libstore: asyncify Store::exportPath{,s}

Change-Id: I92915a3cb27bda73e7b9f3b32dc1feea3f47abda

lix/legacy/nix-store.cc

@@ -713,7 +713,7 @@ static void opExport(AsyncIoRoot & aio, Strings opFlags, Strings opArgs)
         paths.insert(store->followLinksToStorePath(i));
 
     FdSink sink(STDOUT_FILENO);
-    store->exportPaths(paths, sink);
+    aio.blockOn(store->exportPaths(paths, sink));
     sink.flush();
 }
 
@@ -927,7 +927,9 @@ static void opServe(AsyncIoRoot & aio, Strings opFlags, Strings opArgs)
 
             case ServeProto::Command::ExportPaths: {
                 readInt(in); // obsolete
-                store->exportPaths(ServeProto::Serialise<StorePathSet>::read(*store, rconn), out);
+                aio.blockOn(store->exportPaths(
+                    ServeProto::Serialise<StorePathSet>::read(*store, rconn), out
+                ));
                 break;
             }
 

lix/libstore/export-import.cc

@@ -1,3 +1,4 @@
+#include "lix/libutil/result.hh"
 #include "lix/libutil/serialise.hh"
 #include "lix/libstore/store-api.hh"
 #include "lix/libutil/archive.hh"
@@ -8,21 +9,24 @@
 
 namespace nix {
 
-void Store::exportPaths(const StorePathSet & paths, Sink & sink)
-{
+kj::Promise<Result<void>> Store::exportPaths(const StorePathSet & paths, Sink & sink)
+try {
     auto sorted = topoSortPaths(paths);
     std::reverse(sorted.begin(), sorted.end());
 
     for (auto & path : sorted) {
         sink << 1;
-        exportPath(path, sink);
+        TRY_AWAIT(exportPath(path, sink));
     }
 
     sink << 0;
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
-void Store::exportPath(const StorePath & path, Sink & sink)
-{
+kj::Promise<Result<void>> Store::exportPath(const StorePath & path, Sink & sink)
+try {
     auto info = queryPathInfo(path);
 
     HashSink hashSink(HashType::SHA256);
@@ -47,6 +51,9 @@ void Store::exportPath(const StorePath & path, Sink & sink)
     teeSink
         << (info->deriver ? printStorePath(*info->deriver) : "")
         << 0;
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
 kj::Promise<Result<StorePaths>> Store::importPaths(Source & source, CheckSigsFlag checkSigs)

lix/libstore/store-api.hh

@@ -793,9 +793,9 @@ public:
      * Export multiple paths in the format expected by ‘nix-store
      * --import’.
      */
-    void exportPaths(const StorePathSet & paths, Sink & sink);
+    kj::Promise<Result<void>> exportPaths(const StorePathSet & paths, Sink & sink);
 
-    void exportPath(const StorePath & path, Sink & sink);
+    kj::Promise<Result<void>> exportPath(const StorePath & path, Sink & sink);
 
     /**
      * Import a sequence of NAR dumps created by exportPaths() into the

perl/lib/Nix/Store.xs

@@ -197,7 +197,7 @@ void exportPaths(int fd, ...)
             StorePathSet paths;
             for (int n = 1; n < items; ++n) paths.insert(store()->parseStorePath(SvPV_nolen(ST(n))));
             FdSink sink(fd);
-            store()->exportPaths(paths, sink);
+            aio().blockOn(store()->exportPaths(paths, sink));
         } catch (Error & e) {
             croak("%s", e.what());
         }