SourceFormat Enforcement

[thirdparty/squid.git] / src / StoreFileSystem.h

diff --git a/src/StoreFileSystem.h b/src/StoreFileSystem.h
index 1601dcb5367784225ff01c0106fd8cb3aae82283..bde0eb92941645655541d528451a429b2c8506fd 100644 (file)
--- a/src/StoreFileSystem.h
+++ b/src/StoreFileSystem.h
@@ -1,6 +1,5 @@
-
 /*
- * $Id: StoreFileSystem.h,v 1.2 2006/05/29 00:15:01 robertc Exp $
+ * $Id$
  *
  * SQUID Web Proxy Cache          http://www.squid-cache.org/
  * ----------------------------------------------------------
@@ -18,12 +17,12 @@
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
- *  
+ *
  *  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 General Public License for more details.
- *  
+ *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
@@ -34,20 +33,88 @@
 #ifndef SQUID_STOREFILESYSTEM_H
 #define SQUID_STOREFILESYSTEM_H
 
-#include "squid.h"
 #include "Array.h"
 
-/* forward decls */
+/* ****** DOCUMENTATION ***** */
 
-class CacheManager;
+/**
+ \defgroup FileSystems Storage Filesystems
+ *
+ \section Introduction Introduction
+ \par
+ * Traditionally, Squid has always used the Unix filesystem (\link UFS UFS\endlink)
+ * to store cache objects on disk.  Over the years, the
+ * poor performance of \link UFS UFS\endlink has become very obvious.  In most
+ * cases, \link UFS UFS\endlink limits Squid to about 30-50 requests per second.
+ * Our work indicates that the poor performance is mostly
+ * due to the synchronous nature of open() and unlink()
+ * system calls, and perhaps thrashing of inode/buffer caches.
+ *
+ \par
+ * We want to try out our own, customized filesystems with Squid.
+ * In order to do that, we need a well-defined interface
+ * for the bits of Squid that access the permanent storage
+ * devices. We also require tighter control of the replacement
+ * policy by each storage module, rather than a single global
+ * replacement policy.
+ *
+ \section BuildStructure Build structure
+ \par
+ * The storage types live in \em src/fs/. Each subdirectory corresponds
+ * to the name of the storage type. When a new storage type is implemented
+ * configure.ac must be updated to autogenerate a Makefile in
+ * \em src/fs/foo/ from a Makefile.in file.
+ *
+ \todo DOCS: add template addition to configure.ac for storage module addition.
+ \todo DOCS: add template Makefile.am for storage module addition.
+ *
+ \par
+ * configure will take a list of storage types through the
+ * --enable-store-io parameter. This parameter takes a list of
+ * space seperated storage types. For example,
+ * --enable-store-io="ufs coss" .
+ *
+ \par
+ * Each storage type must create an archive file
+ * in \em src/fs/foo/.a . This file is automatically linked into
+ * squid at compile time.
+ *
+ \par
+ * Each storage filesystem must inherit from StoreFileSystem and provide
+ * all virtual function hooks for squid to operate with.
+ *
+ \section OperationOfStorageModules Operation of a Storage Module
+ \par
+ *    Squid understands the concept of multiple diverse storage directories.
+ *    Each storage directory provides a caching object store, with object
+ *    storage, retrieval, indexing and replacement.
+ *
+ \par
+ *    Each open object has associated with it a storeIOState object. The
+ *    storeIOState object is used to record the state of the current
+ *    object. Each storeIOState can have a storage module specific data
+ *    structure containing information private to the storage module.
+ *
+ \par
+ *    Each SwapDir has the concept of a maximum object size. This is used
+ *    as a basic hint to the storage layer in first choosing a suitable
+ *    SwapDir. The checkobj function is then called for suitable
+ *    candidate SwapDirs to find out whether it wants to store a
+ *    given StoreEntry. A maxobjsize of -1 means 'any size'.
+ */
 
 class SwapDir;
 
+/**
+ \ingroup FileSystems
+ *
+ * The core API for storage modules this class provides all the hooks
+ * squid uses to interact with a filesystem IO module.
+ */
 class StoreFileSystem
 {
 
 public:
-    static void RegisterAllFsWithCacheManager(CacheManager & manager);
     static void SetupAllFs();
     static void FsAdd(StoreFileSystem &);
     static void FreeAllFs();
@@ -56,12 +123,11 @@ public:
     typedef Vector<StoreFileSystem*>::const_iterator const_iterator;
     StoreFileSystem() : initialised(false) {}
 
-    virtual ~StoreFileSystem(){}
+    virtual ~StoreFileSystem() {}
 
     virtual char const *type () const = 0;
     virtual SwapDir *createSwapDir() = 0;
     virtual void done() = 0;
-    virtual void registerWithCacheManager(CacheManager & manager);
     virtual void setup() = 0;
     // Not implemented
     StoreFileSystem(StoreFileSystem const &);
@@ -69,13 +135,15 @@ public:
 
 protected:
     bool initialised;
+    virtual void registerWithCacheManager(void);
 
 private:
     static Vector<StoreFileSystem*> &GetFileSystems();
     static Vector<StoreFileSystem*> *_FileSystems;
+    static void RegisterAllFsWithCacheManager(void);
 };
 
+// TODO: Kill this typedef!
 typedef StoreFileSystem storefs_entry_t;
 
-
 #endif /* SQUID_STOREFILESYSTEM_H */