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