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