1 files changed, 31 insertions, 3 deletions
diff --git a/src/libstore/remote-fs-accessor.cc b/src/libstore/remote-fs-accessor.cc
index 098151f8c0f6..ba9620a175bb 100644
--- a/src/libstore/remote-fs-accessor.cc
+++ b/src/libstore/remote-fs-accessor.cc
@@ -3,10 +3,29 @@
 
 namespace nix {
 
-
-RemoteFSAccessor::RemoteFSAccessor(ref<Store> store)
+RemoteFSAccessor::RemoteFSAccessor(ref<Store> store, const Path & cacheDir)
     : store(store)
+    , cacheDir(cacheDir)
 {
+    if (cacheDir != "")
+        createDirs(cacheDir);
+}
+
+Path RemoteFSAccessor::makeCacheFile(const Path & storePath)
+{
+    assert(cacheDir != "");
+    return fmt("%s/%s.nar", cacheDir, storePathToHash(storePath));
+}
+
+void RemoteFSAccessor::addToCache(const Path & storePath, const std::string & nar)
+{
+    try {
+        if (cacheDir == "") return;
+        /* FIXME: do this asynchronously. */
+        writeFile(makeCacheFile(storePath), nar);
+    } catch (...) {
+        ignoreException();
+    }
 }
 
 std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_)
@@ -23,7 +42,16 @@ std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_)
     if (i != nars.end()) return {i->second, restPath};
 
     StringSink sink;
-    store->narFromPath(storePath, sink);
+
+    try {
+        if (cacheDir != "")
+            *sink.s = nix::readFile(makeCacheFile(storePath));
+    } catch (SysError &) { }
+
+    if (sink.s->empty()) {
+        store->narFromPath(storePath, sink);
+        addToCache(storePath, *sink.s);
+    }
 
     auto accessor = makeNarAccessor(sink.s);
     nars.emplace(storePath, accessor);