151 lines
4.5 KiB
C++
151 lines
4.5 KiB
C++
/* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
|
|
|
|
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 St, Fifth Floor, Boston, MA 02110-1301 USA */
|
|
|
|
#ifndef MEMROOT_ALLOCATOR_INCLUDED
|
|
#define MEMROOT_ALLOCATOR_INCLUDED
|
|
|
|
#include "sql_alloc.h"
|
|
|
|
#include <new>
|
|
#include <limits>
|
|
|
|
|
|
/**
|
|
Memroot_allocator is a C++ STL memory allocator based on MEM_ROOT.
|
|
|
|
No deallocation is done by this allocator. Calling init_sql_alloc()
|
|
and free_root() on the supplied MEM_ROOT is the responsibility of
|
|
the caller. Do *not* call free_root() until the destructor of any
|
|
objects using this allocator has completed. This includes iterators.
|
|
|
|
Example of use:
|
|
vector<int, Memroot_allocator<int> > v((Memroot_allocator<int>(&mem_root)));
|
|
|
|
@note allocate() throws std::bad_alloc() similarly to the default
|
|
STL memory allocator. This is necessary - STL functions which allocates
|
|
memory expects it. Otherwise these functions will try to use the memory,
|
|
leading to seg faults if memory allocation was not successful.
|
|
|
|
@note This allocator cannot be used for std::basic_string
|
|
because of this libstd++ bug:
|
|
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56437
|
|
"basic_string assumes that allocators are default-constructible"
|
|
|
|
@note C++98 says that STL implementors can assume that allocator objects
|
|
of the same type always compare equal. This will only be the case for
|
|
two Memroot_allocators that use the same MEM_ROOT. Care should be taken
|
|
when this is not the case. Especially:
|
|
- Using list::splice() on two lists with allocators using two different
|
|
MEM_ROOTs causes undefined behavior. Most implementations seem to give
|
|
runtime errors in such cases.
|
|
- swap() on two collections with allocators using two different MEM_ROOTs
|
|
is not well defined. At least some implementations also swap allocators,
|
|
but this should not be depended on.
|
|
*/
|
|
|
|
template <class T> class Memroot_allocator
|
|
{
|
|
// This cannot be const if we want to be able to swap.
|
|
MEM_ROOT *m_memroot;
|
|
|
|
public:
|
|
typedef T value_type;
|
|
typedef size_t size_type;
|
|
typedef ptrdiff_t difference_type;
|
|
|
|
typedef T* pointer;
|
|
typedef const T* const_pointer;
|
|
|
|
typedef T& reference;
|
|
typedef const T& const_reference;
|
|
|
|
pointer address(reference r) const { return &r; }
|
|
const_pointer address(const_reference r) const { return &r; }
|
|
|
|
explicit Memroot_allocator(MEM_ROOT *memroot) : m_memroot(memroot)
|
|
{}
|
|
|
|
template <class U> Memroot_allocator(const Memroot_allocator<U> &other)
|
|
: m_memroot(other.memroot())
|
|
{}
|
|
|
|
template <class U> Memroot_allocator & operator=
|
|
(const Memroot_allocator<U> &other)
|
|
{
|
|
DBUG_ASSERT(m_memroot == other.memroot()); // Don't swap memroot.
|
|
}
|
|
|
|
~Memroot_allocator()
|
|
{}
|
|
|
|
pointer allocate(size_type n, const_pointer hint= 0)
|
|
{
|
|
if (n == 0)
|
|
return NULL;
|
|
if (n > max_size())
|
|
throw std::bad_alloc();
|
|
|
|
pointer p= static_cast<pointer>(alloc_root(m_memroot, n * sizeof(T)));
|
|
if (p == NULL)
|
|
throw std::bad_alloc();
|
|
return p;
|
|
}
|
|
|
|
void deallocate(pointer p, size_type n) { }
|
|
|
|
void construct(pointer p, const T& val)
|
|
{
|
|
DBUG_ASSERT(p != NULL);
|
|
try {
|
|
new(p) T(val);
|
|
} catch (...) {
|
|
DBUG_ASSERT(false); // Constructor should not throw an exception.
|
|
}
|
|
}
|
|
|
|
void destroy(pointer p)
|
|
{
|
|
DBUG_ASSERT(p != NULL);
|
|
try {
|
|
p->~T();
|
|
} catch (...) {
|
|
DBUG_ASSERT(false); // Destructor should not throw an exception
|
|
}
|
|
}
|
|
|
|
size_type max_size() const
|
|
{
|
|
return std::numeric_limits<size_t>::max() / sizeof(T);
|
|
}
|
|
|
|
template <class U> struct rebind { typedef Memroot_allocator<U> other; };
|
|
|
|
MEM_ROOT *memroot() const { return m_memroot; }
|
|
};
|
|
|
|
template <class T>
|
|
bool operator== (const Memroot_allocator<T>& a1, const Memroot_allocator<T>& a2)
|
|
{
|
|
return a1.memroot() == a2.memroot();
|
|
}
|
|
|
|
template <class T>
|
|
bool operator!= (const Memroot_allocator<T>& a1, const Memroot_allocator<T>& a2)
|
|
{
|
|
return a1.memroot() != a2.memroot();
|
|
}
|
|
|
|
#endif // MEMROOT_ALLOCATOR_INCLUDED
|