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package nack
import (
"fmt"
"github.com/pion/rtp"
)
const (
uint16SizeHalf = 1 << 15
)
type sendBuffer struct {
packets []*rtp.Packet
size uint16
lastAdded uint16
started bool
}
func newSendBuffer(size uint16) (*sendBuffer, error) {
allowedSizes := make([]uint16, 0)
correctSize := false
for i := 0; i < 16; i++ {
if size == 1<<i {
correctSize = true
break
}
allowedSizes = append(allowedSizes, 1<<i)
}
if !correctSize {
return nil, fmt.Errorf("%w: %d is not a valid size, allowed sizes: %v", ErrInvalidSize, size, allowedSizes)
}
return &sendBuffer{
packets: make([]*rtp.Packet, size),
size: size,
}, nil
}
func (s *sendBuffer) add(packet *rtp.Packet) {
seq := packet.SequenceNumber
if !s.started {
s.packets[seq%s.size] = packet
s.lastAdded = seq
s.started = true
return
}
diff := seq - s.lastAdded
if diff == 0 {
return
} else if diff < uint16SizeHalf {
for i := s.lastAdded + 1; i != seq; i++ {
s.packets[i%s.size] = nil
}
}
s.packets[seq%s.size] = packet
s.lastAdded = seq
}
func (s *sendBuffer) get(seq uint16) *rtp.Packet {
diff := s.lastAdded - seq
if diff >= uint16SizeHalf {
return nil
}
if diff >= s.size {
return nil
}
return s.packets[seq%s.size]
}
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