From c505702265833a762d681952bcc72562d64a242e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Thu, 27 Jan 2005 15:21:29 +0000
Subject: * Fix and simplify the garbage collector (it's still not concurrent, 
  though).  In particular it's now much easier to register a GC root.   Just
 place a symlink to whatever store path it is that you want to   keep in
 /nix/var/nix/gcroots.

---
 src/libstore/gc.cc | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

(limited to 'src/libstore/gc.cc')

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 4f3306505440..ba6e6bb9d4bb 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -1,12 +1,68 @@
 #include "globals.hh"
 #include "gc.hh"
-
+#include "build.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
 
+void collectGarbage(const PathSet & roots, GCAction action,
+    PathSet & result)
+{
+    result.clear();
+    
+    /* !!! TODO: Acquire an exclusive lock on the gcroots directory.
+       This prevents the set of live paths from increasing after this
+       point. */
+    
+    /* Determine the live paths which is just the closure of the
+       roots under the `references' relation. */
+    PathSet livePaths;
+    for (PathSet::const_iterator i = roots.begin(); i != roots.end(); ++i)
+        computeFSClosure(canonPath(*i), livePaths);
+
+    if (action == gcReturnLive) {
+        result = livePaths;
+        return;
+    }
+
+    /* !!! TODO: Try to acquire (without blocking) exclusive locks on
+       the files in the `pending' directory.  Delete all files for
+       which we managed to acquire such a lock (since if we could get
+       such a lock, that means that the process that owned the file
+       has died). */
+
+    /* !!! TODO: Acquire shared locks on all files in the pending
+       directories.  This prevents the set of pending paths from
+       increasing while we are garbage-collecting.  Read the set of
+       pending paths from those files. */
+
+    /* Read the Nix store directory to find all currently existing
+       paths. */
+    Strings storeNames = readDirectory(nixStore);
+
+    for (Strings::iterator i = storeNames.begin(); i != storeNames.end(); ++i) {
+        Path path = canonPath(nixStore + "/" + *i);
+
+        if (livePaths.find(path) != livePaths.end()) {
+            debug(format("live path `%1%'") % path);
+            continue;
+        }
+
+        debug(format("dead path `%1%'") % path);
+        result.insert(path);
+
+        if (action == gcDeleteDead) {
+            printMsg(lvlInfo, format("deleting `%1%'") % path);
+            deleteFromStore(path);
+        }
+        
+    }
+}
+
+
+
 #if 0
 void followLivePaths(Path nePath, PathSet & live)
 {
-- 
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