// $Id$
// vim:tabstop=2
/***********************************************************************
Moses - factored phrase-based language decoder
Copyright (C) 2006 University of Edinburgh

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
***********************************************************************/

#ifndef moses_MmapAllocator_h
#define moses_MmapAllocator_h

#include <limits>
#include <iostream>
#include <sys/mman.h>
#include <cstdio>
#include <unistd.h>

namespace Moses
{
template <class T>
class MmapAllocator
{
protected:
  std::FILE* m_file_ptr;
  size_t m_file_desc;

  size_t m_page_size;
  size_t m_map_size;

  char* m_data_ptr;
  size_t m_data_offset;
  bool m_fixed;
  size_t* m_count;

public:
  typedef T        value_type;
  typedef T*       pointer;
  typedef const T* const_pointer;
  typedef T&       reference;
  typedef const T& const_reference;
  typedef std::size_t    size_type;
  typedef std::ptrdiff_t difference_type;

  MmapAllocator() throw()
    : m_file_ptr(std::tmpfile()), m_file_desc(fileno(m_file_ptr)),
      m_page_size(sysconf(_SC_PAGE_SIZE)), m_map_size(0), m_data_ptr(0),
      m_data_offset(0), m_fixed(false), m_count(new size_t(0)) {
  }

  MmapAllocator(std::FILE* f_ptr) throw()
    : m_file_ptr(f_ptr), m_file_desc(fileno(m_file_ptr)),
      m_page_size(sysconf(_SC_PAGE_SIZE)), m_map_size(0), m_data_ptr(0),
      m_data_offset(0), m_fixed(false), m_count(new size_t(0)) {
  }

  MmapAllocator(std::FILE* f_ptr, size_t data_offset) throw()
    : m_file_ptr(f_ptr), m_file_desc(fileno(m_file_ptr)),
      m_page_size(sysconf(_SC_PAGE_SIZE)), m_map_size(0), m_data_ptr(0),
      m_data_offset(data_offset), m_fixed(true), m_count(new size_t(0)) {
  }

  MmapAllocator(std::string fileName) throw()
    : m_file_ptr(std::fopen(fileName.c_str(), "wb+")), m_file_desc(fileno(m_file_ptr)),
      m_page_size(sysconf(_SC_PAGE_SIZE)), m_map_size(0), m_data_ptr(0),
      m_data_offset(0), m_fixed(false), m_count(new size_t(0)) {
  }

  MmapAllocator(const MmapAllocator& c) throw()
    : m_file_ptr(c.m_file_ptr), m_file_desc(c.m_file_desc),
      m_page_size(c.m_page_size), m_map_size(c.m_map_size),
      m_data_ptr(c.m_data_ptr), m_data_offset(c.m_data_offset),
      m_fixed(c.m_fixed), m_count(c.m_count) {
    (*m_count)++;
  }

  ~MmapAllocator() throw() {
    if(m_data_ptr && *m_count == 0) {
      munmap(m_data_ptr, m_map_size);
      if(!m_fixed && std::ftell(m_file_ptr) != -1)
        std::fclose(m_file_ptr);
    }
    (*m_count)--;
  }

  template <class U>
  struct rebind {
    typedef MmapAllocator<U> other;
  };

  pointer address (reference value) const {
    return &value;
  }

  const_pointer address (const_reference value) const {
    return &value;
  }

  size_type max_size () const throw() {
    return std::numeric_limits<size_t>::max() / sizeof(value_type);
  }

  pointer allocate (size_type num, const void* = 0) {
    m_map_size = num * sizeof(T);

    if(!m_fixed) {
      size_t read = 0;
      read += ftruncate(m_file_desc, m_map_size);
      m_data_ptr = (char*)mmap(0, m_map_size, PROT_READ|PROT_WRITE, MAP_SHARED,
                               m_file_desc, 0);
      if(m_data_ptr == MAP_FAILED)
        std::cerr << "Error: mmapping" << std::endl;
      return (pointer)m_data_ptr;
    } else {
      size_t map_offset = (m_data_offset / m_page_size) * m_page_size;
      size_t relative_offset = m_data_offset - map_offset;

      size_t map_size = m_map_size + relative_offset;

      m_data_ptr = (char*)mmap(0, map_size, PROT_READ, MAP_SHARED,
                               m_file_desc, map_offset);

      return (pointer)(m_data_ptr + relative_offset);
    }
  }

  void deallocate (pointer p, size_type num) {
    if(!m_fixed) {
      munmap(p, num * sizeof(T));
    } else {
      size_t map_offset = (m_data_offset / m_page_size) * m_page_size;
      size_t relative_offset = m_data_offset - map_offset;
      munmap((pointer)((char*)p - relative_offset), num * sizeof(T));
    }

  }

  void construct (pointer p, const T& value) {
    if(!m_fixed)
      new(p) value_type(value);
  }
  void destroy (pointer p) {
    if(!m_fixed)
      p->~T();
  }

  template <class T1, class T2>
  friend bool operator== (const MmapAllocator<T1>&, const MmapAllocator<T2>&) throw();

  template <class T1, class T2>
  friend bool operator!= (const MmapAllocator<T1>&, const MmapAllocator<T2>&) throw();
};

template <class T1, class T2>
bool operator== (const MmapAllocator<T1>& a1,
                 const MmapAllocator<T2>& a2) throw()
{
  bool equal = true;
  equal &= a1.m_file_ptr == a2.m_file_ptr;
  equal &= a1.m_file_desc == a2.m_file_desc;
  equal &= a1.m_page_size == a2.m_page_size;
  equal &= a1.m_map_size == a2.m_map_size;
  equal &= a1.m_data_ptr == a2.m_data_ptr;
  equal &= a1.m_data_offset == a2.m_data_offset;
  equal &= a1.m_fixed == a2.m_fixed;
  return equal;
}

template <class T1, class T2>
bool operator!=(const MmapAllocator<T1>& a1,
                const MmapAllocator<T2>& a2) throw()
{
  return !(a1 == a2);
}

}

#endif