The Tor Browser: startupcache/StartupCache.h@925c144e1f1f (annotated)

startupcache/StartupCache.h@925c144e1f1f (annotated)

startupcache/StartupCache.h

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /* -*-  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_

The Tor Browser / annotate

startupcache/StartupCache.h@925c144e1f1f (annotated)

startupcache/StartupCache.h