The way the mime_ and http_entity_ events are structure is a mess:
First, I think we should have only a single set of events for all MIME data.
the mime_ events don't come with is_orig.
http_header vs. mime_one_header
http_entity_data delivers segments of size http_entity_data_delivery_size while mime_entity_data delivers complete entities (and mime_segment_data delivers segments…)
There are further inconsistencies I didn't record.