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authortoma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da>2009-11-25 17:56:58 +0000
committertoma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da>2009-11-25 17:56:58 +0000
commitce4a32fe52ef09d8f5ff1dd22c001110902b60a2 (patch)
tree5ac38a06f3dde268dc7927dc155896926aaf7012 /kdecore/kallocator.h
downloadtdelibs-ce4a32fe52ef09d8f5ff1dd22c001110902b60a2.tar.gz
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Copy the KDE 3.5 branch to branches/trinity for new KDE 3.5 features.
BUG:215923 git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdelibs@1054174 283d02a7-25f6-0310-bc7c-ecb5cbfe19da
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+/*
+ This file is part of the KDE libraries
+
+ Copyright (C) 1999 Waldo Bastian (bastian@kde.org)
+ Copyright (C) 2002 Michael Matz (matz@kde.org)
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public
+ License as published by the Free Software Foundation; either
+ version 2 of the License, or (at your option) any later version.
+
+ This library 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
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public License
+ along with this library; see the file COPYING.LIB. If not, write to
+ the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ Boston, MA 02110-1301, USA.
+*/
+//----------------------------------------------------------------------------
+//
+// KDE Memory Allocator
+
+#ifndef KALLOCATOR_H
+#define KALLOCATOR_H
+
+#include <qvaluelist.h>
+#include "kdelibs_export.h"
+
+class KZoneAllocatorPrivate;
+
+
+/**
+ * Memory allocator for large groups of small objects.
+ * This should be used for large groups of objects that are created and
+ * destroyed together. When used carefully for this purpose it is faster
+ * and more memory efficient than malloc. Additionally to a usual obstack
+ * like allocator you can also free the objects individually. Because it
+ * does no compaction it still is faster then malloc()/free(). Depending
+ * on the exact usage pattern that might come at the expense of some
+ * memory though.
+ * @author Waldo Bastian <bastian@kde.org>, Michael Matz <matz@kde.org>
+ */
+class KDECORE_EXPORT KZoneAllocator
+{
+public:
+ /**
+ * Creates a KZoneAllocator object.
+ * @param _blockSize Size in bytes of the blocks requested from malloc.
+ */
+ KZoneAllocator(unsigned long _blockSize = 8*1024);
+
+ /**
+ * Destructs the ZoneAllocator and free all memory allocated by it.
+ */
+ ~KZoneAllocator();
+
+ /**
+ * Allocates a memory block.
+ * @param _size Size in bytes of the memory block. Memory is aligned to
+ * the size of a pointer.
+ */
+ void* allocate(size_t _size);
+
+ /**
+ * Gives back a block returned by allocate() to the zone
+ * allocator, and possibly deallocates the block holding it (when it's
+ * empty). The first deallocate() after many allocate() calls
+ * (or the first at all) builds an internal data structure for speeding
+ * up deallocation. The consistency of that structure is maintained
+ * from then on (by allocate() and deallocate()) unless many
+ * more objects are allocated without any intervening deallocation, in
+ * which case it's thrown away and rebuilt at the next deallocate().
+ *
+ * The effect of this is, that such initial deallocate() calls take
+ * more time then the normal calls, and that after this list is built, i.e.
+ * generally if deallocate() is used at all, also allocate() is a
+ * little bit slower. This means, that if you want to squeeze out the last
+ * bit performance you would want to use KZoneAllocator as an obstack, i.e.
+ * just use the functions allocate() and free_since(). All the
+ * remaining memory is returned to the system if the zone allocator
+ * is destroyed.
+ * @param ptr Pointer as returned by allocate().
+ */
+ void deallocate(void *ptr);
+
+ /**
+ * Deallocate many objects at once.
+ * free_since() deallocates all objects allocated after @p ptr,
+ * @em including @p ptr itself.
+ *
+ * The intended use is something along the lines of:
+ * \code
+ * KZoneAllocator alloc(8192);
+ * void *remember_me = alloc.allocate(0);
+ * for (int i = 0; i < 1000; i++)
+ * do_something_with (alloc.allocate(12));
+ * alloc.free_since (remember_me);
+ * \endcode
+ * Note, that we don't need to remember all the pointers to the 12-byte
+ * objects for freeing them. The free_since() does deallocate them
+ * all at once.
+ * @param ptr Pointer as returned by allocate(). It acts like
+ * a kind of mark of a certain position in the stack of all objects,
+ * off which you can throw away everything above that mark.
+ */
+ void free_since(void *ptr);
+
+protected:
+ /** A single chunk of memory from the heap. @internal */
+ class MemBlock;
+ /**< A list of chunks. @internal */
+ typedef QValueList<MemBlock *> MemList;
+ void addBlock(MemBlock *b);
+ void delBlock(MemBlock *b);
+ void insertHash(MemBlock *b);
+ void initHash();
+ /** One block is 'current' to satisfy requests. @internal */
+ MemBlock *currentBlock;
+ /** Store block size from constructor. @internal */
+ unsigned long blockSize;
+ /** Store offset into current block; size-offset is free. @internal */
+ unsigned long blockOffset;
+ /** base-2 log of the block size. @internal */
+ unsigned int log2;
+ /** Count total number of allocated blocks. @internal */
+ unsigned int num_blocks;
+ /** Collection of lists of blocks, for lookups. @internal */
+ MemList **hashList;
+ /** Count of hashes. @internal */
+ unsigned int hashSize;
+ /** Flag the hashes as in need of reorganization. @internal */
+ bool hashDirty;
+private:
+ KZoneAllocatorPrivate *d;
+};
+
+#endif