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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 (
"encoding/binary"
"errors"
"github.com/ethereum/go-ethereum/swarm/log"
"github.com/ethereum/go-ethereum/swarm/multihash"
)
// resourceUpdate encapsulates the information sent as part of a resource update
type resourceUpdate struct {
updateHeader // metainformationa about this resource update
data []byte // actual data payload
}
// Update chunk layout
// Prefix:
// 2 bytes updateHeaderLength
// 2 bytes data length
const chunkPrefixLength = 2 + 2
// Header: (see updateHeader)
// Data:
// data (datalength bytes)
//
// Minimum size is Header + 1 (minimum data length, enforced)
const minimumUpdateDataLength = updateHeaderLength + 1
const maxUpdateDataLength = chunkSize - signatureLength - updateHeaderLength - chunkPrefixLength
// binaryPut serializes the resource update information into the given slice
func (r *resourceUpdate) binaryPut(serializedData []byte) error {
datalength := len(r.data)
if datalength == 0 {
return NewError(ErrInvalidValue, "cannot update a resource with no data")
}
if datalength > maxUpdateDataLength {
return NewErrorf(ErrInvalidValue, "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())
}
if r.multihash {
if _, _, err := multihash.GetMultihashLength(r.data); err != nil {
return NewError(ErrInvalidValue, "Invalid multihash")
}
}
// Add prefix: updateHeaderLength and actual data length
cursor := 0
binary.LittleEndian.PutUint16(serializedData[cursor:], uint16(updateHeaderLength))
cursor += 2
// data length
binary.LittleEndian.PutUint16(serializedData[cursor:], uint16(datalength))
cursor += 2
// serialize header (see updateHeader)
if err := r.updateHeader.binaryPut(serializedData[cursor : cursor+updateHeaderLength]); err != nil {
return err
}
cursor += updateHeaderLength
// 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 *resourceUpdate) binaryLength() int {
return chunkPrefixLength + updateHeaderLength + len(r.data)
}
// binaryGet populates this instance from the information contained in the passed byte slice
func (r *resourceUpdate) binaryGet(serializedData []byte) error {
if len(serializedData) < minimumUpdateDataLength {
return NewErrorf(ErrNothingToReturn, "chunk less than %d bytes cannot be a resource update chunk", minimumUpdateDataLength)
}
cursor := 0
declaredHeaderlength := binary.LittleEndian.Uint16(serializedData[cursor : cursor+2])
if declaredHeaderlength != updateHeaderLength {
return NewErrorf(ErrCorruptData, "Invalid header length. Expected %d, got %d", updateHeaderLength, declaredHeaderlength)
}
cursor += 2
datalength := int(binary.LittleEndian.Uint16(serializedData[cursor : cursor+2]))
cursor += 2
if chunkPrefixLength+updateHeaderLength+datalength+signatureLength != len(serializedData) {
return NewError(ErrNothingToReturn, "length specified in header is different than actual chunk size")
}
// at this point we can be satisfied that we have the correct data length to read
if err := r.updateHeader.binaryGet(serializedData[cursor : cursor+updateHeaderLength]); err != nil {
return err
}
cursor += updateHeaderLength
data := serializedData[cursor : cursor+datalength]
cursor += datalength
// if multihash content is indicated we check the validity of the multihash
if r.updateHeader.multihash {
mhLength, mhHeaderLength, err := multihash.GetMultihashLength(data)
if err != nil {
log.Error("multihash parse error", "err", err)
return err
}
if datalength != mhLength+mhHeaderLength {
log.Debug("multihash error", "datalength", datalength, "mhLength", mhLength, "mhHeaderLength", mhHeaderLength)
return errors.New("Corrupt multihash data")
}
}
// now that all checks have passed, copy data into structure
r.data = make([]byte, datalength)
copy(r.data, data)
return nil
}
// Multihash specifies whether the resource data should be interpreted as multihash
func (r *resourceUpdate) Multihash() bool {
return r.multihash
}
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