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// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package mru
import (
"fmt"
"strconv"
"github.com/ethereum/go-ethereum/swarm/chunk"
)
// ProtocolVersion defines the current version of the protocol that will be included in each update message
const ProtocolVersion uint8 = 0
const headerLength = 8
// Header defines a update message header including a protocol version byte
type Header struct {
Version uint8 // Protocol version
Padding [headerLength - 1]uint8 // reserved for future use
}
// Update encapsulates the information sent as part of a feed update
type Update struct {
Header Header //
ID // Resource update identifying information
data []byte // actual data payload
}
const minimumUpdateDataLength = idLength + headerLength + 1
const maxUpdateDataLength = chunk.DefaultSize - signatureLength - idLength - headerLength
// binaryPut serializes the feed update information into the given slice
func (r *Update) binaryPut(serializedData []byte) error {
datalength := len(r.data)
if datalength == 0 {
return NewError(ErrInvalidValue, "a feed update must contain data")
}
if datalength > maxUpdateDataLength {
return NewErrorf(ErrInvalidValue, "feed update data is too big (length=%d). Max length=%d", datalength, maxUpdateDataLength)
}
if len(serializedData) != r.binaryLength() {
return NewErrorf(ErrInvalidValue, "slice passed to putBinary must be of exact size. Expected %d bytes", r.binaryLength())
}
var cursor int
// serialize Header
serializedData[cursor] = r.Header.Version
copy(serializedData[cursor+1:headerLength], r.Header.Padding[:headerLength-1])
cursor += headerLength
// serialize ID
if err := r.ID.binaryPut(serializedData[cursor : cursor+idLength]); err != nil {
return err
}
cursor += idLength
// add the data
copy(serializedData[cursor:], r.data)
cursor += datalength
return nil
}
// binaryLength returns the expected number of bytes this structure will take to encode
func (r *Update) binaryLength() int {
return idLength + headerLength + len(r.data)
}
// binaryGet populates this instance from the information contained in the passed byte slice
func (r *Update) binaryGet(serializedData []byte) error {
if len(serializedData) < minimumUpdateDataLength {
return NewErrorf(ErrNothingToReturn, "chunk less than %d bytes cannot be a resource update chunk", minimumUpdateDataLength)
}
dataLength := len(serializedData) - idLength - headerLength
// at this point we can be satisfied that we have the correct data length to read
var cursor int
// deserialize Header
r.Header.Version = serializedData[cursor] // extract the protocol version
copy(r.Header.Padding[:headerLength-1], serializedData[cursor+1:headerLength]) // extract the padding
cursor += headerLength
if err := r.ID.binaryGet(serializedData[cursor : cursor+idLength]); err != nil {
return err
}
cursor += idLength
data := serializedData[cursor : cursor+dataLength]
cursor += dataLength
// now that all checks have passed, copy data into structure
r.data = make([]byte, dataLength)
copy(r.data, data)
return nil
}
// FromValues deserializes this instance from a string key-value store
// useful to parse query strings
func (r *Update) FromValues(values Values, data []byte) error {
r.data = data
version, _ := strconv.ParseUint(values.Get("protocolVersion"), 10, 32)
r.Header.Version = uint8(version)
return r.ID.FromValues(values)
}
// AppendValues serializes this structure into the provided string key-value store
// useful to build query strings
func (r *Update) AppendValues(values Values) []byte {
r.ID.AppendValues(values)
values.Set("protocolVersion", fmt.Sprintf("%d", r.Header.Version))
return r.data
}
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