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header.go
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/
header.go
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// Copyright (C) 2014 The Syncthing Authors.
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along
// with this program. If not, see <http://www.gnu.org/licenses/>.
package protocol
import "github.com/calmh/xdr"
type header struct {
version int
msgID int
msgType int
compression bool
}
func (h header) encodeXDR(xw *xdr.Writer) (int, error) {
u := encodeHeader(h)
return xw.WriteUint32(u)
}
func (h *header) decodeXDR(xr *xdr.Reader) error {
u := xr.ReadUint32()
*h = decodeHeader(u)
return xr.Error()
}
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,
}
}