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wire.go
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wire.go
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// copied from github.com/quic-go/quic-go
package util
import (
"bytes"
"fmt"
"io"
)
// taken from the QUIC draft
const (
// Min is the minimum value allowed for a QUIC varint.
Min = 0
// Max is the maximum allowed value for a QUIC varint (2^62-1).
Max = maxVarInt8
maxVarInt1 = 63
maxVarInt2 = 16383
maxVarInt4 = 1073741823
maxVarInt8 = 4611686018427387903
)
// Reader implements both the io.ByteReader and io.Reader interfaces.
type Reader interface {
io.ByteReader
io.Reader
}
type byteReader struct {
io.Reader
}
var _ Reader = &byteReader{}
// NewReader returns a Reader for r.
// If r already implements both io.ByteReader and io.Reader, NewReader returns r.
// Otherwise, r is wrapped to add the missing interfaces.
func NewReader(r io.Reader) Reader {
if r, ok := r.(Reader); ok {
return r
}
return &byteReader{r}
}
func (r *byteReader) ReadByte() (byte, error) {
var b [1]byte
n, err := r.Reader.Read(b[:])
if n == 1 && err == io.EOF {
err = nil
}
return b[0], err
}
// Writer implements both the io.ByteWriter and io.Writer interfaces.
type Writer interface {
io.ByteWriter
io.Writer
}
var _ Writer = &bytes.Buffer{}
type byteWriter struct {
io.Writer
}
var _ Writer = &byteWriter{}
// NewWriter returns a Writer for w.
// If r already implements both io.ByteWriter and io.Writer, NewWriter returns w.
// Otherwise, w is wrapped to add the missing interfaces.
func NewWriter(w io.Writer) Writer {
if w, ok := w.(Writer); ok {
return w
}
return &byteWriter{w}
}
func (w *byteWriter) WriteByte(c byte) error {
_, err := w.Writer.Write([]byte{c})
return err
}
// ReadVarInt reads a number in the QUIC varint format from r.
func ReadVarInt(r Reader) (uint64, error) {
firstByte, err := r.ReadByte()
if err != nil {
return 0, err
}
// the first two bits of the first byte encode the length
len := 1 << ((firstByte & 0xc0) >> 6)
b1 := firstByte & (0xff - 0xc0)
if len == 1 {
return uint64(b1), nil
}
b2, err := r.ReadByte()
if err != nil {
return 0, err
}
if len == 2 {
return uint64(b2) + uint64(b1)<<8, nil
}
b3, err := r.ReadByte()
if err != nil {
return 0, err
}
b4, err := r.ReadByte()
if err != nil {
return 0, err
}
if len == 4 {
return uint64(b4) + uint64(b3)<<8 + uint64(b2)<<16 + uint64(b1)<<24, nil
}
b5, err := r.ReadByte()
if err != nil {
return 0, err
}
b6, err := r.ReadByte()
if err != nil {
return 0, err
}
b7, err := r.ReadByte()
if err != nil {
return 0, err
}
b8, err := r.ReadByte()
if err != nil {
return 0, err
}
return uint64(b8) + uint64(b7)<<8 + uint64(b6)<<16 + uint64(b5)<<24 + uint64(b4)<<32 + uint64(b3)<<40 + uint64(b2)<<48 + uint64(b1)<<56, nil
}
// AppendVarInt appends i in the QUIC varint format.
func AppendVarInt(b []byte, i uint64) []byte {
if i <= maxVarInt1 {
return append(b, uint8(i))
}
if i <= maxVarInt2 {
return append(b, []byte{uint8(i>>8) | 0x40, uint8(i)}...)
}
if i <= maxVarInt4 {
return append(b, []byte{uint8(i>>24) | 0x80, uint8(i >> 16), uint8(i >> 8), uint8(i)}...)
}
if i <= maxVarInt8 {
return append(b, []byte{
uint8(i>>56) | 0xc0, uint8(i >> 48), uint8(i >> 40), uint8(i >> 32),
uint8(i >> 24), uint8(i >> 16), uint8(i >> 8), uint8(i),
}...)
}
panic(fmt.Sprintf("%#x doesn't fit into 62 bits", i))
}
// AppendVarIntWithLen append i in the QUIC varint format with the desired length.
func AppendVarIntWithLen(b []byte, i uint64, length uint64) []byte {
if length != 1 && length != 2 && length != 4 && length != 8 {
panic("invalid varint length")
}
l := VarIntLen(i)
if l == length {
return AppendVarInt(b, i)
}
if l > length {
panic(fmt.Sprintf("cannot encode %d in %d bytes", i, length))
}
if length == 2 {
b = append(b, 0b01000000)
} else if length == 4 {
b = append(b, 0b10000000)
} else if length == 8 {
b = append(b, 0b11000000)
}
for j := uint64(1); j < length-l; j++ {
b = append(b, 0)
}
for j := uint64(0); j < l; j++ {
b = append(b, uint8(i>>(8*(l-1-j))))
}
return b
}
// VarIntLen determines the number of bytes that will be needed to write the number i.
func VarIntLen(i uint64) uint64 {
if i <= maxVarInt1 {
return 1
}
if i <= maxVarInt2 {
return 2
}
if i <= maxVarInt4 {
return 4
}
if i <= maxVarInt8 {
return 8
}
// Don't use a fmt.Sprintf here to format the error message.
// The function would then exceed the inlining budget.
panic(struct {
message string
num uint64
}{"value doesn't fit into 62 bits: ", i})
}
func ParseSSHString(buf Reader) (string, error) {
length, err := ReadVarInt(buf)
if err != nil {
return "", InvalidSSHString{err}
}
out := make([]byte, length)
n, err := io.ReadFull(buf, out)
if n != int(length) {
return "", InvalidSSHString{fmt.Errorf("expected length %d, read length %d", length, n)}
}
if err != nil && err != io.EOF {
return "", err
}
return string(out[:n]), err
}
func WriteSSHString(out []byte, s string) (int, error) {
if uint64(len(out)) < uint64(SSHStringLen(s)) {
return 0, fmt.Errorf("buffer too small to write varint: %d < %d", len(out), SSHStringLen(s))
}
buf := AppendVarInt(nil, uint64(len(s)))
copied := copy(out, buf)
copied += copy(out[copied:], s)
return copied, nil
}
func SSHStringLen(s string) int {
return int(VarIntLen(uint64(len(s)))) + len(s)
}
func MinUint64(a uint64, b uint64) uint64 {
if a <= b {
return a
}
return b
}