intersegment_ptr.hpp

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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2005-2008. 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/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////

#ifndef BOOST_INTERPROCESS_INTERSEGMENT_PTR_HPP
#define BOOST_INTERPROCESS_INTERSEGMENT_PTR_HPP

#if (defined _MSC_VER) && (_MSC_VER >= 1200)
#  pragma once
#endif

#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>

#include <boost/interprocess/interprocess_fwd.hpp>
#include <boost/interprocess/detail/utilities.hpp>
#include <boost/interprocess/detail/math_functions.hpp>
#include <boost/interprocess/detail/cast_tags.hpp>
#include <boost/assert.hpp>
#include <boost/interprocess/sync/scoped_lock.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/interprocess/containers/flat_map.hpp>
#include <boost/interprocess/containers/vector.hpp>   //vector
#include <boost/interprocess/containers/set.hpp>      //set
#include <boost/detail/no_exceptions_support.hpp>
#include <boost/interprocess/detail/mpl.hpp>
#include <climits>
#include <iterator>
#include <boost/static_assert.hpp>  //BOOST_STATIC_ASSERT
#include <climits>   //CHAR_BIT
#include <boost/integer/static_log2.hpp>
#include <cassert>   //assert
#include <boost/interprocess/detail/multi_segment_services.hpp>

//!\file
//!
namespace boost {

//Predeclarations
template <class T>
struct has_trivial_constructor;

template <class T>
struct has_trivial_destructor;

namespace interprocess {

template <class T>
struct is_multisegment_ptr;

struct intersegment_base
{
   typedef intersegment_base  self_t;
   BOOST_STATIC_ASSERT((sizeof(std::size_t) == sizeof(void*)));
   BOOST_STATIC_ASSERT((sizeof(void*)*CHAR_BIT == 32 || sizeof(void*)*CHAR_BIT == 64));
   static const std::size_t size_t_bits = (sizeof(void*)*CHAR_BIT == 32) ? 32 : 64;
   static const std::size_t ctrl_bits = 2;
   static const std::size_t align_bits = 12;
   static const std::size_t align      = std::size_t(1) << align_bits;
   static const std::size_t max_segment_size_bits = size_t_bits - 2;
   static const std::size_t max_segment_size = std::size_t(1) << max_segment_size_bits;

   static const std::size_t begin_bits             = max_segment_size_bits - align_bits;
   static const std::size_t pow_size_bits_helper = static_log2<max_segment_size_bits>::value;
   static const std::size_t pow_size_bits = 
      (max_segment_size_bits == (std::size_t(1) << pow_size_bits_helper)) ? 
      pow_size_bits_helper : pow_size_bits_helper + 1;
   static const std::size_t frc_size_bits =
      size_t_bits - ctrl_bits - begin_bits - pow_size_bits;

   BOOST_STATIC_ASSERT(((size_t_bits - pow_size_bits - frc_size_bits) >= ctrl_bits ));

   static const std::size_t relative_size_bits =
      size_t_bits - max_segment_size_bits - ctrl_bits;

   static const std::size_t is_pointee_outside  = 0;
   static const std::size_t is_in_stack         = 1;
   static const std::size_t is_relative         = 2;
   static const std::size_t is_segmented        = 3;
   static const std::size_t is_max_mode         = 4;

   intersegment_base()
   {
      this->set_mode(is_pointee_outside);
      this->set_null();
   }

   struct relative_addressing
   {
      std::size_t ctrl     :  2;
      std::size_t pow      :  pow_size_bits;
      std::size_t frc      :  frc_size_bits;
      std::size_t beg      :  begin_bits;
      std::ptrdiff_t off   :  sizeof(ptrdiff_t)*CHAR_BIT - 2;
      std::ptrdiff_t bits  :  2;
   };

   struct direct_addressing
   {
      std::size_t ctrl     :  2;
      std::size_t dummy    :  sizeof(std::size_t)*CHAR_BIT - 2;
      void * addr;
   };

   struct segmented_addressing
   {
      std::size_t ctrl     :  2;
      std::size_t segment  :  sizeof(std::size_t)*CHAR_BIT - 2;
      std::size_t off      :  sizeof(std::size_t)*CHAR_BIT - 2;
      std::size_t bits     :  2;
   };

   union members_t{
      relative_addressing  relative;
      direct_addressing    direct;
      segmented_addressing segmented;
   } members;

   BOOST_STATIC_ASSERT(sizeof(members_t) == 2*sizeof(std::size_t));

   void *relative_calculate_begin_addr() const
   {
      const std::size_t mask = ~(align - 1);
      std::size_t beg = this->members.relative.beg;
      return reinterpret_cast<void*>((((std::size_t)this) & mask) - (beg << align_bits));
   }

   void relative_set_begin_from_base(void *addr)
   {
      assert(addr < static_cast<void*>(this));
      std::size_t off = reinterpret_cast<char*>(this) - reinterpret_cast<char*>(addr);
      members.relative.beg = off >> align_bits;
   }

   //!Obtains the address pointed by the
   //!object
   std::size_t relative_size() const
   {
      std::size_t pow  = members.relative.pow;
      std::size_t size = (std::size_t(1u) << pow);
      assert(pow >= frc_size_bits);
      size |= members.relative.frc << (pow - frc_size_bits);
      return size;
   }

   static std::size_t calculate_size(std::size_t orig_size, std::size_t &pow, std::size_t &frc)
   {
      if(orig_size < align)
         orig_size = align;
      orig_size = detail::get_rounded_size_po2(orig_size, align);
      pow = detail::floor_log2(orig_size);
      std::size_t low_size = (std::size_t(1) << pow);
      std::size_t diff = orig_size - low_size;
      assert(pow >= frc_size_bits);
      std::size_t rounded = detail::get_rounded_size_po2
                              (diff, (1u << (pow - frc_size_bits)));
      if(rounded == low_size){
         ++pow;
         frc = 0;
         rounded  = 0;
      }
      else{
         frc = rounded >> (pow - frc_size_bits);
      }
      assert(((frc << (pow - frc_size_bits)) & (align-1))==0);
      return low_size + rounded;
   }

   std::size_t get_mode()const
   {  return members.direct.ctrl;   }

   void set_mode(std::size_t mode)
   {
      assert(mode < is_max_mode);      
      members.direct.ctrl = mode;
   }

   //!Returns true if object represents
   //!null pointer
   bool is_null() const
   {
      return   (this->get_mode() < is_relative) && 
               !members.direct.dummy &&
               !members.direct.addr;
   }

   //!Sets the object to represent
   //!the null pointer
   void set_null()
   {
      if(this->get_mode() >= is_relative){
         this->set_mode(is_pointee_outside);
      }
      members.direct.dummy = 0;
      members.direct.addr  = 0;
   }

   static std::size_t round_size(std::size_t orig_size)
   {
      std::size_t pow, frc;
      return calculate_size(orig_size, pow, frc);
   }
};



//!Configures intersegment_ptr with the capability to address:
//!2^(sizeof(std::size_t)*CHAR_BIT/2) segment groups
//!2^(sizeof(std::size_t)*CHAR_BIT/2) segments per group.
//!2^(sizeof(std::size_t)*CHAR_BIT/2)-1 bytes maximum per segment.
//!The mapping is implemented through flat_maps synchronized with mutexes.
template <class Mutex>
struct flat_map_intersegment
   :  public intersegment_base
{
   typedef flat_map_intersegment<Mutex>   self_t;

   void set_from_pointer(const volatile void *ptr)
   {  this->set_from_pointer(const_cast<const void *>(ptr));  }

   //!Obtains the address pointed
   //!by the object
   void *get_pointer() const
   {
      if(is_null()){
         return 0;
      }
      switch(this->get_mode()){
         case is_relative:
            return const_cast<char*>(reinterpret_cast<const char*>(this)) + members.relative.off;
         break;
         case is_segmented:
            {
            segment_info_t segment_info;
            std::size_t offset;
            void *this_base;
            get_segment_info_and_offset(this, segment_info, offset, this_base);
            char *base  = static_cast<char*>(segment_info.group->address_of(this->members.segmented.segment));
            return base + this->members.segmented.off;
            }
         break;
         case is_in_stack:
         case is_pointee_outside:
            return members.direct.addr;
         break;
         default:
         return 0;
         break;
      }
   }

   //!Calculates the distance between two basic_intersegment_ptr-s.
   //!This only works with two basic_intersegment_ptr pointing
   //!to the same segment. Otherwise undefined
   std::ptrdiff_t diff(const self_t &other) const
   {  return static_cast<char*>(this->get_pointer()) - static_cast<char*>(other.get_pointer());   }

   //!Returns true if both point to
   //!the same object
   bool equal(const self_t &y) const
   {  return this->get_pointer() == y.get_pointer();  }

   //!Returns true if *this is less than other.
   //!This only works with two basic_intersegment_ptr pointing
   //!to the same segment group. Otherwise undefined. Never throws
   bool less(const self_t &y) const
   {  return this->get_pointer() < y.get_pointer(); }

   void swap(self_t &other)
   {
      void *ptr_this  = this->get_pointer();
      void *ptr_other = other.get_pointer();
      other.set_from_pointer(ptr_this);
      this->set_from_pointer(ptr_other);
   }

   //!Sets the object internals to represent the
   //!address pointed by ptr
   void set_from_pointer(const void *ptr)
   {
      if(!ptr){
         this->set_null();
         return;
      }

      std::size_t mode = this->get_mode();
      if(mode == is_in_stack){
         members.direct.addr = const_cast<void*>(ptr);
         return;
      }
      if(mode == is_relative){
         char *beg_addr = static_cast<char*>(this->relative_calculate_begin_addr());
         std::size_t seg_size = this->relative_size();
         if(ptr >= beg_addr && ptr < (beg_addr + seg_size)){
            members.relative.off = static_cast<const char*>(ptr) - reinterpret_cast<const char*>(this);
            return;
         }
      }
      std::size_t ptr_offset;
      std::size_t this_offset;
      segment_info_t ptr_info;
      segment_info_t this_info;
      void *ptr_base;
      void *this_base;
      get_segment_info_and_offset(this, this_info, this_offset, this_base);
   
      if(!this_info.group){
         this->set_mode(is_in_stack);
         this->members.direct.addr = const_cast<void*>(ptr);
      }
      else{
         get_segment_info_and_offset(ptr, ptr_info, ptr_offset, ptr_base);      

         if(ptr_info.group != this_info.group){
            this->set_mode(is_pointee_outside);
            this->members.direct.addr =  const_cast<void*>(ptr);
         }
         else if(ptr_info.id == this_info.id){
            this->set_mode(is_relative);
            members.relative.off = (static_cast<const char*>(ptr) - reinterpret_cast<const char*>(this));
            this->relative_set_begin_from_base(this_base);
            std::size_t pow, frc;
            std::size_t s = calculate_size(this_info.size, pow, frc);
            (void)s;
            assert(this_info.size == s);
            this->members.relative.pow = pow;
            this->members.relative.frc = frc;
         }
         else{
            this->set_mode(is_segmented);
            this->members.segmented.segment = ptr_info.id;
            this->members.segmented.off     = ptr_offset;
         }
      }
   }

   //!Sets the object internals to represent the address pointed 
   //!by another flat_map_intersegment
   void set_from_other(const self_t &other)
   {
      this->set_from_pointer(other.get_pointer());
   }