xpcom/base/nsCycleCollector.h
author Andrew McCreight <amccreight@mozilla.com>
Mon, 05 Mar 2012 13:48:04 -0800
changeset 88505 d00e5203b958bbb974c4c1bc531f85a1743c83a8
parent 87807 66a56113abeb9f5ebc43a029b087be95f7770899
child 91832 d9964e231f469686a109f1da0a30a107c79e2ace
permissions -rw-r--r--
Bug 728460, part 1 - add forget_skippable option to remove childless nodes. r=smaug

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

// NOTE: If you use header files to define DEBUG_CC, you must do so here
// *and* in nsCycleCollectionParticipant.h
//#define DEBUG_CC

class nsISupports;
class nsICycleCollectorListener;
class nsCycleCollectionParticipant;
class nsCycleCollectionTraversalCallback;

// An nsCycleCollectionLanguageRuntime is a per-language object that
// implements language-specific aspects of the cycle collection task.

struct nsCycleCollectionLanguageRuntime
{
    virtual nsresult BeginCycleCollection(nsCycleCollectionTraversalCallback &cb,
                                          bool explainLiveExpectedGarbage) = 0;
    virtual nsresult FinishTraverse() = 0;
    virtual nsresult FinishCycleCollection() = 0;
    virtual nsCycleCollectionParticipant *ToParticipant(void *p) = 0;
#ifdef DEBUG_CC
    virtual void PrintAllReferencesTo(void *p) = 0;
#endif
};

// Contains various stats about the cycle collection.
class nsCycleCollectorResults
{
public:
    nsCycleCollectorResults() :
        mForcedGC(false), mVisitedRefCounted(0), mVisitedGCed(0),
        mFreedRefCounted(0), mFreedGCed(0) {}
    bool mForcedGC;
    PRUint32 mVisitedRefCounted;
    PRUint32 mVisitedGCed;
    PRUint32 mFreedRefCounted;
    PRUint32 mFreedGCed;
};

nsresult nsCycleCollector_startup();

typedef void (*CC_BeforeUnlinkCallback)(void);
void nsCycleCollector_setBeforeUnlinkCallback(CC_BeforeUnlinkCallback aCB);

typedef void (*CC_ForgetSkippableCallback)(void);
void nsCycleCollector_setForgetSkippableCallback(CC_ForgetSkippableCallback aCB);

void nsCycleCollector_forgetSkippable(bool aRemoveChildlessNodes = false);

#ifdef DEBUG_CC
void nsCycleCollector_logPurpleRemoval(void* aObject);
#endif

void nsCycleCollector_collect(nsCycleCollectorResults *aResults,
                              nsICycleCollectorListener *aListener);
PRUint32 nsCycleCollector_suspectedCount();
void nsCycleCollector_shutdownThreads();
void nsCycleCollector_shutdown();

// The JS runtime is special, it needs to call cycle collection during its GC.
// If the JS runtime is registered nsCycleCollector_collect will call
// nsCycleCollectionJSRuntime::Collect which will call
// nsCycleCollector_doCollect, else nsCycleCollector_collect will call
// nsCycleCollector_doCollect directly.
struct nsCycleCollectionJSRuntime : public nsCycleCollectionLanguageRuntime
{
    /**
     * Called before/after transitioning to/from the main thread.
     *
     * NotifyLeaveMainThread may return 'false' to prevent the cycle collector
     * from leaving the main thread.
     */
    virtual bool NotifyLeaveMainThread() = 0;
    virtual void NotifyEnterCycleCollectionThread() = 0;
    virtual void NotifyLeaveCycleCollectionThread() = 0;
    virtual void NotifyEnterMainThread() = 0;

    /**
     * Should we force a JavaScript GC before a CC?
     */
    virtual bool NeedCollect() = 0;

    /**
     * Runs the JavaScript GC. |reason| is a gcreason::Reason from jsfriendapi.h.
     * |kind| is a nsGCType from nsIXPConnect.idl.
     */
    virtual void Collect(PRUint32 reason, PRUint32 kind) = 0;
};

#ifdef DEBUG
void nsCycleCollector_DEBUG_shouldBeFreed(nsISupports *n);
void nsCycleCollector_DEBUG_wasFreed(nsISupports *n);
#endif

// Helpers for interacting with language-identified scripts

void nsCycleCollector_registerRuntime(PRUint32 langID, nsCycleCollectionLanguageRuntime *rt);
nsCycleCollectionLanguageRuntime * nsCycleCollector_getRuntime(PRUint32 langID);
void nsCycleCollector_forgetRuntime(PRUint32 langID);

#define NS_CYCLE_COLLECTOR_LOGGER_CID \
{ 0x58be81b4, 0x39d2, 0x437c, \
{ 0x94, 0xea, 0xae, 0xde, 0x2c, 0x62, 0x08, 0xd3 } }

extern nsresult
nsCycleCollectorLoggerConstructor(nsISupports* outer,
                                  const nsIID& aIID,
                                  void* *aInstancePtr);

#endif // nsCycleCollector_h__