retool image cache to be generic cache

src/core/SkScaledImageCache.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 SkScaledImageCache_DEFINED
 #define SkScaledImageCache_DEFINED
 
 #include "SkBitmap.h"
 
 class SkDiscardableMemory;
 class SkMipMap;
 
 /**
  *  Cache object for bitmaps (with possible scale in X Y as part of the key).
  *
  *  Multiple caches can be instantiated, but each instance is not implicitly
  *  thread-safe, so if a given instance is to be shared across threads, the
  *  caller must manage the access itself (e.g. via a mutex).
  *
  *  As a convenience, a global instance is also defined, which can be safely
  *  access across threads via the static methods (e.g. FindAndLock, etc.).
  */
 class SkScaledImageCache {
 public:
-    struct ID;
-
     struct Key {
         // Call this to access your private contents. Must not use the address after calling init()
         void* writableContents() { return this + 1; }
 
         // must call this after your private data has been written.
         // length must be a multiple of 4
         void init(size_t length);
 
         // This is only valid after having called init().
         uint32_t hash() const { return fHash; }
 
         bool operator==(const Key& other) const {
             const uint32_t* a = this->as32();
             const uint32_t* b = other.as32();
             for (int i = 0; i < fCount32; ++i) {
                 if (a[i] != b[i]) {
                     return false;
                 }
             }
             return true;
         }
 
-        // delete using sk_free
-        Key* clone() const;
-
     private:
         // store fCount32 first, so we don't consider it in operator<
         int32_t  fCount32;  // 2 + user contents count32
         uint32_t fHash;
         /* uint32_t fContents32[] */
 
         const uint32_t* as32() const { return (const uint32_t*)this; }
         const uint32_t* as32SkipCount() const { return this->as32() + 1; }
     };
 
+    struct Rec {
+        typedef SkScaledImageCache::Key Key;
+
+        Rec() : fLockCount(1) {}
+        virtual ~Rec() {}
+
+        uint32_t getHash() const { return this->getKey().hash(); }
+        
+        virtual const Key& getKey() const = 0;
+        virtual size_t bytesUsed() const = 0;
+        
+        // for SkTDynamicHash::Traits
+        static uint32_t Hash(const Key& key) { return key.hash(); }
+        static const Key& GetKey(const Rec& rec) { return rec.getKey(); }
+
+    private:
+        Rec*    fNext;
+        Rec*    fPrev;
+        int32_t fLockCount;
+        int32_t fPad;
+        
+        friend class SkScaledImageCache;
+    };
+
+    typedef const Rec* ID;
+
     /**
      *  Returns a locked/pinned SkDiscardableMemory instance for the specified
      *  number of bytes, or NULL on failure.
      */
     typedef SkDiscardableMemory* (*DiscardableFactory)(size_t bytes);
 
     /*
      *  The following static methods are thread-safe wrappers around a global
      *  instance of this cache.
      */
 
-    static ID* FindAndLock(const Key&, SkBitmap* result);
-    static ID* AddAndLock(const Key&, const SkBitmap& result);
-
-    static ID* FindAndLock(const Key&, const SkMipMap** result);
-    static ID* AddAndLock(const Key&, const SkMipMap* result);
-
-    static void Unlock(ID*);
+    static const Rec* FindAndLock(const Key& key);
+    static const Rec* AddAndLock(Rec*);
+    static void Unlock(ID);
 
     static size_t GetTotalBytesUsed();
     static size_t GetTotalByteLimit();
     static size_t SetTotalByteLimit(size_t newLimit);
 
     static size_t SetSingleAllocationByteLimit(size_t);
     static size_t GetSingleAllocationByteLimit();
 
     static SkBitmap::Allocator* GetAllocator();
 
@@ skipping 15 matching lines @@
 
     /**
      *  Construct the cache, allocating memory with malloc, and respect the
      *  byteLimit, purging automatically when a new image is added to the cache
      *  that pushes the total bytesUsed over the limit. Note: The limit can be
      *  changed at runtime with setTotalByteLimit.
      */
     explicit SkScaledImageCache(size_t byteLimit);
     ~SkScaledImageCache();
 
-    /**
-     *  Search the cache for a matching key. If found, return its bitmap and return its ID pointer.
-     *  Use the returned ID to unlock the cache when you are done using outBitmap.
-     *
-     *  If a match is not found, outBitmap will be unmodifed, and NULL will be returned.
-     */
-    ID* findAndLock(const Key& key, SkBitmap* outBitmap);
-    ID* findAndLock(const Key& key, const SkMipMap** returnedMipMap);
-
-    /**
-     *  To add a new bitmap (or mipMap) to the cache, call
-     *  AddAndLock. Use the returned ptr to unlock the cache when you
-     *  are done using scaled.
-     */
-    ID* addAndLock(const Key&, const SkBitmap& bitmap);
-    ID* addAndLock(const Key&, const SkMipMap* mipMap);
+    const Rec* findAndLock(const Key& key);
+    const Rec* addAndLock(Rec*);
 
     /**
      *  Given a non-null ID ptr returned by either findAndLock or addAndLock,
      *  this releases the associated resources to be available to be purged
      *  if needed. After this, the cached bitmap should no longer be
      *  referenced by the caller.
      */
-    void unlock(ID*);
+    void unlock(ID);
 
     size_t getTotalBytesUsed() const { return fTotalBytesUsed; }
     size_t getTotalByteLimit() const { return fTotalByteLimit; }
 
     /**
      *  This is respected by SkBitmapProcState::possiblyScaleImage.
      *  0 is no maximum at all; this is the default.
      *  setSingleAllocationByteLimit() returns the previous value.
      */
     size_t setSingleAllocationByteLimit(size_t maximumAllocationSize);
     size_t getSingleAllocationByteLimit() const;
     /**
      *  Set the maximum number of bytes available to this cache. If the current
      *  cache exceeds this new value, it will be purged to try to fit within
      *  this new limit.
      */
     size_t setTotalByteLimit(size_t newLimit);
 
     SkBitmap::Allocator* allocator() const { return fAllocator; };
 
     /**
      *  Call SkDebugf() with diagnostic information about the state of the cache
      */
     void dump() const;
 
-public:
-    struct Rec;
 private:
     Rec*    fHead;
     Rec*    fTail;
 
     class Hash;
     Hash*   fHash;
 
     DiscardableFactory  fDiscardableFactory;
     // the allocator is NULL or one that matches discardables
     SkBitmap::Allocator* fAllocator;
 
     size_t  fTotalBytesUsed;
     size_t  fTotalByteLimit;
     size_t  fSingleAllocationByteLimit;
     int     fCount;
 
-    Rec* findAndLock(const Key& key);
-    ID* addAndLock(Rec* rec);
-
     void purgeRec(Rec*);
     void purgeAsNeeded();
 
     // linklist management
     void moveToHead(Rec*);
     void addToHead(Rec*);
     void detach(Rec*);
 
     void init();    // called by constructors
 
 #ifdef SK_DEBUG
     void validate() const;
 #else
     void validate() const {}
 #endif
 };
 #endif