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 /* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #ifndef StartupCache_h_

 #define StartupCache_h_

 #include "nsClassHashtable.h"

 #include "nsComponentManagerUtils.h"

 #include "nsZipArchive.h"

 #include "nsIStartupCache.h"

 #include "nsITimer.h"

 #include "nsIMemoryReporter.h"

 #include "nsIObserverService.h"

 #include "nsIObserver.h"

 #include "nsIOutputStream.h"

 #include "nsIFile.h"

 #include "mozilla/Attributes.h"

 #include "mozilla/MemoryReporting.h"

 #include "mozilla/StaticPtr.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.

  * Additionally, the static method IgnoreDiskCache() can be called if it is

  * believed that the on-disk cache file is itself corrupt. This call implicitly

  * calls InvalidateCache (if the singleton has been initialized) to ensure any

  * data already read from disk is discarded. The cache will not load data from

  * the disk file until a successful write occurs.

  *

  * 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;

   uint32_t size;

   CacheEntry() : data(nullptr), size(0) { }

   // Takes possession of buf

   CacheEntry(char* buf, uint32_t len) : data(buf), size(len) { }

   ~CacheEntry()

   {

   }

   size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) {

     return mallocSizeOf(data);

   }

 };

 // We don't want to refcount StartupCache, and ObserverService wants to

 // refcount its listeners, so we'll let it refcount this instead.

 class StartupCacheListener MOZ_FINAL : public nsIObserver

 {

   NS_DECL_THREADSAFE_ISUPPORTS

   NS_DECL_NSIOBSERVER

 };

 class StartupCache : public nsIMemoryReporter

 {

 friend class StartupCacheListener;

 friend class StartupCacheWrapper;

 public:

   NS_DECL_THREADSAFE_ISUPPORTS

   NS_DECL_NSIMEMORYREPORTER

   // 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, uint32_t* length);

   // Stores a buffer. Caller keeps ownership, we make a copy.

   nsresult PutBuffer(const char* id, const char* inbuf, uint32_t length);

   // Removes the cache file.

   void InvalidateCache();

   // Signal that data should not be loaded from the cache file

   static void IgnoreDiskCache();

   // 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);

   nsresult RecordAgesAlways();

   static StartupCache* GetSingleton();

   static void DeleteSingleton();

   // This measures all the heap memory used by the StartupCache, i.e. it

   // excludes the mapping.

   size_t HeapSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf);

   size_t SizeOfMapping();

 private:

   StartupCache();

   virtual ~StartupCache();

   enum TelemetrifyAge {

     IGNORE_AGE = 0,

     RECORD_AGE = 1

   };

   static enum TelemetrifyAge gPostFlushAgeAction;

   nsresult LoadArchive(enum TelemetrifyAge flag);

   nsresult Init();

   void WriteToDisk();

   nsresult ResetStartupWriteTimer();

   void WaitOnWriteThread();

   static nsresult InitSingleton();

   static void WriteTimeout(nsITimer *aTimer, void *aClosure);

   static void ThreadedWrite(void *aClosure);

   static size_t SizeOfEntryExcludingThis(const nsACString& key,

                                          const nsAutoPtr<CacheEntry>& data,

                                          mozilla::MallocSizeOf mallocSizeOf,

                                          void *);

   nsClassHashtable<nsCStringHashKey, CacheEntry> mTable;

   nsRefPtr<nsZipArchive> mArchive;

   nsCOMPtr<nsIFile> mFile;

   nsCOMPtr<nsIObserverService> mObserverService;

   nsRefPtr<StartupCacheListener> mListener;

   nsCOMPtr<nsITimer> mTimer;

   bool mStartupWriteInitiated;

   static StaticRefPtr<StartupCache> gStartupCache;

   static bool gShutdownInitiated;

   static bool gIgnoreDiskCache;

   PRThread *mWriteThread;

 #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 MOZ_FINAL

   : 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)

   bool 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 MOZ_FINAL

   : public nsIStartupCache

 {

   NS_DECL_THREADSAFE_ISUPPORTS

   NS_DECL_NSISTARTUPCACHE

   static StartupCacheWrapper* GetSingleton();

   static StartupCacheWrapper *gStartupCacheWrapper;

 };

 } // namespace scache

 } // namespace mozilla

 #endif //StartupCache_h_