boost/asio/basic_random_access_file.hpp
//
// basic_random_access_file.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 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::async_immediate().
*
* @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::async_immediate().
*
* @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