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76 lines
3.0 KiB
C++
76 lines
3.0 KiB
C++
/*
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* Copyright (C) 2013 Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef SKY_ENGINE_PUBLIC_PLATFORM_WEBDISCARDABLEMEMORY_H_
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#define SKY_ENGINE_PUBLIC_PLATFORM_WEBDISCARDABLEMEMORY_H_
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namespace blink {
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// A memory allocation that can be automatically discarded by the operating
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// system under memory pressure.
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//
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// Discardable usage is typically:
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// WebDiscardableMemory* mem = allocateAndLockedDiscardableMemory(1024*1024);
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// void* data = mem->data();
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// memset(data, 3, 1024*1024);
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// mem->unlock();
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//
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// Later, when you need it again:
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// if (!mem->lock()) {
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// ... handle the fact that the memory is gone...
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// delete mem; // Make sure to destroy it. It is never going to come back.
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// return;
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// }
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// ... use mem->data() as much as you want
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// mem->unlock();
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//
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class WebDiscardableMemory {
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public:
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// Must not be called while locked.
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virtual ~WebDiscardableMemory() { }
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// Locks the memory, prevent it from being discarded. Once locked. you may
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// obtain a pointer to that memory using the data() method.
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//
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// lock() may return false, indicating that the underlying memory was
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// discarded and that the lock failed. In this case, the
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// WebDiscardableMemory is effectively dead.
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//
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// Nested calls to lock are not allowed.
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virtual bool lock() = 0;
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// Returns the current pointer for the discardable memory. This call is ONLY
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// valid when the discardable memory object is locked.
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virtual void* data() = 0;
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// Unlock the memory so that it can be purged by the system. Must be called
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// after every successful lock call.
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virtual void unlock() = 0;
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};
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} // namespace blink
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#endif // SKY_ENGINE_PUBLIC_PLATFORM_WEBDISCARDABLEMEMORY_H_
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