2018-11-20 17:51:25 -05:00
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package utils
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import (
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"bytes"
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"fmt"
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2019-01-17 09:33:18 -05:00
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"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/protocol"
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2018-11-20 17:51:25 -05:00
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)
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// ReadVarIntPacketNumber reads a number in the QUIC varint packet number format
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func ReadVarIntPacketNumber(b *bytes.Reader) (protocol.PacketNumber, protocol.PacketNumberLen, error) {
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b1, err := b.ReadByte()
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if err != nil {
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return 0, 0, err
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}
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if b1&0x80 == 0 {
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return protocol.PacketNumber(b1), protocol.PacketNumberLen1, nil
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}
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b2, err := b.ReadByte()
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if err != nil {
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return 0, 0, err
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}
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if b1&0x40 == 0 {
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return protocol.PacketNumber(uint64(b1&0x3f)<<8 + uint64(b2)), protocol.PacketNumberLen2, nil
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}
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b3, err := b.ReadByte()
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if err != nil {
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return 0, 0, err
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}
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b4, err := b.ReadByte()
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if err != nil {
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return 0, 0, err
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}
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return protocol.PacketNumber(uint64(b1&0x3f)<<24 + uint64(b2)<<16 + uint64(b3)<<8 + uint64(b4)), protocol.PacketNumberLen4, nil
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}
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// WriteVarIntPacketNumber writes a packet number in the QUIC varint packet number format
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func WriteVarIntPacketNumber(b *bytes.Buffer, i protocol.PacketNumber, len protocol.PacketNumberLen) error {
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switch len {
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case protocol.PacketNumberLen1:
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b.WriteByte(uint8(i & 0x7f))
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case protocol.PacketNumberLen2:
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b.Write([]byte{(uint8(i>>8) & 0x3f) | 0x80, uint8(i)})
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case protocol.PacketNumberLen4:
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b.Write([]byte{(uint8(i>>24) & 0x3f) | 0xc0, uint8(i >> 16), uint8(i >> 8), uint8(i)})
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default:
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return fmt.Errorf("invalid packet number length: %d", len)
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}
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return nil
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}
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