Convert UTF-8 to HTML entities?

Sunday, August 12, 2012; 5:37:20 PM Eastern

I wish there was a simple C routine, possibly table-driven, that converts a string of characters from UTF-8 to HTML entities. Also these.
This problem must have come up a million times. I bet it's out there. Do you know where it is?

This is part of a restoration posts from 2012 and 2013. See these notes on the restoration. Last built: Sunday, July 8, 2018; 7:35:07 PM Eastern.