BinaryCacheStore: Optionally write a NAR listing

The store parameter "write-nar-listing=1" will cause BinaryCacheStore
to write a file ‘<store-hash>.ls.xz’ for each ‘<store-hash>.narinfo’
added to the binary cache. This file contains an XZ-compressed JSON
file describing the contents of the NAR, excluding the contents of
regular files.

E.g.

  {
    "version": 1,
    "root": {
      "type": "directory",
      "entries": {
        "lib": {
          "type": "directory",
          "entries": {
            "Mcrt1.o": {
              "type": "regular",
              "size": 1288
            },
            "Scrt1.o": {
              "type": "regular",
              "size": 3920
            },
          }
        }
      }
      ...
    }
  }

(The actual file has no indentation.)

This is intended to speed up the NixOS channels programs index
generator [1], since fetching gazillions of large NARs from
cache.nixos.org is currently a bottleneck for updating the regular
(non-small) channel.

[1] https://github.com/NixOS/nixos-channel-scripts/blob/master/generate-programs-index.cc

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index ce1583b0c6..d6e1811963 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -365,7 +365,7 @@ public:
     virtual bool wantMassQuery() { return false; }
 
     /* Import a path into the store. */
-    virtual void addToStore(const ValidPathInfo & info, const std::string & nar,
+    virtual void addToStore(const ValidPathInfo & info, const ref<std::string> & nar,
         bool repair = false, bool dontCheckSigs = false) = 0;
 
     /* Copy the contents of a path to the store and register the