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/* Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#ifndef MEM_ROOT_ARRAY_INCLUDED
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#define MEM_ROOT_ARRAY_INCLUDED
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A typesafe replacement for DYNAMIC_ARRAY.
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We use MEM_ROOT for allocating storage, rather than the C++ heap.
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The interface is chosen to be similar to std::vector.
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Unlike DYNAMIC_ARRAY, elements are properly copied
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(rather than memcpy()d) if the underlying array needs to be expanded.
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Depending on has_trivial_destructor, we destroy objects which are
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removed from the array (including when the array object itself is destroyed).
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Note that MEM_ROOT has no facility for reusing free space,
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so don't use this if multiple re-expansions are likely to happen.
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@param Element_type The type of the elements of the container.
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Elements must be copyable.
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@param has_trivial_destructor If true, we don't destroy elements.
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We could have used type traits to determine this.
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__has_trivial_destructor is supported by some (but not all)
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template<typename Element_type, bool has_trivial_destructor>
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Mem_root_array(MEM_ROOT *root)
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: m_root(root), m_array(NULL), m_size(0), m_capacity(0)
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DBUG_ASSERT(m_root != NULL);
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Element_type &at(size_t n)
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DBUG_ASSERT(n < size());
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const Element_type &at(size_t n) const
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DBUG_ASSERT(n < size());
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// Returns a pointer to the first element in the array.
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Element_type *begin() { return &m_array[0]; }
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// Returns a pointer to the past-the-end element in the array.
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Element_type *end() { return &m_array[size()]; }
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// Erases all of the elements.
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Chops the tail off the array, erasing all tail elements.
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@param pos Index of first element to erase.
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void chop(const size_t pos)
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DBUG_ASSERT(pos < m_size);
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if (!has_trivial_destructor)
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for (size_t ix= pos; ix < m_size; ++ix)
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Element_type *p= &m_array[ix];
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p->~Element_type(); // Destroy discarded element.
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Reserves space for array elements.
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Copies over existing elements, in case we are re-expanding the array.
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@param n number of elements.
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@retval true if out-of-memory, false otherwise.
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bool reserve(size_t n)
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void *mem= alloc_root(m_root, n * element_size());
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Element_type *array= static_cast<Element_type*>(mem);
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// Copy all the existing elements into the new array.
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for (size_t ix= 0; ix < m_size; ++ix)
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Element_type *new_p= &array[ix];
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Element_type *old_p= &m_array[ix];
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new (new_p) Element_type(*old_p); // Copy into new location.
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if (!has_trivial_destructor)
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old_p->~Element_type(); // Destroy the old element.
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// Forget the old array.
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Adds a new element at the end of the array, after its current last
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element. The content of this new element is initialized to a copy of
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@param element Object to copy.
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@retval true if out-of-memory, false otherwise.
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bool push_back(const Element_type &element)
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const size_t min_capacity= 20;
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const size_t expansion_factor= 2;
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if (0 == m_capacity && reserve(min_capacity))
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if (m_size == m_capacity && reserve(m_capacity * expansion_factor))
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Element_type *p= &m_array[m_size++];
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new (p) Element_type(element);
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size_t capacity() const { return m_capacity; }
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size_t element_size() const { return sizeof(Element_type); }
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bool empty() const { return size() == 0; }
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size_t size() const { return m_size; }
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MEM_ROOT *const m_root;
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Element_type *m_array;
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// Not (yet) implemented.
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Mem_root_array(const Mem_root_array&);
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Mem_root_array &operator=(const Mem_root_array&);
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#endif // MEM_ROOT_ARRAY_INCLUDED
added
removed
sql/mem_root_array.h
