path: root/swarm/storage/feed/feed.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 feed

import (
    "hash"
    "unsafe"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/common/hexutil"
    "github.com/dexon-foundation/dexon/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())
}