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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 */
#ifndef StartupCache_h_
#define StartupCache_h_
#include "nsClassHashtable.h"
#include "nsComponentManagerUtils.h"
#include "nsTArray.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"
#include "mozilla/UniquePtr.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 XPCOMInit.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
UniquePtr<char[]> data;
uint32_t size;
CacheEntry() : size(0) { }
// Takes possession of buf
CacheEntry(UniquePtr<char[]> buf, uint32_t len) : data(Move(buf)), size(len) { }
size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) {
return mallocSizeOf(this) + mallocSizeOf(data.get());
// We don't want to refcount StartupCache, and ObserverService wants to
// refcount its listeners, so we'll let it refcount this instead.
class StartupCacheListener final : public nsIObserver
~StartupCacheListener() {}
class StartupCache : public nsIMemoryReporter
friend class StartupCacheListener;
friend class StartupCacheWrapper;
// 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, UniquePtr<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);
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) const;
size_t SizeOfMapping();
virtual ~StartupCache();
enum TelemetrifyAge {
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);
nsClassHashtable<nsCStringHashKey, CacheEntry> mTable;
nsTArray<nsCString> mPendingWrites;
RefPtr<nsZipArchive> mArchive;
nsCOMPtr<nsIFile> mFile;
nsCOMPtr<nsIObserverService> mObserverService;
RefPtr<StartupCacheListener> mListener;
nsCOMPtr<nsITimer> mTimer;
bool mStartupWriteInitiated;
static StaticRefPtr<StartupCache> gStartupCache;
static bool gShutdownInitiated;
static bool gIgnoreDiskCache;
PRThread *mWriteThread;
#ifdef DEBUG
nsTHashtable<nsISupportsHashKey> mWriteObjectMap;
// 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 final
: public nsIObjectOutputStream
~StartupCacheDebugOutputStream() {}
StartupCacheDebugOutputStream (nsIObjectOutputStream* binaryStream,
nsTHashtable<nsISupportsHashKey>* objectMap)
: mBinaryStream(binaryStream), mObjectMap(objectMap) { }
bool CheckReferences(nsISupports* aObject);
nsCOMPtr<nsIObjectOutputStream> mBinaryStream;
nsTHashtable<nsISupportsHashKey> *mObjectMap;
#endif // DEBUG
// XPCOM wrapper interface provided for tests only.
{0xae4505a9, 0x87ab, 0x477c, \
{0xb5, 0x77, 0xf9, 0x23, 0x57, 0xed, 0xa8, 0x84}}
// contract id: ";1"
class StartupCacheWrapper final
: public nsIStartupCache
static StartupCacheWrapper* GetSingleton();
static StartupCacheWrapper *gStartupCacheWrapper;
} // namespace scache
} // namespace mozilla
#endif //StartupCache_h_