vectorstream.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.
//
//////////////////////////////////////////////////////////////////////////////
//
// This file comes from SGI's sstream file. Modified by Ion Gaztanaga 2005.
// Changed internal SGI string to a generic, templatized vector. Added efficient
// internal buffer get/set/swap functions, so that we can obtain/establish the
// internal buffer without any reallocation or copy. Kill those temporaries!
///////////////////////////////////////////////////////////////////////////////
/*
 * Copyright (c) 1998
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

//!\file
//!This file defines basic_vectorbuf, basic_ivectorstream,
//!basic_ovectorstream, and basic_vectorstreamclasses.  These classes
//!represent streamsbufs and streams whose sources or destinations are
//!STL-like vectors that can be swapped with external vectors to avoid 
//!unnecessary allocations/copies.

#ifndef BOOST_INTERPROCESS_VECTORSTREAM_HPP
#define BOOST_INTERPROCESS_VECTORSTREAM_HPP

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

#include <iosfwd>
#include <ios>
#include <istream>
#include <ostream>
#include <string>    // char traits            
#include <cstddef>   // ptrdiff_t
#include <boost/interprocess/interprocess_fwd.hpp>
#include <cassert>

namespace boost {  namespace interprocess {

//!A streambuf class that controls the transmission of elements to and from
//!a basic_ivectorstream, basic_ovectorstream or basic_vectorstream. 
//!It holds a character vector specified by CharVector template parameter
//!as its formatting buffer. The vector must have contiguous storage, like 
//!std::vector, boost::interprocess::vector or boost::interprocess::basic_string
template <class CharVector, class CharTraits>
class basic_vectorbuf
   : public std::basic_streambuf<typename CharVector::value_type, CharTraits>
{
   public:
   typedef CharVector                        vector_type;
   typedef typename CharVector::value_type   char_type;
   typedef typename CharTraits::int_type     int_type;
   typedef typename CharTraits::pos_type     pos_type;
   typedef typename CharTraits::off_type     off_type;
   typedef CharTraits                        traits_type;

   /// @cond
   private:
   typedef std::basic_streambuf<char_type, traits_type> base_t;

   basic_vectorbuf(const basic_vectorbuf&);
   basic_vectorbuf & operator =(const basic_vectorbuf&);
   /// @endcond

   public:
   //!Constructor. Throws if vector_type default
   //!constructor throws.
   explicit basic_vectorbuf(std::ios_base::openmode mode
                              = std::ios_base::in | std::ios_base::out)
      :  base_t(), m_mode(mode)
   {  this->initialize_pointers();   }

   //!Constructor. Throws if
   //!vector_type(const VectorParameter &param) throws.
   template<class VectorParameter>
   explicit basic_vectorbuf(const VectorParameter &param,
                            std::ios_base::openmode mode
                                 = std::ios_base::in | std::ios_base::out)
      :  base_t(), m_mode(mode), m_vect(param)
   {  this->initialize_pointers();   }

   virtual ~basic_vectorbuf(){}

   public:

   //!Swaps the underlying vector with the passed vector. 
   //!This function resets the read/write position in the stream.
   //!Does not throw.
   void swap_vector(vector_type &vect)
   {  
      if (this->m_mode & std::ios_base::out){
         //Update high water if necessary
         //And resize vector to remove extra size
         if (mp_high_water < base_t::pptr()){
            //Restore the vector's size if necessary
            mp_high_water = base_t::pptr();
         }
         m_vect.resize(mp_high_water - (m_vect.size() ? &m_vect[0] : 0));

         //Now swap vector
         m_vect.swap(vect);

         //If the stream is writable put the high water mark
         //and maximize the size.
         typename vector_type::size_type old_size = m_vect.size();
         m_vect.resize(m_vect.capacity());
         this->initialize_pointers();
         mp_high_water = old_size ? &m_vect[0] + old_size : 0;
      }
      else{
         //Now swap vector
         m_vect.swap(vect);
         this->initialize_pointers();
      }
   }

   //!Returns a const reference to the internal vector.
   //!Does not throw.
   const vector_type &vector() const 
   {  
      if (this->m_mode & std::ios_base::out){
         if (mp_high_water < base_t::pptr()){
            //Restore the vector's size if necessary
            mp_high_water = base_t::pptr();
         }
         m_vect.resize(mp_high_water - (m_vect.size() ? &m_vect[0] : 0));
         const_cast<basic_vectorbuf * const>(this)->initialize_pointers();
      }
      return m_vect; 
   }

   //!Preallocates memory from the internal vector.
   //!Resets the stream to the first position.
   //!Throws if the internals vector's memory allocation throws.
   void reserve(typename vector_type::size_type size) 
   {
      m_vect.reserve(size);
      //Now update pointer data
      typename vector_type::size_type old_size = m_vect.size();
      m_vect.resize(m_vect.capacity());
      this->initialize_pointers();
      mp_high_water = old_size ? &m_vect[0] + old_size : 0;
   }

   //!Calls clear() method of the internal vector.
   //!Resets the stream to the first position.
   void clear() 
   {  m_vect.clear();   this->initialize_pointers();   }

   /// @cond
   private:
   void initialize_pointers()
   {
      // The initial read position is the beginning of the vector.
      if(m_mode & std::ios_base::in){
         if(m_vect.empty()){
            this->setg(0, 0, 0);
         }
         else{
            this->setg(&m_vect[0], &m_vect[0], &m_vect[0] + m_vect.size());
         }
      }

      // The initial write position is the beginning of the vector.
      if(m_mode & std::ios_base::out){
         if(m_vect.empty()){
            this->setp(0, 0);
         }
         else{
            this->setp(&m_vect[0], &m_vect[0] + m_vect.size());
         }

         if (m_mode & (std::ios_base::app | std::ios_base::ate))
            base_t::pbump((int)m_vect.size());
      }
      mp_high_water = m_vect.empty() ? 0 : (&m_vect[0] + m_vect.size());
   }

   protected:
   virtual int_type underflow()
   {
      if (base_t::gptr() == 0)
         return CharTraits::eof();
      if (mp_high_water < base_t::pptr())
         mp_high_water = base_t::pptr();
      if (base_t::egptr() < mp_high_water)
         base_t::setg(base_t::eback(), base_t::gptr(), mp_high_water);
      if (base_t::gptr() < base_t::egptr())
         return CharTraits::to_int_type(*base_t::gptr());
      return CharTraits::eof();
   }

   virtual int_type pbackfail(int_type c = CharTraits::eof())
   {
      if(this->gptr() != this->eback()) {
         if(!CharTraits::eq_int_type(c, CharTraits::eof())) {
            if(CharTraits::eq(CharTraits::to_char_type(c), this->gptr()[-1])) {
               this->gbump(-1);
               return c;
            }
            else if(m_mode & std::ios_base::out) {
               this->gbump(-1);
               *this->gptr() = c;
               return c;
            }
            else
               return CharTraits::eof();
         }
         else {
            this->gbump(-1);
            return CharTraits::not_eof(c);
         }
      }
      else
         return CharTraits::eof();
   }

   virtual int_type overflow(int_type c = CharTraits::eof())
   {
      if(m_mode & std::ios_base::out) {
         if(!CharTraits::eq_int_type(c, CharTraits::eof())) {
//            if(!(m_mode & std::ios_base::in)) {
//               if(this->pptr() < this->epptr()) {
//                  *this->pptr() = CharTraits::to_char_type(c);
//                           this->pbump(1);
//                  if (mp_high_water < base_t::pptr())
//                     mp_high_water = base_t::pptr();
//                  if ((m_mode & std::ios_base::in) && base_t::egptr() < mp_high_water)
//                     base_t::setg(base_t::eback(), base_t::gptr(), mp_high_water);
//                  return c;
//               }
//               else
//                  return CharTraits::eof();
//            }
//            else {
//               try{
                  typedef typename vector_type::difference_type dif_t;
                  dif_t inpos  = base_t::gptr() - base_t::eback();
                  //The new output position is the previous one plus one
                  //because 'overflow' requires putting 'c' on the buffer
                  dif_t new_outpos = base_t::pptr() - base_t::pbase() + 1;
                  //Adjust high water if necessary
                  dif_t hipos = mp_high_water - base_t::pbase();
                  if (hipos < new_outpos)
                     hipos = new_outpos;
                  //Insert the new data
                  m_vect.push_back(CharTraits::to_char_type(c));
                  m_vect.resize(m_vect.capacity());
                  char_type* p = const_cast<char_type*>(&m_vect[0]);
                  //A reallocation has happened, update pointers
                  if (m_mode & std::ios_base::in)
                     base_t::setg(p, p + inpos, p + hipos);
                  base_t::setp(p, p + (dif_t)m_vect.size());
                  //Update write position to the old position + 1
                  base_t::pbump((int)new_outpos);
                  //Update high water pointer, since the buffer has been reallocated
                  mp_high_water = base_t::pbase() + hipos;
                  return c;
//               }
//               catch(...){
//                  return CharTraits::eof();
//               }
//            }
         }
         else  // c is EOF, so we don't have to do anything
            return CharTraits::not_eof(c);
      }
      else     // Overflow always fails if it's read-only.
         return CharTraits::eof();
   }

   virtual pos_type seekoff(off_type off, std::ios_base::seekdir dir,
                              std::ios_base::openmode mode 
                                 = std::ios_base::in | std::ios_base::out)
   {
      bool in = false, out = false;
         
      const std::ios_base::openmode inout = 
         std::ios_base::in | std::ios_base::out;

      if((mode & inout) == inout) {
         if(dir == std::ios_base::beg || dir == std::ios_base::end)
            in = out = true;
      }