Line data    Source code

       1             : //
       2             : // Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
       3             : //
       4             : // Distributed under the Boost Software License, Version 1.0. (See accompanying
       5             : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
       6             : //
       7             : // Official repository: https://github.com/cppalliance/http_proto
       8             : //
       9             : 
      10             : #ifndef BOOST_HTTP_PROTO_DETAIL_WORKSPACE_HPP
      11             : #define BOOST_HTTP_PROTO_DETAIL_WORKSPACE_HPP
      12             : 
      13             : #include <boost/http_proto/detail/except.hpp>
      14             : #include <boost/assert.hpp>
      15             : #include <cstdlib>
      16             : #include <new>
      17             : #include <utility>
      18             : #include <stddef.h> // ::max_align_t
      19             : 
      20             : namespace boost {
      21             : namespace http_proto {
      22             : namespace detail {
      23             : 
      24             : /** A contiguous buffer of storage used by algorithms.
      25             : 
      26             :     Objects of this type retain ownership of a
      27             :     contiguous buffer of storage allocated upon
      28             :     construction. This storage is divided into
      29             :     three regions:
      30             : 
      31             :     @code
      32             :     | front | free | acquired | back |
      33             :     @endcode
      34             : 
      35             :     @li The reserved area, which starts at the
      36             :         beginning of the buffer and can grow
      37             :         upwards towards the end of the buffer.
      38             : 
      39             :     @li The acquired area, which starts at the
      40             :         end of the buffer and can grow downwards
      41             :         towards the beginning of the buffer.
      42             : 
      43             :     @li The unused area, which starts from the
      44             :         end of the reserved area and stretches
      45             :         until the beginning of the acquired area.
      46             : */
      47             : class workspace
      48             : {
      49             :     unsigned char* begin_ = nullptr;
      50             :     unsigned char* front_ = nullptr;
      51             :     unsigned char* head_ = nullptr;
      52             :     unsigned char* back_ = nullptr;
      53             :     unsigned char* end_ = nullptr;
      54             : 
      55             :     template<class>
      56             :     struct any_impl;
      57             :     struct any;
      58             :     struct undo;
      59             : 
      60             : public:
      61             :     /** Return the number of aligned bytes required for T
      62             :     */
      63             :     template<class T>
      64             :     static
      65             :     constexpr
      66             :     std::size_t
      67             :     space_needed();
      68             : 
      69             :     /** Destructor.
      70             :     */
      71             :     ~workspace();
      72             : 
      73             :     /** Constructor.
      74             : 
      75             :         @param n The number of bytes of storage
      76             :             to allocate for the internal buffer.
      77             :     */
      78             :     explicit
      79             :     workspace(
      80             :         std::size_t n);
      81             : 
      82             :     /** Constructor.
      83             :     */
      84        1044 :     workspace() = default;
      85             : 
      86             :     /** Constructor.
      87             :     */
      88             :     workspace(workspace&&) noexcept;
      89             : 
      90             :     /** Allocate internal storage.
      91             : 
      92             :         @throws std::logic_error this->size() > 0
      93             : 
      94             :         @throws std::invalid_argument n == 0
      95             :     */
      96             :     void
      97             :     allocate(
      98             :         std::size_t n);
      99             : 
     100             :     /** Return a pointer to the unused area.
     101             :     */
     102             :     unsigned char*
     103       15819 :     data() noexcept
     104             :     {
     105       15819 :         return front_;
     106             :     }
     107             : 
     108             :     /** Return the size of the unused area.
     109             :     */
     110             :     std::size_t
     111        3567 :     size() const noexcept
     112             :     {
     113        3567 :         return head_ - front_;
     114             :     }
     115             : 
     116             :     /** Clear the contents while preserving capacity.
     117             :     */
     118             :     BOOST_HTTP_PROTO_DECL
     119             :     void
     120             :     clear() noexcept;
     121             : 
     122             :     /** Convert unused storage to reserved storage.
     123             : 
     124             :         @throws std::invalid_argument n >= this->size()
     125             :     */
     126             :     BOOST_HTTP_PROTO_DECL
     127             :     unsigned char*
     128             :     reserve_front(
     129             :         std::size_t n);
     130             : 
     131             :     template<class T, class... Args>
     132             :     typename std::decay<T>::type&
     133             :     emplace(Args&&... args);
     134             : 
     135             :     template<class T>
     136             :     T*
     137             :     push_array(
     138             :         std::size_t n,
     139             :         T const& t);
     140             : 
     141             :     BOOST_HTTP_PROTO_DECL
     142             :     unsigned char*
     143             :     reserve_back(
     144             :         std::size_t n);
     145             : 
     146             : private:
     147             :     BOOST_HTTP_PROTO_DECL
     148             :     unsigned char*
     149             :     bump_down(
     150             :         std::size_t size,
     151             :         std::size_t align);
     152             : };
     153             : 
     154             : } // detail
     155             : } // http_proto
     156             : } // boost
     157             : 
     158             : #include <boost/http_proto/detail/impl/workspace.hpp>
     159             : 
     160             : #endif