SkDiscardableMemory::Factory class

src/lazy/SkImageCache.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 "SkImageCache.h"
+
+namespace {
+class ImageCacheBackedDM : public SkDiscardableMemory {
+public:
+    static SkDiscardableMemory * create(SkImageCache* cache, size_t size);

[scroggo, 2013/12/02 19:00:09]

SkDiscardableMemory* create

+    virtual ~ImageCacheBackedDM();
+    virtual bool lock() SK_OVERRIDE;
+    virtual void* data() SK_OVERRIDE;
+    virtual void unlock() SK_OVERRIDE;
+private:
+    ImageCacheBackedDM(SkImageCache* cache, SkImageCache::ID id, void* ptr);
+    SkImageCache*    fCache;
+    SkImageCache::ID fId;
+    void*            fPtr;
+};
+
+SkDiscardableMemory * ImageCacheBackedDM::create(SkImageCache* cache,

[scroggo, 2013/12/02 19:00:09]

SkDiscardableMemory* ImageCacheBackedDM...

+                                                 size_t bytes) {
+    SkASSERT(cache);
+    SkImageCache::ID id(SkImageCache::UNINITIALIZED_ID);
+    void* ptr = cache->allocAndPinCache(bytes, &id);
+    SkASSERT((NULL == ptr) == (SkImageCache::UNINITIALIZED_ID == id));
+    if (ptr == NULL) {
+        return NULL;
+    }
+    return SkNEW_ARGS(ImageCacheBackedDM, (cache, id, ptr));
+}
+
+ImageCacheBackedDM::ImageCacheBackedDM(SkImageCache* cache,
+                                       SkImageCache::ID id, void* ptr)
+    : fCache(cache), fId(id), fPtr(ptr) {

[scroggo, 2013/12/02 19:00:09]

These should be on their own line:

: fCache(cache)
, fId(id)
, fPtr(ptr) {

The brace could go on the next line (the style guide has not been updated to
reflect that, but I think we're leaning towards changing it to place the brace
on the next line).

+    fCache->ref();
+}
+
+ImageCacheBackedDM::~ImageCacheBackedDM() {
+    if (fId != SkImageCache::UNINITIALIZED_ID) {
+        fCache->throwAwayCache(fId);
+    }
+    fCache->unref();
+}
+
+bool ImageCacheBackedDM::lock() {
+    SkImageCache::DataStatus status;
+    SkASSERT(NULL == fPtr);
+    fPtr = fCache->pinCache(fId, &status);
+    if (NULL == fPtr) {
+        fId = SkImageCache::UNINITIALIZED_ID;
+        return false;
+    }
+    if (SkImageCache::kRetained_DataStatus == status) {
+        return true;
+    }
+    // not retained, fail.
+    fCache->releaseCache(fId);
+    fCache->throwAwayCache(fId);
+    fId = SkImageCache::UNINITIALIZED_ID;
+    fPtr = NULL;
+    return false;
+}
+
+void* ImageCacheBackedDM::data() {
+    return fPtr;
+}
+
+void ImageCacheBackedDM::unlock() {
+    if (fId != SkImageCache::UNINITIALIZED_ID) {
+        fCache->releaseCache(fId);
+    }
+    fPtr = NULL;
+}
+}  // namespace
+
+SkDiscardableMemory* SkImageCache::create(size_t bytes) {
+    return ImageCacheBackedDM::create(this, bytes);
+}