text: /*
   * 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"
  
  #include <utils/RefBase.h>
  
  #include <utils/Atomic.h>
  #include <utils/CallStack.h>
  #include <utils/KeyedVector.h>
  #include <utils/Log.h>
  #include <utils/threads.h>
  
  #include <stdlib.h>
  #include <stdio.h>
  #include <typeinfo>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <unistd.h>
  
  // compile with refcounting debugging enabled
  #define DEBUG_REFS                      0
  #define DEBUG_REFS_ENABLED_BY_DEFAULT   1
  #define DEBUG_REFS_CALLSTACK_ENABLED    1
  
  // 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 addWeakRef(const void* /*id*/) { }
      void removeWeakRef(const void* /*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)
      {
          //LOGI("NEW weakref_impl %p for RefBase %p", this, base);
      }
      
      ~weakref_impl()
      {
          LOG_ALWAYS_FATAL_IF(!mRetain && mStrongRefs != NULL, "Strong references remain!");
          LOG_ALWAYS_FATAL_IF(!mRetain && mWeakRefs != NULL, "Weak references remain!");
      }
  
      void addStrongRef(const void* id)
      {
          addRef(&mStrongRefs, id, mStrong);
      }
  
      void removeStrongRef(const void* id)
      {
          if (!mRetain)
              removeRef(&mStrongRefs, id);
          else
              addRef(&mStrongRefs, id, -mStrong);
      }
  
      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 trackMe(bool track, bool retain)
      { 
          mTrackEnabled = track;
          mRetain = retain;
      }
  
      void printRefs() const
      {
          String8 text;
  
          {
              AutoMutex _l(const_cast<weakref_impl*>(this)->mMutex);
      
              char buf[128];
              sprintf(buf, "Strong references on RefBase %p (weakref_type %p):\n", mBase, this);
              text.append(buf);
              printRefsLocked(&text, mStrongRefs);
              sprintf(buf, "Weak references on RefBase %p (weakref_type %p):\n", mBase, this);
              text.append(buf);
              printRefsLocked(&text, mWeakRefs);
          }
  
          {
              char name[100];
              snprintf(name, 100, "/data/%p.stack", this);
              int rc = open(name, O_RDWR | O_CREAT | O_APPEND);
              if (rc >= 0) {
                  write(rc, text.string(), text.length());
                  close(rc);
                  LOGD("STACK TRACE for %p saved in %s", this, name);
              }
              else LOGE("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* ref = *refs;
              while (ref != NULL) {
                  if (ref->id == id) {
                      *refs = ref->next;
                      delete ref;
                      return;
                  }
                  
                  refs = &ref->next;
                  ref = *refs;
              }
              
              LOG_ALWAYS_FATAL("RefBase: removing id %p on RefBase %p (weakref_type %p) that doesn't exist!",
                               id, mBase, this);
          }
      }
  
      void printRefsLocked(String8* out, const ref_entry* refs) const
      {
          char buf[128];
          while (refs) {
              char inc = refs->ref >= 0 ? '+' : '-';
              sprintf(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;
          }
      }
  
      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;
  
  #if 0
      void addRef(KeyedVector<const void*, int32_t>* refs, const void* id)
      {
          AutoMutex _l(mMutex);
          ssize_t i = refs->indexOfKey(id);
          if (i >= 0) {
              ++(refs->editValueAt(i));
          } else {
              i = refs->add(id, 1);
          }
      }
  
      void removeRef(KeyedVector<const void*, int32_t>* refs, const void* id)
      {
          AutoMutex _l(mMutex);
          ssize_t i = refs->indexOfKey(id);
          LOG_ALWAYS_FATAL_IF(i < 0, "RefBase: removing id %p that doesn't exist!", id);
          if (i >= 0) {
              int32_t val = --(refs->editValueAt(i));
              if (val == 0) {
                  refs->removeItemsAt(i);
              }
          }
      }
  
      void printRefs(const KeyedVector<const void*, int32_t>& refs)
      {
          const size_t N=refs.size();
          for (size_t i=0; i<N; i++) {
              printf("\tID %p: %d remain\n", refs.keyAt(i), refs.valueAt(i));
          }
      }
  
      mutable Mutex mMutex;
      KeyedVector<const void*, int32_t> mStrongRefs;
      KeyedVector<const void*, int32_t> mWeakRefs;
  #endif
  
  #endif
  };
  
  // ---------------------------------------------------------------------------
  
  void RefBase::incStrong(const void* id) const
  {
      weakref_impl* const refs = mRefs;
      refs->addWeakRef(id);
      refs->incWeak(id);
      
      refs->addStrongRef(id);
      const int32_t c = android_atomic_inc(&refs->mStrong);
      LOG_ASSERT(c > 0, "incStrong() called on %p after last strong ref", refs);
  #if PRINT_REFS
      LOGD("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);
      const_cast<RefBase*>(this)->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
      LOGD("decStrong of %p from %p: cnt=%d\n", this, id, c);
  #endif
      LOG_ASSERT(c >= 1, "decStrong() called on %p too many times", refs);
      if (c == 1) {
          const_cast<RefBase*>(this)->onLastStrongRef(id);
          if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
              delete this;
          }
      }
      refs->removeWeakRef(id);
      refs->decWeak(id);
  }
  
  void RefBase::forceIncStrong(const void* id) const
  {
      weakref_impl* const refs = mRefs;
      refs->addWeakRef(id);
      refs->incWeak(id);
      
      refs->addStrongRef(id);
      const int32_t c = android_atomic_inc(&refs->mStrong);
      LOG_ASSERT(c >= 0, "forceIncStrong called on %p after ref count underflow",
                 refs);
  #if PRINT_REFS
      LOGD("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:
          const_cast<RefBase*>(this)->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 = android_atomic_inc(&impl->mWeak);
      LOG_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);
      LOG_ASSERT(c >= 1, "decWeak called on %p too many times", this);
      if (c != 1) return;
      
      if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
          if (impl->mStrong == INITIAL_STRONG_VALUE)
              delete impl->mBase;
          else {
  //            LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
              delete impl;
          }
      } else {
          impl->mBase->onLastWeakRef(id);
          if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
              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;
      LOG_ASSERT(curCount >= 0, "attemptIncStrong called on %p after underflow",
                 this);
      while (curCount > 0 && curCount != INITIAL_STRONG_VALUE) {
          if (android_atomic_cmpxchg(curCount, curCount+1, &impl->mStrong) == 0) {
              break;
          }
          curCount = impl->mStrong;
      }
      
      if (curCount <= 0 || curCount == INITIAL_STRONG_VALUE) {
          bool allow;
          if (curCount == INITIAL_STRONG_VALUE) {
              // Attempting to acquire first strong reference...  this is allowed
              // if the object does NOT have a longer lifetime (meaning the
              // implementation doesn't need to see this), or if the implementation
              // allows it to happen.
              allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK
                    || impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
          } else {
              // Attempting to revive the object...  this is allowed
              // if the object DOES have a longer lifetime (so we can safely
              // call the object with only a weak ref) and the implementation
              // allows it to happen.
              allow = (impl->mFlags&OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK
                    && impl->mBase->onIncStrongAttempted(FIRST_INC_STRONG, id);
          }
          if (!allow) {
              decWeak(id);
              return false;
          }
          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->addWeakRef(id);
      impl->addStrongRef(id);
  
  #if PRINT_REFS
      LOGD("attemptIncStrong of %p from %p: cnt=%d\n", this, id, curCount);
  #endif
  
      if (curCount == INITIAL_STRONG_VALUE) {
          android_atomic_add(-INITIAL_STRONG_VALUE, &impl->mStrong);
          impl->mBase->onFirstRef();
      }
      
      return true;
  }
  
  bool RefBase::weakref_type::attemptIncWeak(const void* id)
  {
      weakref_impl* const impl = static_cast<weakref_impl*>(this);
      
      int32_t curCount = impl->mWeak;
      LOG_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))
  {
  //    LOGV("Creating refs %p with RefBase %p\n", mRefs, this);
  }
  
  RefBase::~RefBase()
  {
  //    LOGV("Destroying RefBase %p (refs %p)\n", this, mRefs);
      if (mRefs->mWeak == 0) {
  //        LOGV("Freeing refs %p of old RefBase %p\n", mRefs, this);
          delete mRefs;
      }
  }
  
  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*/)
  {
  }
          
  }; // namespace android
  