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topic.go
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topic.go
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// Copyright 2019 The Waku Library Authors.
//
// The Waku 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 Waku library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty off
// 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 Waku library. If not, see <http://www.gnu.org/licenses/>.
//
// This software uses the go-ethereum library, which is licensed
// under the GNU Lesser General Public Library, version 3 or any later.
package common
import (
"github.com/ethereum/go-ethereum/common/hexutil"
)
// TopicType represents a cryptographically secure, probabilistic partial
// classifications of a message, determined as the first (leftmost) 4 bytes of the
// SHA3 hash of some arbitrary data given by the original author of the message.
type TopicType [TopicLength]byte
// BytesToTopic converts from the byte array representation of a topic
// into the TopicType type.
func BytesToTopic(b []byte) (t TopicType) {
sz := TopicLength
if x := len(b); x < TopicLength {
sz = x
}
for i := 0; i < sz; i++ {
t[i] = b[i]
}
return t
}
// String converts a topic byte array to a string representation.
func (t *TopicType) String() string {
return hexutil.Encode(t[:])
}
// MarshalText returns the hex representation of t.
func (t TopicType) MarshalText() ([]byte, error) {
return hexutil.Bytes(t[:]).MarshalText()
}
// UnmarshalText parses a hex representation to a topic.
func (t *TopicType) UnmarshalText(input []byte) error {
return hexutil.UnmarshalFixedText("Topic", input, t[:])
}
// ToBloom converts the topic (4 bytes) to the bloom filter (64 bytes)
func (t TopicType) ToBloom() []byte {
b := make([]byte, BloomFilterSize)
var index [3]int
for j := 0; j < 3; j++ {
index[j] = int(t[j])
if (t[3] & (1 << uint(j))) != 0 {
index[j] += 256
}
}
for j := 0; j < 3; j++ {
byteIndex := index[j] / 8
bitIndex := index[j] % 8
b[byteIndex] = 1 << uint(bitIndex)
}
return b
}