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/* Copyright 2003-2008 Joaquin M Lopez Munoz.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org/libs/multi_index for library home page.
*/
#ifndef BOOST_MULTI_INDEX_DETAIL_RND_INDEX_LOADER_HPP
#define BOOST_MULTI_INDEX_DETAIL_RND_INDEX_LOADER_HPP
#if defined(_MSC_VER)&&(_MSC_VER>=1200)
#pragma once
#endif
#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
#include <algorithm>
#include <boost/detail/allocator_utilities.hpp>
#include <boost/multi_index/detail/auto_space.hpp>
#include <boost/multi_index/detail/prevent_eti.hpp>
#include <boost/multi_index/detail/rnd_index_ptr_array.hpp>
#include <boost/noncopyable.hpp>
#include <cstddef>
namespace boost{
namespace multi_index{
namespace detail{
/* This class implements a serialization rearranger for random access
* indices. In order to achieve O(n) performance, the following strategy
* is followed: the nodes of the index are handled as if in a bidirectional
* list, where the next pointers are stored in the original
* random_access_index_ptr_array and the prev pointers are stored in
* an auxiliary array. Rearranging of nodes in such a bidirectional list
* is constant time. Once all the arrangements are performed (on destruction
* time) the list is traversed in reverse order and
* pointers are swapped and set accordingly so that they recover its
* original semantics ( *(node->up())==node ) while retaining the
* new order.
*/
template<typename Allocator>
class random_access_index_loader_base:private noncopyable
{
protected:
typedef typename prevent_eti<
Allocator,
random_access_index_node_impl<
typename boost::detail::allocator::rebind_to<
Allocator,
char
>::type
>
>::type node_impl_type;
typedef typename node_impl_type::pointer node_impl_pointer;
typedef random_access_index_ptr_array<Allocator> ptr_array;
random_access_index_loader_base(const Allocator& al_,ptr_array& ptrs_):
al(al_),
ptrs(ptrs_),
header(*ptrs.end()),
prev_spc(al,0),
preprocessed(false)
{}
~random_access_index_loader_base()
{
if(preprocessed)
{
node_impl_pointer n=header;
next(n)=n;
for(std::size_t i=ptrs.size();i--;){
n=prev(n);
std::size_t d=position(n);
if(d!=i){
node_impl_pointer m=prev(next_at(i));
std::swap(m->up(),n->up());
next_at(d)=next_at(i);
std::swap(prev_at(d),prev_at(i));
}
next(n)=n;
}
}
}
void rearrange(node_impl_pointer position,node_impl_pointer x)
{
preprocess(); /* only incur this penalty if rearrange() is ever called */
if(position==node_impl_pointer(0))position=header;
next(prev(x))=next(x);
prev(next(x))=prev(x);
prev(x)=position;
next(x)=next(position);
next(prev(x))=prev(next(x))=x;
}
private:
void preprocess()
{
if(!preprocessed){
/* get space for the auxiliary prev array */
auto_space<node_impl_pointer,Allocator> tmp(al,ptrs.size()+1);
prev_spc.swap(tmp);
/* prev_spc elements point to the prev nodes */
std::rotate_copy(
&*ptrs.begin(),&*ptrs.end(),&*ptrs.end()+1,&*prev_spc.data());
/* ptrs elements point to the next nodes */
std::rotate(&*ptrs.begin(),&*ptrs.begin()+1,&*ptrs.end()+1);
preprocessed=true;
}
}
std::size_t position(node_impl_pointer x)const
{
return (std::size_t)(x->up()-ptrs.begin());
}
node_impl_pointer& next_at(std::size_t n)const
{
return *ptrs.at(n);
}
node_impl_pointer& prev_at(std::size_t n)const
{
return *(prev_spc.data()+n);
}
node_impl_pointer& next(node_impl_pointer x)const
{
return *(x->up());
}
node_impl_pointer& prev(node_impl_pointer x)const
{
return prev_at(position(x));
}
Allocator al;
ptr_array& ptrs;
node_impl_pointer header;
auto_space<node_impl_pointer,Allocator> prev_spc;
bool preprocessed;
};
template<typename Node,typename Allocator>
class random_access_index_loader:
private random_access_index_loader_base<Allocator>
{
typedef random_access_index_loader_base<Allocator> super;
typedef typename super::node_impl_pointer node_impl_pointer;
typedef typename super::ptr_array ptr_array;
public:
random_access_index_loader(const Allocator& al_,ptr_array& ptrs_):
super(al_,ptrs_)
{}
void rearrange(Node* position,Node *x)
{
super::rearrange(position?position->impl():node_impl_pointer(0),x->impl());
}
};
} /* namespace multi_index::detail */
} /* namespace multi_index */
} /* namespace boost */
#endif
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