gecko-dev/startupcache/StartupCache.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Startup Cache.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation <http://www.mozilla.org/>.
* Portions created by the Initial Developer are Copyright (C) 2009
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Benedict Hsieh <bhsieh@mozilla.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef StartupCache_h_
#define StartupCache_h_
#include "prio.h"
#include "prtypes.h"
#include "nsClassHashtable.h"
#include "nsIZipWriter.h"
#include "nsIZipReader.h"
#include "nsComponentManagerUtils.h"
#include "nsZipArchive.h"
#include "nsIStartupCache.h"
#include "nsIStorageStream.h"
#include "nsITimer.h"
#include "nsIObserverService.h"
#include "nsIObserver.h"
#include "nsIOutputStream.h"
#include "nsIFile.h"
/**
* The StartupCache is a persistent cache of simple key-value pairs,
* where the keys are null-terminated c-strings and the values are
* arbitrary data, passed as a (char*, size) tuple.
*
* Clients should use the GetSingleton() static method to access the cache. It
* will be available from the end of XPCOM init (NS_InitXPCOM3 in nsXPComInit.cpp),
* until XPCOM shutdown begins. The GetSingleton() method will return null if the cache
* is unavailable. The cache is only provided for libxul builds --
* it will fail to link in non-libxul builds. The XPCOM interface is provided
* only to allow compiled-code tests; clients should avoid using it.
*
* The API provided is very simple: GetBuffer() returns a buffer that was previously
* stored in the cache (if any), and PutBuffer() inserts a buffer into the cache.
* GetBuffer returns a new buffer, and the caller must take ownership of it.
* PutBuffer will assert if the client attempts to insert a buffer with the same name as
* an existing entry. The cache makes a copy of the passed-in buffer, so client
* retains ownership.
*
* InvalidateCache() may be called if a client suspects data corruption
* or wishes to invalidate for any other reason. This will remove all existing cache data.
* Finally, getDebugObjectOutputStream() allows debug code to wrap an objectstream
* with a debug objectstream, to check for multiply-referenced objects. These will
* generally fail to deserialize correctly, unless they are stateless singletons or the
* client maintains their own object data map for deserialization.
*
* Writes before the final-ui-startup notification are placed in an intermediate
* cache in memory, then written out to disk at a later time, to get writes off the
* startup path. In any case, clients should not rely on being able to GetBuffer()
* data that is written to the cache, since it may not have been written to disk or
* another client may have invalidated the cache. In other words, it should be used as
* a cache only, and not a reliable persistent store.
*
* Some utility functions are provided in StartupCacheUtils. These functions wrap the
* buffers into object streams, which may be useful for serializing objects. Note
* the above caution about multiply-referenced objects, though -- the streams are just
* as 'dumb' as the underlying buffers about multiply-referenced objects. They just
* provide some convenience in writing out data.
*/
namespace mozilla {
namespace scache {
struct CacheEntry
{
nsAutoArrayPtr<char> data;
PRUint32 size;
CacheEntry() : data(nsnull), size(0) { }
// Takes possession of buf
CacheEntry(char* buf, PRUint32 len) : data(buf), size(len) { }
~CacheEntry()
{
}
};
// We don't want to refcount StartupCache, and ObserverService wants to
// refcount its listeners, so we'll let it refcount this instead.
class StartupCacheListener : public nsIObserver
{
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
};
class StartupCache
{
friend class StartupCacheListener;
friend class StartupCacheWrapper;
public:
// StartupCache methods. See above comments for a more detailed description.
// Returns a buffer that was previously stored, caller takes ownership.
nsresult GetBuffer(const char* id, char** outbuf, PRUint32* length);
// Stores a buffer. Caller keeps ownership, we make a copy.
nsresult PutBuffer(const char* id, const char* inbuf, PRUint32 length);
// Removes the cache file.
void InvalidateCache();
// In DEBUG builds, returns a stream that will attempt to check for
// and disallow multiple writes of the same object.
nsresult GetDebugObjectOutputStream(nsIObjectOutputStream* aStream,
nsIObjectOutputStream** outStream);
static StartupCache* GetSingleton();
static void DeleteSingleton();
private:
StartupCache();
~StartupCache();
nsresult LoadArchive();
nsresult Init();
void WriteToDisk();
static nsresult InitSingleton();
static void WriteTimeout(nsITimer *aTimer, void *aClosure);
nsClassHashtable<nsCStringHashKey, CacheEntry> mTable;
nsCOMPtr<nsIZipWriter> mZipW;
nsAutoPtr<nsZipArchive> mArchive;
nsCOMPtr<nsILocalFile> mFile;
nsCOMPtr<nsIObserverService> mObserverService;
nsRefPtr<StartupCacheListener> mListener;
nsCOMPtr<nsITimer> mTimer;
PRBool mStartupWriteInitiated;
static StartupCache *gStartupCache;
static PRBool gShutdownInitiated;
#ifdef DEBUG
nsTHashtable<nsISupportsHashKey> mWriteObjectMap;
#endif
};
// This debug outputstream attempts to detect if clients are writing multiple
// references to the same object. We only support that if that object
// is a singleton.
#ifdef DEBUG
class StartupCacheDebugOutputStream
: public nsIObjectOutputStream
{
NS_DECL_ISUPPORTS
NS_DECL_NSIOBJECTOUTPUTSTREAM
StartupCacheDebugOutputStream (nsIObjectOutputStream* binaryStream,
nsTHashtable<nsISupportsHashKey>* objectMap)
: mBinaryStream(binaryStream), mObjectMap(objectMap) { }
NS_FORWARD_SAFE_NSIBINARYOUTPUTSTREAM(mBinaryStream)
NS_FORWARD_SAFE_NSIOUTPUTSTREAM(mBinaryStream)
PRBool CheckReferences(nsISupports* aObject);
nsCOMPtr<nsIObjectOutputStream> mBinaryStream;
nsTHashtable<nsISupportsHashKey> *mObjectMap;
};
#endif // DEBUG
// XPCOM wrapper interface provided for tests only.
#define NS_STARTUPCACHE_CID \
{0xae4505a9, 0x87ab, 0x477c, \
{0xb5, 0x77, 0xf9, 0x23, 0x57, 0xed, 0xa8, 0x84}}
// contract id: "@mozilla.org/startupcache/cache;1"
class StartupCacheWrapper
: public nsIStartupCache
{
NS_DECL_ISUPPORTS
NS_DECL_NSISTARTUPCACHE
static StartupCacheWrapper* GetSingleton();
static StartupCacheWrapper *gStartupCacheWrapper;
};
} // namespace scache
} // namespace mozilla
#endif //StartupCache_h_