tarball.cc: Use ETags

1 files changed, 11 insertions, 0 deletions

diff --git a/src/libstore/fetchers/cache.hh b/src/libstore/fetchers/cache.hh
index ba2d30629..a25b05985 100644
--- a/src/libstore/fetchers/cache.hh
+++ b/src/libstore/fetchers/cache.hh
@@ -17,6 +17,17 @@ struct Cache
     virtual std::optional<std::pair<Attrs, StorePath>> lookup(
         ref<Store> store,
         const Attrs & inAttrs) = 0;
+
+    struct Result
+    {
+        bool expired = false;
+        Attrs infoAttrs;
+        StorePath storePath;
+    };
+
+    virtual std::optional<Result> lookupExpired(
+        ref<Store> store,
+        const Attrs & inAttrs) = 0;
 };
 
 ref<Cache> getCache();