forked from quic-go/quic-go
45 lines
1.5 KiB
Go
45 lines
1.5 KiB
Go
package quic
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import "github.com/lucas-clemente/quic-go/protocol"
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func inferPacketNumber(packetNumberLength protocol.PacketNumberLen, lastPacketNumber protocol.PacketNumber, wirePacketNumber protocol.PacketNumber) protocol.PacketNumber {
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epochDelta := protocol.PacketNumber(1) << (uint8(packetNumberLength) * 8)
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epoch := lastPacketNumber & ^(epochDelta - 1)
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prevEpochBegin := epoch - epochDelta
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nextEpochBegin := epoch + epochDelta
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return closestTo(
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lastPacketNumber+1,
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epoch+wirePacketNumber,
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closestTo(lastPacketNumber+1, prevEpochBegin+wirePacketNumber, nextEpochBegin+wirePacketNumber),
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)
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}
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func closestTo(target, a, b protocol.PacketNumber) protocol.PacketNumber {
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if delta(target, a) < delta(target, b) {
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return a
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}
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return b
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}
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func delta(a, b protocol.PacketNumber) protocol.PacketNumber {
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if a < b {
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return b - a
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}
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return a - b
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}
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func getPacketNumberLength(packetNumber protocol.PacketNumber, highestAckedPacketNumber protocol.PacketNumber) protocol.PacketNumberLen {
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diff := uint64(packetNumber - highestAckedPacketNumber)
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if diff < (2 << (uint8(protocol.PacketNumberLen1)*8 - 2)) {
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return protocol.PacketNumberLen1
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}
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if diff < (2 << (uint8(protocol.PacketNumberLen2)*8 - 2)) {
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return protocol.PacketNumberLen2
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}
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if diff < (2 << (uint8(protocol.PacketNumberLen4)*8 - 2)) {
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return protocol.PacketNumberLen4
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}
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// we do not check if there are less than 2^46 packets in flight, since flow control and congestion control will limit this number *a lot* sooner
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return protocol.PacketNumberLen6
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}
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