Add a ScaledData() getter that scales the data to the desired bit width and

converts the signed-ness as specified.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@41843 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/drivers/input/usb_hid/HIDReportItem.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2009, Michael Lotz, [email protected].
+ * Copyright 2009-2011, Michael Lotz, [email protected].
  * Distributed under the terms of the MIT License.
  */
 
@@ -21,6 +21,7 @@ HIDReportItem::HIDReportItem(HIDReport *report, uint32 bitOffset,
 		fByteOffset(bitOffset / 8),
 		fShift(bitOffset % 8),
 		fMask(~(0xffffffff << bitLength)),
+		fBitCount(bitLength),
 		fHasData(hasData),
 		fArray(isArray),
 		fRelative(isRelative),
@@ -114,6 +115,32 @@ HIDReportItem::SetData(uint32 data)
 }
 
 
+uint32
+HIDReportItem::ScaledData(uint8 scaleToBits, bool toBeSigned)
+{
+	uint32 source = fData;
+	if (Signed() && !toBeSigned)
+		source = (uint32)((int32)fData - (int32)fMinimum);
+
+	if (fBitCount == scaleToBits)
+		return source;
+
+	int8 shift;
+	uint32 result = 0;
+	do {
+		shift = scaleToBits - fBitCount;
+		if (shift > 0) {
+			result |= source << shift;
+			scaleToBits = shift;
+		} else
+			result |= source >> -shift;
+
+	} while (shift > 0);
+
+	return result;
+}
+
+
 void
 HIDReportItem::PrintToStream(uint32 indentLevel)
 {

src/add-ons/kernel/drivers/input/usb_hid/HIDReportItem.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2009, Michael Lotz, [email protected].
+ * Copyright 2009-2011, Michael Lotz, [email protected].
  * Distributed under the terms of the MIT License.
  */
 #ifndef HID_REPORT_ITEM_H
@@ -36,6 +36,8 @@ public:
 		status_t				SetData(uint32 data);
 		uint32					Data() { return fData; };
 
+		uint32					ScaledData(uint8 scaleToBits, bool toBeSigned);
+
 		bool					Valid() { return fValid; };
 
 		void					PrintToStream(uint32 indentLevel = 0);
@@ -44,6 +46,7 @@ private:
 		uint32					fByteOffset;
 		uint8					fShift;
 		uint32					fMask;
+		uint8					fBitCount;
 		bool					fHasData;
 		bool					fArray;
 		bool					fRelative;