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// opcode represents a WebSocket opcode.
type opcode int
// List at https://tools.ietf.org/html/rfc6455#section-11.8.
const (
opContinuation opcode = iota
opText
opBinary
// 3 - 7 are reserved for further non-control frames.
_
_
_
_
_
opClose
opPing
opPong
// 11-16 are reserved for further control frames.
)
// header represents a WebSocket frame header.
// See https://tools.ietf.org/html/rfc6455#section-5.2.
type header struct {
fin bool
rsv1 bool
rsv2 bool
rsv3 bool
opcode opcode
payloadLength int64
masked bool
maskKey uint32
}
// readFrameHeader reads a header from the reader.
// See https://tools.ietf.org/html/rfc6455#section-5.2.
func readFrameHeader(r *bufio.Reader) (_ header, err error) {
defer errd.Wrap(&err, "failed to read frame header")
b, err := r.ReadByte()
if err != nil {
return header{}, err
}
var h header
h.fin = b&(1<<7) != 0
h.rsv1 = b&(1<<6) != 0
h.rsv2 = b&(1<<5) != 0
h.rsv3 = b&(1<<4) != 0
h.opcode = opcode(b & 0xf)
b, err = r.ReadByte()
if err != nil {
return header{}, err
}
h.masked = b&(1<<7) != 0
payloadLength := b &^ (1 << 7)
switch {
case payloadLength < 126:
h.payloadLength = int64(payloadLength)
case payloadLength == 126:
var pl uint16
err = binary.Read(r, binary.BigEndian, &pl)
h.payloadLength = int64(pl)
case payloadLength == 127:
err = binary.Read(r, binary.BigEndian, &h.payloadLength)
}
if err != nil {
return header{}, err
}
if h.masked {
err = binary.Read(r, binary.LittleEndian, &h.maskKey)
if err != nil {
return header{}, err
}
}
return h, nil
}
// maxControlPayload is the maximum length of a control frame payload.
// See https://tools.ietf.org/html/rfc6455#section-5.5.
const maxControlPayload = 125
// writeFrameHeader writes the bytes of the header to w.
// See https://tools.ietf.org/html/rfc6455#section-5.2
func writeFrameHeader(h header, w *bufio.Writer) (err error) {
defer errd.Wrap(&err, "failed to write frame header")
var b byte
if h.fin {
b |= 1 << 7
}
if h.rsv1 {
b |= 1 << 6
}
if h.rsv2 {
b |= 1 << 5
}
if h.rsv3 {
b |= 1 << 4
}
b |= byte(h.opcode)
err = w.WriteByte(b)
if err != nil {
return err
}
lengthByte := byte(0)
if h.masked {
lengthByte |= 1 << 7
}
switch {
case h.payloadLength > math.MaxUint16:
lengthByte |= 127
case h.payloadLength > 125:
lengthByte |= 126
case h.payloadLength >= 0:
lengthByte |= byte(h.payloadLength)
}
err = w.WriteByte(lengthByte)
if err != nil {
return err
}
switch {
case h.payloadLength > math.MaxUint16:
err = binary.Write(w, binary.BigEndian, h.payloadLength)
case h.payloadLength > 125:
err = binary.Write(w, binary.BigEndian, uint16(h.payloadLength))
}
if err != nil {
return err
}
if h.masked {
err = binary.Write(w, binary.LittleEndian, h.maskKey)
if err != nil {
return err
}
}
return nil
}
// mask applies the WebSocket masking algorithm to p
// with the given key.
// See https://tools.ietf.org/html/rfc6455#section-5.3
//
// The returned value is the correctly rotated key to
// to continue to mask/unmask the message.
//
// It is optimized for LittleEndian and expects the key
// to be in little endian.
//
// See https://github.com/golang/go/issues/31586
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if len(b) >= 8 {
key64 := uint64(key)<<32 | uint64(key)
// At some point in the future we can clean these unrolled loops up.
// See https://github.com/golang/go/issues/31586#issuecomment-487436401
// Then we xor until b is less than 128 bytes.
for len(b) >= 128 {
v := binary.LittleEndian.Uint64(b)
binary.LittleEndian.PutUint64(b, v^key64)
v = binary.LittleEndian.Uint64(b[8:16])
binary.LittleEndian.PutUint64(b[8:16], v^key64)
v = binary.LittleEndian.Uint64(b[16:24])
binary.LittleEndian.PutUint64(b[16:24], v^key64)
v = binary.LittleEndian.Uint64(b[24:32])
binary.LittleEndian.PutUint64(b[24:32], v^key64)
v = binary.LittleEndian.Uint64(b[32:40])
binary.LittleEndian.PutUint64(b[32:40], v^key64)
v = binary.LittleEndian.Uint64(b[40:48])
binary.LittleEndian.PutUint64(b[40:48], v^key64)
v = binary.LittleEndian.Uint64(b[48:56])
binary.LittleEndian.PutUint64(b[48:56], v^key64)
v = binary.LittleEndian.Uint64(b[56:64])
binary.LittleEndian.PutUint64(b[56:64], v^key64)
v = binary.LittleEndian.Uint64(b[64:72])
binary.LittleEndian.PutUint64(b[64:72], v^key64)
v = binary.LittleEndian.Uint64(b[72:80])
binary.LittleEndian.PutUint64(b[72:80], v^key64)
v = binary.LittleEndian.Uint64(b[80:88])
binary.LittleEndian.PutUint64(b[80:88], v^key64)
v = binary.LittleEndian.Uint64(b[88:96])
binary.LittleEndian.PutUint64(b[88:96], v^key64)
v = binary.LittleEndian.Uint64(b[96:104])
binary.LittleEndian.PutUint64(b[96:104], v^key64)
v = binary.LittleEndian.Uint64(b[104:112])
binary.LittleEndian.PutUint64(b[104:112], v^key64)
v = binary.LittleEndian.Uint64(b[112:120])
binary.LittleEndian.PutUint64(b[112:120], v^key64)
v = binary.LittleEndian.Uint64(b[120:128])
binary.LittleEndian.PutUint64(b[120:128], v^key64)
b = b[128:]
}
// Then we xor until b is less than 64 bytes.
for len(b) >= 64 {
v := binary.LittleEndian.Uint64(b)
binary.LittleEndian.PutUint64(b, v^key64)
v = binary.LittleEndian.Uint64(b[8:16])
binary.LittleEndian.PutUint64(b[8:16], v^key64)
v = binary.LittleEndian.Uint64(b[16:24])
binary.LittleEndian.PutUint64(b[16:24], v^key64)
v = binary.LittleEndian.Uint64(b[24:32])
binary.LittleEndian.PutUint64(b[24:32], v^key64)
v = binary.LittleEndian.Uint64(b[32:40])
binary.LittleEndian.PutUint64(b[32:40], v^key64)
v = binary.LittleEndian.Uint64(b[40:48])
binary.LittleEndian.PutUint64(b[40:48], v^key64)
v = binary.LittleEndian.Uint64(b[48:56])
binary.LittleEndian.PutUint64(b[48:56], v^key64)
v = binary.LittleEndian.Uint64(b[56:64])
binary.LittleEndian.PutUint64(b[56:64], v^key64)
b = b[64:]
}
// Then we xor until b is less than 32 bytes.
for len(b) >= 32 {
v := binary.LittleEndian.Uint64(b)
binary.LittleEndian.PutUint64(b, v^key64)
v = binary.LittleEndian.Uint64(b[8:16])
binary.LittleEndian.PutUint64(b[8:16], v^key64)
v = binary.LittleEndian.Uint64(b[16:24])
binary.LittleEndian.PutUint64(b[16:24], v^key64)
v = binary.LittleEndian.Uint64(b[24:32])
binary.LittleEndian.PutUint64(b[24:32], v^key64)
b = b[32:]
}
// Then we xor until b is less than 16 bytes.
for len(b) >= 16 {
v := binary.LittleEndian.Uint64(b)
binary.LittleEndian.PutUint64(b, v^key64)
v = binary.LittleEndian.Uint64(b[8:16])
binary.LittleEndian.PutUint64(b[8:16], v^key64)
b = b[16:]
}
// Then we xor until b is less than 8 bytes.
for len(b) >= 8 {
v := binary.LittleEndian.Uint64(b)
binary.LittleEndian.PutUint64(b, v^key64)
b = b[8:]
}
}
// Then we xor until b is less than 4 bytes.
for len(b) >= 4 {
v := binary.LittleEndian.Uint32(b)
binary.LittleEndian.PutUint32(b, v^key)
b = b[4:]
}
// xor remaining bytes.
for i := range b {
b[i] ^= byte(key)
key = bits.RotateLeft32(key, -8)
}
return key
}