path: root/swarm/storage/mru/update.go

// 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            // Feed 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 feed 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
}