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/*
* Copyright 2012, The Android Open Source Project
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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 THE COPYRIGHT HOLDERS ``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 THE COPYRIGHT OWNER OR
* 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 ANDROID_LINEARALLOCATOR_H
#define ANDROID_LINEARALLOCATOR_H
#include <stddef.h>
namespace android {
/**
* A memory manager that internally allocates multi-kbyte buffers for placing objects in. It avoids
* the overhead of malloc when many objects are allocated. It is most useful when creating many
* small objects with a similar lifetime, and doesn't add significant overhead for large
* allocations.
*/
class LinearAllocator {
public:
LinearAllocator();
~LinearAllocator();
/**
* Reserves and returns a region of memory of at least size 'size', aligning as needed.
* Typically this is used in an object's overridden new() method or as a replacement for malloc.
*
* The lifetime of the returned buffers is tied to that of the LinearAllocator. If calling
* delete() on an object stored in a buffer is needed, it should be overridden to use
* rewindIfLastAlloc()
*/
void* alloc(size_t size);
/**
* Attempt to deallocate the given buffer, with the LinearAllocator attempting to rewind its
* state if possible. No destructors are called.
*/
void rewindIfLastAlloc(void* ptr, size_t allocSize);
/**
* Dump memory usage statistics to the log (allocated and wasted space)
*/
void dumpMemoryStats(const char* prefix = "");
/**
* The number of bytes used for buffers allocated in the LinearAllocator (does not count space
* wasted)
*/
size_t usedSize() const { return mTotalAllocated - mWastedSpace; }
private:
LinearAllocator(const LinearAllocator& other);
class Page;
Page* newPage(size_t pageSize);
bool fitsInCurrentPage(size_t size);
void ensureNext(size_t size);
void* start(Page *p);
void* end(Page* p);
size_t mPageSize;
size_t mMaxAllocSize;
void* mNext;
Page* mCurrentPage;
Page* mPages;
// Memory usage tracking
size_t mTotalAllocated;
size_t mWastedSpace;
size_t mPageCount;
size_t mDedicatedPageCount;
};
}; // namespace android
#endif // ANDROID_LINEARALLOCATOR_H
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