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datagram.go
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datagram.go
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package http3
import (
"context"
"sync"
)
const maxQuarterStreamID = 1<<60 - 1
const streamDatagramQueueLen = 32
type datagrammer struct {
sendDatagram func([]byte) error
hasData chan struct{}
queue [][]byte // TODO: use a ring buffer
mx sync.Mutex
sendErr error
receiveErr error
}
func newDatagrammer(sendDatagram func([]byte) error) *datagrammer {
return &datagrammer{
sendDatagram: sendDatagram,
hasData: make(chan struct{}, 1),
}
}
func (d *datagrammer) SetReceiveError(err error) {
d.mx.Lock()
defer d.mx.Unlock()
d.receiveErr = err
d.signalHasData()
}
func (d *datagrammer) SetSendError(err error) {
d.mx.Lock()
defer d.mx.Unlock()
d.sendErr = err
}
func (d *datagrammer) Send(b []byte) error {
d.mx.Lock()
sendErr := d.sendErr
d.mx.Unlock()
if sendErr != nil {
return sendErr
}
return d.sendDatagram(b)
}
func (d *datagrammer) signalHasData() {
select {
case d.hasData <- struct{}{}:
default:
}
}
func (d *datagrammer) enqueue(data []byte) {
d.mx.Lock()
defer d.mx.Unlock()
if d.receiveErr != nil {
return
}
if len(d.queue) >= streamDatagramQueueLen {
return
}
d.queue = append(d.queue, data)
d.signalHasData()
}
func (d *datagrammer) Receive(ctx context.Context) ([]byte, error) {
start:
d.mx.Lock()
if len(d.queue) >= 1 {
data := d.queue[0]
d.queue = d.queue[1:]
d.mx.Unlock()
return data, nil
}
if receiveErr := d.receiveErr; receiveErr != nil {
d.mx.Unlock()
return nil, receiveErr
}
d.mx.Unlock()
select {
case <-ctx.Done():
return nil, context.Cause(ctx)
case <-d.hasData:
}
goto start
}