libutils/RefBase.cpp - platform/system/core - Gitiles

 /*
  * Copyright (C) 2005 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #define LOG_TAG "RefBase"
 // #define LOG_NDEBUG 0

 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <typeinfo>
 #include <unistd.h>

 #include <utils/RefBase.h>

 #include <utils/Atomic.h>
 #include <utils/CallStack.h>
 #include <utils/Log.h>
 #include <utils/threads.h>

 #ifndef __unused
 #define __unused __attribute__((__unused__))
 #endif

 // compile with refcounting debugging enabled
 #define DEBUG_REFS                      0

 // whether ref-tracking is enabled by default, if not, trackMe(true, false)
 // needs to be called explicitly
 #define DEBUG_REFS_ENABLED_BY_DEFAULT   0

 // whether callstack are collected (significantly slows things down)
 #define DEBUG_REFS_CALLSTACK_ENABLED    1

 // folder where stack traces are saved when DEBUG_REFS is enabled
 // this folder needs to exist and be writable
 #define DEBUG_REFS_CALLSTACK_PATH       "/data/debug"

 // log all reference counting operations
 #define PRINT_REFS                      0

 // ---------------------------------------------------------------------------

 namespace android {

 #define INITIAL_STRONG_VALUE (1<<28)

 // ---------------------------------------------------------------------------

 class RefBase::weakref_impl : public RefBase::weakref_type
 {
 public:
     volatile int32_t    mStrong;
     volatile int32_t    mWeak;
     RefBase* const      mBase;
     volatile int32_t    mFlags;

 #if !DEBUG_REFS

     weakref_impl(RefBase* base)
         : mStrong(INITIAL_STRONG_VALUE)
         , mWeak(0)
         , mBase(base)
         , mFlags(0)
     {
     }

     void addStrongRef(const void* /*id*/) { }
     void removeStrongRef(const void* /*id*/) { }
     void renameStrongRefId(const void* /*old_id*/, const void* /*new_id*/) { }
     void addWeakRef(const void* /*id*/) { }
     void removeWeakRef(const void* /*id*/) { }
     void renameWeakRefId(const void* /*old_id*/, const void* /*new_id*/) { }
     void printRefs() const { }
     void trackMe(bool, bool) { }

 #else

     weakref_impl(RefBase* base)
         : mStrong(INITIAL_STRONG_VALUE)
         , mWeak(0)
         , mBase(base)
         , mFlags(0)
         , mStrongRefs(NULL)
         , mWeakRefs(NULL)
         , mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
         , mRetain(false)
     {
     }

     ~weakref_impl()
     {
         bool dumpStack = false;
         if (!mRetain && mStrongRefs != NULL) {
             dumpStack = true;
             ALOGE("Strong references remain:");
             ref_entry* refs = mStrongRefs;
             while (refs) {
                 char inc = refs->ref >= 0 ? '+' : '-';
                 ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
 #if DEBUG_REFS_CALLSTACK_ENABLED
                 refs->stack.log(LOG_TAG);
 #endif
                 refs = refs->next;
             }
         }

         if (!mRetain && mWeakRefs != NULL) {
             dumpStack = true;
             ALOGE("Weak references remain!");
             ref_entry* refs = mWeakRefs;
             while (refs) {
                 char inc = refs->ref >= 0 ? '+' : '-';
                 ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
 #if DEBUG_REFS_CALLSTACK_ENABLED
                 refs->stack.log(LOG_TAG);
 #endif
                 refs = refs->next;
             }
         }
         if (dumpStack) {
             ALOGE("above errors at:");
             CallStack stack(LOG_TAG);
         }
     }

     void addStrongRef(const void* id) {
         //ALOGD_IF(mTrackEnabled,
         //        "addStrongRef: RefBase=%p, id=%p", mBase, id);
         addRef(&mStrongRefs, id, mStrong);
     }

     void removeStrongRef(const void* id) {
         //ALOGD_IF(mTrackEnabled,
         //        "removeStrongRef: RefBase=%p, id=%p", mBase, id);
         if (!mRetain) {
             removeRef(&mStrongRefs, id);
         } else {
             addRef(&mStrongRefs, id, -mStrong);
         }
     }

     void renameStrongRefId(const void* old_id, const void* new_id) {
         //ALOGD_IF(mTrackEnabled,
         //        "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
         //        mBase, old_id, new_id);
         renameRefsId(mStrongRefs, old_id, new_id);
     }

     void addWeakRef(const void* id) {
         addRef(&mWeakRefs, id, mWeak);
     }

     void removeWeakRef(const void* id) {
         if (!mRetain) {
             removeRef(&mWeakRefs, id);
         } else {
             addRef(&mWeakRefs, id, -mWeak);
         }
     }

     void renameWeakRefId(const void* old_id, const void* new_id) {
         renameRefsId(mWeakRefs, old_id, new_id);
     }

     void trackMe(bool track, bool retain)
     {
         mTrackEnabled = track;
         mRetain = retain;
     }

     void printRefs() const
     {
         String8 text;

         {
             Mutex::Autolock _l(mMutex);
             char buf[128];
             snprintf(buf, sizeof(buf),
                      "Strong references on RefBase %p (weakref_type %p):\n",
                      mBase, this);
             text.append(buf);
             printRefsLocked(&text, mStrongRefs);
             snprintf(buf, sizeof(buf),
                      "Weak references on RefBase %p (weakref_type %p):\n",
                      mBase, this);
             text.append(buf);
             printRefsLocked(&text, mWeakRefs);
         }

         {
             char name[100];
             snprintf(name, sizeof(name), DEBUG_REFS_CALLSTACK_PATH "/%p.stack",
                      this);
             int rc = open(name, O_RDWR | O_CREAT | O_APPEND, 644);
             if (rc >= 0) {
                 write(rc, text.string(), text.length());
                 close(rc);
                 ALOGD("STACK TRACE for %p saved in %s", this, name);
             }
             else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
                       name, strerror(errno));
         }
     }

 private:
     struct ref_entry
     {
         ref_entry* next;
         const void* id;
 #if DEBUG_REFS_CALLSTACK_ENABLED
         CallStack stack;
 #endif
         int32_t ref;
     };

     void addRef(ref_entry** refs, const void* id, int32_t mRef)
     {
         if (mTrackEnabled) {
             AutoMutex _l(mMutex);

             ref_entry* ref = new ref_entry;
             // Reference count at the time of the snapshot, but before the
             // update.  Positive value means we increment, negative--we
             // decrement the reference count.
             ref->ref = mRef;
             ref->id = id;
 #if DEBUG_REFS_CALLSTACK_ENABLED
             ref->stack.update(2);
 #endif
             ref->next = *refs;
             *refs = ref;
         }
     }

     void removeRef(ref_entry** refs, const void* id)
     {
         if (mTrackEnabled) {
             AutoMutex _l(mMutex);

             ref_entry* const head = *refs;
             ref_entry* ref = head;
             while (ref != NULL) {
                 if (ref->id == id) {
                     *refs = ref->next;
                     delete ref;
                     return;
                 }
                 refs = &ref->next;
                 ref = *refs;
             }

             ALOGE("RefBase: removing id %p on RefBase %p"
                     "(weakref_type %p) that doesn't exist!",
                     id, mBase, this);

             ref = head;
             while (ref) {
                 char inc = ref->ref >= 0 ? '+' : '-';
                 ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
                 ref = ref->next;
             }

             CallStack stack(LOG_TAG);
         }
     }

     void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
     {
         if (mTrackEnabled) {
             AutoMutex _l(mMutex);
             ref_entry* ref = r;
             while (ref != NULL) {
                 if (ref->id == old_id) {
                     ref->id = new_id;
                 }
                 ref = ref->next;
             }
         }
     }

     void printRefsLocked(String8* out, const ref_entry* refs) const
     {
         char buf[128];
         while (refs) {
             char inc = refs->ref >= 0 ? '+' : '-';
             snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n",
                      inc, refs->id, refs->ref);
             out->append(buf);
 #if DEBUG_REFS_CALLSTACK_ENABLED
             out->append(refs->stack.toString("\t\t"));
 #else
             out->append("\t\t(call stacks disabled)");
 #endif
             refs = refs->next;
         }
     }

     mutable Mutex mMutex;
     ref_entry* mStrongRefs;
     ref_entry* mWeakRefs;

     bool mTrackEnabled;
     // Collect stack traces on addref and removeref, instead of deleting the stack references
     // on removeref that match the address ones.
     bool mRetain;

 #endif
 };

 // ---------------------------------------------------------------------------

 void RefBase::incStrong(const void* id) const
 {
     weakref_impl* const refs = mRefs;
     refs->incWeak(id);

     refs->addStrongRef(id);
     const int32_t c = android_atomic_inc(&refs->mStrong);
     ALOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
 #if PRINT_REFS
     ALOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
 #endif
     if (c != INITIAL_STRONG_VALUE)  {
         return;
     }

     android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
     refs->mBase->onFirstRef();
 }

 void RefBase::decStrong(const void* id) const
 {
     weakref_impl* const refs = mRefs;
     refs->removeStrongRef(id);
     const int32_t c = android_atomic_dec(&refs->mStrong);
 #if PRINT_REFS
     ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
 #endif
     ALOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
     if (c == 1) {
         refs->mBase->onLastStrongRef(id);
         if ((refs->mFlags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
             delete this;
         }
     }
     refs->decWeak(id);
 }

 void RefBase::forceIncStrong(const void* id) const
 {
     weakref_impl* const refs = mRefs;
     refs->incWeak(id);

     refs->addStrongRef(id);
     const int32_t c = android_atomic_inc(&refs->mStrong);
     ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
                refs);
 #if PRINT_REFS
     ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
 #endif

     switch (c) {
     case INITIAL_STRONG_VALUE:
         android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
         // fall through...
     case 0:
         refs->mBase->onFirstRef();
     }
 }

 int32_t RefBase::getStrongCount() const
 {
     return mRefs->mStrong;
 }

 RefBase* RefBase::weakref_type::refBase() const
 {
     return static_cast<const weakref_impl*>(this)->mBase;
 }

 void RefBase::weakref_type::incWeak(const void* id)
 {
     weakref_impl* const impl = static_cast<weakref_impl*>(this);
     impl->addWeakRef(id);
     const int32_t c __unused = android_atomic_inc(&impl->mWeak);
     ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
 }


 void RefBase::weakref_type::decWeak(const void* id)
 {
     weakref_impl* const impl = static_cast<weakref_impl*>(this);
     impl->removeWeakRef(id);
     const int32_t c = android_atomic_dec(&impl->mWeak);
     ALOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
     if (c != 1) return;

     if ((impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_STRONG) {
         // This is the regular lifetime case. The object is destroyed
         // when the last strong reference goes away. Since weakref_impl
         // outlive the object, it is not destroyed in the dtor, and
         // we'll have to do it here.
         if (impl->mStrong == INITIAL_STRONG_VALUE) {
             // Special case: we never had a strong reference, so we need to
             // destroy the object now.
             delete impl->mBase;
         } else {
             // ALOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
             delete impl;
         }
     } else {
         // less common case: lifetime is OBJECT_LIFETIME_{WEAK|FOREVER}
         impl->mBase->onLastWeakRef(id);
         if ((impl->mFlags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_WEAK) {
             // this is the OBJECT_LIFETIME_WEAK case. The last weak-reference
             // is gone, we can destroy the object.
             delete impl->mBase;
         }
     }
 }

 bool RefBase::weakref_type::attemptIncStrong(const void* id)
 {
     incWeak(id);

     weakref_impl* const impl = static_cast<weakref_impl*>(this);
     int32_t curCount = impl->mStrong;

     ALOG_ASSERT(curCount >= 0,
             "attemptIncStrong called on %p after underflow", this);

     while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
         // we're in the easy/common case of promoting a weak-reference
         // from an existing strong reference.
         if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
             break;
         }
         // the strong count has changed on us, we need to re-assert our
         // situation.
         curCount = impl->mStrong;
     }

     if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
         // we're now in the harder case of either:
         // - there never was a strong reference on us
         // - or, all strong references have been released
         if ((impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_STRONG) {
             // this object has a "normal" life-time, i.e.: it gets destroyed
             // when the last strong reference goes away
             if (curCount <= 0) {
                 // the last strong-reference got released, the object cannot
                 // be revived.
                 decWeak(id);
                 return false;
             }

             // here, curCount == INITIAL_STRONG_VALUE, which means
             // there never was a strong-reference, so we can try to
             // promote this object; we need to do that atomically.
             while (curCount > 0) {
                 if (android_atomic_cmpxchg(curCount, curCount + 1,
                         &impl->mStrong) == 0) {
                     break;
                 }
                 // the strong count has changed on us, we need to re-assert our
                 // situation (e.g.: another thread has inc/decStrong'ed us)
                 curCount = impl->mStrong;
             }

             if (curCount <= 0) {
                 // promote() failed, some other thread destroyed us in the
                 // meantime (i.e.: strong count reached zero).
                 decWeak(id);
                 return false;
             }
         } else {
             // this object has an "extended" life-time, i.e.: it can be
             // revived from a weak-reference only.
             // Ask the object's implementation if it agrees to be revived
             if (!impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id)) {
                 // it didn't so give-up.
                 decWeak(id);
                 return false;
             }
             // grab a strong-reference, which is always safe due to the
             // extended life-time.
             curCount = android_atomic_inc(&impl->mStrong);
         }

         // If the strong reference count has already been incremented by
         // someone else, the implementor of onIncStrongAttempted() is holding
         // an unneeded reference.  So call onLastStrongRef() here to remove it.
         // (No, this is not pretty.)  Note that we MUST NOT do this if we
         // are in fact acquiring the first reference.
         if (curCount > 0 && curCount < INITIAL_STRONG_VALUE) {
             impl->mBase->onLastStrongRef(id);
         }
     }

     impl->addStrongRef(id);

 #if PRINT_REFS
     ALOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
 #endif

     // now we need to fix-up the count if it was INITIAL_STRONG_VALUE
     // this must be done safely, i.e.: handle the case where several threads
     // were here in attemptIncStrong().
     curCount = impl->mStrong;
     while (curCount >= INITIAL_STRONG_VALUE) {
         ALOG_ASSERT(curCount > INITIAL_STRONG_VALUE,
                 "attemptIncStrong in %p underflowed to INITIAL_STRONG_VALUE",
                 this);
         if (android_atomic_cmpxchg(curCount, curCount-INITIAL_STRONG_VALUE,
                 &impl->mStrong) == 0) {
             break;
         }
         // the strong-count changed on us, we need to re-assert the situation,
         // for e.g.: it's possible the fix-up happened in another thread.
         curCount = impl->mStrong;
     }

     return true;
 }

 bool RefBase::weakref_type::attemptIncWeak(const void* id)
 {
     weakref_impl* const impl = static_cast<weakref_impl*>(this);

     int32_t curCount = impl->mWeak;
     ALOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
                this);
     while (curCount > 0) {
         if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
             break;
         }
         curCount = impl->mWeak;
     }

     if (curCount > 0) {
         impl->addWeakRef(id);
     }

     return curCount > 0;
 }

 int32_t RefBase::weakref_type::getWeakCount() const
 {
     return static_cast<const weakref_impl*>(this)->mWeak;
 }

 void RefBase::weakref_type::printRefs() const
 {
     static_cast<const weakref_impl*>(this)->printRefs();
 }

 void RefBase::weakref_type::trackMe(bool enable, bool retain)
 {
     static_cast<weakref_impl*>(this)->trackMe(enable, retain);
 }

 RefBase::weakref_type* RefBase::createWeak(const void* id) const
 {
     mRefs->incWeak(id);
     return mRefs;
 }

 RefBase::weakref_type* RefBase::getWeakRefs() const
 {
     return mRefs;
 }

 RefBase::RefBase()
     : mRefs(new weakref_impl(this))
 {
 }

 RefBase::~RefBase()
 {
     if (mRefs->mStrong == INITIAL_STRONG_VALUE) {
         // we never acquired a strong (and/or weak) reference on this object.
         delete mRefs;
     } else {
         // life-time of this object is extended to WEAK or FOREVER, in
         // which case weakref_impl doesn't out-live the object and we
         // can free it now.
         if ((mRefs->mFlags & OBJECT_LIFETIME_MASK) != OBJECT_LIFETIME_STRONG) {
             // It's possible that the weak count is not 0 if the object
             // re-acquired a weak reference in its destructor
             if (mRefs->mWeak == 0) {
                 delete mRefs;
             }
         }
     }
     // for debugging purposes, clear this.
     const_cast<weakref_impl*&>(mRefs) = NULL;
 }

 void RefBase::extendObjectLifetime(int32_t mode)
 {
     android_atomic_or(mode, &mRefs->mFlags);
 }

 void RefBase::onFirstRef()
 {
 }

 void RefBase::onLastStrongRef(const void* /*id*/)
 {
 }

 bool RefBase::onIncStrongAttempted(uint32_t flags, const void* /*id*/)
 {
     return (flags&FIRST_INC_STRONG) ? true : false;
 }

 void RefBase::onLastWeakRef(const void* /*id*/)
 {
 }

 // ---------------------------------------------------------------------------

 #if DEBUG_REFS
 void RefBase::renameRefs(size_t n, const ReferenceRenamer& renamer) {
     for (size_t i=0 ; i<n ; i++) {
         renamer(i);
     }
 }
 #else
 void RefBase::renameRefs(size_t /*n*/, const ReferenceRenamer& /*renamer*/) { }
 #endif

 void RefBase::renameRefId(weakref_type* ref,
         const void* old_id, const void* new_id) {
     weakref_impl* const impl = static_cast<weakref_impl*>(ref);
     impl->renameStrongRefId(old_id, new_id);
     impl->renameWeakRefId(old_id, new_id);
 }

 void RefBase::renameRefId(RefBase* ref,
         const void* old_id, const void* new_id) {
     ref->mRefs->renameStrongRefId(old_id, new_id);
     ref->mRefs->renameWeakRefId(old_id, new_id);
 }

 }; // namespace android
	/*
	* Copyright (C) 2005 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#define LOG_TAG "RefBase"
	// #define LOG_NDEBUG 0

	#include <fcntl.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <typeinfo>
	#include <unistd.h>

	#include <utils/RefBase.h>

	#include <utils/Atomic.h>
	#include <utils/CallStack.h>
	#include <utils/Log.h>
	#include <utils/threads.h>

	#ifndef __unused
	#define __unused __attribute__((__unused__))
	#endif

	// compile with refcounting debugging enabled
	#define DEBUG_REFS 0

	// whether ref-tracking is enabled by default, if not, trackMe(true, false)
	// needs to be called explicitly
	#define DEBUG_REFS_ENABLED_BY_DEFAULT 0

	// whether callstack are collected (significantly slows things down)
	#define DEBUG_REFS_CALLSTACK_ENABLED 1

	// folder where stack traces are saved when DEBUG_REFS is enabled
	// this folder needs to exist and be writable
	#define DEBUG_REFS_CALLSTACK_PATH "/data/debug"

	// log all reference counting operations
	#define PRINT_REFS 0

	// ---------------------------------------------------------------------------

	namespace android {

	#define INITIAL_STRONG_VALUE (1<<28)

	// ---------------------------------------------------------------------------

	class RefBase::weakref_impl : public RefBase::weakref_type
	{
	public:
	volatile int32_t mStrong;
	volatile int32_t mWeak;
	RefBase* const mBase;
	volatile int32_t mFlags;

	#if !DEBUG_REFS

	weakref_impl(RefBase* base)
	: mStrong(INITIAL_STRONG_VALUE)
	, mWeak(0)
	, mBase(base)
	, mFlags(0)
	{
	}

	void addStrongRef(const void* /id/) { }
	void removeStrongRef(const void* /id/) { }
	void renameStrongRefId(const void* /old_id/, const void* /new_id/) { }
	void addWeakRef(const void* /id/) { }
	void removeWeakRef(const void* /id/) { }
	void renameWeakRefId(const void* /old_id/, const void* /new_id/) { }
	void printRefs() const { }
	void trackMe(bool, bool) { }

	#else

	weakref_impl(RefBase* base)
	: mStrong(INITIAL_STRONG_VALUE)
	, mWeak(0)
	, mBase(base)
	, mFlags(0)
	, mStrongRefs(NULL)
	, mWeakRefs(NULL)
	, mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
	, mRetain(false)
	{
	}

	~weakref_impl()
	{
	bool dumpStack = false;
	if (!mRetain && mStrongRefs != NULL) {
	dumpStack = true;
	ALOGE("Strong references remain:");
	ref_entry* refs = mStrongRefs;
	while (refs) {
	char inc = refs->ref >= 0 ? '+' : '-';
	ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
	#if DEBUG_REFS_CALLSTACK_ENABLED
	refs->stack.log(LOG_TAG);
	#endif
	refs = refs->next;
	}
	}

	if (!mRetain && mWeakRefs != NULL) {
	dumpStack = true;
	ALOGE("Weak references remain!");
	ref_entry* refs = mWeakRefs;
	while (refs) {
	char inc = refs->ref >= 0 ? '+' : '-';
	ALOGD("\t%c ID %p (ref %d):", inc, refs->id, refs->ref);
	#if DEBUG_REFS_CALLSTACK_ENABLED
	refs->stack.log(LOG_TAG);
	#endif
	refs = refs->next;
	}
	}
	if (dumpStack) {
	ALOGE("above errors at:");
	CallStack stack(LOG_TAG);
	}
	}

	void addStrongRef(const void* id) {
	//ALOGD_IF(mTrackEnabled,
	// "addStrongRef: RefBase=%p, id=%p", mBase, id);
	addRef(&mStrongRefs, id, mStrong);
	}

	void removeStrongRef(const void* id) {
	//ALOGD_IF(mTrackEnabled,
	// "removeStrongRef: RefBase=%p, id=%p", mBase, id);
	if (!mRetain) {
	removeRef(&mStrongRefs, id);
	} else {
	addRef(&mStrongRefs, id, -mStrong);
	}
	}

	void renameStrongRefId(const void* old_id, const void* new_id) {
	//ALOGD_IF(mTrackEnabled,
	// "renameStrongRefId: RefBase=%p, oid=%p, nid=%p",
	// mBase, old_id, new_id);
	renameRefsId(mStrongRefs, old_id, new_id);
	}

	void addWeakRef(const void* id) {
	addRef(&mWeakRefs, id, mWeak);
	}

	void removeWeakRef(const void* id) {
	if (!mRetain) {
	removeRef(&mWeakRefs, id);
	} else {
	addRef(&mWeakRefs, id, -mWeak);
	}
	}

	void renameWeakRefId(const void* old_id, const void* new_id) {
	renameRefsId(mWeakRefs, old_id, new_id);
	}

	void trackMe(bool track, bool retain)
	{
	mTrackEnabled = track;
	mRetain = retain;
	}

	void printRefs() const
	{
	String8 text;

	{
	Mutex::Autolock _l(mMutex);
	char buf[128];
	snprintf(buf, sizeof(buf),
	"Strong references on RefBase %p (weakref_type %p):\n",
	mBase, this);
	text.append(buf);
	printRefsLocked(&text, mStrongRefs);
	snprintf(buf, sizeof(buf),
	"Weak references on RefBase %p (weakref_type %p):\n",
	mBase, this);
	text.append(buf);
	printRefsLocked(&text, mWeakRefs);
	}

	{
	char name[100];
	snprintf(name, sizeof(name), DEBUG_REFS_CALLSTACK_PATH "/%p.stack",
	this);
	int rc = open(name, O_RDWR \| O_CREAT \| O_APPEND, 644);
	if (rc >= 0) {
	write(rc, text.string(), text.length());
	close(rc);
	ALOGD("STACK TRACE for %p saved in %s", this, name);
	}
	else ALOGE("FAILED TO PRINT STACK TRACE for %p in %s: %s", this,
	name, strerror(errno));
	}
	}

	private:
	struct ref_entry
	{
	ref_entry* next;
	const void* id;
	#if DEBUG_REFS_CALLSTACK_ENABLED
	CallStack stack;
	#endif
	int32_t ref;
	};

	void addRef(ref_entry** refs, const void* id, int32_t mRef)
	{
	if (mTrackEnabled) {
	AutoMutex _l(mMutex);

	ref_entry* ref = new ref_entry;
	// Reference count at the time of the snapshot, but before the
	// update. Positive value means we increment, negative--we
	// decrement the reference count.
	ref->ref = mRef;
	ref->id = id;
	#if DEBUG_REFS_CALLSTACK_ENABLED
	ref->stack.update(2);
	#endif
	ref->next = *refs;
	*refs = ref;
	}
	}

	void removeRef(ref_entry** refs, const void* id)
	{
	if (mTrackEnabled) {
	AutoMutex _l(mMutex);

	ref_entry* const head = *refs;
	ref_entry* ref = head;
	while (ref != NULL) {
	if (ref->id == id) {
	*refs = ref->next;
	delete ref;
	return;
	}
	refs = &ref->next;
	ref = *refs;
	}

	ALOGE("RefBase: removing id %p on RefBase %p"
	"(weakref_type %p) that doesn't exist!",
	id, mBase, this);

	ref = head;
	while (ref) {
	char inc = ref->ref >= 0 ? '+' : '-';
	ALOGD("\t%c ID %p (ref %d):", inc, ref->id, ref->ref);
	ref = ref->next;
	}

	CallStack stack(LOG_TAG);
	}
	}

	void renameRefsId(ref_entry* r, const void* old_id, const void* new_id)
	{
	if (mTrackEnabled) {
	AutoMutex _l(mMutex);
	ref_entry* ref = r;
	while (ref != NULL) {
	if (ref->id == old_id) {
	ref->id = new_id;
	}
	ref = ref->next;
	}
	}
	}

	void printRefsLocked(String8* out, const ref_entry* refs) const
	{
	char buf[128];
	while (refs) {
	char inc = refs->ref >= 0 ? '+' : '-';
	snprintf(buf, sizeof(buf), "\t%c ID %p (ref %d):\n",
	inc, refs->id, refs->ref);
	out->append(buf);
	#if DEBUG_REFS_CALLSTACK_ENABLED
	out->append(refs->stack.toString("\t\t"));
	#else
	out->append("\t\t(call stacks disabled)");
	#endif
	refs = refs->next;
	}
	}

	mutable Mutex mMutex;
	ref_entry* mStrongRefs;
	ref_entry* mWeakRefs;

	bool mTrackEnabled;
	// Collect stack traces on addref and removeref, instead of deleting the stack references
	// on removeref that match the address ones.
	bool mRetain;

	#endif
	};

	// ---------------------------------------------------------------------------

	void RefBase::incStrong(const void* id) const
	{
	weakref_impl* const refs = mRefs;
	refs->incWeak(id);

	refs->addStrongRef(id);
	const int32_t c = android_atomic_inc(&refs->mStrong);
	ALOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
	#if PRINT_REFS
	ALOGD("incStrong of %p from %p: cnt=%d\n", this, id, c);
	#endif
	if (c != INITIAL_STRONG_VALUE) {
	return;
	}

	android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
	refs->mBase->onFirstRef();
	}

	void RefBase::decStrong(const void* id) const
	{
	weakref_impl* const refs = mRefs;
	refs->removeStrongRef(id);
	const int32_t c = android_atomic_dec(&refs->mStrong);
	#if PRINT_REFS
	ALOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
	#endif
	ALOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
	if (c == 1) {
	refs->mBase->onLastStrongRef(id);
	if ((refs->mFlags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_STRONG) {
	delete this;
	}
	}
	refs->decWeak(id);
	}

	void RefBase::forceIncStrong(const void* id) const
	{
	weakref_impl* const refs = mRefs;
	refs->incWeak(id);

	refs->addStrongRef(id);
	const int32_t c = android_atomic_inc(&refs->mStrong);
	ALOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
	refs);
	#if PRINT_REFS
	ALOGD("forceIncStrong of %p from %p: cnt=%d\n", this, id, c);
	#endif

	switch (c) {
	case INITIAL_STRONG_VALUE:
	android_atomic_add(-INITIAL_STRONG_VALUE, &refs->mStrong);
	// fall through...
	case 0:
	refs->mBase->onFirstRef();
	}
	}

	int32_t RefBase::getStrongCount() const
	{
	return mRefs->mStrong;
	}

	RefBase* RefBase::weakref_type::refBase() const
	{
	return static_cast<const weakref_impl*>(this)->mBase;
	}

	void RefBase::weakref_type::incWeak(const void* id)
	{
	weakref_impl* const impl = static_cast<weakref_impl*>(this);
	impl->addWeakRef(id);
	const int32_t c __unused = android_atomic_inc(&impl->mWeak);
	ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
	}


	void RefBase::weakref_type::decWeak(const void* id)
	{
	weakref_impl* const impl = static_cast<weakref_impl*>(this);
	impl->removeWeakRef(id);
	const int32_t c = android_atomic_dec(&impl->mWeak);
	ALOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
	if (c != 1) return;

	if ((impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_STRONG) {
	// This is the regular lifetime case. The object is destroyed
	// when the last strong reference goes away. Since weakref_impl
	// outlive the object, it is not destroyed in the dtor, and
	// we'll have to do it here.
	if (impl->mStrong == INITIAL_STRONG_VALUE) {
	// Special case: we never had a strong reference, so we need to
	// destroy the object now.
	delete impl->mBase;
	} else {
	// ALOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
	delete impl;
	}
	} else {
	// less common case: lifetime is OBJECT_LIFETIME_{WEAK\|FOREVER}
	impl->mBase->onLastWeakRef(id);
	if ((impl->mFlags&OBJECT_LIFETIME_MASK) == OBJECT_LIFETIME_WEAK) {
	// this is the OBJECT_LIFETIME_WEAK case. The last weak-reference
	// is gone, we can destroy the object.
	delete impl->mBase;
	}
	}
	}

	bool RefBase::weakref_type::attemptIncStrong(const void* id)
	{
	incWeak(id);

	weakref_impl* const impl = static_cast<weakref_impl*>(this);
	int32_t curCount = impl->mStrong;

	ALOG_ASSERT(curCount >= 0,
	"attemptIncStrong called on %p after underflow", this);

	while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
	// we're in the easy/common case of promoting a weak-reference
	// from an existing strong reference.
	if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
	break;
	}
	// the strong count has changed on us, we need to re-assert our
	// situation.
	curCount = impl->mStrong;
	}

	if (curCount <= 0 \|\| curCount == INITIAL_STRONG_VALUE) {
	// we're now in the harder case of either:
	// - there never was a strong reference on us
	// - or, all strong references have been released
	if ((impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_STRONG) {
	// this object has a "normal" life-time, i.e.: it gets destroyed
	// when the last strong reference goes away
	if (curCount <= 0) {
	// the last strong-reference got released, the object cannot
	// be revived.
	decWeak(id);
	return false;
	}

	// here, curCount == INITIAL_STRONG_VALUE, which means
	// there never was a strong-reference, so we can try to
	// promote this object; we need to do that atomically.
	while (curCount > 0) {
	if (android_atomic_cmpxchg(curCount, curCount + 1,
	&impl->mStrong) == 0) {
	break;
	}
	// the strong count has changed on us, we need to re-assert our
	// situation (e.g.: another thread has inc/decStrong'ed us)
	curCount = impl->mStrong;
	}

	if (curCount <= 0) {
	// promote() failed, some other thread destroyed us in the
	// meantime (i.e.: strong count reached zero).
	decWeak(id);
	return false;
	}
	} else {
	// this object has an "extended" life-time, i.e.: it can be
	// revived from a weak-reference only.
	// Ask the object's implementation if it agrees to be revived
	if (!impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id)) {
	// it didn't so give-up.
	decWeak(id);
	return false;
	}
	// grab a strong-reference, which is always safe due to the
	// extended life-time.
	curCount = android_atomic_inc(&impl->mStrong);
	}

	// If the strong reference count has already been incremented by
	// someone else, the implementor of onIncStrongAttempted() is holding
	// an unneeded reference. So call onLastStrongRef() here to remove it.
	// (No, this is not pretty.) Note that we MUST NOT do this if we
	// are in fact acquiring the first reference.
	if (curCount > 0 && curCount < INITIAL_STRONG_VALUE) {
	impl->mBase->onLastStrongRef(id);
	}
	}

	impl->addStrongRef(id);

	#if PRINT_REFS
	ALOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
	#endif

	// now we need to fix-up the count if it was INITIAL_STRONG_VALUE
	// this must be done safely, i.e.: handle the case where several threads
	// were here in attemptIncStrong().
	curCount = impl->mStrong;
	while (curCount >= INITIAL_STRONG_VALUE) {
	ALOG_ASSERT(curCount > INITIAL_STRONG_VALUE,
	"attemptIncStrong in %p underflowed to INITIAL_STRONG_VALUE",
	this);
	if (android_atomic_cmpxchg(curCount, curCount-INITIAL_STRONG_VALUE,
	&impl->mStrong) == 0) {
	break;
	}
	// the strong-count changed on us, we need to re-assert the situation,
	// for e.g.: it's possible the fix-up happened in another thread.
	curCount = impl->mStrong;
	}

	return true;
	}

	bool RefBase::weakref_type::attemptIncWeak(const void* id)
	{
	weakref_impl* const impl = static_cast<weakref_impl*>(this);

	int32_t curCount = impl->mWeak;
	ALOG_ASSERT(curCount >= 0, "attemptIncWeak called on %p after underflow",
	this);
	while (curCount > 0) {
	if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mWeak) == 0) {
	break;
	}
	curCount = impl->mWeak;
	}

	if (curCount > 0) {
	impl->addWeakRef(id);
	}

	return curCount > 0;
	}

	int32_t RefBase::weakref_type::getWeakCount() const
	{
	return static_cast<const weakref_impl*>(this)->mWeak;
	}

	void RefBase::weakref_type::printRefs() const
	{
	static_cast<const weakref_impl*>(this)->printRefs();
	}

	void RefBase::weakref_type::trackMe(bool enable, bool retain)
	{
	static_cast<weakref_impl*>(this)->trackMe(enable, retain);
	}

	RefBase::weakref_type* RefBase::createWeak(const void* id) const
	{
	mRefs->incWeak(id);
	return mRefs;
	}

	RefBase::weakref_type* RefBase::getWeakRefs() const
	{
	return mRefs;
	}

	RefBase::RefBase()
	: mRefs(new weakref_impl(this))
	{
	}

	RefBase::~RefBase()
	{
	if (mRefs->mStrong == INITIAL_STRONG_VALUE) {
	// we never acquired a strong (and/or weak) reference on this object.
	delete mRefs;
	} else {
	// life-time of this object is extended to WEAK or FOREVER, in
	// which case weakref_impl doesn't out-live the object and we
	// can free it now.
	if ((mRefs->mFlags & OBJECT_LIFETIME_MASK) != OBJECT_LIFETIME_STRONG) {
	// It's possible that the weak count is not 0 if the object
	// re-acquired a weak reference in its destructor
	if (mRefs->mWeak == 0) {
	delete mRefs;
	}
	}
	}
	// for debugging purposes, clear this.
	const_cast<weakref_impl*&>(mRefs) = NULL;
	}

	void RefBase::extendObjectLifetime(int32_t mode)
	{
	android_atomic_or(mode, &mRefs->mFlags);
	}

	void RefBase::onFirstRef()
	{
	}

	void RefBase::onLastStrongRef(const void* /id/)
	{
	}

	bool RefBase::onIncStrongAttempted(uint32_t flags, const void* /id/)
	{
	return (flags&FIRST_INC_STRONG) ? true : false;
	}

	void RefBase::onLastWeakRef(const void* /id/)
	{
	}

	// ---------------------------------------------------------------------------

	#if DEBUG_REFS
	void RefBase::renameRefs(size_t n, const ReferenceRenamer& renamer) {
	for (size_t i=0 ; i<n ; i++) {
	renamer(i);
	}
	}
	#else
	void RefBase::renameRefs(size_t /n/, const ReferenceRenamer& /renamer/) { }
	#endif

	void RefBase::renameRefId(weakref_type* ref,
	const void* old_id, const void* new_id) {
	weakref_impl* const impl = static_cast<weakref_impl*>(ref);
	impl->renameStrongRefId(old_id, new_id);
	impl->renameWeakRefId(old_id, new_id);
	}

	void RefBase::renameRefId(RefBase* ref,
	const void* old_id, const void* new_id) {
	ref->mRefs->renameStrongRefId(old_id, new_id);
	ref->mRefs->renameWeakRefId(old_id, new_id);
	}

	}; // namespace android