tvl-depot/third_party/nix/src/libstore/remote-fs-accessor.cc

#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