pad

type Padding interface {

	// BlockSize returns the block size of the padding.
	BlockSize() int

	// Returns the overhead, the padding will cause
	// by padding the given byte slice. The overhead
	// will always be between 1 and BlockSize() inclusively.
	Overhead(src []byte) int

	// Pads the last (may incomplete) block of the src slice
	// to a padded and complete block, appends the padding bytes
	// to the src slice and returns this slice.
	// The length of the returned slice is len(src) + Overhead(src)
	Pad(src []byte) []byte

	// Takes a slice and tries to remove the padding bytes
	// form the last block. Therefore the length of the
	// src argument must be a multiply of the blocksize.
	// If the returned error is nil, the padding could be
	// removed successfully. The returned slice holds the
	// unpadded src bytes.
	Unpad(src []byte) ([]byte, error)
}