100 lines
2.3 KiB
Go
100 lines
2.3 KiB
Go
package types
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import (
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"github.com/ethereum/go-ethereum/common/hexutil"
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)
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const (
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// TopicLength is the expected length of the topic, in bytes
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TopicLength = 4
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// BloomFilterSize is the expected length of a bloom filter byte array, in bytes
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BloomFilterSize = 64
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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 EncodeHex(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 HexBytes(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 UnmarshalFixedText("Topic", input, t[:])
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}
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// TopicToBloom converts the topic (4 bytes) to the bloom filter (64 bytes)
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func TopicToBloom(topic TopicType) []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(topic[j])
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if (topic[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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// BloomFilterMatch returns true if a sample matches a bloom filter
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func BloomFilterMatch(filter, sample []byte) bool {
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if filter == nil {
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return true
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}
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for i := 0; i < BloomFilterSize; i++ {
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f := filter[i]
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s := sample[i]
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if (f | s) != f {
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return false
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}
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}
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return true
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}
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// MakeFullNodeBloom returns a bloom filter which matches all topics
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func MakeFullNodeBloom() []byte {
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bloom := make([]byte, BloomFilterSize)
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for i := 0; i < BloomFilterSize; i++ {
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bloom[i] = 0xFF
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}
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return bloom
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}
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func StringToTopic(s string) (t TopicType) {
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str, _ := hexutil.Decode(s)
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return BytesToTopic(str)
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}
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func TopicTypeToByteArray(t TopicType) []byte {
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return t[:4]
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}
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