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98 lines
3.1 KiB
C++
98 lines
3.1 KiB
C++
/* Copyright (C) 2014 InfiniDB, Inc.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; version 2 of
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the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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/******************************************************************************************
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* $Id$
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*
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******************************************************************************************/
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/* This allocator is for frequent small allocations that all get deallocated at once.
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It allocates large blocks of memory from the system and distributes 'allocsize'
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units to the caller. When the large allocation is used up, it will allocate
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more unless the 'tmpspace' flag is set. If it is, it will reuse the memory it
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already allocated. This is useful for short-lived vars that are guaranteed to be
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out of scope by the time the allocator wraps around.
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TODO: make it STL and boost compliant...
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*/
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#ifndef FIXEDALLOCATOR_H_
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#define FIXEDALLOCATOR_H_
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#include <stdint.h>
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#include <boost/shared_array.hpp>
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#include <vector>
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#include <limits>
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#include <unistd.h>
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#if defined(_MSC_VER) && defined(xxxFIXEDALLOCATOR_DLLEXPORT)
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#define EXPORT __declspec(dllexport)
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#else
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#define EXPORT
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#endif
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namespace utils {
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class FixedAllocator
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{
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public:
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EXPORT static const unsigned long DEFAULT_NUM_ELEMENTS=(4096 * 4); // should be a multiple of pagesize
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EXPORT FixedAllocator() :
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capacityRemaining(0),
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elementCount(std::numeric_limits<unsigned long>::max()),
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elementSize(0),
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currentlyStored(0),
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tmpSpace(false),
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nextAlloc(0) {}
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EXPORT explicit FixedAllocator(unsigned long allocSize, bool isTmpSpace = false,
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unsigned long numElements = DEFAULT_NUM_ELEMENTS) :
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capacityRemaining(0),
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elementCount(numElements),
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elementSize(allocSize),
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currentlyStored(0),
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tmpSpace(isTmpSpace),
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nextAlloc(0) {}
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EXPORT FixedAllocator(const FixedAllocator &);
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EXPORT FixedAllocator & operator=(const FixedAllocator &);
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virtual ~FixedAllocator() {}
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EXPORT void * allocate();
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EXPORT void * allocate(uint32_t len); // a hack to make it work more like a pool allocator (use PoolAllocator instead)
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EXPORT void truncateBy(uint32_t amt); // returns a portion of mem just allocated; use with caution
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void deallocate() { } // does nothing
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EXPORT void deallocateAll(); // drops all memory in use
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EXPORT uint64_t getMemUsage() const;
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private:
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void newBlock();
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std::vector<boost::shared_array<uint8_t> > mem;
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unsigned long capacityRemaining;
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uint64_t elementCount;
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unsigned long elementSize;
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uint64_t currentlyStored;
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bool tmpSpace;
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uint8_t* nextAlloc;
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};
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}
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#undef EXPORT
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#endif
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