* Started removing closure store expressions, i.e., the explicit

  representation of closures as ATerms in the Nix store.  Instead, the
  file system pointer graph is now stored in the Nix database.  This
  has many advantages:

  - It greatly simplifies the implementation (we can drop the notion
    of `successors', and so on).

  - It makes registering roots for the garbage collector much easier.
    Instead of specifying the closure expression as a root, you can
    simply specify the store path that must be retained as a root.
    This could not be done previously, since there was no way to find
    the closure store expression containing a given store path.
    
  - Better traceability: it is now possible to query what paths are
    referenced by a path, and what paths refer to a path.

1 files changed, 23 insertions, 6 deletions

diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 6dc054fb43..24a522c1ed 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -1,16 +1,32 @@
 #include "normalise.hh"
 
 
-StoreExpr storeExprFromPath(const Path & path)
+Derivation derivationFromPath(const Path & drvPath)
 {
-    assertStorePath(path);
-    ensurePath(path);
-    ATerm t = ATreadFromNamedFile(path.c_str());
-    if (!t) throw Error(format("cannot read aterm from `%1%'") % path);
-    return parseStoreExpr(t);
+    assertStorePath(drvPath);
+    ensurePath(drvPath);
+    ATerm t = ATreadFromNamedFile(drvPath.c_str());
+    if (!t) throw Error(format("cannot read aterm from `%1%'") % drvPath);
+    return parseDerivation(t);
 }
 
 
+void computeFSClosure(const Path & storePath,
+    PathSet & paths)
+{
+    if (paths.find(storePath) != paths.end()) return;
+    paths.insert(storePath);
+
+    PathSet references;
+    queryReferences(storePath, references);
+
+    for (PathSet::iterator i = references.begin();
+         i != references.end(); ++i)
+        computeFSClosure(*i, paths);
+}
+
+
+#if 0
 PathSet storeExprRoots(const Path & nePath)
 {
     PathSet paths;
@@ -71,3 +87,4 @@ PathSet storeExprRequisites(const Path & nePath,
         paths, doneSet);
     return paths;
 }
+#endif