object/store/packed: Basic reading functionality

1 files changed, 38 insertions, 0 deletions

diff --git a/object/store/packed/basecache.go b/object/store/packed/basecache.go
new file mode 100644
index 00000000..7de4ec7b
--- /dev/null
+++ b/object/store/packed/basecache.go
@@ -0,0 +1,38 @@
+package packed
+
+import (
+	"lindenii.org/go/furgit/internal/cache/clock"
+	"lindenii.org/go/furgit/internal/format/packfile"
+)
+
+// baseCacheMaxWeight bounds the delta base cache weight.
+const baseCacheMaxWeight = 96 << 20
+
+// baseKey addresses an entry in one pack
+// as a delta base cache key.
+type baseKey struct {
+	pack   *pack
+	offset uint64
+}
+
+// cachedBase is a cached delta base, i.e.,
+// its resolved object entry type and full content.
+//
+// content is shared with concurrent users;
+// it may only be returned to callers as a copy.
+//
+// Labels: Mut-No.
+type cachedBase struct {
+	entryType packfile.EntryType
+	content   []byte
+}
+
+// newBaseCache creates the delta base cache.
+func newBaseCache() *clock.Clock[baseKey, cachedBase] {
+	return clock.New(baseCacheMaxWeight, baseWeight)
+}
+
+// baseWeight weighs one cached delta base.
+func baseWeight(_ baseKey, base cachedBase) uint64 {
+	return uint64(len(base.content)) + 32
+}