This contract is given a DSValue as a source to read from. You set a time interval with step. Whenever that step time has passed, it will let you poke. When you poke it reads the value from the source and stores it. The previous stored value becomes the current value.
This contracts implements read and peek from DSValue, but it is not one. It also has a new function peep to read what the next value will be after a poke.
// create
OSM osm = new OSM(DSValue(src));
// can be poked every hour, on the hour
osm.step(3600);
(val, ok) = osm.peek() // get current value
(val, ok) = osm.peep() // get upcoming value
val = osm.read() // get current value, or fail
If this DSValue has a valid value on creation, the OSM with start with that same value.