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#ifndef IMAGE_IO_BASE_DATA_DESTINATION_H_ // NOLINT
#define IMAGE_IO_BASE_DATA_DESTINATION_H_ // NOLINT
#include "image_io/base/data_range.h"
#include "image_io/base/data_segment.h"
#include "image_io/base/types.h"
namespace photos_editing_formats {
namespace image_io {
/// DataDestination is the abstract base class for implementations that can
/// efficiently move data from one location and/or form to another. In such
/// a transfer, the StartTransfer() and FinishTransfer() functions are always
/// called, and in between the Transfer() function may be called zero or more
/// times. See the DataSource class to see how to initiate a transfer operation.
class DataDestination {
public:
/// These values indicate what should be done after a DataSource calls a
/// DataDestination's Transfer() function.
enum TransferStatus {
/// An error occurred in the transfer process. DataSource's TransferData()
/// function should stop calling DataDestination's Transfer() function, and
/// return to its caller.
kTransferError,
/// The transfer was successful. DataSource's TransferData() function can
/// keep calling DataDestination's Transfer() of needed, or if not,
/// return to its caller.
kTransferOk,
/// The transfer was successful and the DataDestination has decided that
/// it has enough data. DataSource's TransferData() function should stop
/// calling DataDestination's Transfer() function and return to its caller.
kTransferDone
};
virtual ~DataDestination() = default;
/// This function is called prior to the first call to the Transfer() function
/// to allow implementation subclasses a chance to initialize their data
/// members for the transfer process. If a data destination sends its bytes
/// to another data destination, this function must call its StartTransfer()
/// function.
virtual void StartTransfer() = 0;
/// This function is called to transfer a portion or all of the data in the
/// data segment from the caller to wherever the receiver needs it to go.
/// @param transfer_range The portion of the data in the data_segment that is
/// to be transferred.
/// @param data_segment The data, some or all of which is to be transferred.
/// @return A transfer status value indicating what should be done next.
virtual TransferStatus Transfer(const DataRange& transfer_range,
const DataSegment& data_segment) = 0;
/// This function is called after the final call to the Transfer() function to
/// allow implementation subclasses a chance to finalize their transfer
/// operations. If a data destination sends its bytes to another data
/// destination, this function must call its FinishTransfer() function.
virtual void FinishTransfer() = 0;
/// @return The number of bytes written to the data destination. There is some
/// flexibility in the actual value returned. Most "end-point" destination
/// subclasses return the actual number of bytes received/written. Other
/// "mid-point" destinations are allowed to return the value from the next
/// destination in the chain, or the actual number of bytes they are asked
/// to transfer via the transfer_range parameter of the Transfer()
/// function.
virtual size_t GetBytesTransferred() const = 0;
};
} // namespace image_io
} // namespace photos_editing_formats
#endif // IMAGE_IO_BASE_DATA_DESTINATION_H_ // NOLINT
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