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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_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT
     14 //#define SK_TRACE_PIXELREF_LIFETIME
     15 
     16 #include "SkNextID.h"
     17 
     18 uint32_t SkNextID::ImageID() {
     19     static uint32_t gID = 0;
     20     uint32_t id;
     21     // Loop in case our global wraps around, as we never want to return a 0.
     22     do {
     23         id = sk_atomic_fetch_add(&gID, 2u) + 2;  // Never set the low bit.
     24     } while (0 == id);
     25     return id;
     26 }
     27 
     28 ///////////////////////////////////////////////////////////////////////////////
     29 
     30 // just need a > 0 value, so pick a funny one to aid in debugging
     31 #define SKPIXELREF_PRELOCKED_LOCKCOUNT     123456789
     32 
     33 static SkImageInfo validate_info(const SkImageInfo& info) {
     34     SkAlphaType newAlphaType = info.alphaType();
     35     SkAssertResult(SkColorTypeValidateAlphaType(info.colorType(), info.alphaType(), &newAlphaType));
     36     return info.makeAlphaType(newAlphaType);
     37 }
     38 
     39 #ifdef SK_TRACE_PIXELREF_LIFETIME
     40     static int32_t gInstCounter;
     41 #endif
     42 
     43 SkPixelRef::SkPixelRef(const SkImageInfo& info)
     44     : fInfo(validate_info(info))
     45 #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
     46     , fStableID(SkNextID::ImageID())
     47 #endif
     48 
     49 {
     50 #ifdef SK_TRACE_PIXELREF_LIFETIME
     51     SkDebugf(" pixelref %d\n", sk_atomic_inc(&gInstCounter));
     52 #endif
     53     fRec.zero();
     54     fLockCount = 0;
     55     this->needsNewGenID();
     56     fMutability = kMutable;
     57     fPreLocked = false;
     58     fAddedToCache.store(false);
     59 }
     60 
     61 SkPixelRef::~SkPixelRef() {
     62 #ifndef SK_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT
     63     SkASSERT(SKPIXELREF_PRELOCKED_LOCKCOUNT == fLockCount || 0 == fLockCount);
     64 #endif
     65 
     66 #ifdef SK_TRACE_PIXELREF_LIFETIME
     67     SkDebugf("~pixelref %d\n", sk_atomic_dec(&gInstCounter) - 1);
     68 #endif
     69     this->callGenIDChangeListeners();
     70 }
     71 
     72 void SkPixelRef::needsNewGenID() {
     73     fTaggedGenID.store(0);
     74     SkASSERT(!this->genIDIsUnique()); // This method isn't threadsafe, so the assert should be fine.
     75 }
     76 
     77 void SkPixelRef::cloneGenID(const SkPixelRef& that) {
     78     // This is subtle.  We must call that.getGenerationID() to make sure its genID isn't 0.
     79     uint32_t genID = that.getGenerationID();
     80 
     81     // Neither ID is unique any more.
     82     // (These & ~1u are actually redundant.  that.getGenerationID() just did it for us.)
     83     this->fTaggedGenID.store(genID & ~1u);
     84     that. fTaggedGenID.store(genID & ~1u);
     85 
     86     // This method isn't threadsafe, so these asserts should be fine.
     87     SkASSERT(!this->genIDIsUnique());
     88     SkASSERT(!that. genIDIsUnique());
     89 }
     90 
     91 static void validate_pixels_ctable(const SkImageInfo& info, const SkColorTable* ctable) {
     92     if (info.isEmpty()) {
     93         return; // can't require ctable if the dimensions are empty
     94     }
     95     if (kIndex_8_SkColorType == info.colorType()) {
     96         SkASSERT(ctable);
     97     } else {
     98         SkASSERT(nullptr == ctable);
     99     }
    100 }
    101 
    102 void SkPixelRef::setPreLocked(void* pixels, size_t rowBytes, SkColorTable* ctable) {
    103     SkASSERT(pixels);
    104     validate_pixels_ctable(fInfo, ctable);
    105     // only call me in your constructor, otherwise fLockCount tracking can get
    106     // out of sync.
    107     fRec.fPixels = pixels;
    108     fRec.fColorTable = ctable;
    109     fRec.fRowBytes = rowBytes;
    110     fLockCount = SKPIXELREF_PRELOCKED_LOCKCOUNT;
    111     fPreLocked = true;
    112 }
    113 
    114 // Increments fLockCount only on success
    115 bool SkPixelRef::lockPixelsInsideMutex() {
    116     fMutex.assertHeld();
    117 
    118     if (1 == ++fLockCount) {
    119         SkASSERT(fRec.isZero());
    120         if (!this->onNewLockPixels(&fRec)) {
    121             fRec.zero();
    122             fLockCount -= 1;    // we return fLockCount unchanged if we fail.
    123             return false;
    124         }
    125     }
    126     if (fRec.fPixels) {
    127         validate_pixels_ctable(fInfo, fRec.fColorTable);
    128         return true;
    129     }
    130     // no pixels, so we failed (somehow)
    131     --fLockCount;
    132     return false;
    133 }
    134 
    135 // For historical reasons, we always inc fLockCount, even if we return false.
    136 // It would be nice to change this (it seems), and only inc if we actually succeed...
    137 bool SkPixelRef::lockPixels() {
    138     SkASSERT(!fPreLocked || SKPIXELREF_PRELOCKED_LOCKCOUNT == fLockCount);
    139 
    140     if (!fPreLocked) {
    141         TRACE_EVENT_BEGIN0("skia", "SkPixelRef::lockPixelsMutex");
    142         SkAutoMutexAcquire  ac(fMutex);
    143         TRACE_EVENT_END0("skia", "SkPixelRef::lockPixelsMutex");
    144         SkDEBUGCODE(int oldCount = fLockCount;)
    145         bool success = this->lockPixelsInsideMutex();
    146         // lockPixelsInsideMutex only increments the count if it succeeds.
    147         SkASSERT(oldCount + (int)success == fLockCount);
    148 
    149         if (!success) {
    150             // For compatibility with SkBitmap calling lockPixels, we still want to increment
    151             // fLockCount even if we failed. If we updated SkBitmap we could remove this oddity.
    152             fLockCount += 1;
    153             return false;
    154         }
    155     }
    156     if (fRec.fPixels) {
    157         validate_pixels_ctable(fInfo, fRec.fColorTable);
    158         return true;
    159     }
    160     return false;
    161 }
    162 
    163 bool SkPixelRef::lockPixels(LockRec* rec) {
    164     if (this->lockPixels()) {
    165         *rec = fRec;
    166         return true;
    167     }
    168     return false;
    169 }
    170 
    171 void SkPixelRef::unlockPixels() {
    172     SkASSERT(!fPreLocked || SKPIXELREF_PRELOCKED_LOCKCOUNT == fLockCount);
    173 
    174     if (!fPreLocked) {
    175         SkAutoMutexAcquire  ac(fMutex);
    176 
    177         SkASSERT(fLockCount > 0);
    178         if (0 == --fLockCount) {
    179             // don't call onUnlockPixels unless onLockPixels succeeded
    180             if (fRec.fPixels) {
    181                 this->onUnlockPixels();
    182                 fRec.zero();
    183             } else {
    184                 SkASSERT(fRec.isZero());
    185             }
    186         }
    187     }
    188 }
    189 
    190 bool SkPixelRef::requestLock(const LockRequest& request, LockResult* result) {
    191     SkASSERT(result);
    192     if (request.fSize.isEmpty()) {
    193         return false;
    194     }
    195     // until we support subsets, we have to check this...
    196     if (request.fSize.width() != fInfo.width() || request.fSize.height() != fInfo.height()) {
    197         return false;
    198     }
    199 
    200     if (fPreLocked) {
    201         result->fUnlockProc = nullptr;
    202         result->fUnlockContext = nullptr;
    203         result->fCTable = fRec.fColorTable;
    204         result->fPixels = fRec.fPixels;
    205         result->fRowBytes = fRec.fRowBytes;
    206         result->fSize.set(fInfo.width(), fInfo.height());
    207     } else {
    208         SkAutoMutexAcquire  ac(fMutex);
    209         if (!this->onRequestLock(request, result)) {
    210             return false;
    211         }
    212     }
    213     if (result->fPixels) {
    214         validate_pixels_ctable(fInfo, result->fCTable);
    215         return true;
    216     }
    217     return false;
    218 }
    219 
    220 bool SkPixelRef::lockPixelsAreWritable() const {
    221     return this->onLockPixelsAreWritable();
    222 }
    223 
    224 bool SkPixelRef::onLockPixelsAreWritable() const {
    225     return true;
    226 }
    227 
    228 uint32_t SkPixelRef::getGenerationID() const {
    229     uint32_t id = fTaggedGenID.load();
    230     if (0 == id) {
    231         uint32_t next = SkNextID::ImageID() | 1u;
    232         if (fTaggedGenID.compare_exchange(&id, next)) {
    233             id = next;  // There was no race or we won the race.  fTaggedGenID is next now.
    234         } else {
    235             // We lost a race to set fTaggedGenID. compare_exchange() filled id with the winner.
    236         }
    237         // We can't quite SkASSERT(this->genIDIsUnique()). It could be non-unique
    238         // if we got here via the else path (pretty unlikely, but possible).
    239     }
    240     return id & ~1u;  // Mask off bottom unique bit.
    241 }
    242 
    243 void SkPixelRef::addGenIDChangeListener(GenIDChangeListener* listener) {
    244     if (nullptr == listener || !this->genIDIsUnique()) {
    245         // No point in tracking this if we're not going to call it.
    246         delete listener;
    247         return;
    248     }
    249     *fGenIDChangeListeners.append() = listener;
    250 }
    251 
    252 // we need to be called *before* the genID gets changed or zerod
    253 void SkPixelRef::callGenIDChangeListeners() {
    254     // We don't invalidate ourselves if we think another SkPixelRef is sharing our genID.
    255     if (this->genIDIsUnique()) {
    256         for (int i = 0; i < fGenIDChangeListeners.count(); i++) {
    257             fGenIDChangeListeners[i]->onChange();
    258         }
    259 
    260         // TODO: SkAtomic could add "old_value = atomic.xchg(new_value)" to make this clearer.
    261         if (fAddedToCache.load()) {
    262             SkNotifyBitmapGenIDIsStale(this->getGenerationID());
    263             fAddedToCache.store(false);
    264         }
    265     }
    266     // Listeners get at most one shot, so whether these triggered or not, blow them away.
    267     fGenIDChangeListeners.deleteAll();
    268 }
    269 
    270 void SkPixelRef::notifyPixelsChanged() {
    271 #ifdef SK_DEBUG
    272     if (this->isImmutable()) {
    273         SkDebugf("========== notifyPixelsChanged called on immutable pixelref");
    274     }
    275 #endif
    276     this->callGenIDChangeListeners();
    277     this->needsNewGenID();
    278     this->onNotifyPixelsChanged();
    279 }
    280 
    281 void SkPixelRef::changeAlphaType(SkAlphaType at) {
    282     *const_cast<SkImageInfo*>(&fInfo) = fInfo.makeAlphaType(at);
    283 }
    284 
    285 void SkPixelRef::setImmutable() {
    286     fMutability = kImmutable;
    287 }
    288 
    289 void SkPixelRef::setImmutableWithID(uint32_t genID) {
    290     /*
    291      *  We are forcing the genID to match an external value. The caller must ensure that this
    292      *  value does not conflict with other content.
    293      *
    294      *  One use is to force this pixelref's id to match an SkImage's id
    295      */
    296     fMutability = kImmutable;
    297     fTaggedGenID.store(genID);
    298 }
    299 
    300 void SkPixelRef::setTemporarilyImmutable() {
    301     SkASSERT(fMutability != kImmutable);
    302     fMutability = kTemporarilyImmutable;
    303 }
    304 
    305 void SkPixelRef::restoreMutability() {
    306     SkASSERT(fMutability != kImmutable);
    307     fMutability = kMutable;
    308 }
    309 
    310 ///////////////////////////////////////////////////////////////////////////////////////////////////
    311 
    312 
    313 void SkPixelRef::onNotifyPixelsChanged() { }
    314 
    315 size_t SkPixelRef::getAllocatedSizeInBytes() const {
    316     return 0;
    317 }
    318 
    319 static void unlock_legacy_result(void* ctx) {
    320     SkPixelRef* pr = (SkPixelRef*)ctx;
    321     pr->unlockPixels();
    322     pr->unref();    // balancing the Ref in onRequestLoc
    323 }
    324 
    325 bool SkPixelRef::onRequestLock(const LockRequest& request, LockResult* result) {
    326     if (!this->lockPixelsInsideMutex()) {
    327         return false;
    328     }
    329 
    330     result->fUnlockProc = unlock_legacy_result;
    331     result->fUnlockContext = SkRef(this);   // this is balanced in our fUnlockProc
    332     result->fCTable = fRec.fColorTable;
    333     result->fPixels = fRec.fPixels;
    334     result->fRowBytes = fRec.fRowBytes;
    335     result->fSize.set(fInfo.width(), fInfo.height());
    336     return true;
    337 }
    338