102 lines
2.4 KiB
Go
102 lines
2.4 KiB
Go
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package astits
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import (
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"sort"
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"sync"
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)
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// packetPool represents a pool of packets
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type packetPool struct {
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b map[uint16][]*Packet // Indexed by PID
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m *sync.Mutex
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}
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// newPacketPool creates a new packet pool
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func newPacketPool() *packetPool {
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return &packetPool{
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b: make(map[uint16][]*Packet),
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m: &sync.Mutex{},
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}
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}
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// add adds a new packet to the pool
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func (b *packetPool) add(p *Packet) (ps []*Packet) {
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// Throw away packet if error indicator
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if p.Header.TransportErrorIndicator {
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return
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}
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// Throw away packets that don't have a payload until we figure out what we're going to do with them
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// TODO figure out what we're going to do with them :D
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if !p.Header.HasPayload {
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return
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}
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// Lock
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b.m.Lock()
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defer b.m.Unlock()
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// Init buffer
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var mps []*Packet
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var ok bool
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if mps, ok = b.b[p.Header.PID]; !ok {
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mps = []*Packet{}
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}
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// Empty buffer if we detect a discontinuity
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if hasDiscontinuity(mps, p) {
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mps = []*Packet{}
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}
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// Throw away packet if it's the same as the previous one
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if isSameAsPrevious(mps, p) {
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return
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}
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// Add packet
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if len(mps) > 0 || (len(mps) == 0 && p.Header.PayloadUnitStartIndicator) {
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mps = append(mps, p)
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}
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// Check payload unit start indicator
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if p.Header.PayloadUnitStartIndicator && len(mps) > 1 {
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ps = mps[:len(mps)-1]
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mps = []*Packet{p}
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}
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// Assign
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b.b[p.Header.PID] = mps
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return
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}
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// dump dumps the packet pool by looking for the first item with packets inside
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func (b *packetPool) dump() (ps []*Packet) {
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b.m.Lock()
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defer b.m.Unlock()
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var keys []int
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for k := range b.b {
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keys = append(keys, int(k))
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}
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sort.Ints(keys)
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for _, k := range keys {
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ps = b.b[uint16(k)]
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delete(b.b, uint16(k))
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if len(ps) > 0 {
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return
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}
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}
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return
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}
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// hasDiscontinuity checks whether a packet is discontinuous with a set of packets
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func hasDiscontinuity(ps []*Packet, p *Packet) bool {
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return (p.Header.HasAdaptationField && p.AdaptationField.DiscontinuityIndicator) ||
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(len(ps) > 0 && p.Header.HasPayload && p.Header.ContinuityCounter != (ps[len(ps)-1].Header.ContinuityCounter+1)%16) ||
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(len(ps) > 0 && !p.Header.HasPayload && p.Header.ContinuityCounter != ps[len(ps)-1].Header.ContinuityCounter)
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}
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// isSameAsPrevious checks whether a packet is the same as the last packet of a set of packets
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func isSameAsPrevious(ps []*Packet, p *Packet) bool {
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return len(ps) > 0 && p.Header.HasPayload && p.Header.ContinuityCounter == ps[len(ps)-1].Header.ContinuityCounter
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}
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