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use std::{
path::Path,
sync::{atomic::Ordering, Arc},
};
use crate::store::{handle, types};
impl super::Store {
/// If Ok(None) is returned, the pack-id was stale and referred to an unloaded pack or a pack which couldn't be
/// loaded as its file didn't exist on disk anymore.
/// If the oid is known, just load indices again to continue
/// (objects rarely ever removed so should be present, maybe in another pack though),
/// and redo the entire lookup for a valid pack id whose pack can probably be loaded next time.
pub(crate) fn load_pack(
&self,
id: types::PackId,
marker: types::SlotIndexMarker,
) -> std::io::Result<Option<Arc<git_pack::data::File>>> {
let index = self.index.load();
if index.generation != marker.generation {
return Ok(None);
}
fn load_pack(
path: &Path,
id: types::PackId,
object_hash: git_hash::Kind,
) -> std::io::Result<Arc<git_pack::data::File>> {
git_pack::data::File::at(path, object_hash)
.map(|mut pack| {
pack.id = id.to_intrinsic_pack_id();
Arc::new(pack)
})
.map_err(|err| match err {
git_pack::data::header::decode::Error::Io { source, .. } => source,
other => std::io::Error::new(std::io::ErrorKind::Other, other),
})
}
let slot = &self.files[id.index];
// pin the current state before loading in the generation. That way we won't risk seeing the wrong value later.
let slot_files = &**slot.files.load();
if slot.generation.load(Ordering::SeqCst) > marker.generation {
// There is a disk consolidation in progress which just overwrote a slot that could be disposed with some other
// pack, one we didn't intend to load.
// Hope that when the caller returns/retries the new index is set so they can fetch it and retry.
return Ok(None);
}
match id.multipack_index {
None => {
match slot_files {
Some(types::IndexAndPacks::Index(bundle)) => {
match bundle.data.loaded() {
Some(pack) => Ok(Some(pack.clone())),
None => {
let _lock = slot.write.lock();
let mut files = slot.files.load_full();
let files_mut = Arc::make_mut(&mut files);
let pack = match files_mut {
Some(types::IndexAndPacks::Index(bundle)) => bundle
.data
.load_with_recovery(|path| load_pack(path, id, self.object_hash))?,
Some(types::IndexAndPacks::MultiIndex(_)) => {
// something changed between us getting the lock, trigger a complete index refresh.
None
}
None => {
unreachable!("BUG: must set this handle to be stable to avoid slots to be cleared/changed")
}
};
slot.files.store(files);
Ok(pack)
}
}
}
// This can also happen if they use an old index into our new and refreshed data which might have a multi-index
// here.
Some(types::IndexAndPacks::MultiIndex(_)) => Ok(None),
None => {
unreachable!("BUG: must set this handle to be stable to avoid slots to be cleared/changed")
}
}
}
Some(pack_index) => {
match slot_files {
Some(types::IndexAndPacks::MultiIndex(bundle)) => {
match bundle.data.get(pack_index as usize) {
None => Ok(None), // somewhat unexpected, data must be stale
Some(on_disk_pack) => match on_disk_pack.loaded() {
Some(pack) => Ok(Some(pack.clone())),
None => {
let _lock = slot.write.lock();
let mut files = slot.files.load_full();
let files_mut = Arc::make_mut(&mut files);
let pack = match files_mut {
Some(types::IndexAndPacks::Index(_)) => {
// something changed between us getting the lock, trigger a complete index refresh.
None
}
Some(types::IndexAndPacks::MultiIndex(bundle)) => bundle
.data
.get_mut(pack_index as usize)
.expect("BUG: must set this handle to be stable")
.load_with_recovery(|path| load_pack(path, id, self.object_hash))?,
None => {
unreachable!("BUG: must set this handle to be stable to avoid slots to be cleared/changed")
}
};
slot.files.store(files);
Ok(pack)
}
},
}
}
// This can also happen if they use an old index into our new and refreshed data which might have a multi-index
// here.
Some(types::IndexAndPacks::Index(_)) => Ok(None),
None => {
unreachable!("BUG: must set this handle to be stable to avoid slots to be cleared/changed")
}
}
}
}
}
/// Similar to `.load_pack()`, but for entire indices, bypassing the index entirely and going solely by marker and id.
/// Returns `None` if the index wasn't available anymore or could otherwise not be loaded, which can be considered a bug
/// as we should always keep needed indices available.
pub(crate) fn index_by_id(&self, id: types::PackId, marker: types::SlotIndexMarker) -> Option<handle::IndexLookup> {
let slot = self.files.get(id.index)?;
// Pin this value before we check the generation to avoid seeing something newer later.
let slot_files = &**slot.files.load();
if slot.generation.load(Ordering::SeqCst) > marker.generation {
// This means somebody just overwrote our trashed slot with a new (or about to be stored) index, which means the slot isn't
// what we need it to be.
// This shouldn't as we won't overwrite slots while handles need stable indices.
return None;
}
let lookup = match (slot_files).as_ref()? {
types::IndexAndPacks::Index(bundle) => handle::SingleOrMultiIndex::Single {
index: bundle.index.loaded()?.clone(),
data: bundle.data.loaded().cloned(),
},
types::IndexAndPacks::MultiIndex(multi) => handle::SingleOrMultiIndex::Multi {
index: multi.multi_index.loaded()?.clone(),
data: multi.data.iter().map(|f| f.loaded().cloned()).collect(),
},
};
handle::IndexLookup {
id: id.index,
file: lookup,
}
.into()
}
}