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package protocol
import (
"crypto/rand"
"errors"
"fmt"
"io"
)
var ErrInvalidConnectionIDLen = errors.New("invalid Connection ID length")
// An ArbitraryLenConnectionID is a QUIC Connection ID able to represent Connection IDs according to RFC 8999.
// Future QUIC versions might allow connection ID lengths up to 255 bytes, while QUIC v1
// restricts the length to 20 bytes.
type ArbitraryLenConnectionID []byte
func (c ArbitraryLenConnectionID) Len() int {
return len(c)
}
func (c ArbitraryLenConnectionID) Bytes() []byte {
return c
}
func (c ArbitraryLenConnectionID) String() string {
if c.Len() == 0 {
return "(empty)"
}
return fmt.Sprintf("%x", c.Bytes())
}
const maxConnectionIDLen = 20
// A ConnectionID in QUIC
type ConnectionID struct {
b [20]byte
l uint8
}
// GenerateConnectionID generates a connection ID using cryptographic random
func GenerateConnectionID(l int) (ConnectionID, error) {
var c ConnectionID
c.l = uint8(l)
_, err := rand.Read(c.b[:l])
return c, err
}
// ParseConnectionID interprets b as a Connection ID.
// It panics if b is longer than 20 bytes.
func ParseConnectionID(b []byte) ConnectionID {
if len(b) > maxConnectionIDLen {
panic("invalid conn id length")
}
var c ConnectionID
c.l = uint8(len(b))
copy(c.b[:c.l], b)
return c
}
// GenerateConnectionIDForInitial generates a connection ID for the Initial packet.
// It uses a length randomly chosen between 8 and 20 bytes.
func GenerateConnectionIDForInitial() (ConnectionID, error) {
r := make([]byte, 1)
if _, err := rand.Read(r); err != nil {
return ConnectionID{}, err
}
l := MinConnectionIDLenInitial + int(r[0])%(maxConnectionIDLen-MinConnectionIDLenInitial+1)
return GenerateConnectionID(l)
}
// ReadConnectionID reads a connection ID of length len from the given io.Reader.
// It returns io.EOF if there are not enough bytes to read.
func ReadConnectionID(r io.Reader, l int) (ConnectionID, error) {
var c ConnectionID
if l == 0 {
return c, nil
}
if l > maxConnectionIDLen {
return c, ErrInvalidConnectionIDLen
}
c.l = uint8(l)
_, err := io.ReadFull(r, c.b[:l])
if err == io.ErrUnexpectedEOF {
return c, io.EOF
}
return c, err
}
// Len returns the length of the connection ID in bytes
func (c ConnectionID) Len() int {
return int(c.l)
}
// Bytes returns the byte representation
func (c ConnectionID) Bytes() []byte {
return c.b[:c.l]
}
func (c ConnectionID) String() string {
if c.Len() == 0 {
return "(empty)"
}
return fmt.Sprintf("%x", c.Bytes())
}
type DefaultConnectionIDGenerator struct {
ConnLen int
}
func (d *DefaultConnectionIDGenerator) GenerateConnectionID() (ConnectionID, error) {
return GenerateConnectionID(d.ConnLen)
}
func (d *DefaultConnectionIDGenerator) ConnectionIDLen() int {
return d.ConnLen
}
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