chore(op): add uint64 converter to block-number

Author: ezdac

rolling-shutter/medley/encodeable/number/block.go

@@ -2,6 +2,7 @@ package number
 
 import (
 	"bytes"
+	"errors"
 	"math/big"
 )
 
@@ -11,6 +12,8 @@ var (
 	LatestStr            = []byte("latest")
 )
 
+var ErrLatestBlockToUint = errors.New("'latest' block can't be converted to uint64")
+
 func BigToBlockNumber(i *big.Int) *BlockNumber {
 	return &BlockNumber{
 		Int: i,
@@ -46,6 +49,14 @@ func (k *BlockNumber) IsLatest() bool {
 	return k.Equal(LatestBlock)
 }
 
+func (k *BlockNumber) ToUInt64() (uint64, error) {
+	p := k.ToUInt64Ptr()
+	if p == nil {
+		return 0, ErrLatestBlockToUint
+	}
+	return *p, nil
+}
+
 func (k *BlockNumber) ToUInt64Ptr() *uint64 {
 	if k.IsLatest() {
 		return nil