the begginning

utils/common/fixedallocator.h

@@ -0,0 +1,97 @@
+/* Copyright (C) 2014 InfiniDB, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+/******************************************************************************************
+* $Id$
+*
+******************************************************************************************/
+
+/* This allocator is for frequent small allocations that all get deallocated at once.
+   It allocates large blocks of memory from the system and distributes 'allocsize'
+   units to the caller.  When the large allocation is used up, it will allocate 
+   more unless the 'tmpspace' flag is set.  If it is, it will reuse the memory it
+   already allocated.  This is useful for short-lived vars that are guaranteed to be
+   out of scope by the time the allocator wraps around.
+
+   TODO: make it STL and boost compliant...
+*/
+
+#ifndef FIXEDALLOCATOR_H_
+#define FIXEDALLOCATOR_H_
+
+#include <stdint.h>
+#include <boost/shared_array.hpp>
+#include <vector>
+#include <limits>
+#include <unistd.h>
+
+#if defined(_MSC_VER) && defined(xxxFIXEDALLOCATOR_DLLEXPORT)
+#define EXPORT __declspec(dllexport)
+#else
+#define EXPORT
+#endif
+
+namespace utils {
+
+class FixedAllocator
+{
+public:
+	EXPORT static const unsigned long DEFAULT_NUM_ELEMENTS=(4096 * 4);  // should be a multiple of pagesize
+
+	EXPORT FixedAllocator() :
+		capacityRemaining(0),
+		elementCount(std::numeric_limits<unsigned long>::max()),
+		elementSize(0),
+		currentlyStored(0),
+		tmpSpace(false),
+		nextAlloc(0) {}
+	EXPORT explicit FixedAllocator(unsigned long allocSize, bool isTmpSpace = false,
+	  unsigned long numElements = DEFAULT_NUM_ELEMENTS) :
+		capacityRemaining(0),
+		elementCount(numElements),
+		elementSize(allocSize),
+		currentlyStored(0),
+		tmpSpace(isTmpSpace),
+		nextAlloc(0) {}
+	EXPORT FixedAllocator(const FixedAllocator &);
+	EXPORT FixedAllocator & operator=(const FixedAllocator &);
+	virtual ~FixedAllocator() {}
+
+	EXPORT void * allocate(); 
+	EXPORT void * allocate(uint32_t len);  // a hack to make it work more like a pool allocator (use PoolAllocator instead)
+	EXPORT void truncateBy(uint32_t amt);   // returns a portion of mem just allocated; use with caution
+	void deallocate() { }   // does nothing
+	EXPORT void deallocateAll();		// drops all memory in use
+	EXPORT uint64_t getMemUsage() const;
+	
+private:
+	void newBlock();
+
+	std::vector<boost::shared_array<uint8_t> > mem;
+	unsigned long capacityRemaining;
+	uint64_t elementCount;
+	unsigned long elementSize;
+	uint64_t currentlyStored;
+	bool tmpSpace;
+	uint8_t* nextAlloc;
+};
+
+}
+
+#undef EXPORT
+
+#endif