util/Bitmap: add more utility methods

Change-Id: I021c2fafa01266e8a38c1cb2fd748fd89a4b75bd
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6742
Reviewed-by: waddlesplash <[email protected]>

headers/private/kernel/util/Bitmap.h

@@ -22,7 +22,7 @@ namespace BKernel {
 
 class Bitmap {
 public:
-						Bitmap(size_t bitCount);
+						Bitmap(size_t bitCount = 0);
 						~Bitmap();
 
 			status_t	InitCheck();
@@ -34,6 +34,11 @@ public:
 	inline	void		Set(size_t index);
 	inline	void		Clear(size_t index);
 
+			void		SetRange(size_t index, size_t count);
+			void		ClearRange(size_t index, size_t count);
+
+			ssize_t		GetLowestClear(size_t fromIndex = 0) const;
+			ssize_t		GetLowestContiguousClear(size_t count, size_t fromIndex = 0) const;
 			ssize_t		GetHighestSet() const;
 
 private:

src/system/kernel/util/Bitmap.cpp

@@ -70,6 +70,67 @@ Bitmap::Shift(ssize_t bitCount)
 }
 
 
+void
+Bitmap::SetRange(size_t index, size_t count)
+{
+	// TODO: optimize
+	for (; count > 0; count--)
+		Set(index++);
+}
+
+
+void
+Bitmap::ClearRange(size_t index, size_t count)
+{
+	// TODO: optimize
+	for (; count > 0; count--)
+		Clear(index++);
+}
+
+
+ssize_t
+Bitmap::GetLowestClear(size_t fromIndex) const
+{
+	// TODO: optimize
+
+	for (size_t i = fromIndex; i < fSize; i++) {
+		if (!Get(i))
+			return i;
+	}
+	return -1;
+}
+
+
+ssize_t
+Bitmap::GetLowestContiguousClear(size_t count, size_t fromIndex) const
+{
+	// TODO: optimize
+
+	// nothing to find
+	if (count == 0)
+		return fromIndex;
+
+	for (;;) {
+		ssize_t index = GetLowestClear(fromIndex);
+		if (index < 0)
+			return index;
+
+		// overflow check
+		if ((size_t)index + count - 1 < (size_t)index)
+			return -1;
+
+		size_t curCount = 1;
+		while (curCount < count && Get(index + curCount))
+			curCount++;
+
+		if (curCount == count)
+			return index;
+
+		fromIndex = index + curCount;
+	}
+}
+
+
 ssize_t
 Bitmap::GetHighestSet() const
 {