op-bindings: error handling

Ensure that the deployed bytecode is properly formatted hex to ensure
that an empty value is not returned. This should never happen but is a
sanity check to ensure that unexpected values are not returned.

fixup

op-bindings/bindings/registry.go

@@ -2,15 +2,20 @@ package bindings
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/ethereum-optimism/optimism/op-bindings/solc"
 	"github.com/ethereum/go-ethereum/common"
 )
 
+// layouts respresents the set of storage layouts. It is populated in an init function.
 var layouts = make(map[string]*solc.StorageLayout)
 
+// deployedBytecodes represents the set of deployed bytecodes. It is populated
+// in an init function.
 var deployedBytecodes = make(map[string]string)
 
+// GetStorageLayout returns the storage layout of a contract by name.
 func GetStorageLayout(name string) (*solc.StorageLayout, error) {
 	layout := layouts[name]
 	if layout == nil {
@@ -19,11 +24,36 @@ func GetStorageLayout(name string) (*solc.StorageLayout, error) {
 	return layout, nil
 }
 
+// GetDeployedBytecode returns the deployed bytecode of a contract by name.
 func GetDeployedBytecode(name string) ([]byte, error) {
 	bc := deployedBytecodes[name]
 	if bc == "" {
 		return nil, fmt.Errorf("%s: deployed bytecode not found", name)
 	}
 
+	if !isHex(bc) {
+		return nil, fmt.Errorf("%s: invalid deployed bytecode", name)
+	}
+
 	return common.FromHex(bc), nil
 }
+
+// isHexCharacter returns bool of c being a valid hexadecimal.
+func isHexCharacter(c byte) bool {
+	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')
+}
+
+// isHex validates whether each byte is valid hexadecimal string.
+func isHex(str string) bool {
+	if len(str)%2 != 0 {
+		return false
+	}
+	str = strings.TrimPrefix(str, "0x")
+
+	for _, c := range []byte(str) {
+		if !isHexCharacter(c) {
+			return false
+		}
+	}
+	return true
+}