Method update_userdata

arc-disk-cache/src/lib.rs:682–722

Given key, update the ud.

(&self, q: &Q, mut func: F)

    // Given key, update the ud.
    pub fn update_userdata<Q, F>(&self, q: &Q, mut func: F)
    where
        K: Borrow<Q>,
        Q: Hash + Eq + Ord + ?Sized,
        F: FnMut(&mut D),
    {
        let mut wrtxn = self.cache.write_stats(TraceStat::default());

        if let Some(mref) = wrtxn.get_mut(q, false) {
            func(&mut mref.userdata);

            let objmeta = CacheObjMeta {
                key: mref.key.clone(),
                path: mref.fhandle.path.clone(),
                crc: mref.fhandle.crc,
                userdata: mref.userdata.clone(),
            };

            // This will truncate the metadata if it does exist.
            let m_file = File::create(&mref.fhandle.meta_path)
                .map(BufWriter::new)
                .map_err(|e| {
                    error!("Failed to open metadata {:?}", e);
                })
                .unwrap();

            serde_json::to_writer(m_file, &objmeta)
                .map_err(|e| {
                    error!("Failed to write metadata {:?}", e);
                })
                .unwrap();

            info!("Persisted metadata for {:?}", &mref.fhandle.meta_path);
        }

        debug!("commit");
        let stats = wrtxn.commit();
        let mut stat_guard = self.stats.write();
        (*stat_guard).update(stats);
        stat_guard.commit();
    }

    pub fn update_all_userdata<F, C>(&self, check: C, mut func: F)
    where