106 lines
3.2 KiB
Go
106 lines
3.2 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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"bytes"
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"encoding/json"
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"fmt"
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"github.com/ethereum/go-ethereum/common/bitutil"
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"github.com/ethereum/go-ethereum/common/hexutil"
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"github.com/ethersphere/swarm/storage"
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)
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// TopicLength establishes the max length of a topic string
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const TopicLength = storage.AddressLength
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// Topic represents what a feed is about
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type Topic [TopicLength]byte
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// ErrTopicTooLong is returned when creating a topic with a name/related content too long
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var ErrTopicTooLong = fmt.Errorf("Topic is too long. Max length is %d", TopicLength)
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// NewTopic creates a new topic from a provided name and "related content" byte array,
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// merging the two together.
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// If relatedContent or name are longer than TopicLength, they will be truncated and an error returned
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// name can be an empty string
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// relatedContent can be nil
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func NewTopic(name string, relatedContent []byte) (topic Topic, err error) {
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if relatedContent != nil {
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contentLength := len(relatedContent)
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if contentLength > TopicLength {
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contentLength = TopicLength
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err = ErrTopicTooLong
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}
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copy(topic[:], relatedContent[:contentLength])
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}
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nameBytes := []byte(name)
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nameLength := len(nameBytes)
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if nameLength > TopicLength {
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nameLength = TopicLength
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err = ErrTopicTooLong
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}
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bitutil.XORBytes(topic[:], topic[:], nameBytes[:nameLength])
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return topic, err
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}
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// Hex will return the topic encoded as an hex string
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func (t *Topic) Hex() string {
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return hexutil.Encode(t[:])
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}
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// FromHex will parse a hex string into this Topic instance
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func (t *Topic) FromHex(hex string) error {
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bytes, err := hexutil.Decode(hex)
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if err != nil || len(bytes) != len(t) {
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return NewErrorf(ErrInvalidValue, "Cannot decode topic")
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}
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copy(t[:], bytes)
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return nil
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}
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// Name will try to extract the topic name out of the Topic
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func (t *Topic) Name(relatedContent []byte) string {
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nameBytes := *t
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if relatedContent != nil {
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contentLength := len(relatedContent)
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if contentLength > TopicLength {
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contentLength = TopicLength
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}
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bitutil.XORBytes(nameBytes[:], t[:], relatedContent[:contentLength])
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}
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z := bytes.IndexByte(nameBytes[:], 0)
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if z < 0 {
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z = TopicLength
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}
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return string(nameBytes[:z])
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}
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// UnmarshalJSON implements the json.Unmarshaller interface
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func (t *Topic) UnmarshalJSON(data []byte) error {
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var hex string
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json.Unmarshal(data, &hex)
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return t.FromHex(hex)
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}
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// MarshalJSON implements the json.Marshaller interface
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func (t *Topic) MarshalJSON() ([]byte, error) {
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return json.Marshal(t.Hex())
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}
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