countRealOneofs function
Implementation
int countRealOneofs(DescriptorProto descriptor) {
var highestIndexSeen = -1;
for (final field in descriptor.field) {
if (field.hasOneofIndex() && !field.proto3Optional) {
highestIndexSeen = math.max(highestIndexSeen, field.oneofIndex);
}
}
// The number of entries is one higher than the highest seen index.
return highestIndexSeen + 1;
}