Chris@16: //
Chris@16: // detail/consuming_buffers.hpp
Chris@16: // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chris@16: //
Chris@101: // Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff dot com)
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: 
Chris@16: #ifndef BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP
Chris@16: #define BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP
Chris@16: 
Chris@16: #if defined(_MSC_VER) && (_MSC_VER >= 1200)
Chris@16: # pragma once
Chris@16: #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
Chris@16: 
Chris@16: #include <boost/asio/detail/config.hpp>
Chris@16: #include <cstddef>
Chris@16: #include <iterator>
Chris@16: #include <boost/asio/buffer.hpp>
Chris@16: #include <boost/asio/detail/limits.hpp>
Chris@16: 
Chris@16: #include <boost/asio/detail/push_options.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace asio {
Chris@16: namespace detail {
Chris@16: 
Chris@16: // A proxy iterator for a sub-range in a list of buffers.
Chris@16: template <typename Buffer, typename Buffer_Iterator>
Chris@16: class consuming_buffers_iterator
Chris@16: {
Chris@16: public:
Chris@16:   /// The type used for the distance between two iterators.
Chris@16:   typedef std::ptrdiff_t difference_type;
Chris@16: 
Chris@16:   /// The type of the value pointed to by the iterator.
Chris@16:   typedef Buffer value_type;
Chris@16: 
Chris@16:   /// The type of the result of applying operator->() to the iterator.
Chris@16:   typedef const Buffer* pointer;
Chris@16: 
Chris@16:   /// The type of the result of applying operator*() to the iterator.
Chris@16:   typedef const Buffer& reference;
Chris@16: 
Chris@16:   /// The iterator category.
Chris@16:   typedef std::forward_iterator_tag iterator_category;
Chris@16: 
Chris@16:   // Default constructor creates an end iterator.
Chris@16:   consuming_buffers_iterator()
Chris@16:     : at_end_(true)
Chris@16:   {
Chris@16:   }
Chris@16: 
Chris@16:   // Construct with a buffer for the first entry and an iterator
Chris@16:   // range for the remaining entries.
Chris@16:   consuming_buffers_iterator(bool at_end, const Buffer& first,
Chris@16:       Buffer_Iterator begin_remainder, Buffer_Iterator end_remainder,
Chris@16:       std::size_t max_size)
Chris@16:     : at_end_(max_size > 0 ? at_end : true),
Chris@16:       first_(buffer(first, max_size)),
Chris@16:       begin_remainder_(begin_remainder),
Chris@16:       end_remainder_(end_remainder),
Chris@16:       offset_(0),
Chris@16:       max_size_(max_size)
Chris@16:   {
Chris@16:   }
Chris@16: 
Chris@16:   // Dereference an iterator.
Chris@16:   const Buffer& operator*() const
Chris@16:   {
Chris@16:     return dereference();
Chris@16:   }
Chris@16: 
Chris@16:   // Dereference an iterator.
Chris@16:   const Buffer* operator->() const
Chris@16:   {
Chris@16:     return &dereference();
Chris@16:   }
Chris@16: 
Chris@16:   // Increment operator (prefix).
Chris@16:   consuming_buffers_iterator& operator++()
Chris@16:   {
Chris@16:     increment();
Chris@16:     return *this;
Chris@16:   }
Chris@16: 
Chris@16:   // Increment operator (postfix).
Chris@16:   consuming_buffers_iterator operator++(int)
Chris@16:   {
Chris@16:     consuming_buffers_iterator tmp(*this);
Chris@16:     ++*this;
Chris@16:     return tmp;
Chris@16:   }
Chris@16: 
Chris@16:   // Test two iterators for equality.
Chris@16:   friend bool operator==(const consuming_buffers_iterator& a,
Chris@16:       const consuming_buffers_iterator& b)
Chris@16:   {
Chris@16:     return a.equal(b);
Chris@16:   }
Chris@16: 
Chris@16:   // Test two iterators for inequality.
Chris@16:   friend bool operator!=(const consuming_buffers_iterator& a,
Chris@16:       const consuming_buffers_iterator& b)
Chris@16:   {
Chris@16:     return !a.equal(b);
Chris@16:   }
Chris@16: 
Chris@16: private:
Chris@16:   void increment()
Chris@16:   {
Chris@16:     if (!at_end_)
Chris@16:     {
Chris@16:       if (begin_remainder_ == end_remainder_
Chris@16:           || offset_ + buffer_size(first_) >= max_size_)
Chris@16:       {
Chris@16:         at_end_ = true;
Chris@16:       }
Chris@16:       else
Chris@16:       {
Chris@16:         offset_ += buffer_size(first_);
Chris@16:         first_ = buffer(*begin_remainder_++, max_size_ - offset_);
Chris@16:       }
Chris@16:     }
Chris@16:   }
Chris@16: 
Chris@16:   bool equal(const consuming_buffers_iterator& other) const
Chris@16:   {
Chris@16:     if (at_end_ && other.at_end_)
Chris@16:       return true;
Chris@16:     return !at_end_ && !other.at_end_
Chris@16:       && buffer_cast<const void*>(first_)
Chris@16:         == buffer_cast<const void*>(other.first_)
Chris@16:       && buffer_size(first_) == buffer_size(other.first_)
Chris@16:       && begin_remainder_ == other.begin_remainder_
Chris@16:       && end_remainder_ == other.end_remainder_;
Chris@16:   }
Chris@16: 
Chris@16:   const Buffer& dereference() const
Chris@16:   {
Chris@16:     return first_;
Chris@16:   }
Chris@16: 
Chris@16:   bool at_end_;
Chris@16:   Buffer first_;
Chris@16:   Buffer_Iterator begin_remainder_;
Chris@16:   Buffer_Iterator end_remainder_;
Chris@16:   std::size_t offset_;
Chris@16:   std::size_t max_size_;
Chris@16: };
Chris@16: 
Chris@16: // A proxy for a sub-range in a list of buffers.
Chris@16: template <typename Buffer, typename Buffers>
Chris@16: class consuming_buffers
Chris@16: {
Chris@16: public:
Chris@16:   // The type for each element in the list of buffers.
Chris@16:   typedef Buffer value_type;
Chris@16: 
Chris@16:   // A forward-only iterator type that may be used to read elements.
Chris@16:   typedef consuming_buffers_iterator<Buffer, typename Buffers::const_iterator>
Chris@16:     const_iterator;
Chris@16: 
Chris@16:   // Construct to represent the entire list of buffers.
Chris@16:   consuming_buffers(const Buffers& buffers)
Chris@16:     : buffers_(buffers),
Chris@16:       at_end_(buffers_.begin() == buffers_.end()),
Chris@16:       begin_remainder_(buffers_.begin()),
Chris@16:       max_size_((std::numeric_limits<std::size_t>::max)())
Chris@16:   {
Chris@16:     if (!at_end_)
Chris@16:     {
Chris@16:       first_ = *buffers_.begin();
Chris@16:       ++begin_remainder_;
Chris@16:     }
Chris@16:   }
Chris@16: 
Chris@16:   // Copy constructor.
Chris@16:   consuming_buffers(const consuming_buffers& other)
Chris@16:     : buffers_(other.buffers_),
Chris@16:       at_end_(other.at_end_),
Chris@16:       first_(other.first_),
Chris@16:       begin_remainder_(buffers_.begin()),
Chris@16:       max_size_(other.max_size_)
Chris@16:   {
Chris@16:     typename Buffers::const_iterator first = other.buffers_.begin();
Chris@16:     typename Buffers::const_iterator second = other.begin_remainder_;
Chris@16:     std::advance(begin_remainder_, std::distance(first, second));
Chris@16:   }
Chris@16: 
Chris@16:   // Assignment operator.
Chris@16:   consuming_buffers& operator=(const consuming_buffers& other)
Chris@16:   {
Chris@16:     buffers_ = other.buffers_;
Chris@16:     at_end_ = other.at_end_;
Chris@16:     first_ = other.first_;
Chris@16:     begin_remainder_ = buffers_.begin();
Chris@16:     typename Buffers::const_iterator first = other.buffers_.begin();
Chris@16:     typename Buffers::const_iterator second = other.begin_remainder_;
Chris@16:     std::advance(begin_remainder_, std::distance(first, second));
Chris@16:     max_size_ = other.max_size_;
Chris@16:     return *this;
Chris@16:   }
Chris@16: 
Chris@16:   // Get a forward-only iterator to the first element.
Chris@16:   const_iterator begin() const
Chris@16:   {
Chris@16:     return const_iterator(at_end_, first_,
Chris@16:         begin_remainder_, buffers_.end(), max_size_);
Chris@16:   }
Chris@16: 
Chris@16:   // Get a forward-only iterator for one past the last element.
Chris@16:   const_iterator end() const
Chris@16:   {
Chris@16:     return const_iterator();
Chris@16:   }
Chris@16: 
Chris@16:   // Set the maximum size for a single transfer.
Chris@16:   void prepare(std::size_t max_size)
Chris@16:   {
Chris@16:     max_size_ = max_size;
Chris@16:   }
Chris@16: 
Chris@16:   // Consume the specified number of bytes from the buffers.
Chris@16:   void consume(std::size_t size)
Chris@16:   {
Chris@16:     // Remove buffers from the start until the specified size is reached.
Chris@16:     while (size > 0 && !at_end_)
Chris@16:     {
Chris@16:       if (buffer_size(first_) <= size)
Chris@16:       {
Chris@16:         size -= buffer_size(first_);
Chris@16:         if (begin_remainder_ == buffers_.end())
Chris@16:           at_end_ = true;
Chris@16:         else
Chris@16:           first_ = *begin_remainder_++;
Chris@16:       }
Chris@16:       else
Chris@16:       {
Chris@16:         first_ = first_ + size;
Chris@16:         size = 0;
Chris@16:       }
Chris@16:     }
Chris@16: 
Chris@16:     // Remove any more empty buffers at the start.
Chris@16:     while (!at_end_ && buffer_size(first_) == 0)
Chris@16:     {
Chris@16:       if (begin_remainder_ == buffers_.end())
Chris@16:         at_end_ = true;
Chris@16:       else
Chris@16:         first_ = *begin_remainder_++;
Chris@16:     }
Chris@16:   }
Chris@16: 
Chris@16: private:
Chris@16:   Buffers buffers_;
Chris@16:   bool at_end_;
Chris@16:   Buffer first_;
Chris@16:   typename Buffers::const_iterator begin_remainder_;
Chris@16:   std::size_t max_size_;
Chris@16: };
Chris@16: 
Chris@16: // Specialisation for null_buffers to ensure that the null_buffers type is
Chris@16: // always passed through to the underlying read or write operation.
Chris@16: template <typename Buffer>
Chris@16: class consuming_buffers<Buffer, boost::asio::null_buffers>
Chris@16:   : public boost::asio::null_buffers
Chris@16: {
Chris@16: public:
Chris@16:   consuming_buffers(const boost::asio::null_buffers&)
Chris@16:   {
Chris@16:     // No-op.
Chris@16:   }
Chris@16: 
Chris@16:   void prepare(std::size_t)
Chris@16:   {
Chris@16:     // No-op.
Chris@16:   }
Chris@16: 
Chris@16:   void consume(std::size_t)
Chris@16:   {
Chris@16:     // No-op.
Chris@16:   }
Chris@16: };
Chris@16: 
Chris@16: } // namespace detail
Chris@16: } // namespace asio
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/asio/detail/pop_options.hpp>
Chris@16: 
Chris@16: #endif // BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP