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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 feed
import (
"hash"
"unsafe"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/swarm/storage"
)
// Feed represents a particular user's stream of updates on a topic
type Feed struct {
Topic Topic `json:"topic"`
User common.Address `json:"user"`
}
// Feed layout:
// TopicLength bytes
// userAddr common.AddressLength bytes
const feedLength = TopicLength + common.AddressLength
// mapKey calculates a unique id for this feed. Used by the cache map in `Handler`
func (f *Feed) mapKey() uint64 {
serializedData := make([]byte, feedLength)
f.binaryPut(serializedData)
hasher := hashPool.Get().(hash.Hash)
defer hashPool.Put(hasher)
hasher.Reset()
hasher.Write(serializedData)
hash := hasher.Sum(nil)
return *(*uint64)(unsafe.Pointer(&hash[0]))
}
// binaryPut serializes this feed instance into the provided slice
func (f *Feed) binaryPut(serializedData []byte) error {
if len(serializedData) != feedLength {
return NewErrorf(ErrInvalidValue, "Incorrect slice size to serialize feed. Expected %d, got %d", feedLength, len(serializedData))
}
var cursor int
copy(serializedData[cursor:cursor+TopicLength], f.Topic[:TopicLength])
cursor += TopicLength
copy(serializedData[cursor:cursor+common.AddressLength], f.User[:])
cursor += common.AddressLength
return nil
}
// binaryLength returns the expected size of this structure when serialized
func (f *Feed) binaryLength() int {
return feedLength
}
// binaryGet restores the current instance from the information contained in the passed slice
func (f *Feed) binaryGet(serializedData []byte) error {
if len(serializedData) != feedLength {
return NewErrorf(ErrInvalidValue, "Incorrect slice size to read feed. Expected %d, got %d", feedLength, len(serializedData))
}
var cursor int
copy(f.Topic[:], serializedData[cursor:cursor+TopicLength])
cursor += TopicLength
copy(f.User[:], serializedData[cursor:cursor+common.AddressLength])
cursor += common.AddressLength
return nil
}
// Hex serializes the feed to a hex string
func (f *Feed) Hex() string {
serializedData := make([]byte, feedLength)
f.binaryPut(serializedData)
return hexutil.Encode(serializedData)
}
// FromValues deserializes this instance from a string key-value store
// useful to parse query strings
func (f *Feed) FromValues(values Values) (err error) {
topic := values.Get("topic")
if topic != "" {
if err := f.Topic.FromHex(values.Get("topic")); err != nil {
return err
}
} else { // see if the user set name and relatedcontent
name := values.Get("name")
relatedContent, _ := hexutil.Decode(values.Get("relatedcontent"))
if len(relatedContent) > 0 {
if len(relatedContent) < storage.AddressLength {
return NewErrorf(ErrInvalidValue, "relatedcontent field must be a hex-encoded byte array exactly %d bytes long", storage.AddressLength)
}
relatedContent = relatedContent[:storage.AddressLength]
}
f.Topic, err = NewTopic(name, relatedContent)
if err != nil {
return err
}
}
f.User = common.HexToAddress(values.Get("user"))
return nil
}
// AppendValues serializes this structure into the provided string key-value store
// useful to build query strings
func (f *Feed) AppendValues(values Values) {
values.Set("topic", f.Topic.Hex())
values.Set("user", f.User.Hex())
}
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