The Tor Browser: comparison startupcache/StartupCache.h

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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_

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comparison: startupcache/StartupCache.h

startupcache/StartupCache.h