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package smux
import (
"encoding/binary"
"fmt"
)
const ( // cmds
// protocol version 1:
cmdSYN byte = iota // stream open
cmdFIN // stream close, a.k.a EOF mark
cmdPSH // data push
cmdNOP // no operation
// protocol version 2 extra commands
// notify bytes consumed by remote peer-end
cmdUPD
)
const (
// data size of cmdUPD, format:
// |4B data consumed(ACK)| 4B window size(WINDOW) |
szCmdUPD = 8
)
const (
// initial peer window guess, a slow-start
initialPeerWindow = 262144
)
const (
sizeOfVer = 1
sizeOfCmd = 1
sizeOfLength = 2
sizeOfSid = 4
headerSize = sizeOfVer + sizeOfCmd + sizeOfSid + sizeOfLength
)
// Frame defines a packet from or to be multiplexed into a single connection
type Frame struct {
ver byte
cmd byte
sid uint32
data []byte
}
func newFrame(version byte, cmd byte, sid uint32) Frame {
return Frame{ver: version, cmd: cmd, sid: sid}
}
type rawHeader [headerSize]byte
func (h rawHeader) Version() byte {
return h[0]
}
func (h rawHeader) Cmd() byte {
return h[1]
}
func (h rawHeader) Length() uint16 {
return binary.LittleEndian.Uint16(h[2:])
}
func (h rawHeader) StreamID() uint32 {
return binary.LittleEndian.Uint32(h[4:])
}
func (h rawHeader) String() string {
return fmt.Sprintf("Version:%d Cmd:%d StreamID:%d Length:%d",
h.Version(), h.Cmd(), h.StreamID(), h.Length())
}
type updHeader [szCmdUPD]byte
func (h updHeader) Consumed() uint32 {
return binary.LittleEndian.Uint32(h[:])
}
func (h updHeader) Window() uint32 {
return binary.LittleEndian.Uint32(h[4:])
}
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