From d5b54a1c9137ffce6852344fce8328ed5b56855f Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Tue, 7 Apr 2026 17:20:10 -0300
Subject: [PATCH] negentropy: fix varint encoding.

---
 nip77/negentropy/encoding.go            | 24 ++++++++----------------
 nip77/negentropy/negentropy.go          |  4 ++--
 nip77/negentropy/storage/accumulator.go |  7 ++++---
 3 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/nip77/negentropy/encoding.go b/nip77/negentropy/encoding.go
index c501af9..62b9059 100644
--- a/nip77/negentropy/encoding.go
+++ b/nip77/negentropy/encoding.go
@@ -66,13 +66,13 @@ func (bw *BoundWriter) WriteTimestamp(w *bytes.Buffer, timestamp nostr.Timestamp
 	bw.lastTimestampOut = timestamp
 
 	// add 1 to prevent zeroes from being read as infinites
-	WriteVarInt(w, int(delta+1))
+	WriteVarInt(w, uint64(delta)+1)
 	return
 }
 
 func (bw *BoundWriter) WriteBound(w *bytes.Buffer, bound Bound) {
 	bw.WriteTimestamp(w, bound.Timestamp)
-	WriteVarInt(w, len(bound.IDPrefix))
+	WriteVarInt(w, uint64(len(bound.IDPrefix)))
 	w.Write(bound.IDPrefix)
 }
 
@@ -111,33 +111,25 @@ func ReadVarInt(reader *bytes.Reader) (int, error) {
 	return res, nil
 }
 
-func WriteVarInt(w *bytes.Buffer, n int) {
+func WriteVarInt(w *bytes.Buffer, n uint64) {
 	if n == 0 {
 		w.WriteByte(0)
 		return
 	}
 
-	w.Write(EncodeVarInt(n))
-}
-
-func EncodeVarInt(n int) []byte {
-	if n == 0 {
-		return []byte{0}
-	}
-
-	result := make([]byte, 8)
-	idx := 7
+	var buf [10]byte
+	idx := 9
 
 	for n != 0 {
-		result[idx] = byte(n & 0x7F)
+		buf[idx] = byte(n & 0x7F)
 		n >>= 7
 		idx--
 	}
 
-	result = result[idx+1:]
+	result := buf[idx+1:]
 	for i := 0; i < len(result)-1; i++ {
 		result[i] |= 0x80
 	}
 
-	return result
+	w.Write(result)
 }
diff --git a/nip77/negentropy/negentropy.go b/nip77/negentropy/negentropy.go
index 83e07a5..58cb35e 100644
--- a/nip77/negentropy/negentropy.go
+++ b/nip77/negentropy/negentropy.go
@@ -230,7 +230,7 @@ func (n *Negentropy) reconcileAux(reader *bytes.Reader) ([]byte, error) {
 				finishSkip()
 
 				responseIds := make([]byte, 0, 32*100)
-				responses := 0
+				var responses uint64 = 0
 
 				endBound := currBound
 
@@ -284,7 +284,7 @@ func (n *Negentropy) SplitRange(lower, upper int, upperBound Bound, output *byte
 		// we just send the full ids here
 		n.WriteBound(output, upperBound)
 		output.WriteByte(byte(IdListMode))
-		WriteVarInt(output, numElems)
+		WriteVarInt(output, uint64(numElems))
 
 		for _, item := range n.storage.Range(lower, upper) {
 			output.Write(item.ID[:])
diff --git a/nip77/negentropy/storage/accumulator.go b/nip77/negentropy/storage/accumulator.go
index 9368df3..cefc207 100644
--- a/nip77/negentropy/storage/accumulator.go
+++ b/nip77/negentropy/storage/accumulator.go
@@ -1,6 +1,7 @@
 package storage
 
 import (
+	"bytes"
 	"crypto/sha256"
 	"encoding/binary"
 
@@ -41,8 +42,8 @@ func (acc *Accumulator) AddBytes(other []byte) {
 }
 
 func (acc *Accumulator) GetFingerprint(n int) [negentropy.FingerprintSize]byte {
-	input := acc.Buf[:32]
-	input = append(input, negentropy.EncodeVarInt(n)...)
-	hash := sha256.Sum256(input)
+	input := bytes.NewBuffer(acc.Buf[:32])
+	negentropy.WriteVarInt(input, uint64(n))
+	hash := sha256.Sum256(input.Bytes())
 	return [negentropy.FingerprintSize]byte(hash[:negentropy.FingerprintSize])
 }