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