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