exportReferencesGraph: Export more complete info in JSON format

This writes info about every path in the closure in the same format as
‘nix path-info --json’. Thus it also includes NAR hashes and sizes.

Example:

  [
    {
      "path": "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
      "narHash": "sha256:0ckdc4z20kkmpqdilx0wl6cricxv90lh85xpv2qljppcmz6vzcxl",
      "narSize": 197648,
      "references": [
        "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
        "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
      ],
      "closureSize": 20939776
    },
    {
      "path": "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24",
      "narHash": "sha256:1nfn3m3p98y1c0kd0brp80dn9n5mycwgrk183j17rajya0h7gax3",
      "narSize": 20742128,
      "references": [
        "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
      ],
      "closureSize": 20742128
    }
  ]

Fixes #1134.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index ec3bf5a6fd83..3fee999072fa 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -22,6 +22,7 @@ struct Derivation;
 class FSAccessor;
 class NarInfoDiskCache;
 class Store;
+class JSONPlaceholder;
 
 
 /* Size of the hash part of store paths, in base-32 characters. */
@@ -469,6 +470,19 @@ public:
     string makeValidityRegistration(const PathSet & paths,
         bool showDerivers, bool showHash);
 
+    /* Write a JSON representation of store path metadata, such as the
+       hash and the references. If ‘includeImpureInfo’ is true,
+       variable elements such as the registration time are
+       included. If ‘showClosureSize’ is true, the closure size of
+       each path is included. */
+    void pathInfoToJSON(JSONPlaceholder & jsonOut, const PathSet & storePaths,
+        bool includeImpureInfo, bool showClosureSize);
+
+    /* Return the size of the closure of the specified path, that is,
+       the sum of the size of the NAR serialisation of each path in
+       the closure. */
+    unsigned long long getClosureSize(const Path & storePath);
+
     /* Optimise the disk space usage of the Nix store by hard-linking files
        with the same contents. */
     virtual void optimiseStore() = 0;