src/monotonic_buffer_resource.cpp

//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2015-2015. 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/container for documentation.
//
//////////////////////////////////////////////////////////////////////////////

#define BOOST_CONTAINER_SOURCE
#include <boost/container/detail/config_begin.hpp>
#include <boost/container/detail/workaround.hpp>

#include <boost/container/pmr/monotonic_buffer_resource.hpp>
#include <boost/container/pmr/global_resource.hpp>

#include <boost/container/detail/min_max.hpp>
#include <boost/intrusive/detail/math.hpp>
#include <boost/container/throw_exception.hpp>


#include <cstddef>

namespace {

#ifdef BOOST_HAS_INTPTR_T
typedef boost::uintptr_t   uintptr_type;
#else
typedef std::size_t        uintptr_type;
#endif

static const std::size_t minimum_buffer_size = 2*sizeof(void*);

}  //namespace {

namespace boost {
namespace container {
namespace pmr {

void monotonic_buffer_resource::increase_next_buffer()
{
   m_next_buffer_size = (std::size_t(-1)/2 < m_next_buffer_size) ? std::size_t(-1) : m_next_buffer_size*2;
}

void monotonic_buffer_resource::increase_next_buffer_at_least_to(std::size_t minimum_size)
{
   if(m_next_buffer_size < minimum_size){
      if(bi::detail::is_pow2(minimum_size)){
         m_next_buffer_size = minimum_size;
      }
      else if(std::size_t(-1)/2 < minimum_size){
         m_next_buffer_size = minimum_size;
      }
      else{
         m_next_buffer_size = bi::detail::ceil_pow2(minimum_size);
      }
   }
}

monotonic_buffer_resource::monotonic_buffer_resource(memory_resource* upstream) BOOST_NOEXCEPT
   : m_memory_blocks(upstream ? *upstream : *get_default_resource())
   , m_current_buffer(0)
   , m_current_buffer_size(0u)
   , m_next_buffer_size(initial_next_buffer_size)
   , m_initial_buffer(0)
   , m_initial_buffer_size(0u)
{}

monotonic_buffer_resource::monotonic_buffer_resource(std::size_t initial_size, memory_resource* upstream) BOOST_NOEXCEPT
   : m_memory_blocks(upstream ? *upstream : *get_default_resource())
   , m_current_buffer(0)
   , m_current_buffer_size(0u)
   , m_next_buffer_size(minimum_buffer_size)
   , m_initial_buffer(0)
   , m_initial_buffer_size(0u)
{                                         //In case initial_size is zero
   this->increase_next_buffer_at_least_to(initial_size + !initial_size);
}

monotonic_buffer_resource::monotonic_buffer_resource(void* buffer, std::size_t buffer_size, memory_resource* upstream) BOOST_NOEXCEPT
   : m_memory_blocks(upstream ? *upstream : *get_default_resource())
   , m_current_buffer(buffer)
   , m_current_buffer_size(buffer_size)
   , m_next_buffer_size
      (bi::detail::previous_or_equal_pow2
         (boost::container::dtl::max_value(buffer_size, std::size_t(initial_next_buffer_size))))
   , m_initial_buffer(buffer)
   , m_initial_buffer_size(buffer_size)
{  this->increase_next_buffer(); }

monotonic_buffer_resource::~monotonic_buffer_resource()
{  this->release();  }

void monotonic_buffer_resource::release() BOOST_NOEXCEPT
{
   m_memory_blocks.release();
   m_current_buffer = m_initial_buffer;
   m_current_buffer_size = m_initial_buffer_size;
   m_next_buffer_size = initial_next_buffer_size;
}

memory_resource* monotonic_buffer_resource::upstream_resource() const BOOST_NOEXCEPT
{  return &m_memory_blocks.upstream_resource();   }

std::size_t monotonic_buffer_resource::remaining_storage(std::size_t alignment, std::size_t &wasted_due_to_alignment) const BOOST_NOEXCEPT
{
   const uintptr_type up_alignment_minus1 = alignment - 1u;
   const uintptr_type up_alignment_mask = ~up_alignment_minus1;
   const uintptr_type up_addr = uintptr_type(m_current_buffer);
   const uintptr_type up_aligned_addr = (up_addr + up_alignment_minus1) & up_alignment_mask;
   wasted_due_to_alignment = std::size_t(up_aligned_addr - up_addr);
   return m_current_buffer_size <= wasted_due_to_alignment ? 0u : m_current_buffer_size - wasted_due_to_alignment;
}

std::size_t monotonic_buffer_resource::remaining_storage(std::size_t alignment) const BOOST_NOEXCEPT
{
   std::size_t ignore_this;
   return this->remaining_storage(alignment, ignore_this);
}

const void *monotonic_buffer_resource::current_buffer() const BOOST_NOEXCEPT
{  return m_current_buffer;  }

std::size_t monotonic_buffer_resource::next_buffer_size() const BOOST_NOEXCEPT
{  return m_next_buffer_size;  }

void *monotonic_buffer_resource::allocate_from_current(std::size_t aligner, std::size_t bytes)
{
   char * p = (char*)m_current_buffer + aligner;
   m_current_buffer = p + bytes;
   m_current_buffer_size -= aligner + bytes;
   return p;
}

void* monotonic_buffer_resource::do_allocate(std::size_t bytes, std::size_t alignment)
{
   if(alignment > memory_resource::max_align)
      throw_bad_alloc();

   //See if there is room in current buffer
   std::size_t aligner = 0u;
   if(this->remaining_storage(alignment, aligner) < bytes){
      //Update next_buffer_size to at least bytes
      this->increase_next_buffer_at_least_to(bytes);
      //Now allocate and update internal data
      m_current_buffer = (char*)m_memory_blocks.allocate(m_next_buffer_size);
      m_current_buffer_size = m_next_buffer_size;
      this->increase_next_buffer();
   }
   //Enough internal storage, extract from it
   return this->allocate_from_current(aligner, bytes);
}

void monotonic_buffer_resource::do_deallocate(void* p, std::size_t bytes, std::size_t alignment) BOOST_NOEXCEPT
{  (void)p; (void)bytes;  (void)alignment;  }

bool monotonic_buffer_resource::do_is_equal(const memory_resource& other) const BOOST_NOEXCEPT
{  return this == dynamic_cast<const monotonic_buffer_resource*>(&other);  }

}  //namespace pmr {
}  //namespace container {
}  //namespace boost {

#include <boost/container/detail/config_end.hpp>