object/store: Rename back from storer; rename Store to ReadingStore v0.1.118

1 files changed, 136 insertions, 0 deletions

diff --git a/object/store/packed/idx_candidates_mru.go b/object/store/packed/idx_candidates_mru.go
new file mode 100644
index 00000000..d0cc7052
--- /dev/null
+++ b/object/store/packed/idx_candidates_mru.go
@@ -0,0 +1,136 @@
+package packed
+
+// packCandidateNode is one node in the candidate MRU order list.
+type packCandidateNode struct {
+	packName string
+	prev     *packCandidateNode
+	next     *packCandidateNode
+}
+
+func (store *Store) reconcileMRU(candidates []packCandidate) {
+	store.mruMu.Lock()
+	defer store.mruMu.Unlock()
+
+	if store.mruNodeByPack == nil {
+		store.mruNodeByPack = make(map[string]*packCandidateNode, len(candidates))
+	}
+
+	present := make(map[string]struct{}, len(candidates))
+	for _, candidate := range candidates {
+		present[candidate.packName] = struct{}{}
+	}
+
+	ordered := make([]string, 0, len(candidates))
+
+	for node := store.mruHead; node != nil; node = node.next {
+		if _, ok := present[node.packName]; !ok {
+			continue
+		}
+
+		ordered = append(ordered, node.packName)
+		delete(present, node.packName)
+	}
+
+	for _, candidate := range candidates {
+		if _, ok := present[candidate.packName]; !ok {
+			continue
+		}
+
+		ordered = append(ordered, candidate.packName)
+		delete(present, candidate.packName)
+	}
+
+	store.mruHead = nil
+	store.mruTail = nil
+	store.mruNodeByPack = make(map[string]*packCandidateNode, len(ordered))
+
+	for _, packName := range ordered {
+		node := &packCandidateNode{
+			packName: packName,
+			prev:     store.mruTail,
+		}
+		if store.mruTail != nil {
+			store.mruTail.next = node
+		}
+
+		if store.mruHead == nil {
+			store.mruHead = node
+		}
+
+		store.mruTail = node
+		store.mruNodeByPack[packName] = node
+	}
+}
+
+// touchCandidate moves one candidate to the front of the lookup order.
+// This is done on a best-effort basis.
+func (store *Store) touchCandidate(packName string) {
+	if !store.mruMu.TryLock() {
+		return
+	}
+	defer store.mruMu.Unlock()
+
+	node := store.mruNodeByPack[packName]
+	if node == nil || node == store.mruHead {
+		return
+	}
+
+	if node.prev != nil {
+		node.prev.next = node.next
+	}
+
+	if node.next != nil {
+		node.next.prev = node.prev
+	}
+
+	if store.mruTail == node {
+		store.mruTail = node.prev
+	}
+
+	node.prev = nil
+
+	node.next = store.mruHead
+	if store.mruHead != nil {
+		store.mruHead.prev = node
+	}
+
+	store.mruHead = node
+	if store.mruTail == nil {
+		store.mruTail = node
+	}
+}
+
+// firstCandidatePackName returns the current head pack name, or "" when none
+// are available.
+func (store *Store) firstCandidatePackName(snapshot *candidateSnapshot) string {
+	store.mruMu.RLock()
+	defer store.mruMu.RUnlock()
+
+	for node := store.mruHead; node != nil; node = node.next {
+		if _, ok := snapshot.candidateByPack[node.packName]; ok {
+			return node.packName
+		}
+	}
+
+	return ""
+}
+
+// nextCandidatePackName returns the pack name after currentPack in current MRU
+// order, or "" at end / when currentPack is not present.
+func (store *Store) nextCandidatePackName(currentPack string, snapshot *candidateSnapshot) string {
+	store.mruMu.RLock()
+	defer store.mruMu.RUnlock()
+
+	node := store.mruNodeByPack[currentPack]
+	if node == nil {
+		return ""
+	}
+
+	for node = node.next; node != nil; node = node.next {
+		if _, ok := snapshot.candidateByPack[node.packName]; ok {
+			return node.packName
+		}
+	}
+
+	return ""
+}