fson runs no watcher thread. You drive the check — on a timer, or from an OS file event (inotify, kqueue, ReadDirectoryChangesW).
auto result = Fson::load( "service.fson" );
auto snap = Fson::snapshot( "service.fson" );
// ... later ...
if( Fson::isStale( "service.fson", snap, Fson::StaleMode::ContentHash ) )
{
result = Fson::load( "service.fson" );
snap = Fson::snapshot( "service.fson" ); // re-snapshot after a reload
}
The two modes
StaleMode | Cost | A bare touch (mtime bump, same bytes) |
|---|---|---|
MtimeSize | cheap — stat only, no re-read | counts as a change |
ContentHash | re-reads every file | ignored — only real content changes |
Both modes also catch:
- a deleted dependency (an
%includetarget that vanished); - an include-graph change — a new or removed
%includedirective, even if every existing file is byte-identical.
What "the file" means
snapshot and isStale cover the whole dependency set — the host file plus every file reachable through %include, transitively. You pass only the host path; the snapshot carries the rest.
If you keep the document, LoadResult::dependencySet is the same list, already sorted — useful as the set of paths to register with your OS watcher. Without a document, Fson::dependenciesOf("service.fson") returns it directly.
