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Diffstat (limited to 'include/utils/LinearAllocator.h')
-rw-r--r-- | include/utils/LinearAllocator.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/include/utils/LinearAllocator.h b/include/utils/LinearAllocator.h new file mode 100644 index 0000000..4772bc8 --- /dev/null +++ b/include/utils/LinearAllocator.h @@ -0,0 +1,97 @@ +/* + * 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 |