The Tor Browser: gfx/skia/trunk/src/core/SkBitmapHeap.h@97036ab72558 (annotated)

gfx/skia/trunk/src/core/SkBitmapHeap.h@97036ab72558 (annotated)

gfx/skia/trunk/src/core/SkBitmapHeap.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkBitmapHeap_DEFINED
 #define SkBitmapHeap_DEFINED
 #include "SkBitmap.h"
 #include "SkFlattenable.h"
 #include "SkRefCnt.h"
 #include "SkTDArray.h"
 #include "SkThread.h"
 #include "SkTRefArray.h"
 /**
  * SkBitmapHeapEntry provides users of SkBitmapHeap (using internal storage) with a means to...
  *  (1) get access a bitmap in the heap
  *  (2) indicate they are done with bitmap by releasing their reference (if they were an owner).
  */
 class SkBitmapHeapEntry : SkNoncopyable {
 public:
     ~SkBitmapHeapEntry();
     int32_t getSlot() { return fSlot; }
     SkBitmap* getBitmap() { return &fBitmap; }
     void releaseRef() {
         sk_atomic_dec(&fRefCount);
     }
 private:
     SkBitmapHeapEntry();
     void addReferences(int count);
     int32_t fSlot;
     int32_t fRefCount;
     SkBitmap fBitmap;
     // Keep track of the bytes allocated for this bitmap. When replacing the
     // bitmap or removing this HeapEntry we know how much memory has been
     // reclaimed.
     size_t fBytesAllocated;
     friend class SkBitmapHeap;
     friend class SkBitmapHeapTester;
 };
 class SkBitmapHeapReader : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkBitmapHeapReader)
     SkBitmapHeapReader() : INHERITED() {}
     virtual SkBitmap* getBitmap(int32_t slot) const = 0;
     virtual void releaseRef(int32_t slot) = 0;
 private:
     typedef SkRefCnt INHERITED;
 };
 /**
  * TODO: stores immutable bitmaps into a heap
  */
 class SkBitmapHeap : public SkBitmapHeapReader {
 public:
     class ExternalStorage : public SkRefCnt {
      public:
         SK_DECLARE_INST_COUNT(ExternalStorage)
         virtual bool insert(const SkBitmap& bitmap, int32_t slot) = 0;
      private:
         typedef SkRefCnt INHERITED;
     };
     static const int32_t UNLIMITED_SIZE = -1;
     static const int32_t IGNORE_OWNERS  = -1;
     static const int32_t INVALID_SLOT   = -1;
     /**
      * Constructs a heap that is responsible for allocating and managing its own storage.  In the
      * case where we choose to allow the heap to grow indefinitely (i.e. UNLIMITED_SIZE) we
      * guarantee that once allocated in the heap a bitmap's index in the heap is immutable.
      * Otherwise we guarantee the bitmaps placement in the heap until its owner count goes to zero.
      *
      * @param preferredSize  Specifies the preferred maximum number of bitmaps to store. This is
      *   not a hard limit as it can grow larger if the number of bitmaps in the heap with active
      *   owners exceeds this limit.
      * @param ownerCount  The number of owners to assign to each inserted bitmap. NOTE: while a
      *   bitmap in the heap has a least one owner it can't be removed.
      */
     SkBitmapHeap(int32_t preferredSize = UNLIMITED_SIZE, int32_t ownerCount = IGNORE_OWNERS);
     /**
      * Constructs a heap that defers the responsibility of storing the bitmaps to an external
      * function. This is especially useful if the bitmaps will be used in a separate process as the
      * external storage can ensure the data is properly shuttled to the appropriate processes.
      *
      * Our LRU implementation assumes that inserts into the external storage are consumed in the
      * order that they are inserted (i.e. SkPipe). This ensures that we don't need to query the
      * external storage to see if a slot in the heap is eligible to be overwritten.
      *
      * @param externalStorage  The class responsible for storing the bitmaps inserted into the heap
      * @param heapSize  The maximum size of the heap. Because of the sequential limitation imposed
      *   by our LRU implementation we can guarantee that the heap will never grow beyond this size.
      */
     SkBitmapHeap(ExternalStorage* externalStorage, int32_t heapSize = UNLIMITED_SIZE);
     virtual ~SkBitmapHeap();
     /**
      * Makes a shallow copy of all bitmaps currently in the heap and returns them as an array. The
      * array indices match their position in the heap.
      *
      * @return  a ptr to an array of bitmaps or NULL if external storage is being used.
      */
     SkTRefArray<SkBitmap>* extractBitmaps() const;
     /**
      * Retrieves the bitmap from the specified slot in the heap
      *
      * @return  The bitmap located at that slot or NULL if external storage is being used.
      */
     virtual SkBitmap* getBitmap(int32_t slot) const SK_OVERRIDE {
         SkASSERT(fExternalStorage == NULL);
         SkBitmapHeapEntry* entry = getEntry(slot);
         if (entry) {
             return &entry->fBitmap;
         }
         return NULL;
     }
     /**
      * Retrieves the bitmap from the specified slot in the heap
      *
      * @return  The bitmap located at that slot or NULL if external storage is being used.
      */
     virtual void releaseRef(int32_t slot) SK_OVERRIDE {
         SkASSERT(fExternalStorage == NULL);
         if (fOwnerCount != IGNORE_OWNERS) {
             SkBitmapHeapEntry* entry = getEntry(slot);
             if (entry) {
                 entry->releaseRef();
             }
         }
     }
     /**
      * Inserts a bitmap into the heap. The stored version of bitmap is guaranteed to be immutable
      * and is not dependent on the lifecycle of the provided bitmap.
      *
      * @param bitmap  the bitmap to be inserted into the heap
      * @return  the slot in the heap where the bitmap is stored or INVALID_SLOT if the bitmap could
      *          not be added to the heap. If it was added the slot will remain valid...
      *            (1) indefinitely if no owner count has been specified.
      *            (2) until all owners have called releaseRef on the appropriate SkBitmapHeapEntry*
      */
     int32_t insert(const SkBitmap& bitmap);
     /**
      * Retrieves an entry from the heap at a given slot.
      *
      * @param slot  the slot in the heap where a bitmap was stored.
      * @return  a SkBitmapHeapEntry that wraps the bitmap or NULL if external storage is used.
      */
     SkBitmapHeapEntry* getEntry(int32_t slot) const {
         SkASSERT(slot <= fStorage.count());
         if (fExternalStorage != NULL) {
             return NULL;
         }
         return fStorage[slot];
     }
     /**
      * Returns a count of the number of items currently in the heap
      */
     int count() const {
         SkASSERT(fExternalStorage != NULL ||
                  fStorage.count() - fUnusedSlots.count() == fLookupTable.count());
         return fLookupTable.count();
     }
     /**
      * Returns the total number of bytes allocated by the bitmaps in the heap
      */
     size_t bytesAllocated() const {
         return fBytesAllocated;
     }
     /**
      * Attempt to reduce the storage allocated.
      * @param bytesToFree minimum number of bytes that should be attempted to
      *   be freed.
      * @return number of bytes actually freed.
      */
     size_t freeMemoryIfPossible(size_t bytesToFree);
     /**
      * Defer any increments of owner counts until endAddingOwnersDeferral is called. So if an
      * existing SkBitmap is inserted into the SkBitmapHeap, its corresponding SkBitmapHeapEntry will
      * not have addReferences called on it, and the client does not need to make a corresponding
      * call to releaseRef. Only meaningful if this SkBitmapHeap was created with an owner count not
      * equal to IGNORE_OWNERS.
      */
     void deferAddingOwners();
     /**
      * Resume adding references when duplicate SkBitmaps are inserted.
      * @param add If true, add references to the SkBitmapHeapEntrys whose SkBitmaps were re-inserted
      *            while deferring.
      */
     void endAddingOwnersDeferral(bool add);
 private:
     struct LookupEntry {
         LookupEntry(const SkBitmap& bm)
         : fGenerationId(bm.getGenerationID())
         , fPixelOrigin(bm.pixelRefOrigin())
         , fWidth(bm.width())
         , fHeight(bm.height())
         , fMoreRecentlyUsed(NULL)
         , fLessRecentlyUsed(NULL){}
         const uint32_t fGenerationId; // SkPixelRef GenerationID.
         const SkIPoint fPixelOrigin;
         const uint32_t fWidth;
         const uint32_t fHeight;
         // TODO: Generalize the LRU caching mechanism
         LookupEntry* fMoreRecentlyUsed;
         LookupEntry* fLessRecentlyUsed;
         uint32_t fStorageSlot; // slot of corresponding bitmap in fStorage.
         /**
          * Compare two LookupEntry pointers for sorting and searching.
          */
         static bool Less(const LookupEntry& a, const LookupEntry& b);
     };
     /**
      * Remove the entry from the lookup table. Also deletes the entry pointed
      * to by the table. Therefore, if a pointer to that one was passed in, the
      * pointer should no longer be used, since the object to which it points has
      * been deleted.
      * @return The index in the lookup table of the entry before removal.
      */
     int removeEntryFromLookupTable(LookupEntry*);
     /**
      * Searches for the bitmap in the lookup table and returns the bitmaps index within the table.
      * If the bitmap was not already in the table it is added.
      *
      * @param key    The key to search the lookup table, created from a bitmap.
      * @param entry  A pointer to a SkBitmapHeapEntry* that if non-null AND the bitmap is found
      *               in the lookup table is populated with the entry from the heap storage.
      */
     int findInLookupTable(const LookupEntry& key, SkBitmapHeapEntry** entry);
     LookupEntry* findEntryToReplace(const SkBitmap& replacement);
     bool copyBitmap(const SkBitmap& originalBitmap, SkBitmap& copiedBitmap);
     /**
      * Remove a LookupEntry from the LRU, in preparation for either deleting or appending as most
      * recent. Points the LookupEntry's old neighbors at each other, and sets fLeastRecentlyUsed
      * (if there is still an entry left). Sets LookupEntry's fMoreRecentlyUsed to NULL and leaves
      * its fLessRecentlyUsed unmodified.
      */
     void removeFromLRU(LookupEntry* entry);
     /**
      * Append a LookupEntry to the end of the LRU cache, marking it as the most
      * recently used. Assumes that the LookupEntry is already in fLookupTable,
      * but is not in the LRU cache. If it is in the cache, removeFromLRU should
      * be called first.
      */
     void appendToLRU(LookupEntry*);
     // searchable index that maps to entries in the heap
     SkTDArray<LookupEntry*> fLookupTable;
     // heap storage
     SkTDArray<SkBitmapHeapEntry*> fStorage;
     // Used to mark slots in fStorage as deleted without actually deleting
     // the slot so as not to mess up the numbering.
     SkTDArray<int> fUnusedSlots;
     ExternalStorage* fExternalStorage;
     LookupEntry* fMostRecentlyUsed;
     LookupEntry* fLeastRecentlyUsed;
     const int32_t fPreferredCount;
     const int32_t fOwnerCount;
     size_t fBytesAllocated;
     bool fDeferAddingOwners;
     SkTDArray<int> fDeferredEntries;
     typedef SkBitmapHeapReader INHERITED;
 };
 #endif // SkBitmapHeap_DEFINED

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gfx/skia/trunk/src/core/SkBitmapHeap.h@97036ab72558 (annotated)

gfx/skia/trunk/src/core/SkBitmapHeap.h