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comparison: gfx/skia/trunk/src/core/SkScaledImageCache.h

gfx/skia/trunk/src/core/SkScaledImageCache.h

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1 /*
2 * Copyright 2013 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 #ifndef SkScaledImageCache_DEFINED
9 #define SkScaledImageCache_DEFINED
10
11 #include "SkBitmap.h"
12
13 class SkDiscardableMemory;
14 class SkMipMap;
15
16 /**
17 * Cache object for bitmaps (with possible scale in X Y as part of the key).
18 *
19 * Multiple caches can be instantiated, but each instance is not implicitly
20 * thread-safe, so if a given instance is to be shared across threads, the
21 * caller must manage the access itself (e.g. via a mutex).
22 *
23 * As a convenience, a global instance is also defined, which can be safely
24 * access across threads via the static methods (e.g. FindAndLock, etc.).
25 */
26 class SkScaledImageCache {
27 public:
28 struct ID;
29
30 /**
31 * Returns a locked/pinned SkDiscardableMemory instance for the specified
32 * number of bytes, or NULL on failure.
33 */
34 typedef SkDiscardableMemory* (*DiscardableFactory)(size_t bytes);
35
36 /*
37 * The following static methods are thread-safe wrappers around a global
38 * instance of this cache.
39 */
40
41 static ID* FindAndLock(uint32_t pixelGenerationID,
42 int32_t width,
43 int32_t height,
44 SkBitmap* returnedBitmap);
45
46 static ID* FindAndLock(const SkBitmap& original, SkScalar scaleX,
47 SkScalar scaleY, SkBitmap* returnedBitmap);
48 static ID* FindAndLockMip(const SkBitmap& original,
49 SkMipMap const** returnedMipMap);
50
51
52 static ID* AddAndLock(uint32_t pixelGenerationID,
53 int32_t width,
54 int32_t height,
55 const SkBitmap& bitmap);
56
57 static ID* AddAndLock(const SkBitmap& original, SkScalar scaleX,
58 SkScalar scaleY, const SkBitmap& bitmap);
59 static ID* AddAndLockMip(const SkBitmap& original, const SkMipMap* mipMap);
60
61 static void Unlock(ID*);
62
63 static size_t GetBytesUsed();
64 static size_t GetByteLimit();
65 static size_t SetByteLimit(size_t newLimit);
66
67 static SkBitmap::Allocator* GetAllocator();
68
69 /**
70 * Call SkDebugf() with diagnostic information about the state of the cache
71 */
72 static void Dump();
73
74 ///////////////////////////////////////////////////////////////////////////
75
76 /**
77 * Construct the cache to call DiscardableFactory when it
78 * allocates memory for the pixels. In this mode, the cache has
79 * not explicit budget, and so methods like getBytesUsed() and
80 * getByteLimit() will return 0, and setByteLimit will ignore its argument
81 * and return 0.
82 */
83 SkScaledImageCache(DiscardableFactory);
84
85 /**
86 * Construct the cache, allocating memory with malloc, and respect the
87 * byteLimit, purging automatically when a new image is added to the cache
88 * that pushes the total bytesUsed over the limit. Note: The limit can be
89 * changed at runtime with setByteLimit.
90 */
91 SkScaledImageCache(size_t byteLimit);
92
93 ~SkScaledImageCache();
94
95 /**
96 * Search the cache for a matching bitmap (using generationID,
97 * width, and height as a search key). If found, return it in
98 * returnedBitmap, and return its ID pointer. Use the returned
99 * ptr to unlock the cache when you are done using
100 * returnedBitmap.
101 *
102 * If a match is not found, returnedBitmap will be unmodifed, and
103 * NULL will be returned.
104 *
105 * This is used if there is no scaling or subsetting, for example
106 * by SkLazyPixelRef.
107 */
108 ID* findAndLock(uint32_t pixelGenerationID, int32_t width, int32_t height,
109 SkBitmap* returnedBitmap);
110
111 /**
112 * Search the cache for a scaled version of original. If found,
113 * return it in returnedBitmap, and return its ID pointer. Use
114 * the returned ptr to unlock the cache when you are done using
115 * returnedBitmap.
116 *
117 * If a match is not found, returnedBitmap will be unmodifed, and
118 * NULL will be returned.
119 */
120 ID* findAndLock(const SkBitmap& original, SkScalar scaleX,
121 SkScalar scaleY, SkBitmap* returnedBitmap);
122 ID* findAndLockMip(const SkBitmap& original,
123 SkMipMap const** returnedMipMap);
124
125 /**
126 * To add a new bitmap (or mipMap) to the cache, call
127 * AddAndLock. Use the returned ptr to unlock the cache when you
128 * are done using scaled.
129 *
130 * Use (generationID, width, and height) or (original, scaleX,
131 * scaleY) or (original) as a search key
132 */
133 ID* addAndLock(uint32_t pixelGenerationID, int32_t width, int32_t height,
134 const SkBitmap& bitmap);
135 ID* addAndLock(const SkBitmap& original, SkScalar scaleX,
136 SkScalar scaleY, const SkBitmap& bitmap);
137 ID* addAndLockMip(const SkBitmap& original, const SkMipMap* mipMap);
138
139 /**
140 * Given a non-null ID ptr returned by either findAndLock or addAndLock,
141 * this releases the associated resources to be available to be purged
142 * if needed. After this, the cached bitmap should no longer be
143 * referenced by the caller.
144 */
145 void unlock(ID*);
146
147 size_t getBytesUsed() const { return fBytesUsed; }
148 size_t getByteLimit() const { return fByteLimit; }
149
150 /**
151 * Set the maximum number of bytes available to this cache. If the current
152 * cache exceeds this new value, it will be purged to try to fit within
153 * this new limit.
154 */
155 size_t setByteLimit(size_t newLimit);
156
157 SkBitmap::Allocator* allocator() const { return fAllocator; };
158
159 /**
160 * Call SkDebugf() with diagnostic information about the state of the cache
161 */
162 void dump() const;
163
164 public:
165 struct Rec;
166 struct Key;
167 private:
168 Rec* fHead;
169 Rec* fTail;
170
171 class Hash;
172 Hash* fHash;
173
174 DiscardableFactory fDiscardableFactory;
175 // the allocator is NULL or one that matches discardables
176 SkBitmap::Allocator* fAllocator;
177
178 size_t fBytesUsed;
179 size_t fByteLimit;
180 int fCount;
181
182 Rec* findAndLock(uint32_t generationID, SkScalar sx, SkScalar sy,
183 const SkIRect& bounds);
184 Rec* findAndLock(const Key& key);
185 ID* addAndLock(Rec* rec);
186
187 void purgeRec(Rec*);
188 void purgeAsNeeded();
189
190 // linklist management
191 void moveToHead(Rec*);
192 void addToHead(Rec*);
193 void detach(Rec*);
194
195 void init(); // called by constructors
196
197 #ifdef SK_DEBUG
198 void validate() const;
199 #else
200 void validate() const {}
201 #endif
202 };
203 #endif

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