/*
* 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 SkResourceCache_DEFINED
#define SkResourceCache_DEFINED
#include "SkBitmap.h"
#include "SkMessageBus.h"
#include "SkTDArray.h"
class SkCachedData;
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 SkResourceCache {
public:
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.
// nameSpace must be unique per Key subclass.
// sharedID == 0 means ignore this field : does not support group purging.
// length must be a multiple of 4
void init(void* nameSpace, uint64_t sharedID, size_t length);
void* getNamespace() const { return fNamespace; }
uint64_t getSharedID() const { return ((uint64_t)fSharedID_hi << 32) | fSharedID_lo; }
// 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) { // (This checks fCount == other.fCount first.)
if (a[i] != b[i]) {
return false;
}
}
return true;
}
private:
int32_t fCount32; // local + user contents count32
uint32_t fHash;
// split uint64_t into hi and lo so we don't force ourselves to pad on 32bit machines.
uint32_t fSharedID_lo;
uint32_t fSharedID_hi;
void* fNamespace; // A unique namespace tag. This is hashed.
/* uint32_t fContents32[] */
const uint32_t* as32() const { return (const uint32_t*)this; }
};
struct Rec {
typedef SkResourceCache::Key Key;
Rec() {}
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;
friend class SkResourceCache;
};
// Used with SkMessageBus
struct PurgeSharedIDMessage {
PurgeSharedIDMessage(uint64_t sharedID) : fSharedID(sharedID) {}
uint64_t fSharedID;
};
typedef const Rec* ID;
/**
* Callback function for find(). If called, the cache will have found a match for the
* specified Key, and will pass in the corresponding Rec, along with a caller-specified
* context. The function can read the data in Rec, and copy whatever it likes into context
* (casting context to whatever it really is).
*
* The return value determines what the cache will do with the Rec. If the function returns
* true, then the Rec is considered "valid". If false is returned, the Rec will be considered
* "stale" and will be purged from the cache.
*/
typedef bool (*FindVisitor)(const Rec&, void* context);
/**
* 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.
*/
/**
* Returns true if the visitor was called on a matching Key, and the visitor returned true.
*
* Find() will search the cache for the specified Key. If no match is found, return false and
* do not call the FindVisitor. If a match is found, return whatever the visitor returns.
* Its return value is interpreted to mean:
* true : Rec is valid
* false : Rec is "stale" -- the cache will purge it.
*/
static bool Find(const Key& key, FindVisitor, void* context);
static void Add(Rec*);
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 size_t GetEffectiveSingleAllocationByteLimit();
static void PurgeAll();
/**
* Returns the DiscardableFactory used by the global cache, or NULL.
*/
static DiscardableFactory GetDiscardableFactory();
/**
* Use this allocator for bitmaps, so they can use ashmem when available.
* Returns NULL if the ResourceCache has not been initialized with a DiscardableFactory.
*/
static SkBitmap::Allocator* GetAllocator();
static SkCachedData* NewCachedData(size_t bytes);
static void PostPurgeSharedID(uint64_t sharedID);
/**
* Call SkDebugf() with diagnostic information about the state of the cache
*/
static void Dump();
///////////////////////////////////////////////////////////////////////////
/**
* Construct the cache to call DiscardableFactory when it
* allocates memory for the pixels. In this mode, the cache has
* not explicit budget, and so methods like getTotalBytesUsed()
* and getTotalByteLimit() will return 0, and setTotalByteLimit
* will ignore its argument and return 0.
*/
SkResourceCache(DiscardableFactory);
/**
* 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 SkResourceCache(size_t byteLimit);
~SkResourceCache();
/**
* Returns true if the visitor was called on a matching Key, and the visitor returned true.
*
* find() will search the cache for the specified Key. If no match is found, return false and
* do not call the FindVisitor. If a match is found, return whatever the visitor returns.
* Its return value is interpreted to mean:
* true : Rec is valid
* false : Rec is "stale" -- the cache will purge it.
*/
bool find(const Key&, FindVisitor, void* context);
void add(Rec*);
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;
// returns the logical single allocation size (pinning against the budget when the cache
// is not backed by discardable memory.
size_t getEffectiveSingleAllocationByteLimit() 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);
void purgeSharedID(uint64_t sharedID);
void purgeAll() {
this->purgeAsNeeded(true);
}
DiscardableFactory discardableFactory() const { return fDiscardableFactory; }
SkBitmap::Allocator* allocator() const { return fAllocator; };
SkCachedData* newCachedData(size_t bytes);
/**
* Call SkDebugf() with diagnostic information about the state of the cache
*/
void dump() const;
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;
SkMessageBus<PurgeSharedIDMessage>::Inbox fPurgeSharedIDInbox;
void checkMessages();
void purgeAsNeeded(bool forcePurge = false);
// linklist management
void moveToHead(Rec*);
void addToHead(Rec*);
void detach(Rec*);
void remove(Rec*);
void init(); // called by constructors
#ifdef SK_DEBUG
void validate() const;
#else
void validate() const {}
#endif
};
#endif