kernel/util: Add heap implementation
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Pawel Dziepak
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/*
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* Copyright 2013 Haiku, Inc. All rights reserved.
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* Distributed under the terms of the MIT License.
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*
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* Authors:
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* Paweł Dziepak, [email protected]
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*/
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#ifndef KERNEL_UTIL_HEAP_H
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#define KERNEL_UTIL_HEAP_H
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#include <debug.h>
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#include <SupportDefs.h>
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template<typename Element, typename Key>
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struct HeapLink {
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HeapLink();
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int fIndex;
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Key fKey;
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};
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template<typename Element, typename Key>
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class HeapLinkImpl {
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private:
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typedef HeapLink<Element, Key> Link;
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public:
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inline Link* GetHeapLink();
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private:
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Link fHeapLink;
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};
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template<typename Element, typename Key>
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class HeapStandardGetLink {
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private:
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typedef HeapLink<Element, Key> Link;
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public:
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inline Link* operator()(Element* element) const;
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};
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template<typename Element, typename Key,
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HeapLink<Element, Key> Element::*LinkMember>
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class HeapMemberGetLink {
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private:
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typedef HeapLink<Element, Key> Link;
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public:
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inline Link* operator()(Element* element) const;
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};
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template<typename Key>
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class HeapLesserCompare {
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public:
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inline bool operator()(Key a, Key b);
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};
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template<typename Key>
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class HeapGreaterCompare {
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public:
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inline bool operator()(Key a, Key b);
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};
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#define HEAP_TEMPLATE_LIST \
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template<typename Element, typename Key, typename Compare, typename GetLink>
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#define HEAP_CLASS_NAME Heap<Element, Key, Compare, GetLink>
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template<typename Element, typename Key,
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typename Compare = HeapLesserCompare<Key>,
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typename GetLink = HeapStandardGetLink<Element, Key> >
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class Heap {
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public:
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Heap();
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~Heap();
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inline Element* PeekRoot();
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inline void ModifyKey(Element* element, Key newKey);
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inline void RemoveRoot();
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inline status_t Insert(Element* element, Key key);
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private:
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status_t _GrowHeap();
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void _MoveUp(HeapLink<Element, Key>* link);
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void _MoveDown(HeapLink<Element, Key>* link);
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Element** fElements;
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int fLastElement;
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int fSize;
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Compare sCompare;
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GetLink sGetLink;
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};
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#if KDEBUG
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template<typename Element, typename Key>
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HeapLink<Element, Key>::HeapLink()
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:
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fIndex(-1)
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{
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}
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#else
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template<typename Element, typename Key>
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HeapLink<Element, Key>::HeapLink()
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{
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}
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#endif
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template<typename Element, typename Key>
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HeapLink<Element, Key>*
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HeapLinkImpl<Element, Key>::GetHeapLink()
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{
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return &fHeapLink;
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}
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template<typename Element, typename Key>
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HeapLink<Element, Key>*
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HeapStandardGetLink<Element, Key>::operator()(Element* element) const
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{
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return element->GetHeapLink();
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}
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template<typename Element, typename Key,
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HeapLink<Element, Key> Element::*LinkMember>
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HeapLink<Element, Key>*
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HeapMemberGetLink<Element, Key, LinkMember>::operator()(Element* element) const
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{
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return &(element->*LinkMember);
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}
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template<typename Key>
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bool
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HeapLesserCompare<Key>::operator()(Key a, Key b)
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{
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return a < b;
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}
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template<typename Key>
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bool
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HeapGreaterCompare<Key>::operator()(Key a, Key b)
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{
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return a > b;
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}
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HEAP_TEMPLATE_LIST
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HEAP_CLASS_NAME::Heap()
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:
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fElements(NULL),
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fLastElement(0),
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fSize(0)
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{
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}
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HEAP_TEMPLATE_LIST
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HEAP_CLASS_NAME::~Heap()
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{
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free(fElements);
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}
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HEAP_TEMPLATE_LIST
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Element*
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HEAP_CLASS_NAME::PeekRoot()
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{
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if (fLastElement > 0)
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return fElements[0];
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return NULL;
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}
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HEAP_TEMPLATE_LIST
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void
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HEAP_CLASS_NAME::ModifyKey(Element* element, Key newKey)
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{
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HeapLink<Element, Key> link = sGetLink(element);
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ASSERT(link->fIndex >= 0 && link->fIndex < fLastElement);
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Key oldKey = link->fKey;
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link->fKey = newKey;
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if (sCompare(newKey, oldKey))
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_MoveUp(link);
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else
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_MoveDown(link);
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}
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HEAP_TEMPLATE_LIST
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void
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HEAP_CLASS_NAME::RemoveRoot()
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{
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ASSERT(fLastElement > 0);
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#if KDEBUG
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Element* element = PeekRoot();
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HeapLink<Element, Key> link = sGetLink(element);
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link->fIndex = -1;
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#endif
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fLastElement--;
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if (fLastElement > 0) {
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Element* lastElement = fElements[fLastElement];
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fElements[0] = lastElement;
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sGetLink(lastElement)->fIndex = 0;
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_MoveDown(sGetLink(lastElement));
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}
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}
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HEAP_TEMPLATE_LIST
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status_t
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HEAP_CLASS_NAME::Insert(Element* element, Key key)
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{
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if (fLastElement == fSize) {
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status_t result = _GrowHeap();
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if (result != B_OK)
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return result;
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}
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ASSERT(fLastElement != fSize);
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HeapLink<Element, Key>* link = sGetLink(element);
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fElements[fLastElement] = element;
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link->fIndex = fLastElement++;
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link->fKey = key;
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_MoveUp(link);
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}
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HEAP_TEMPLATE_LIST
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status_t
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HEAP_CLASS_NAME::_GrowHeap()
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{
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int newSize = max_c(fSize * 2, 4);
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size_t arraySize = newSize * sizeof(Element*);
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Element** newBuffer
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= reinterpret_cast<Element**>(realloc(fElements, arraySize));
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if (newBuffer == NULL)
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return B_NO_MEMORY;
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fElements = newBuffer;
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fSize = newSize;
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return B_OK;
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}
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HEAP_TEMPLATE_LIST
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void
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HEAP_CLASS_NAME::_MoveUp(HeapLink<Element, Key>* link)
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{
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int i = link->fIndex;
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while (true) {
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int parent = (link->fIndex - 1) / 2;
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if (link->fIndex > 0
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&& sCompare(link->fKey, sGetLink(fElements[parent])->fKey)) {
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sGetLink(fElements[parent])->fIndex = link->fIndex;
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Element* element = fElements[link->fIndex];
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fElements[link->fIndex] = fElements[parent];
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fElements[parent] = element;
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link->fIndex = parent;
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} else
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break;
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}
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}
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HEAP_TEMPLATE_LIST
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void
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HEAP_CLASS_NAME::_MoveDown(HeapLink<Element, Key>* link)
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{
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int current;
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while (true) {
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current = link->fIndex;
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int child = 2 * link->fIndex + 1;
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if (child < fLastElement
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&& sCompare(sGetLink(fElements[child])->fKey, link->fKey)) {
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current = child;
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}
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child = 2 * link->fIndex + 2;
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if (child < fLastElement
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&& sCompare(sGetLink(fElements[child])->fKey,
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sGetLink(fElements[current])->fKey)) {
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current = child;
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}
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if (link->fIndex == current)
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break;
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sGetLink(fElements[current])->fIndex = link->fIndex;
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Element* element = fElements[link->fIndex];
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fElements[link->fIndex] = fElements[current];
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fElements[current] = element;
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link->fIndex = current;
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}
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}
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#endif // KERNEL_UTIL_HEAP_H
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