87 lines
2.1 KiB
Go
87 lines
2.1 KiB
Go
package types
|
|
|
|
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
|
|
}
|