package types import ( "github.com/ethereum/go-ethereum/common/hexutil" ) const ( // TopicLength is the expected length of the topic, in bytes TopicLength = 4 // BloomFilterSize is the expected length of a bloom filter byte array, in bytes BloomFilterSize = 64 ) // TopicType represents a cryptographically secure, probabilistic partial // classifications of a message, determined as the first (left) 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 EncodeHex(t[:]) } // MarshalText returns the hex representation of t. func (t TopicType) MarshalText() ([]byte, error) { return HexBytes(t[:]).MarshalText() } // UnmarshalText parses a hex representation to a topic. func (t *TopicType) UnmarshalText(input []byte) error { return UnmarshalFixedText("Topic", input, t[:]) } // TopicToBloom converts the topic (4 bytes) to the bloom filter (64 bytes) func TopicToBloom(topic TopicType) []byte { b := make([]byte, BloomFilterSize) var index [3]int for j := 0; j < 3; j++ { index[j] = int(topic[j]) if (topic[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 } // BloomFilterMatch returns true if a sample matches a bloom filter func BloomFilterMatch(filter, sample []byte) bool { if filter == nil { return true } for i := 0; i < BloomFilterSize; i++ { f := filter[i] s := sample[i] if (f | s) != f { return false } } return true } // MakeFullNodeBloom returns a bloom filter which matches all topics func MakeFullNodeBloom() []byte { bloom := make([]byte, BloomFilterSize) for i := 0; i < BloomFilterSize; i++ { bloom[i] = 0xFF } return bloom } func StringToTopic(s string) (t TopicType) { str, _ := hexutil.Decode(s) return BytesToTopic(str) } func TopicTypeToByteArray(t TopicType) []byte { topic := make([]byte, 4) for i, b := range t { topic[i] = b } return topic }