added {Address,Hash}.IsZero()

common/types.go

@@ -50,6 +50,9 @@ var (
 
 	// MaxHash represents the maximum possible hash value.
 	MaxHash = HexToHash("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
+
+	addr0 Address // zero Address
+	hash0 Hash    // zero Hash
 )
 
 // Hash represents the 32 byte Keccak256 hash of arbitrary data.
@@ -194,6 +197,11 @@ func (h *Hash) UnmarshalGraphQL(input interface{}) error {
 	return err
 }
 
+// IsZero returns true for the zero hash.
+func (h Hash) IsZero() bool {
+	return h == hash0
+}
+
 // UnprefixedHash allows marshaling a Hash without 0x prefix.
 type UnprefixedHash Hash
 
@@ -371,6 +379,11 @@ func (a *Address) UnmarshalGraphQL(input interface{}) error {
 	return err
 }
 
+// IsZero returns true for the zero address.
+func (a Address) IsZero() bool {
+	return a == addr0
+}
+
 // UnprefixedAddress allows marshaling an Address without 0x prefix.
 type UnprefixedAddress Address