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 //
 // basic_random_access_file.hpp
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2023 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_BASIC_RANDOM_ACCESS_FILE_HPP
 #define BOOST_ASIO_BASIC_RANDOM_ACCESS_FILE_HPP
 
 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
 # pragma once
 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
 
 #include <boost/asio/detail/config.hpp>
 
 #if defined(BOOST_ASIO_HAS_FILE) \
   || defined(GENERATING_DOCUMENTATION)
 
 #include <cstddef>
 #include <boost/asio/async_result.hpp>
 #include <boost/asio/basic_file.hpp>
 #include <boost/asio/detail/handler_type_requirements.hpp>
 #include <boost/asio/detail/non_const_lvalue.hpp>
 #include <boost/asio/detail/throw_error.hpp>
 #include <boost/asio/error.hpp>
 
 #include <boost/asio/detail/push_options.hpp>
 
 namespace boost {
 namespace asio {
 
 #if !defined(BOOST_ASIO_BASIC_RANDOM_ACCESS_FILE_FWD_DECL)
 #define BOOST_ASIO_BASIC_RANDOM_ACCESS_FILE_FWD_DECL
 
 // Forward declaration with defaulted arguments.
 template <typename Executor = any_io_executor>
 class basic_random_access_file;
 
 #endif // !defined(BOOST_ASIO_BASIC_RANDOM_ACCESS_FILE_FWD_DECL)
 
 /// Provides random-access file functionality.
 /**
  * The basic_random_access_file class template provides asynchronous and
  * blocking random-access file functionality.
  *
  * @par Thread Safety
  * @e Distinct @e objects: Safe.@n
  * @e Shared @e objects: Unsafe.
  *
  * Synchronous @c read_some_at and @c write_some_at operations are thread safe
  * with respect to each other, if the underlying operating system calls are
  * also thread safe. This means that it is permitted to perform concurrent
  * calls to these synchronous operations on a single file object. Other
  * synchronous operations, such as @c open or @c close, are not thread safe.
  */
 template <typename Executor>
 class basic_random_access_file
   : public basic_file<Executor>
 {
 private:
   class initiate_async_write_some_at;
   class initiate_async_read_some_at;
 
 public:
   /// The type of the executor associated with the object.
   typedef Executor executor_type;
 
   /// Rebinds the file type to another executor.
   template <typename Executor1>
   struct rebind_executor
   {
     /// The file type when rebound to the specified executor.
     typedef basic_random_access_file<Executor1> other;
   };
 
   /// The native representation of a file.
 #if defined(GENERATING_DOCUMENTATION)
   typedef implementation_defined native_handle_type;
 #else
   typedef typename basic_file<Executor>::native_handle_type native_handle_type;
 #endif
 
   /// Construct a basic_random_access_file without opening it.
   /**
    * This constructor initialises a file without opening it. The file needs to
    * be opened before data can be read from or or written to it.
    *
    * @param ex The I/O executor that the file will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the file.
    */
   explicit basic_random_access_file(const executor_type& ex)
     : basic_file<Executor>(ex)
   {
   }
 
   /// Construct a basic_random_access_file without opening it.
   /**
    * This constructor initialises a file without opening it. The file needs to
    * be opened before data can be read from or or written to it.
    *
    * @param context An execution context which provides the I/O executor that
    * the file will use, by default, to dispatch handlers for any asynchronous
    * operations performed on the file.
    */
   template <typename ExecutionContext>
   explicit basic_random_access_file(ExecutionContext& context,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : basic_file<Executor>(context)
   {
   }
 
   /// Construct and open a basic_random_access_file.
   /**
    * This constructor initialises and opens a file.
    *
    * @param ex The I/O executor that the file will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the file.
    *
    * @param path The path name identifying the file to be opened.
    *
    * @param open_flags A set of flags that determine how the file should be
    * opened.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   basic_random_access_file(const executor_type& ex,
       const char* path, file_base::flags open_flags)
     : basic_file<Executor>(ex, path, open_flags)
   {
   }
 
   /// Construct and open a basic_random_access_file.
   /**
    * This constructor initialises and opens a file.
    *
    * @param context An execution context which provides the I/O executor that
    * the file will use, by default, to dispatch handlers for any asynchronous
    * operations performed on the file.
    *
    * @param path The path name identifying the file to be opened.
    *
    * @param open_flags A set of flags that determine how the file should be
    * opened.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   template <typename ExecutionContext>
   basic_random_access_file(ExecutionContext& context,
       const char* path, file_base::flags open_flags,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : basic_file<Executor>(context, path, open_flags)
   {
   }
 
   /// Construct and open a basic_random_access_file.
   /**
    * This constructor initialises and opens a file.
    *
    * @param ex The I/O executor that the file will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the file.
    *
    * @param path The path name identifying the file to be opened.
    *
    * @param open_flags A set of flags that determine how the file should be
    * opened.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   basic_random_access_file(const executor_type& ex,
       const std::string& path, file_base::flags open_flags)
     : basic_file<Executor>(ex, path, open_flags)
   {
   }
 
   /// Construct and open a basic_random_access_file.
   /**
    * This constructor initialises and opens a file.
    *
    * @param context An execution context which provides the I/O executor that
    * the file will use, by default, to dispatch handlers for any asynchronous
    * operations performed on the file.
    *
    * @param path The path name identifying the file to be opened.
    *
    * @param open_flags A set of flags that determine how the file should be
    * opened.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   template <typename ExecutionContext>
   basic_random_access_file(ExecutionContext& context,
       const std::string& path, file_base::flags open_flags,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : basic_file<Executor>(context, path, open_flags)
   {
   }
 
   /// Construct a basic_random_access_file on an existing native file.
   /**
    * This constructor initialises a random-access file object to hold an
    * existing native file.
    *
    * @param ex The I/O executor that the file will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the file.
    *
    * @param native_file The new underlying file implementation.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   basic_random_access_file(const executor_type& ex,
       const native_handle_type& native_file)
     : basic_file<Executor>(ex, native_file)
   {
   }
 
   /// Construct a basic_random_access_file on an existing native file.
   /**
    * This constructor initialises a random-access file object to hold an
    * existing native file.
    *
    * @param context An execution context which provides the I/O executor that
    * the file will use, by default, to dispatch handlers for any asynchronous
    * operations performed on the file.
    *
    * @param native_file The new underlying file implementation.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   template <typename ExecutionContext>
   basic_random_access_file(ExecutionContext& context,
       const native_handle_type& native_file,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : basic_file<Executor>(context, native_file)
   {
   }
 
   /// Move-construct a basic_random_access_file from another.
   /**
    * This constructor moves a random-access file from one object to another.
    *
    * @param other The other basic_random_access_file object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_random_access_file(const executor_type&)
    * constructor.
    */
   basic_random_access_file(basic_random_access_file&& other) noexcept
     : basic_file<Executor>(std::move(other))
   {
   }
 
   /// Move-assign a basic_random_access_file from another.
   /**
    * This assignment operator moves a random-access file from one object to
    * another.
    *
    * @param other The other basic_random_access_file object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_random_access_file(const executor_type&)
    * constructor.
    */
   basic_random_access_file& operator=(basic_random_access_file&& other)
   {
     basic_file<Executor>::operator=(std::move(other));
     return *this;
   }
 
   /// Move-construct a basic_random_access_file from a file of another executor
   /// type.
   /**
    * This constructor moves a random-access file from one object to another.
    *
    * @param other The other basic_random_access_file object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_random_access_file(const executor_type&)
    * constructor.
    */
   template <typename Executor1>
   basic_random_access_file(basic_random_access_file<Executor1>&& other,
       constraint_t<
         is_convertible<Executor1, Executor>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : basic_file<Executor>(std::move(other))
   {
   }
 
   /// Move-assign a basic_random_access_file from a file of another executor
   /// type.
   /**
    * This assignment operator moves a random-access file from one object to
    * another.
    *
    * @param other The other basic_random_access_file object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_random_access_file(const executor_type&)
    * constructor.
    */
   template <typename Executor1>
   constraint_t<
     is_convertible<Executor1, Executor>::value,
     basic_random_access_file&
   > operator=(basic_random_access_file<Executor1>&& other)
   {
     basic_file<Executor>::operator=(std::move(other));
     return *this;
   }
 
   /// Destroys the file.
   /**
    * This function destroys the file, cancelling any outstanding asynchronous
    * operations associated with the file as if by calling @c cancel.
    */
   ~basic_random_access_file()
   {
   }
 
   /// Write some data to the handle at the specified offset.
   /**
    * This function is used to write data to the random-access handle. The
    * function call will block until one or more bytes of the data has been
    * written successfully, or until an error occurs.
    *
    * @param offset The offset at which the data will be written.
    *
    * @param buffers One or more data buffers to be written to the handle.
    *
    * @returns The number of bytes written.
    *
    * @throws boost::system::system_error Thrown on failure. An error code of
    * boost::asio::error::eof indicates that the end of the file was reached.
    *
    * @note The write_some_at operation may not write all of the data. Consider
    * using the @ref write_at function if you need to ensure that all data is
    * written before the blocking operation completes.
    *
    * @par Example
    * To write a single data buffer use the @ref buffer function as follows:
    * @code
    * handle.write_some_at(42, boost::asio::buffer(data, size));
    * @endcode
    * See the @ref buffer documentation for information on writing multiple
    * buffers in one go, and how to use it with arrays, boost::array or
    * std::vector.
    */
   template <typename ConstBufferSequence>
   std::size_t write_some_at(uint64_t offset,
       const ConstBufferSequence& buffers)
   {
     boost::system::error_code ec;
     std::size_t s = this->impl_.get_service().write_some_at(
         this->impl_.get_implementation(), offset, buffers, ec);
     boost::asio::detail::throw_error(ec, "write_some_at");
     return s;
   }
 
   /// Write some data to the handle at the specified offset.
   /**
    * This function is used to write data to the random-access handle. The
    * function call will block until one or more bytes of the data has been
    * written successfully, or until an error occurs.
    *
    * @param offset The offset at which the data will be written.
    *
    * @param buffers One or more data buffers to be written to the handle.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns The number of bytes written. Returns 0 if an error occurred.
    *
    * @note The write_some operation may not write all of the data to the
    * file. Consider using the @ref write_at function if you need to ensure that
    * all data is written before the blocking operation completes.
    */
   template <typename ConstBufferSequence>
   std::size_t write_some_at(uint64_t offset,
       const ConstBufferSequence& buffers, boost::system::error_code& ec)
   {
     return this->impl_.get_service().write_some_at(
         this->impl_.get_implementation(), offset, buffers, ec);
   }
 
   /// Start an asynchronous write at the specified offset.
   /**
    * This function is used to asynchronously write data to the random-access
    * handle. It is an initiating function for an @ref asynchronous_operation,
    * and always returns immediately.
    *
    * @param offset The offset at which the data will be written.
    *
    * @param buffers One or more data buffers to be written to the handle.
    * Although the buffers object may be copied as necessary, ownership of the
    * underlying memory blocks is retained by the caller, which must guarantee
    * that they remain valid until the completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the write completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   const boost::system::error_code& error, // Result of operation.
    *   std::size_t bytes_transferred // Number of bytes written.
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code, std::size_t) @endcode
    *
    * @note The write operation may not write all of the data to the file.
    * Consider using the @ref async_write_at function if you need to ensure that
    * all data is written before the asynchronous operation completes.
    *
    * @par Example
    * To write a single data buffer use the @ref buffer function as follows:
    * @code
    * handle.async_write_some_at(42, boost::asio::buffer(data, size), handler);
    * @endcode
    * See the @ref buffer documentation for information on writing multiple
    * buffers in one go, and how to use it with arrays, boost::array or
    * std::vector.
    *
    * @par Per-Operation Cancellation
    * This asynchronous operation supports cancellation for the following
    * boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename ConstBufferSequence,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         std::size_t)) WriteToken = default_completion_token_t<executor_type>>
   auto async_write_some_at(uint64_t offset, const ConstBufferSequence& buffers,
       WriteToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<WriteToken,
         void (boost::system::error_code, std::size_t)>(
           declval<initiate_async_write_some_at>(), token, offset, buffers))
   {
     return async_initiate<WriteToken,
       void (boost::system::error_code, std::size_t)>(
         initiate_async_write_some_at(this), token, offset, buffers);
   }
 
   /// Read some data from the handle at the specified offset.
   /**
    * This function is used to read data from the random-access handle. The
    * function call will block until one or more bytes of data has been read
    * successfully, or until an error occurs.
    *
    * @param offset The offset at which the data will be read.
    *
    * @param buffers One or more buffers into which the data will be read.
    *
    * @returns The number of bytes read.
    *
    * @throws boost::system::system_error Thrown on failure. An error code of
    * boost::asio::error::eof indicates that the end of the file was reached.
    *
    * @note The read_some operation may not read all of the requested number of
    * bytes. Consider using the @ref read_at function if you need to ensure that
    * the requested amount of data is read before the blocking operation
    * completes.
    *
    * @par Example
    * To read into a single data buffer use the @ref buffer function as follows:
    * @code
    * handle.read_some_at(42, boost::asio::buffer(data, size));
    * @endcode
    * See the @ref buffer documentation for information on reading into multiple
    * buffers in one go, and how to use it with arrays, boost::array or
    * std::vector.
    */
   template <typename MutableBufferSequence>
   std::size_t read_some_at(uint64_t offset,
       const MutableBufferSequence& buffers)
   {
     boost::system::error_code ec;
     std::size_t s = this->impl_.get_service().read_some_at(
         this->impl_.get_implementation(), offset, buffers, ec);
     boost::asio::detail::throw_error(ec, "read_some_at");
     return s;
   }
 
   /// Read some data from the handle at the specified offset.
   /**
    * This function is used to read data from the random-access handle. The
    * function call will block until one or more bytes of data has been read
    * successfully, or until an error occurs.
    *
    * @param offset The offset at which the data will be read.
    *
    * @param buffers One or more buffers into which the data will be read.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns The number of bytes read. Returns 0 if an error occurred.
    *
    * @note The read_some operation may not read all of the requested number of
    * bytes. Consider using the @ref read_at function if you need to ensure that
    * the requested amount of data is read before the blocking operation
    * completes.
    */
   template <typename MutableBufferSequence>
   std::size_t read_some_at(uint64_t offset,
       const MutableBufferSequence& buffers, boost::system::error_code& ec)
   {
     return this->impl_.get_service().read_some_at(
         this->impl_.get_implementation(), offset, buffers, ec);
   }
 
   /// Start an asynchronous read at the specified offset.
   /**
    * This function is used to asynchronously read data from the random-access
    * handle. It is an initiating function for an @ref asynchronous_operation,
    * and always returns immediately.
    *
    * @param offset The offset at which the data will be read.
    *
    * @param buffers One or more buffers into which the data will be read.
    * Although the buffers object may be copied as necessary, ownership of the
    * underlying memory blocks is retained by the caller, which must guarantee
    * that they remain valid until the completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the read completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   const boost::system::error_code& error, // Result of operation.
    *   std::size_t bytes_transferred // Number of bytes read.
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code, std::size_t) @endcode
    *
    * @note The read operation may not read all of the requested number of bytes.
    * Consider using the @ref async_read_at function if you need to ensure that
    * the requested amount of data is read before the asynchronous operation
    * completes.
    *
    * @par Example
    * To read into a single data buffer use the @ref buffer function as follows:
    * @code
    * handle.async_read_some_at(42, boost::asio::buffer(data, size), handler);
    * @endcode
    * See the @ref buffer documentation for information on reading into multiple
    * buffers in one go, and how to use it with arrays, boost::array or
    * std::vector.
    *
    * @par Per-Operation Cancellation
    * This asynchronous operation supports cancellation for the following
    * boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename MutableBufferSequence,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         std::size_t)) ReadToken = default_completion_token_t<executor_type>>
   auto async_read_some_at(uint64_t offset, const MutableBufferSequence& buffers,
       ReadToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<ReadToken,
         void (boost::system::error_code, std::size_t)>(
           declval<initiate_async_read_some_at>(), token, offset, buffers))
   {
     return async_initiate<ReadToken,
       void (boost::system::error_code, std::size_t)>(
         initiate_async_read_some_at(this), token, offset, buffers);
   }
 
 private:
   // Disallow copying and assignment.
   basic_random_access_file(const basic_random_access_file&) = delete;
   basic_random_access_file& operator=(
       const basic_random_access_file&) = delete;
 
   class initiate_async_write_some_at
   {
   public:
     typedef Executor executor_type;
 
     explicit initiate_async_write_some_at(basic_random_access_file* self)
       : self_(self)
     {
     }
 
     const executor_type& get_executor() const noexcept
     {
       return self_->get_executor();
     }
 
     template <typename WriteHandler, typename ConstBufferSequence>
     void operator()(WriteHandler&& handler,
         uint64_t offset, const ConstBufferSequence& buffers) const
     {
       // If you get an error on the following line it means that your handler
       // does not meet the documented type requirements for a WriteHandler.
       BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;
 
       detail::non_const_lvalue<WriteHandler> handler2(handler);
       self_->impl_.get_service().async_write_some_at(
           self_->impl_.get_implementation(), offset, buffers,
           handler2.value, self_->impl_.get_executor());
     }
 
   private:
     basic_random_access_file* self_;
   };
 
   class initiate_async_read_some_at
   {
   public:
     typedef Executor executor_type;
 
     explicit initiate_async_read_some_at(basic_random_access_file* self)
       : self_(self)
     {
     }
 
     const executor_type& get_executor() const noexcept
     {
       return self_->get_executor();
     }
 
     template <typename ReadHandler, typename MutableBufferSequence>
     void operator()(ReadHandler&& handler,
         uint64_t offset, const MutableBufferSequence& buffers) const
     {
       // If you get an error on the following line it means that your handler
       // does not meet the documented type requirements for a ReadHandler.
       BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
 
       detail::non_const_lvalue<ReadHandler> handler2(handler);
       self_->impl_.get_service().async_read_some_at(
           self_->impl_.get_implementation(), offset, buffers,
           handler2.value, self_->impl_.get_executor());
     }
 
   private:
     basic_random_access_file* self_;
   };
 };
 
 } // namespace asio
 } // namespace boost
 
 #include <boost/asio/detail/pop_options.hpp>
 
 #endif // defined(BOOST_ASIO_HAS_FILE)
        //   || defined(GENERATING_DOCUMENTATION)
 
 #endif // BOOST_ASIO_BASIC_RANDOM_ACCESS_FILE_HPP

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