Hacky fast closure copying mechanism

src/libstore/daemon.cc

@@ -505,6 +505,17 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         break;
     }
 
+    case wopImportPaths2: {
+        logger->startWork();
+        auto paths = store->importPaths(from,
+            trusted ? NoCheckSigs : CheckSigs);
+        logger->stopWork();
+        Strings paths2;
+        for (auto & i : paths) paths2.push_back(store->printStorePath(i));
+        to << paths2;
+        break;
+    }
+
     case wopBuildPaths: {
         auto drvs = readDerivedPaths(*store, clientVersion, from);
         BuildMode mode = bmNormal;

src/libstore/remote-store.cc

@@ -875,6 +875,16 @@ void RemoteStore::queryMissing(const std::vector<DerivedPath> & targets,
 }
 
 
+StorePaths RemoteStore::importPaths(Source & source, CheckSigsFlag checkSigs)
+{
+    auto conn(getConnection());
+    conn->to << wopImportPaths2;
+    source.drainInto(conn->to);
+    conn.processStderr();
+    return worker_proto::read(*this, conn->from, Phantom<StorePaths> {});
+}
+
+
 void RemoteStore::connect()
 {
     auto conn(getConnection());

src/libstore/remote-store.hh

@@ -112,6 +112,8 @@ public:
         StorePathSet & willBuild, StorePathSet & willSubstitute, StorePathSet & unknown,
         uint64_t & downloadSize, uint64_t & narSize) override;
 
+    StorePaths importPaths(Source & source, CheckSigsFlag checkSigs) override;
+
     void connect() override;
 
     unsigned int getProtocol() override;

src/libstore/store-api.hh

@@ -676,7 +676,7 @@ public:
        the Nix store. Optionally, the contents of the NARs are
        preloaded into the specified FS accessor to speed up subsequent
        access. */
-    StorePaths importPaths(Source & source, CheckSigsFlag checkSigs = CheckSigs);
+    virtual StorePaths importPaths(Source & source, CheckSigsFlag checkSigs = CheckSigs);
 
     struct Stats
     {
@@ -766,6 +766,7 @@ std::map<StorePath, StorePath> copyPaths(ref<Store> srcStore, ref<Store> dstStor
     RepairFlag repair = NoRepair,
     CheckSigsFlag checkSigs = CheckSigs,
     SubstituteFlag substitute = NoSubstitute);
+
 std::map<StorePath, StorePath> copyPaths(ref<Store> srcStore, ref<Store> dstStore,
     const StorePathSet & paths,
     RepairFlag repair = NoRepair,

src/libstore/worker-protocol.hh

@@ -55,6 +55,7 @@ typedef enum {
     wopQueryDerivationOutputMap = 41,
     wopRegisterDrvOutput = 42,
     wopQueryRealisation = 43,
+    wopImportPaths2 = 44, // hack
 } WorkerOp;