func getFieldNumber(descriptorSet *descriptor.FileDescriptorSet, rootPkg string, rootMsg string, msg *descriptor.DescriptorProto, fieldNum int32) *descriptor.FieldDescriptorProto {
for _, f := range msg.GetField() {
if f.GetNumber() == fieldNum {
return f
}
}
if !msg.IsExtendable() {
return nil
}
extendee := "." + rootPkg + "." + rootMsg
for _, file := range descriptorSet.GetFile() {
for _, ext := range file.GetExtension() {
if strings.Map(dotToUnderscore, file.GetPackage()) == strings.Map(dotToUnderscore, rootPkg) {
if !(ext.GetExtendee() == rootMsg || ext.GetExtendee() == extendee) {
continue
}
} else {
if ext.GetExtendee() != extendee {
continue
}
}
if ext.GetNumber() == fieldNum {
return ext
}
}
}
return nil
}
