[locale.codecvt.virtuals] (original) (raw)

A codecvt facet that is used by basic_filebuf ([file.streams]) shall have the property that ifdo_out(state, from, from_end, from_next, to, to_end, to_next) would return ok, where from != from_end, thendo_out(state, from, from + 1, from_next, to, to_end, to_next) shall also return ok, and that ifdo_in(state, from, from_end, from_next, to, to_end, to_next) would return ok, where to != to_end, thendo_in(state, from, from_end, from_next, to, to + 1, to_next) shall also return ok.221

[Note 1:

As a result of operations on state, it can return ok or partial and set from_next == from and to_next != to.

— _end note_]