeTest::subtractTest3 ()
 {
@@ -82,3 +86,62 @@ RangeTest::subtractTest3 ()
 	RangeList<int>::List s = sheila.get ();
 	CPPUNIT_ASSERT_EQUAL (size_t (0), s.size ());
 }
+
+/* A bit like subtractTest1, except some of the ranges
+   we are subtracting overlap.
+*/
+void
+RangeTest::subtractTest4 ()
+{
+	Range<int> fred (0, 10);
+
+	RangeList<int> jim;
+	jim.add (Range<int> (2, 4));
+	jim.add (Range<int> (7, 8));
+	jim.add (Range<int> (8, 9));
+
+	RangeList<int> sheila = subtract (fred, jim);
+
+	RangeList<int>::List s = sheila.get ();
+	CPPUNIT_ASSERT_EQUAL (size_t (3), s.size ());
+
+	RangeList<int>::List::iterator i = s.begin ();
+	CPPUNIT_ASSERT_EQUAL (0, i->from);
+	CPPUNIT_ASSERT_EQUAL (1, i->to);
+
+	++i;
+	CPPUNIT_ASSERT_EQUAL (4, i->from);
+	CPPUNIT_ASSERT_EQUAL (6, i->to);
+
+	++i;
+	CPPUNIT_ASSERT_EQUAL (9, i->from);
+	CPPUNIT_ASSERT_EQUAL (10, i->to);
+}
+
+/* A bit like subtractTest1, except some of the ranges
+   we are subtracting overlap the start / end of the
+   initial range.
+*/
+void
+RangeTest::subtractTest5 ()
+{
+	Range<int> fred (1, 12);
+
+	RangeList<int> jim;
+	jim.add (Range<int> (0, 4));
+	jim.add (Range<int> (6, 7));
+	jim.add (Range<int> (9, 42));
+
+	RangeList<int> sheila = subtract (fred, jim);
+
+	RangeList<int>::List s = sheila.get ();
+	CPPUNIT_ASSERT_EQUAL (size_t (2), s.size ());
+
+	RangeList<int>::List::iterator i = s.begin ();
+	CPPUNIT_ASSERT_EQUAL (4, i->from);
+	CPPUNIT_ASSERT_EQUAL (5, i->to);
+
+	++i;
+	CPPUNIT_ASSERT_EQUAL (7, i->from);
+	CPPUNIT_ASSERT_EQUAL (8, i->to);
+}

libs/evoral/test/RangeTest.hpp

@@ -6,7 +6,10 @@ class RangeTest : public CppUnit::TestFixture
 	CPPUNIT_TEST_SUITE (RangeTest);
 	CPPUNIT_TEST (coalesceTest);
 	CPPUNIT_TEST (subtractTest1);
+	CPPUNIT_TEST (subtractTest2);
 	CPPUNIT_TEST (subtractTest3);
+	CPPUNIT_TEST (subtractTest4);
+	CPPUNIT_TEST (subtractTest5);
 	CPPUNIT_TEST_SUITE_END ();
 
 public:
@@ -14,6 +17,8 @@ public:
 	void subtractTest1 ();
 	void subtractTest2 ();
 	void subtractTest3 ();
+	void subtractTest4 ();
+	void subtractTest5 ();
 };