1 files changed, 133 insertions, 0 deletions
diff --git a/third_party/nix/src/libstore/remote-fs-accessor.cc b/third_party/nix/src/libstore/remote-fs-accessor.cc
new file mode 100644
index 000000000000..4178030b55d6
--- /dev/null
+++ b/third_party/nix/src/libstore/remote-fs-accessor.cc
@@ -0,0 +1,133 @@
+#include "libstore/remote-fs-accessor.hh"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "libstore/nar-accessor.hh"
+#include "libutil/json.hh"
+
+namespace nix {
+
+RemoteFSAccessor::RemoteFSAccessor(const ref<Store>& store,
+                                   const Path& cacheDir)
+    : store(store), cacheDir(cacheDir) {
+  if (!cacheDir.empty()) {
+    createDirs(cacheDir);
+  }
+}
+
+Path RemoteFSAccessor::makeCacheFile(const Path& storePath,
+                                     const std::string& ext) {
+  assert(!cacheDir.empty());
+  return fmt("%s/%s.%s", cacheDir, storePathToHash(storePath), ext);
+}
+
+void RemoteFSAccessor::addToCache(const Path& storePath, const std::string& nar,
+                                  const ref<FSAccessor>& narAccessor) {
+  nars.emplace(storePath, narAccessor);
+
+  if (!cacheDir.empty()) {
+    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();
+    }
+  }
+}
+
+std::pair<ref<FSAccessor>, Path> RemoteFSAccessor::fetch(const Path& path_) {
+  auto path = canonPath(path_);
+
+  auto storePath = store->toStorePath(path);
+  std::string restPath = std::string(path, storePath.size());
+
+  if (!store->isValidPath(storePath)) {
+    throw InvalidPath(format("path '%1%' is not a valid store path") %
+                      storePath);
+  }
+
+  auto i = nars.find(storePath);
+  if (i != nars.end()) {
+    return {i->second, restPath};
+  }
+
+  StringSink sink;
+  std::string listing;
+  Path cacheFile;
+
+  if (!cacheDir.empty() &&
+      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) !=
+                static_cast<off_t>(offset)) {
+              throw SysError("seeking in '%s'", cacheFile);
+            }
+
+            std::string buf(length, 0);
+            readFull(fd.get(), reinterpret_cast<unsigned char*>(buf.data()),
+                     length);
+
+            return buf;
+          });
+
+      nars.emplace(storePath, narAccessor);
+      return {narAccessor, restPath};
+
+    } catch (SysError&) {
+    }
+
+    try {
+      *sink.s = nix::readFile(cacheFile);
+
+      auto narAccessor = makeNarAccessor(sink.s);
+      nars.emplace(storePath, narAccessor);
+      return {narAccessor, restPath};
+
+    } catch (SysError&) {
+    }
+  }
+
+  store->narFromPath(storePath, sink);
+  auto narAccessor = makeNarAccessor(sink.s);
+  addToCache(storePath, *sink.s, narAccessor);
+  return {narAccessor, restPath};
+}
+
+FSAccessor::Stat RemoteFSAccessor::stat(const Path& path) {
+  auto res = fetch(path);
+  return res.first->stat(res.second);
+}
+
+StringSet RemoteFSAccessor::readDirectory(const Path& path) {
+  auto res = fetch(path);
+  return res.first->readDirectory(res.second);
+}
+
+std::string RemoteFSAccessor::readFile(const Path& path) {
+  auto res = fetch(path);
+  return res.first->readFile(res.second);
+}
+
+std::string RemoteFSAccessor::readLink(const Path& path) {
+  auto res = fetch(path);
+  return res.first->readLink(res.second);
+}
+
+}  // namespace nix