Improvements/additions to SkImageCache/SkLazyPixelRef.

include/lazy/SkPurgeableImageCache.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPurgeableImageCache_DEFINED
+#define SkPurgeableImageCache_DEFINED
+
+#include "SkImageCache.h"
+
+#ifdef SK_DEBUG
+    #include "SkTDArray.h"
+#endif
+
+/**
+ *  Implementation for SkImageCache that uses system defined purgeable memory.
+ */
+class SkPurgeableImageCache : public SkImageCache {
+
+public:
+    /**
+     *  Get a pointer to the single global instance of the purgeable image cache.
+     *  If there is no Skia implementation for purgeable memory, this returns NULL.
+     *  If non-NULL, the caller must unref it after use.
+     */
+    static SkImageCache* GetPurgeableImageCache();
+
+    virtual void* allocAndPinCache(size_t bytes, intptr_t* ID) SK_OVERRIDE;
+    virtual void* pinCache(intptr_t ID, SkImageCache::DataStatus*) SK_OVERRIDE;
+    virtual void releaseCache(intptr_t ID) SK_OVERRIDE;
+    virtual void throwAwayCache(intptr_t ID) SK_OVERRIDE;
+
+#ifdef SK_DEBUG
+    virtual MemoryStatus getMemoryStatus(intptr_t ID) const SK_OVERRIDE;
+    virtual void purgeAllUnpinnedCaches() SK_OVERRIDE;
+    virtual ~SkPurgeableImageCache();
+#endif
+
+private:
+    /**
+     *  Constructor is private. The correct way to get this cache is through
+     *  GetPurgeableImageCache, which will return the single global.
+     */
+    SkPurgeableImageCache();
+
+#ifdef SK_DEBUG
+    SkTDArray<intptr_t> fRecs;
+    int findRec(intptr_t) const;
+#endif
+    void removeRec(intptr_t);
+};
+#endif // SkPurgeableImageCache_DEFINED