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      1 /*
      2  * Copyright 2011 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkBitmapCache.h"
      9 #include "SkMutex.h"
     10 #include "SkPixelRef.h"
     11 #include "SkTraceEvent.h"
     12 
     13 //#define SK_TRACE_PIXELREF_LIFETIME
     14 
     15 #include "SkNextID.h"
     16 
     17 uint32_t SkNextID::ImageID() {
     18     static uint32_t gID = 0;
     19     uint32_t id;
     20     // Loop in case our global wraps around, as we never want to return a 0.
     21     do {
     22         id = sk_atomic_fetch_add(&gID, 2u) + 2;  // Never set the low bit.
     23     } while (0 == id);
     24     return id;
     25 }
     26 
     27 ///////////////////////////////////////////////////////////////////////////////
     28 
     29 #ifdef SK_TRACE_PIXELREF_LIFETIME
     30     static int32_t gInstCounter;
     31 #endif
     32 
     33 SkPixelRef::SkPixelRef(int width, int height, void* pixels, size_t rowBytes)
     34     : fWidth(width)
     35     , fHeight(height)
     36     , fPixels(pixels)
     37     , fRowBytes(rowBytes)
     38 #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
     39     , fStableID(SkNextID::ImageID())
     40 #endif
     41 {
     42 #ifdef SK_TRACE_PIXELREF_LIFETIME
     43     SkDebugf(" pixelref %d\n", sk_atomic_inc(&gInstCounter));
     44 #endif
     45 
     46     this->needsNewGenID();
     47     fMutability = kMutable;
     48     fAddedToCache.store(false);
     49 }
     50 
     51 SkPixelRef::~SkPixelRef() {
     52 #ifdef SK_TRACE_PIXELREF_LIFETIME
     53     SkDebugf("~pixelref %d\n", sk_atomic_dec(&gInstCounter) - 1);
     54 #endif
     55     this->callGenIDChangeListeners();
     56 }
     57 
     58 // This is undefined if there are clients in-flight trying to use us
     59 void SkPixelRef::android_only_reset(int width, int height, size_t rowBytes) {
     60     fWidth = width;
     61     fHeight = height;
     62     fRowBytes = rowBytes;
     63     // note: we do not change fPixels
     64 
     65     // conservative, since its possible the "new" settings are the same as the old.
     66     this->notifyPixelsChanged();
     67 }
     68 
     69 void SkPixelRef::needsNewGenID() {
     70     fTaggedGenID.store(0);
     71     SkASSERT(!this->genIDIsUnique()); // This method isn't threadsafe, so the assert should be fine.
     72 }
     73 
     74 uint32_t SkPixelRef::getGenerationID() const {
     75     uint32_t id = fTaggedGenID.load();
     76     if (0 == id) {
     77         uint32_t next = SkNextID::ImageID() | 1u;
     78         if (fTaggedGenID.compare_exchange(&id, next)) {
     79             id = next;  // There was no race or we won the race.  fTaggedGenID is next now.
     80         } else {
     81             // We lost a race to set fTaggedGenID. compare_exchange() filled id with the winner.
     82         }
     83         // We can't quite SkASSERT(this->genIDIsUnique()). It could be non-unique
     84         // if we got here via the else path (pretty unlikely, but possible).
     85     }
     86     return id & ~1u;  // Mask off bottom unique bit.
     87 }
     88 
     89 void SkPixelRef::addGenIDChangeListener(GenIDChangeListener* listener) {
     90     if (nullptr == listener || !this->genIDIsUnique()) {
     91         // No point in tracking this if we're not going to call it.
     92         delete listener;
     93         return;
     94     }
     95     *fGenIDChangeListeners.append() = listener;
     96 }
     97 
     98 // we need to be called *before* the genID gets changed or zerod
     99 void SkPixelRef::callGenIDChangeListeners() {
    100     // We don't invalidate ourselves if we think another SkPixelRef is sharing our genID.
    101     if (this->genIDIsUnique()) {
    102         for (int i = 0; i < fGenIDChangeListeners.count(); i++) {
    103             fGenIDChangeListeners[i]->onChange();
    104         }
    105 
    106         // TODO: SkAtomic could add "old_value = atomic.xchg(new_value)" to make this clearer.
    107         if (fAddedToCache.load()) {
    108             SkNotifyBitmapGenIDIsStale(this->getGenerationID());
    109             fAddedToCache.store(false);
    110         }
    111     }
    112     // Listeners get at most one shot, so whether these triggered or not, blow them away.
    113     fGenIDChangeListeners.deleteAll();
    114 }
    115 
    116 void SkPixelRef::notifyPixelsChanged() {
    117 #ifdef SK_DEBUG
    118     if (this->isImmutable()) {
    119         SkDebugf("========== notifyPixelsChanged called on immutable pixelref");
    120     }
    121 #endif
    122     this->callGenIDChangeListeners();
    123     this->needsNewGenID();
    124     this->onNotifyPixelsChanged();
    125 }
    126 
    127 void SkPixelRef::setImmutable() {
    128     fMutability = kImmutable;
    129 }
    130 
    131 void SkPixelRef::setImmutableWithID(uint32_t genID) {
    132     /*
    133      *  We are forcing the genID to match an external value. The caller must ensure that this
    134      *  value does not conflict with other content.
    135      *
    136      *  One use is to force this pixelref's id to match an SkImage's id
    137      */
    138     fMutability = kImmutable;
    139     fTaggedGenID.store(genID);
    140 }
    141 
    142 void SkPixelRef::setTemporarilyImmutable() {
    143     SkASSERT(fMutability != kImmutable);
    144     fMutability = kTemporarilyImmutable;
    145 }
    146 
    147 void SkPixelRef::restoreMutability() {
    148     SkASSERT(fMutability != kImmutable);
    149     fMutability = kMutable;
    150 }
    151 
    152 void SkPixelRef::onNotifyPixelsChanged() { }
    153