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diff --git a/src/mongo/db/dur_journalimpl.h b/src/mongo/db/dur_journalimpl.h
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+++ b/src/mongo/db/dur_journalimpl.h
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+// @file dur_journal.h
+
+/**
+*    Copyright (C) 2010 10gen Inc.
+*
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include "dur_journalformat.h"
+#include "../util/logfile.h"
+
+namespace mongo {
+    namespace dur {
+
+        /** the writeahead journal for durability */
+        class Journal {
+        public:
+            string dir; // set by journalMakeDir() during initialization
+
+            Journal();
+
+            /** call during startup by journalMakeDir() */
+            void init();
+
+            /** check if time to rotate files.  assure a file is open.
+                done separately from the journal() call as we can do this part
+                outside of lock.
+                thread: durThread()
+             */
+            void rotate();
+
+            /** append to the journal file
+            */
+            void journal(const JSectHeader& h, const AlignedBuilder& b);
+
+            boost::filesystem::path getFilePathFor(int filenumber) const;
+
+            unsigned long long lastFlushTime() const { return _lastFlushTime; }
+            void cleanup(bool log); // closes and removes journal files
+
+            unsigned long long curFileId() const { return _curFileId; }
+
+            void assureLogFileOpen() {
+                SimpleMutex::scoped_lock lk(_curLogFileMutex);
+                if( _curLogFile == 0 )
+                    _open();
+            }
+
+            /** open a journal file to journal operations to. */
+            void open();
+
+        private:
+            /** check if time to rotate files.  assure a file is open.
+             *  internally called with every commit
+             */
+            void _rotate();
+
+            void _open();
+            void closeCurrentJournalFile();
+            void removeUnneededJournalFiles();
+
+            unsigned long long _written; // bytes written so far to the current journal (log) file
+            unsigned _nextFileNumber;
+        public:
+            SimpleMutex _curLogFileMutex;
+            bool _ageOut;
+        private:
+
+            LogFile *_curLogFile; // use _curLogFileMutex
+            unsigned long long _curFileId; // current file id see JHeader::fileId
+
+            struct JFile {
+                string filename;
+                unsigned long long lastEventTimeMs;
+            };
+
+            // files which have been closed but not unlinked (rotated out) yet
+            // ordered oldest to newest
+            list<JFile> _oldJournalFiles; // use _curLogFileMutex
+
+            // lsn related
+            static void preFlush();
+            static void postFlush();
+            unsigned long long _preFlushTime;
+            unsigned long long _lastFlushTime; // data < this time is fsynced in the datafiles (unless hard drive controller is caching)
+            bool _writeToLSNNeeded;
+            void updateLSNFile();
+        };
+
+    }
+}