syncthing/lib/protocol/header.go

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// Copyright (C) 2014 The Protocol Authors.
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package protocol
import "github.com/calmh/xdr"
type header struct {
version int
msgID int
msgType int
compression bool
}
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func (h header) MarshalXDRInto(m *xdr.Marshaller) error {
v := encodeHeader(h)
m.MarshalUint32(v)
return m.Error
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}
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func (h *header) UnmarshalXDRFrom(u *xdr.Unmarshaller) error {
v := u.UnmarshalUint32()
*h = decodeHeader(v)
return u.Error
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}
func encodeHeader(h header) uint32 {
var isComp uint32
if h.compression {
isComp = 1 << 0 // the zeroth bit is the compression bit
}
return uint32(h.version&0xf)<<28 +
uint32(h.msgID&0xfff)<<16 +
uint32(h.msgType&0xff)<<8 +
isComp
}
func decodeHeader(u uint32) header {
return header{
version: int(u>>28) & 0xf,
msgID: int(u>>16) & 0xfff,
msgType: int(u>>8) & 0xff,
compression: u&1 == 1,
}
}