Big Cleanup: SkBitmapFactory, SkLazyPixelRef, SkImageCache

src/lazy/SkDiscardableMemoryPool.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkDiscardableMemoryPool.h"
+#include "SkThread.h"
+#include "SkOnce.h"
+
+// Note:
+// A PoolDiscardableMemory is memory that is counted in a pool.
+// A DiscardableMemoryPool is a pool of PoolDiscardableMemorys.
+
+/**
+ *  A SkPoolDiscardableMemory is a SkDiscardableMemory that relies on
+ *  a SkDiscardableMemoryPool object to manage the memory.
+ */
+class SkPoolDiscardableMemory : public SkDiscardableMemory {
+public:
+    SkPoolDiscardableMemory(SkDiscardableMemoryPool* pool,
+                            void* pointer, size_t bytes);
+    virtual ~SkPoolDiscardableMemory();
+    virtual bool lock() SK_OVERRIDE;
+    virtual void* data() SK_OVERRIDE;
+    virtual void unlock() SK_OVERRIDE;
+    friend class SkDiscardableMemoryPool;
+private:
+    SK_DECLARE_INTERNAL_LLIST_INTERFACE(SkPoolDiscardableMemory);
+    SkDiscardableMemoryPool* const fPool;
+    bool                           fLocked;
+    void*                          fPointer;
+    const size_t                   fBytes;
+};
+
+SkPoolDiscardableMemory::SkPoolDiscardableMemory(SkDiscardableMemoryPool* pool,
+                                                 void* pointer,
+                                                 size_t bytes)
+    : fPool(pool)
+    , fLocked(true)
+    , fPointer(pointer)
+    , fBytes(bytes) {
+    SkASSERT(fPool != NULL);
+    SkASSERT(fPointer != NULL);
+    SkASSERT(fBytes > 0);
+    fPool->ref();
+}
+
+SkPoolDiscardableMemory::~SkPoolDiscardableMemory() {
+    fPool->free(this);
+    fPool->unref();
+}
+
+bool SkPoolDiscardableMemory::lock() {
+    return fPool->lock(this);
+}
+
+void* SkPoolDiscardableMemory::data() {
+    return fLocked ? fPointer : NULL;
+}
+
+void SkPoolDiscardableMemory::unlock() {
+    fPool->unlock(this);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+SkDiscardableMemoryPool::SkDiscardableMemoryPool(size_t budget,
+                                                 SkBaseMutex* mutex)
+    : fMutex(mutex)
+    , fBudget(budget)
+    , fUsed(0) {
+    #if LAZY_CACHE_STATS
+    fCacheHits = 0;
+    fCacheMisses = 0;
+    #endif  // LAZY_CACHE_STATS
+}
+SkDiscardableMemoryPool::~SkDiscardableMemoryPool() {
+    // Please delete the SkPoolDiscardableMemory objects that belong
+    // to this pool before deleting this pool.
+    SkASSERT(fList.isEmpty());
+}
+
+void SkDiscardableMemoryPool::dumpDownTo(size_t budget) {
+    // assert((NULL = fMutex) || fMutex->isLocked());
+    // TODO(halcanary) implement bool fMutex::isLocked().
+    // WARNING: only call this function after aquiring lock.
+    if (budget <= fUsed) {
+        return;
+    }
+    typedef SkTInternalLList<SkPoolDiscardableMemory>::Iter Iter;
+    Iter iter;
+    SkPoolDiscardableMemory* cur = iter.init(fList, Iter::kTail_IterStart);
+    while ((budget > fUsed) && (NULL != cur)) {
+        if ((!cur->fLocked) && (cur->fPointer != NULL)) {

[scroggo, 2013/12/03 23:00:01]

Will curr->fPointer ever be NULL? I would think not, since we remove them from
fList after setting the pointer to NULL.

[hal.canary, 2013/12/04 00:01:36]

Done.

+            SkPoolDiscardableMemory* dm = cur;
+            SkASSERT(dm->fPointer != NULL);
+            sk_free(dm->fPointer);

[scroggo, 2013/12/03 23:00:01]

Should this function call this->free(dm)?

[hal.canary, 2013/12/04 00:01:36]

No.  We have the mutex, so we can't directly call that function.  And I didn't
want to add yet another function.

+            dm->fPointer = NULL;
+            SkASSERT(fUsed >= dm->fBytes);
+            fUsed -= dm->fBytes;
+            cur = iter.prev();
+            // Purged DMs are taken out of the list.  This saves times
+            // looking them up.  Purged DMs are NOT deleted.
+            fList.remove(dm);
+        } else {
+            cur = iter.prev();
+        }
+    }
+}
+
+SkDiscardableMemory* SkDiscardableMemoryPool::create(size_t bytes) {
+    void* addr = sk_malloc_flags(bytes, 0);
+    if (NULL == addr) {
+        return NULL;
+    }
+    SkPoolDiscardableMemory* dm = SkNEW_ARGS(SkPoolDiscardableMemory,
+                                             (this, addr, bytes));
+    SkAutoMutexAcquire autoMutexAcquire(fMutex);
+    fList.addToHead(dm);
+    fUsed += bytes;
+    this->dumpDownTo(fBudget);
+    return dm;
+}
+
+void SkDiscardableMemoryPool::free(SkPoolDiscardableMemory* dm) {
+    // This is called by dm's destructor.
+    if (dm->fPointer != NULL) {
+        SkAutoMutexAcquire autoMutexAcquire(fMutex);
+        sk_free(dm->fPointer);
+        dm->fPointer = NULL;
+        SkASSERT(fUsed >= dm->fBytes);
+        fUsed -= dm->fBytes;
+        fList.remove(dm);
+    } else {
+        SkASSERT(!fList.isInList(dm));
+    }
+
+}
+
+bool SkDiscardableMemoryPool::lock(SkPoolDiscardableMemory* dm) {
+    if (NULL == dm->fPointer) {
+        #if LAZY_CACHE_STATS
+        SkAutoMutexAcquire autoMutexAcquire(fMutex);
+        ++fCacheMisses;
+        #endif  // LAZY_CACHE_STATS
+        return false;
+    }
+    SkAutoMutexAcquire autoMutexAcquire(fMutex);
+    if (NULL == dm->fPointer) {
+        // May have been purged while waiting for lock.
+        #if LAZY_CACHE_STATS
+        ++fCacheMisses;
+        #endif  // LAZY_CACHE_STATS
+        return false;
+    }
+    dm->fLocked = true;
+    fList.remove(dm);
+    fList.addToHead(dm);
+    #if LAZY_CACHE_STATS
+    ++fCacheHits;
+    #endif  // LAZY_CACHE_STATS
+    return true;
+}
+
+void SkDiscardableMemoryPool::unlock(SkPoolDiscardableMemory* dm) {
+    SkAutoMutexAcquire autoMutexAcquire(fMutex);
+    dm->fLocked = false;
+    this->dumpDownTo(fBudget);
+}
+
+size_t SkDiscardableMemoryPool::getRAMUsed() {
+    return fUsed;
+}
+void SkDiscardableMemoryPool::setRAMBudget(size_t budget) {
+    SkAutoMutexAcquire autoMutexAcquire(fMutex);
+    fBudget = budget;
+    this->dumpDownTo(fBudget);
+}
+void SkDiscardableMemoryPool::dumpPool() {
+    SkAutoMutexAcquire autoMutexAcquire(fMutex);
+    this->dumpDownTo(0);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+SK_DECLARE_STATIC_MUTEX(gMutex);
+static void create_pool(SkDiscardableMemoryPool** pool) {
+    SkASSERT(NULL == *pool);
+    *pool = SkNEW_ARGS(SkDiscardableMemoryPool,
+                       (SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE,
+                        &gMutex));
+}
+SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool() {
+    static SkDiscardableMemoryPool* gPool(NULL);
+    SK_DECLARE_STATIC_ONCE(create_pool_once);
+    SkOnce(&create_pool_once, create_pool, &gPool);
+    SkASSERT(NULL != gPool);
+    return gPool;
+}
+
+////////////////////////////////////////////////////////////////////////////////