Some *DataReader improvements

* BFDDataReader: Add SetFD().
* BBufferDataReader: Derive from BAbstractBufferedDataReader.

headers/os/package/hpkg/DataReader.h

@@ -41,6 +41,8 @@ class BFDDataReader : public BDataReader {
 public:
 								BFDDataReader(int fd);
 
+			void				SetFD(int fd);
+
 	virtual	status_t			ReadData(off_t offset, void* buffer,
 									size_t size);
 
@@ -64,12 +66,14 @@ private:
 };
 
 
-class BBufferDataReader : public BDataReader {
+class BBufferDataReader : public BAbstractBufferedDataReader {
 public:
 								BBufferDataReader(const void* data, size_t size);
 
 	virtual	status_t			ReadData(off_t offset, void* buffer,
 									size_t size);
+	virtual	status_t			ReadDataToOutput(off_t offset, size_t size,
+									BDataOutput* output);
 
 private:
 			const void*			fData;

src/kits/package/hpkg/DataReader.cpp

@@ -68,6 +68,23 @@ BBufferDataReader::ReadData(off_t offset, void* buffer, size_t size)
 }
 
 
+status_t
+BBufferDataReader::ReadDataToOutput(off_t offset, size_t size,
+	BDataOutput* output)
+{
+	if (size == 0)
+		return B_OK;
+
+	if (offset < 0)
+		return B_BAD_VALUE;
+
+	if (size > fSize || offset > (off_t)fSize - (off_t)size)
+		return B_ERROR;
+
+	return output->WriteData((const uint8*)fData + offset, size);
+}
+
+
 }	// namespace BHPKG
 
 }	// namespace BPackageKit

src/kits/package/hpkg/FDDataReader.cpp

@@ -22,6 +22,13 @@ BFDDataReader::BFDDataReader(int fd)
 }
 
 
+void
+BFDDataReader::SetFD(int fd)
+{
+	fFD = fd;
+}
+
+
 status_t
 BFDDataReader::ReadData(off_t offset, void* buffer, size_t size)
 {