let
  fetch = { file, sha256 }:
    let
      nixFetchurl = import <nix/fetchurl.nix>;
      args = {
        url = "file://${builtins.toString ./.}/${file}";
        inherit sha256;
        executable = true;
      };
    in if (builtins.functionArgs nixFetchurl) ? executable
      then nixFetchurl args
      else derivation {
        name = file;
        builder = "/bin/sh";

        system = builtins.currentSystem;

        args = [ "-c" "echo $message; exit 1" ];

        message = ''
          Sorry, this version of nix cannot download all of the bootstrap tools.
          Please download ${args.url}, make it executable, add it to the store
          with `nix-store --add', and try again.
        '';

        outputHashAlgo = "sha256";

        outputHash = args.sha256;

        outputHashMode = "recursive";

        preferLocalBuild = true;
      };
in {
  sh = fetch {
    file = "sh";
    sha256 = "02jjl49wdq85pgh61aqf78yaknn9mi3rcspbpk7hs9c4mida2rhf";
  };

  bzip2 = fetch {
    file = "bzip2";
    sha256 = "1qn27y3amj9c6mnjk2kyb59y0d2w4yv16z9apaxx91hyq19gf29z";
  };

  mkdir = fetch {
    file = "mkdir";
    sha256 = "1vbp2bv9hkyb2fwl8hjrffpywn1wrl1kc4yrwi2lirawlnc6kymh";
  };

  cpio = fetch {
    file = "cpio";
    sha256 = "0mqxwdx0sl7skxx6049mk35l7d0fnibqsv174284kdp4p7iixwa0";
  };

  ln = fetch {
    file = "ln";
    sha256 = "05lwx8qvga3yv8xhs8bjgsfygsfrcxsfck0lxw6gsdckx25fgi7s";
  };

  curl = fetch {
    file = "curl.bz2";
    sha256 = "0iblnz4my54gryac04i64fn3ksi9g3dx96yjq93fj39z6kx6151c";
  };

  bootstrapTools = {
    url = "http://nixos.org/tarballs/stdenv-linux/loongson2f/r22849/cross-bootstrap-tools.cpio.bz2";
    sha256 = "00aavbk76qjj2gdlmpaaj66r8nzl4d7pyl8cv1gigyzgpbr5vv3j";
  };
}