triedb/pathdb: simplify finish function in block writer

triedb/pathdb/history_index_block.go

@@ -380,25 +380,10 @@ func (b *blockWriter) full() bool {
 //
 // This function is safe to be called multiple times.
 func (b *blockWriter) finish() []byte {
-	var (
+	buf := make([]byte, len(b.restarts)*2+1)
-		restartsLen = len(b.restarts)
-		restartsOff = len(b.data)
-		extra       = restartsLen*2 + 1
-		buf         []byte
-	)
-
-	if cap(b.data)-len(b.data) >= extra {
-		// Enough capacity, just reslice; data is already in place.
-		buf = b.data[:len(b.data)+extra]
-	} else {
-		// Not enough capacity, allocate and copy.
-		buf = make([]byte, len(b.data)+extra)
-		copy(buf, b.data)
-	}
-
 	for i, restart := range b.restarts {
-		binary.BigEndian.PutUint16(buf[restartsOff+2*i:], restart)
+		binary.BigEndian.PutUint16(buf[2*i:], restart)
 	}
-	buf[len(buf)-1] = byte(restartsLen)
+	buf[len(buf)-1] = byte(len(b.restarts))
-	return buf
+	return append(b.data, buf...)
 }