Add an 'optimiseStore' remote procedure call.

nix/libstore/local-store.hh

@@ -167,6 +167,9 @@ public:
        files with the same contents. */
     void optimiseStore(OptimiseStats & stats);
 
+    /* Generic variant of the above method.  */
+    void optimiseStore();
+
     /* Optimise a single store path. */
     void optimisePath(const Path & path);
 

nix/libstore/optimise-store.cc

@@ -225,6 +225,22 @@ void LocalStore::optimiseStore(OptimiseStats & stats)
     }
 }
 
+static string showBytes(unsigned long long bytes)
+{
+    return (format("%.2f MiB") % (bytes / (1024.0 * 1024.0))).str();
+}
+
+void LocalStore::optimiseStore()
+{
+    OptimiseStats stats;
+
+    optimiseStore(stats);
+
+    printMsg(lvlError,
+        format("%1% freed by hard-linking %2% files")
+        % showBytes(stats.bytesFreed)
+        % stats.filesLinked);
+}
 
 void LocalStore::optimisePath(const Path & path)
 {

nix/libstore/remote-store.cc

@@ -577,6 +577,13 @@ void RemoteStore::clearFailedPaths(const PathSet & paths)
     readInt(from);
 }
 
+void RemoteStore::optimiseStore()
+{
+    openConnection();
+    writeInt(wopOptimiseStore, to);
+    processStderr();
+    readInt(from);
+}
 
 void RemoteStore::processStderr(Sink * sink, Source * source)
 {

nix/libstore/remote-store.hh

@@ -82,7 +82,9 @@ public:
     PathSet queryFailedPaths();
 
     void clearFailedPaths(const PathSet & paths);
-    
+
+    void optimiseStore();
+
 private:
     AutoCloseFD fdSocket;
     FdSink to;

nix/libstore/store-api.hh

@@ -250,6 +250,10 @@ public:
        `nix-store --register-validity'. */
     string makeValidityRegistration(const PathSet & paths,
         bool showDerivers, bool showHash);
+
+    /* Optimise the disk space usage of the Nix store by hard-linking files
+       with the same contents. */
+    virtual void optimiseStore() = 0;
 };
 
 

nix/libstore/worker-protocol.hh

@@ -42,6 +42,7 @@ typedef enum {
     wopQueryValidPaths = 31,
     wopQuerySubstitutablePaths = 32,
     wopQueryValidDerivers = 33,
+    wopOptimiseStore = 34
 } WorkerOp;
 
 

nix/nix-daemon/nix-daemon.cc

@@ -640,6 +640,13 @@ static void performOp(bool trusted, unsigned int clientVersion,
         break;
     }
 
+    case wopOptimiseStore:
+	startWork();
+	store->optimiseStore();
+	stopWork();
+	writeInt(1, to);
+	break;
+
     default:
         throw Error(format("invalid operation %1%") % op);
     }