packet

type Handler interface {
	// Headroom returns the amount of extra space required in read/write buffers besides the payload.
	Headroom() Headroom

	// EncryptZeroCopy encrypts a WireGuard packet and returns a swgp packet without copying or incurring any allocations.
	//
	// The WireGuard packet starts at buf[wgPacketStart] and its length is specified by wgPacketLength.
	// The returned swgp packet starts at buf[swgpPacketStart] and its length is specified by swgpPacketLength.
	//
	// buf must have at least FrontOverhead() bytes before and RearOverhead() bytes after the WireGuard packet.
	// In other words, start must not be less than FrontOverhead(), len(buf) must not be less than start + length + RearOverhead().
	EncryptZeroCopy(buf []byte, wgPacketStart, wgPacketLength int) (swgpPacketStart, swgpPacketLength int, err error)

	// DecryptZeroCopy decrypts a swgp packet and returns a WireGuard packet without copying or incurring any allocations.
	//
	// The swgp packet starts at buf[swgpPacketStart] and its length is specified by swgpPacketLength.
	// The returned WireGuard packet starts at buf[wgPacketStart] and its length is specified by wgPacketLength.
	DecryptZeroCopy(buf []byte, swgpPacketStart, swgpPacketLength int) (wgPacketStart, wgPacketLength int, err error)
}

type HandlerErr struct {
	Err     error
	Message string
}

type Headroom struct {
	// Front is the minimum space required at the beginning of the buffer before payload.
	Front int

	// Rear is the minimum space required at the end of the buffer after payload.
	Rear int
}