//
// impl/read_at.hpp
// ~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// 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)
//

#ifndef BOOST_ASIO_IMPL_READ_AT_HPP
#define BOOST_ASIO_IMPL_READ_AT_HPP

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

#include <algorithm>
#include <boost/asio/buffer.hpp>
#include <boost/asio/completion_condition.hpp>
#include <boost/asio/detail/base_from_completion_cond.hpp>
#include <boost/asio/detail/bind_handler.hpp>
#include <boost/asio/detail/consuming_buffers.hpp>
#include <boost/asio/detail/handler_alloc_helpers.hpp>
#include <boost/asio/detail/handler_invoke_helpers.hpp>
#include <boost/asio/detail/throw_error.hpp>
#include <boost/asio/error.hpp>

#include <boost/asio/detail/push_options.hpp>

namespace boost {
namespace asio {

template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
    typename CompletionCondition>
std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, const MutableBufferSequence& buffers,
    CompletionCondition completion_condition, boost::system::error_code& ec)
{
  ec = boost::system::error_code();
  boost::asio::detail::consuming_buffers<
    mutable_buffer, MutableBufferSequence> tmp(buffers);
  std::size_t total_transferred = 0;
  tmp.prepare(detail::adapt_completion_condition_result(
        completion_condition(ec, total_transferred)));
  while (tmp.begin() != tmp.end())
  {
    std::size_t bytes_transferred = d.read_some_at(
        offset + total_transferred, tmp, ec);
    tmp.consume(bytes_transferred);
    total_transferred += bytes_transferred;
    tmp.prepare(detail::adapt_completion_condition_result(
          completion_condition(ec, total_transferred)));
  }
  return total_transferred;
}

template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence>
inline std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, const MutableBufferSequence& buffers)
{
  boost::system::error_code ec;
  std::size_t bytes_transferred = read_at(
      d, offset, buffers, transfer_all(), ec);
  boost::asio::detail::throw_error(ec);
  return bytes_transferred;
}

template <typename SyncRandomAccessReadDevice, typename MutableBufferSequence,
    typename CompletionCondition>
inline std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, const MutableBufferSequence& buffers,
    CompletionCondition completion_condition)
{
  boost::system::error_code ec;
  std::size_t bytes_transferred = read_at(
      d, offset, buffers, completion_condition, ec);
  boost::asio::detail::throw_error(ec);
  return bytes_transferred;
}

#if !defined(BOOST_NO_IOSTREAM)

template <typename SyncRandomAccessReadDevice, typename Allocator,
    typename CompletionCondition>
std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, boost::system::error_code& ec)
{
  ec = boost::system::error_code();
  std::size_t total_transferred = 0;
  std::size_t max_size = detail::adapt_completion_condition_result(
        completion_condition(ec, total_transferred));
  std::size_t bytes_available = read_size_helper(b, max_size);
  while (bytes_available > 0)
  {
    std::size_t bytes_transferred = d.read_some_at(
        offset + total_transferred, b.prepare(bytes_available), ec);
    b.commit(bytes_transferred);
    total_transferred += bytes_transferred;
    max_size = detail::adapt_completion_condition_result(
          completion_condition(ec, total_transferred));
    bytes_available = read_size_helper(b, max_size);
  }
  return total_transferred;
}

template <typename SyncRandomAccessReadDevice, typename Allocator>
inline std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, boost::asio::basic_streambuf<Allocator>& b)
{
  boost::system::error_code ec;
  std::size_t bytes_transferred = read_at(
      d, offset, b, transfer_all(), ec);
  boost::asio::detail::throw_error(ec);
  return bytes_transferred;
}

template <typename SyncRandomAccessReadDevice, typename Allocator,
    typename CompletionCondition>
inline std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition)
{
  boost::system::error_code ec;
  std::size_t bytes_transferred = read_at(
      d, offset, b, completion_condition, ec);
  boost::asio::detail::throw_error(ec);
  return bytes_transferred;
}

#endif // !defined(BOOST_NO_IOSTREAM)

namespace detail
{
  template <typename AsyncRandomAccessReadDevice,
      typename MutableBufferSequence, typename CompletionCondition,
      typename ReadHandler>
  class read_at_op
    : detail::base_from_completion_cond<CompletionCondition>
  {
  public:
    read_at_op(AsyncRandomAccessReadDevice& device,
        boost::uint64_t offset, const MutableBufferSequence& buffers,
        CompletionCondition completion_condition, ReadHandler handler)
      : detail::base_from_completion_cond<
          CompletionCondition>(completion_condition),
        device_(device),
        offset_(offset),
        buffers_(buffers),
        total_transferred_(0),
        handler_(handler)
    {
    }

    void operator()(const boost::system::error_code& ec,
        std::size_t bytes_transferred, int start = 0)
    {
      switch (start)
      {
        case 1:
        buffers_.prepare(this->check_for_completion(ec, total_transferred_));
        for (;;)
        {
          device_.async_read_some_at(
              offset_ + total_transferred_, buffers_, *this);
          return; default:
          total_transferred_ += bytes_transferred;
          buffers_.consume(bytes_transferred);
          buffers_.prepare(this->check_for_completion(ec, total_transferred_));
          if ((!ec && bytes_transferred == 0)
              || buffers_.begin() == buffers_.end())
            break;
        }

        handler_(ec, static_cast<const std::size_t&>(total_transferred_));
      }
    }

  //private:
    AsyncRandomAccessReadDevice& device_;
    boost::uint64_t offset_;
    boost::asio::detail::consuming_buffers<
      mutable_buffer, MutableBufferSequence> buffers_;
    std::size_t total_transferred_;
    ReadHandler handler_;
  };

  template <typename AsyncRandomAccessReadDevice,
      typename CompletionCondition, typename ReadHandler>
  class read_at_op<AsyncRandomAccessReadDevice,
      boost::asio::mutable_buffers_1, CompletionCondition, ReadHandler>
    : detail::base_from_completion_cond<CompletionCondition>
  {
  public:
    read_at_op(AsyncRandomAccessReadDevice& device,
        boost::uint64_t offset, const boost::asio::mutable_buffers_1& buffers,
        CompletionCondition completion_condition, ReadHandler handler)
      : detail::base_from_completion_cond<
          CompletionCondition>(completion_condition),
        device_(device),
        offset_(offset),
        buffer_(buffers),
        total_transferred_(0),
        handler_(handler)
    {
    }

    void operator()(const boost::system::error_code& ec,
        std::size_t bytes_transferred, int start = 0)
    {
      std::size_t n = 0;
      switch (start)
      {
        case 1:
        n = this->check_for_completion(ec, total_transferred_);
        for (;;)
        {
          device_.async_read_some_at(offset_ + total_transferred_,
              boost::asio::buffer(buffer_ + total_transferred_, n), *this);
          return; default:
          total_transferred_ += bytes_transferred;
          if ((!ec && bytes_transferred == 0)
              || (n = this->check_for_completion(ec, total_transferred_)) == 0
              || total_transferred_ == boost::asio::buffer_size(buffer_))
            break;
        }

        handler_(ec, static_cast<const std::size_t&>(total_transferred_));
      }
    }

  //private:
    AsyncRandomAccessReadDevice& device_;
    boost::uint64_t offset_;
    boost::asio::mutable_buffer buffer_;
    std::size_t total_transferred_;
    ReadHandler handler_;
  };

  template <typename AsyncRandomAccessReadDevice,
      typename MutableBufferSequence, typename CompletionCondition,
      typename ReadHandler>
  inline void* asio_handler_allocate(std::size_t size,
      read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
        CompletionCondition, ReadHandler>* this_handler)
  {
    return boost_asio_handler_alloc_helpers::allocate(
        size, this_handler->handler_);
  }

  template <typename AsyncRandomAccessReadDevice,
      typename MutableBufferSequence, typename CompletionCondition,
      typename ReadHandler>
  inline void asio_handler_deallocate(void* pointer, std::size_t size,
      read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
        CompletionCondition, ReadHandler>* this_handler)
  {
    boost_asio_handler_alloc_helpers::deallocate(
        pointer, size, this_handler->handler_);
  }

  template <typename Function, typename AsyncRandomAccessReadDevice,
      typename MutableBufferSequence, typename CompletionCondition,
      typename ReadHandler>
  inline void asio_handler_invoke(const Function& function,
      read_at_op<AsyncRandomAccessReadDevice, MutableBufferSequence,
        CompletionCondition, ReadHandler>* this_handler)
  {
    boost_asio_handler_invoke_helpers::invoke(
        function, this_handler->handler_);
  }
} // namespace detail

template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence,
    typename CompletionCondition, typename ReadHandler>
inline void async_read_at(AsyncRandomAccessReadDevice& d,
    boost::uint64_t offset, const MutableBufferSequence& buffers,
    CompletionCondition completion_condition, ReadHandler handler)
{
  detail::read_at_op<AsyncRandomAccessReadDevice,
    MutableBufferSequence, CompletionCondition, ReadHandler>(
      d, offset, buffers, completion_condition, handler)(
        boost::system::error_code(), 0, 1);
}

template <typename AsyncRandomAccessReadDevice, typename MutableBufferSequence,
    typename ReadHandler>
inline void async_read_at(AsyncRandomAccessReadDevice& d,
    boost::uint64_t offset, const MutableBufferSequence& buffers,
    ReadHandler handler)
{
  async_read_at(d, offset, buffers, transfer_all(), handler);
}

#if !defined(BOOST_NO_IOSTREAM)

namespace detail
{
  template <typename AsyncRandomAccessReadDevice, typename Allocator,
      typename CompletionCondition, typename ReadHandler>
  class read_at_streambuf_op
    : detail::base_from_completion_cond<CompletionCondition>
  {
  public:
    read_at_streambuf_op(AsyncRandomAccessReadDevice& device,
        boost::uint64_t offset, basic_streambuf<Allocator>& streambuf,
        CompletionCondition completion_condition, ReadHandler handler)
      : detail::base_from_completion_cond<
          CompletionCondition>(completion_condition),
        device_(device),
        offset_(offset),
        streambuf_(streambuf),
        total_transferred_(0),
        handler_(handler)
    {
    }

    void operator()(const boost::system::error_code& ec,
        std::size_t bytes_transferred, int start = 0)
    {
      std::size_t max_size, bytes_available;
      switch (start)
      {
        case 1:
        max_size = this->check_for_completion(ec, total_transferred_);
        bytes_available = read_size_helper(streambuf_, max_size);
        for (;;)
        {
          device_.async_read_some_at(offset_ + total_transferred_,
              streambuf_.prepare(bytes_available), *this);
          return; default:
          total_transferred_ += bytes_transferred;
          streambuf_.commit(bytes_transferred);
          max_size = this->check_for_completion(ec, total_transferred_);
          bytes_available = read_size_helper(streambuf_, max_size);
          if ((!ec && bytes_transferred == 0) || bytes_available == 0)
            break;
        }

        handler_(ec, static_cast<const std::size_t&>(total_transferred_));
      }
    }

  //private:
    AsyncRandomAccessReadDevice& device_;
    boost::uint64_t offset_;
    boost::asio::basic_streambuf<Allocator>& streambuf_;
    std::size_t total_transferred_;
    ReadHandler handler_;
  };

  template <typename AsyncRandomAccessReadDevice, typename Allocator,
      typename CompletionCondition, typename ReadHandler>
  inline void* asio_handler_allocate(std::size_t size,
      read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
        CompletionCondition, ReadHandler>* this_handler)
  {
    return boost_asio_handler_alloc_helpers::allocate(
        size, this_handler->handler_);
  }

  template <typename AsyncRandomAccessReadDevice, typename Allocator,
      typename CompletionCondition, typename ReadHandler>
  inline void asio_handler_deallocate(void* pointer, std::size_t size,
      read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
        CompletionCondition, ReadHandler>* this_handler)
  {
    boost_asio_handler_alloc_helpers::deallocate(
        pointer, size, this_handler->handler_);
  }

  template <typename Function, typename AsyncRandomAccessReadDevice,
      typename Allocator, typename CompletionCondition, typename ReadHandler>
  inline void asio_handler_invoke(const Function& function,
      read_at_streambuf_op<AsyncRandomAccessReadDevice, Allocator,
        CompletionCondition, ReadHandler>* this_handler)
  {
    boost_asio_handler_invoke_helpers::invoke(
        function, this_handler->handler_);
  }
} // namespace detail

template <typename AsyncRandomAccessReadDevice, typename Allocator,
    typename CompletionCondition, typename ReadHandler>
inline void async_read_at(AsyncRandomAccessReadDevice& d,
    boost::uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, ReadHandler handler)
{
  detail::read_at_streambuf_op<AsyncRandomAccessReadDevice,
    Allocator, CompletionCondition, ReadHandler>(
      d, offset, b, completion_condition, handler)(
        boost::system::error_code(), 0, 1);
}

template <typename AsyncRandomAccessReadDevice, typename Allocator,
    typename ReadHandler>
inline void async_read_at(AsyncRandomAccessReadDevice& d,
    boost::uint64_t offset, boost::asio::basic_streambuf<Allocator>& b,
    ReadHandler handler)
{
  async_read_at(d, offset, b, transfer_all(), handler);
}

#endif // !defined(BOOST_NO_IOSTREAM)

} // namespace asio
} // namespace boost

#include <boost/asio/detail/pop_options.hpp>

#endif // BOOST_ASIO_IMPL_READ_AT_HPP