1 files changed, 63 insertions, 19 deletions
diff --git a/src/libstore/remote-fs-accessor.cc b/src/libstore/remote-fs-accessor.cc
index ba9620a175bb..5233fb2c239b 100644
--- a/src/libstore/remote-fs-accessor.cc
+++ b/src/libstore/remote-fs-accessor.cc
@@ -1,5 +1,10 @@
 #include "remote-fs-accessor.hh"
 #include "nar-accessor.hh"
+#include "json.hh"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 
 namespace nix {
 
@@ -11,20 +16,30 @@ RemoteFSAccessor::RemoteFSAccessor(ref<Store> store, const Path & cacheDir)
         createDirs(cacheDir);
 }
 
-Path RemoteFSAccessor::makeCacheFile(const Path & storePath)
+Path RemoteFSAccessor::makeCacheFile(const Path & storePath, const std::string & ext)
 {
     assert(cacheDir != "");
-    return fmt("%s/%s.nar", cacheDir, storePathToHash(storePath));
+    return fmt("%s/%s.%s", cacheDir, storePathToHash(storePath), ext);
 }
 
-void RemoteFSAccessor::addToCache(const Path & storePath, const std::string & nar)
+void RemoteFSAccessor::addToCache(const Path & storePath, const std::string & nar,
+    ref<FSAccessor> narAccessor)
 {
-    try {
-        if (cacheDir == "") return;
-        /* FIXME: do this asynchronously. */
-        writeFile(makeCacheFile(storePath), nar);
-    } catch (...) {
-        ignoreException();
+    nars.emplace(storePath, narAccessor);
+
+    if (cacheDir != "") {
+        try {
+            std::ostringstream str;
+            JSONPlaceholder jsonRoot(str);
+            listNar(jsonRoot, narAccessor, "", true);
+            writeFile(makeCacheFile(storePath, "ls"), str.str());
+
+            /* FIXME: do this asynchronously. */
+            writeFile(makeCacheFile(storePath, "nar"), nar);
+
+        } catch (...) {
+            ignoreException();
+        }
     }
 }
 
@@ -42,20 +57,49 @@ std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path & path_)
     if (i != nars.end()) return {i->second, restPath};
 
     StringSink sink;
+    std::string listing;
+    Path cacheFile;
+
+    if (cacheDir != "" && pathExists(cacheFile = makeCacheFile(storePath, "nar"))) {
+
+        try {
+            listing = nix::readFile(makeCacheFile(storePath, "ls"));
+
+            auto narAccessor = makeLazyNarAccessor(listing,
+                [cacheFile](uint64_t offset, uint64_t length) {
+
+                    AutoCloseFD fd = open(cacheFile.c_str(), O_RDONLY | O_CLOEXEC);
+                    if (!fd)
+                        throw SysError("opening NAR cache file '%s'", cacheFile);
+
+                    if (lseek(fd.get(), offset, SEEK_SET) != (off_t) offset)
+                        throw SysError("seeking in '%s'", cacheFile);
+
+                    std::string buf(length, 0);
+                    readFull(fd.get(), (unsigned char *) buf.data(), length);
+
+                    return buf;
+                });
+
+            nars.emplace(storePath, narAccessor);
+            return {narAccessor, restPath};
+
+        } catch (SysError &) { }
+
+        try {
+            *sink.s = nix::readFile(cacheFile);
 
-    try {
-        if (cacheDir != "")
-            *sink.s = nix::readFile(makeCacheFile(storePath));
-    } catch (SysError &) { }
+            auto narAccessor = makeNarAccessor(sink.s);
+            nars.emplace(storePath, narAccessor);
+            return {narAccessor, restPath};
 
-    if (sink.s->empty()) {
-        store->narFromPath(storePath, sink);
-        addToCache(storePath, *sink.s);
+        } catch (SysError &) { }
     }
 
-    auto accessor = makeNarAccessor(sink.s);
-    nars.emplace(storePath, accessor);
-    return {accessor, restPath};
+    store->narFromPath(storePath, sink);
+    auto narAccessor = makeNarAccessor(sink.s);
+    addToCache(storePath, *sink.s, narAccessor);
+    return {narAccessor, restPath};
 }
 
 FSAccessor::Stat RemoteFSAccessor::stat(const Path & path)