negentropy.

- a way to handle custom messages from Relay (NEG-whatever etc)
- negentropy implementation (adapted from that other one)
- nip77 nostr negentropy extension
- QueryEvents method for RelayStore that returns a channel (makes negentropy syncing work more seamlessly)

nip77/negentropy/types.go

@@ -0,0 +1,111 @@
+package negentropy
+
+import (
+	"crypto/sha256"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"strings"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+const FingerprintSize = 16
+
+type Mode int
+
+const (
+	SkipMode        = 0
+	FingerprintMode = 1
+	IdListMode      = 2
+)
+
+type Storage interface {
+	Insert(nostr.Timestamp, string) error
+	Seal()
+	Size() int
+	Iterate(begin, end int, cb func(item Item, i int) bool) error
+	FindLowerBound(begin, end int, value Bound) int
+	GetBound(idx int) Bound
+	Fingerprint(begin, end int) ([FingerprintSize]byte, error)
+}
+
+type Item struct {
+	Timestamp nostr.Timestamp
+	ID        string
+}
+
+func itemCompare(a, b Item) int {
+	if a.Timestamp != b.Timestamp {
+		return int(a.Timestamp - b.Timestamp)
+	}
+	return strings.Compare(a.ID, b.ID)
+}
+
+func (i Item) String() string { return fmt.Sprintf("Item<%d:%s>", i.Timestamp, i.ID) }
+
+type Bound struct{ Item }
+
+func (b Bound) String() string {
+	if b.Timestamp == infiniteBound.Timestamp {
+		return "Bound<infinite>"
+	}
+	return fmt.Sprintf("Bound<%d:%s>", b.Timestamp, b.ID)
+}
+
+type Accumulator struct {
+	Buf []byte
+}
+
+func (acc *Accumulator) SetToZero() {
+	acc.Buf = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+}
+
+func (acc *Accumulator) Add(id string) {
+	b, _ := hex.DecodeString(id)
+	acc.AddBytes(b)
+}
+
+func (acc *Accumulator) AddAccumulator(other Accumulator) {
+	acc.AddBytes(other.Buf)
+}
+
+func (acc *Accumulator) AddBytes(other []byte) {
+	var currCarry, nextCarry uint32
+
+	if len(acc.Buf) < 32 {
+		newBuf := make([]byte, 32)
+		copy(newBuf, acc.Buf)
+		acc.Buf = newBuf
+	}
+
+	for i := 0; i < 8; i++ {
+		offset := i * 4
+		orig := binary.LittleEndian.Uint32(acc.Buf[offset:])
+		otherV := binary.LittleEndian.Uint32(other[offset:])
+
+		next := orig + currCarry + otherV
+		if next < orig || next < otherV {
+			nextCarry = 1
+		}
+
+		binary.LittleEndian.PutUint32(acc.Buf[offset:], next&0xFFFFFFFF)
+		currCarry = nextCarry
+		nextCarry = 0
+	}
+}
+
+func (acc *Accumulator) SV() []byte {
+	return acc.Buf[:]
+}
+
+func (acc *Accumulator) GetFingerprint(n int) [FingerprintSize]byte {
+	input := acc.SV()
+	input = append(input, encodeVarInt(n)...)
+
+	hash := sha256.Sum256(input)
+
+	var fingerprint [FingerprintSize]byte
+	copy(fingerprint[:], hash[:FingerprintSize])
+	return fingerprint
+}