llfio_v2_xxx::byte_io_multiplexer Class Reference

A multiplexer of byte-orientated i/o. More...

#include "byte_io_multiplexer.hpp"

Inheritance diagram for llfio_v2_xxx::byte_io_multiplexer:

Classes
struct	_registered_buffer_type
struct	_synchronised_io_operation_state
	A synchronised i/o operation state. More...
struct	_unsynchronised_io_operation_state
	An unsynchronised i/o operation state. More...
struct	awaitable
	A convenience coroutine awaitable type returned by .co_read(), .co_write() and .co_barrier(). Blocks execution if no i/o multiplexer has been set on this handle! More...
struct	buffer_type
struct	check_for_any_completed_io_statistics
	Statistics about the just returned wait_for_completed_io() operation. More...
struct	const_buffer_type
struct	implementation_information_t
	The implementation information returned. More...
struct	io_operation_state
	An interface to a state for an i/o operation scheduled against an i/o multiplexer. More...
struct	io_operation_state_visitor
	Called by an i/o operation state to inform you of state change. Note that the i/o operation state lock is HELD during these calls! More...
struct	io_request
	The i/o request type used by this handle. Guaranteed to be TrivialType apart from construction, and StandardLayoutType. More...
struct	io_result
	The i/o result type used by this handle. Guaranteed to be TrivialType apart from construction. More...

Public Types
enum class	barrier_kind : uint8_t {   nowait_view_only , wait_view_only , nowait_data_only , wait_data_only ,   nowait_all , wait_all }
	The kinds of write reordering barrier which can be performed. More...
using	path_type = handle::path_type
using	extent_type = handle::extent_type
using	size_type = handle::size_type
using	mode = handle::mode
using	creation = handle::creation
using	caching = handle::caching
using	flag = handle::flag
using	registered_buffer_type = std::shared_ptr< _registered_buffer_type >
	The registered buffer type used by this handle.
using	buffers_type = span< buffer_type >
	The scatter buffers type used by this handle. Guaranteed to be TrivialType apart from construction, and StandardLayoutType.
using	const_buffers_type = span< const_buffer_type >
	The gather buffers type used by this handle. Guaranteed to be TrivialType apart from construction, and StandardLayoutType.

Public Member Functions
	byte_io_multiplexer (byte_io_multiplexer &&)=default
	byte_io_multiplexer (const byte_io_multiplexer &)=delete
byte_io_multiplexer &	operator= (byte_io_multiplexer &&)=default
byte_io_multiplexer &	operator= (const byte_io_multiplexer &)=delete
virtual implementation_information_t	implementation_information () const noexcept=0
	Returns implementation information about an i/o multiplexer.
virtual result< uint8_t >	do_byte_io_handle_register (byte_io_handle *) noexcept
virtual result< void >	do_byte_io_handle_deregister (byte_io_handle *) noexcept
	Implements byte_io_handle deregistration.
virtual result< uint8_t >	do_byte_io_handle_register (listening_byte_socket_handle *) noexcept
virtual result< void >	do_byte_io_handle_deregister (listening_byte_socket_handle *) noexcept
	Implements listening_byte_socket_handle deregistration.
virtual size_t	do_byte_io_handle_max_buffers (const byte_io_handle *h) const noexcept
	Implements byte_io_handle::max_buffers()
virtual result< registered_buffer_type >	do_byte_io_handle_allocate_registered_buffer (byte_io_handle *h, size_t &bytes) noexcept
	Implements byte_io_handle::allocate_registered_buffer()
virtual std::pair< size_t, size_t >	io_state_requirements () noexcept=0
	Returns the number of bytes, and alignment required, for an io_operation_state for this multiplexer.
virtual io_operation_state *	construct (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< buffers_type > reqs) noexcept=0
	Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a read operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().
virtual io_operation_state *	construct (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< const_buffers_type > reqs) noexcept=0
	Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a write operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().
virtual io_operation_state *	construct (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< const_buffers_type > reqs, barrier_kind kind) noexcept=0
	Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a barrier operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().
virtual io_operation_state *	construct (span< byte > storage, byte_socket_handle *_h, io_operation_state_visitor *_visitor, deadline d, const ip::address &) noexcept
	Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a byte_socket_handle read operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().
virtual io_operation_state *	construct (span< byte > storage, listening_byte_socket_handle *_h, io_operation_state_visitor *_visitor, deadline d, std::pair< byte_socket_handle, ip::address > &) noexcept
	Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a listening_byte_socket_handle read operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().
virtual io_operation_state_type	init_io_operation (io_operation_state *state) noexcept=0
	Initiates the i/o in a previously constructed state. Note that you should always call .flush_inited_io_operations() after you finished initiating i/o. After this call returns, you cannot relocate in memory state until is_finished(state->current_state()) returns true.
virtual io_operation_state *	construct_and_init_io_operation (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< buffers_type > reqs) noexcept
	Combines .construct() with .init_io_operation() in a single call for improved efficiency.
virtual io_operation_state *	construct_and_init_io_operation (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< const_buffers_type > reqs) noexcept
	Combines .construct() with .init_io_operation() in a single call for improved efficiency.
virtual io_operation_state *	construct_and_init_io_operation (span< byte > storage, byte_io_handle *_h, io_operation_state_visitor *_visitor, registered_buffer_type &&b, deadline d, io_request< const_buffers_type > reqs, barrier_kind kind) noexcept
	Combines .construct() with .init_io_operation() in a single call for improved efficiency.
virtual io_operation_state *	construct_and_init_io_operation (span< byte > storage, byte_socket_handle *_h, io_operation_state_visitor *_visitor, deadline d, const ip::address &addr) noexcept
	Combines .construct() with .init_io_operation() in a single call for improved efficiency.
virtual io_operation_state *	construct_and_init_io_operation (span< byte > storage, listening_byte_socket_handle *_h, io_operation_state_visitor *_visitor, deadline d, std::pair< byte_socket_handle, ip::address > &req) noexcept
	Combines .construct() with .init_io_operation() in a single call for improved efficiency.
virtual result< void >	flush_inited_io_operations () noexcept
	Flushes any previously initiated i/o, if necessary for this i/o multiplexer.
virtual io_operation_state_type	check_io_operation (io_operation_state *op) noexcept
	Asks the system for the current state of the i/o, returning its current state.
virtual result< io_operation_state_type >	cancel_io_operation (io_operation_state *op, deadline d={}) noexcept=0
	Cancel an initiated i/o, returning its current state if successful.
virtual result< check_for_any_completed_io_statistics >	check_for_any_completed_io (deadline d=std::chrono::seconds(0), size_t max_completions=(size_t) -1) noexcept=0
	Checks all i/o initiated on this i/o multiplexer to see which have completed, trying without guarantee to complete no more than max_completions completions or finisheds, and not to exceed d of waiting (this function never fails with timed out).
virtual result< void >	wake_check_for_any_completed_io () noexcept=0
	Can be called from any thread to wake any other single thread currently blocked within check_for_any_completed_io(). Which thread is woken is not specified.
constexpr	handle ()
constexpr	handle (native_handle_type h, flag flags=flag::none) noexcept
	handle (const handle &)=delete
constexpr	handle (handle &&o) noexcept
flag	flags () const noexcept
	The flags this handle was opened with.
	QUICKCPPLIB_BITFIELD_BEGIN_T (flag, uint16_t)
	Bitwise flags which can be specified.
void	swap (handle &o) noexcept
	Swap with another instance.
virtual result< path_type >	current_path () const noexcept
virtual result< void >	close () noexcept
	Immediately close the native handle type managed by this handle.
result< handle >	clone () const noexcept
virtual native_handle_type	release () noexcept
	Release the native handle type managed by this handle.
bool	is_valid () const noexcept
	True if the handle is valid (and usually open)
bool	is_readable () const noexcept
	True if the handle is readable.
bool	is_writable () const noexcept
	True if the handle is writable.
bool	is_append_only () const noexcept
	True if the handle is append only.
virtual result< void >	set_append_only (bool enable) noexcept
	EXTENSION: Changes whether this handle is append only or not.
bool	is_multiplexable () const noexcept
	True if multiplexable.
bool	is_nonblocking () const noexcept
	True if nonblocking.
bool	is_seekable () const noexcept
	True if seekable.
bool	requires_aligned_io () const noexcept
	True if requires aligned i/o.
bool	is_kernel_handle () const noexcept
	True if native_handle() is a valid kernel handle.
bool	is_regular () const noexcept
	True if a regular file or device.
bool	is_directory () const noexcept
	True if a directory.
bool	is_symlink () const noexcept
	True if a symlink.
bool	is_pipe () const noexcept
	True if a pipe.
bool	is_socket () const noexcept
	True if a socket.
bool	is_multiplexer () const noexcept
	True if a multiplexer like BSD kqueues, Linux epoll or Windows IOCP.
bool	is_process () const noexcept
	True if a process.
bool	is_section () const noexcept
	True if a memory section.
bool	is_allocation () const noexcept
	True if a memory allocation.
bool	is_path () const noexcept
	True if a path or a directory.
bool	is_tls_socket () const noexcept
	True if a TLS socket.
bool	is_http_socket () const noexcept
	True if a HTTP socket.
caching	kernel_caching () const noexcept
	Kernel cache strategy used by this handle.
bool	are_reads_from_cache () const noexcept
	True if the handle uses the kernel page cache for reads.
bool	are_writes_durable () const noexcept
	True if writes are safely on storage on completion.
bool	are_safety_barriers_issued () const noexcept
	True if issuing safety fsyncs is on.
native_handle_type	native_handle () const noexcept
	The native handle used by this handle.

Static Protected Member Functions
static io_result< buffers_type >	_result_type_from_io_operation_state (io_operation_state *state, buffers_type *) noexcept
static io_result< const_buffers_type >	_result_type_from_io_operation_state (io_operation_state *state, const_buffers_type *) noexcept

Protected Attributes
union {
native_handle_type   _v
struct {
intptr_t   _padding0_
uint32_t   _padding1_
flag   flags
uint16_t   _padding2_
}   _
};

Static Protected Attributes
static constexpr size_t	_awaitable_size = 128

Detailed Description

A multiplexer of byte-orientated i/o.

LLFIO does not provide out-of-the-box multiplexing of byte i/o, however it does provide the ability to create byte_io_handle instances with the handle::flag::multiplexable set. With that flag set, the following LLFIO classes change how they create handles with the kernel:

LLFIO i/o class	POSIX	Windows
directory_handle	No effect	Creates HANDLE as OVERLAPPED
file_handle	No effect	Creates HANDLE as OVERLAPPED
map_handle	No effect	No effect
mapped_file_handle	No effect	Creates HANDLE as OVERLAPPED, but i/o is to map not file
pipe_handle	Creates file descriptor as non-blocking	Creates HANDLE as OVERLAPPED
section_handle	No effect	Creates HANDLE as OVERLAPPED
socket_handle	Creates file descriptor as non-blocking	Creates HANDLE as OVERLAPPED and as non-blocking
symlink_handle	No effect	Creates HANDLE as OVERLAPPED

If the i/o handle's multiplexer pointer is not null, the multiplexer instance is invoked to implement byte_io_handle::read(), byte_io_handle::write() and byte_io_handle::barrier() by constructing an i/o operation state on the stack, calling .init_io_operation() followed by .flush_inited_io_operations(), and then spinning on .check_io_operation() and .check_for_any_completed_io() with the deadline specified to the original blocking operation.

If the i/o handle's multiplexer pointer is null, byte_io_handle::read(), byte_io_handle::write() and byte_io_handle::barrier() all use virtually overridable implementations. The default implementations emulate blocking semantics using the kernel's i/o poll function (literally poll() on POSIX, NtWaitForSingleObject() on Windows) to sleep the thread until at least one byte of i/o occurs, or the deadline specified is exceeded. This, obviously enough, can double the number of kernel syscalls done per i/o, so using handles with the handle::flag::multiplexable flag set is not wise unless you really need non-infinite deadline i/o.

Member Enumeration Documentation

barrier_kind

enum class llfio_v2_xxx::byte_io_multiplexer::barrier_kind : uint8_t

strong

The kinds of write reordering barrier which can be performed.

Enumerator
nowait_view_only	Barrier mapped data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using nvram_barrier() for even better performance.
wait_view_only	Barrier mapped data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using nvram_barrier() for even better performance.
nowait_data_only	Barrier data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using nvram_barrier() for even better performance.
wait_data_only	Barrier data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using nvram_barrier() for even better performance.
nowait_all	Barrier data and the metadata to retrieve it, non-blocking.
wait_all	Barrier data and the metadata to retrieve it, block until it is done.

  {
    nowait_view_only,  //!< Barrier mapped data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.
    wait_view_only,  //!< Barrier mapped data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.
    nowait_data_only,  //!< Barrier data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.
    wait_data_only,  //!< Barrier data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.
    nowait_all,  //!< Barrier data and the metadata to retrieve it, non-blocking.
    wait_all     //!< Barrier data and the metadata to retrieve it, block until it is done.
  };

Constructor & Destructor Documentation

byte_io_multiplexer()

constexpr llfio_v2_xxx::byte_io_multiplexer::byte_io_multiplexer ( )

inlineconstexpr

{}

Member Function Documentation

_result_type_from_io_operation_state() [1/2]

static io_result< buffers_type > llfio_v2_xxx::byte_io_multiplexer::_result_type_from_io_operation_state ( io_operation_state *  state, buffers_type *    )

inlinestaticprotectednoexcept

  {
    return std::move(*state).get_completed_read();
  }

_result_type_from_io_operation_state() [2/2]

static io_result< const_buffers_type > llfio_v2_xxx::byte_io_multiplexer::_result_type_from_io_operation_state ( io_operation_state *  state, const_buffers_type *    )

inlinestaticprotectednoexcept

  {
    return std::move(*state).get_completed_write_or_barrier();
  }

are_reads_from_cache()

bool llfio_v2_xxx::handle::are_reads_from_cache ( ) const

inlinenoexceptinherited

True if the handle uses the kernel page cache for reads.

{ return !!(_v.behaviour & native_handle_type::disposition::cache_reads); }

are_safety_barriers_issued()

bool llfio_v2_xxx::handle::are_safety_barriers_issued ( ) const

inlinenoexceptinherited

True if issuing safety fsyncs is on.

{ return !!(_v.behaviour & native_handle_type::disposition::safety_barriers); }

are_writes_durable()

bool llfio_v2_xxx::handle::are_writes_durable ( ) const

inlinenoexceptinherited

True if writes are safely on storage on completion.

{ return !(_v.behaviour & native_handle_type::disposition::cache_writes); }

check_io_operation()

virtual io_operation_state_type llfio_v2_xxx::byte_io_multiplexer::check_io_operation ( io_operation_state *  op )

inlinevirtualnoexcept

Asks the system for the current state of the i/o, returning its current state.

{ return op->current_state(); }

clone()

result< handle > llfio_v2_xxx::handle::clone ( ) const

noexceptinherited

Clone this handle (copy constructor is disabled to avoid accidental copying)

Errors returnable\n Any of the values POSIX dup() or DuplicateHandle() can return.

close()

virtual result< void > llfio_v2_xxx::handle::close ( )

virtualnoexceptinherited

Immediately close the native handle type managed by this handle.

Reimplemented in llfio_v2_xxx::byte_io_handle, llfio_v2_xxx::byte_socket_handle, llfio_v2_xxx::listening_byte_socket_handle, llfio_v2_xxx::directory_handle, llfio_v2_xxx::fast_random_file_handle, llfio_v2_xxx::file_handle, llfio_v2_xxx::section_handle, llfio_v2_xxx::map_handle, llfio_v2_xxx::mapped_file_handle, llfio_v2_xxx::path_handle, llfio_v2_xxx::pipe_handle, llfio_v2_xxx::process_handle, and llfio_v2_xxx::symlink_handle.

construct() [1/2]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct ( span< byte >  storage, byte_socket_handle *  _h, io_operation_state_visitor *  _visitor, deadline  d, const ip::address &    )

inlinevirtualnoexcept

Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a byte_socket_handle read operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().

  {
    (void) storage;
    (void) _h;
    (void) _visitor;
    (void) d;
    return nullptr;
  }

construct() [2/2]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct ( span< byte >  storage, listening_byte_socket_handle *  _h, io_operation_state_visitor *  _visitor, deadline  d, std::pair< byte_socket_handle, ip::address > &    )

inlinevirtualnoexcept

Constructs either a unsynchronised_io_operation_state or a synchronised_io_operation_state for a listening_byte_socket_handle read operation into the storage provided. The i/o is not initiated. The storage must meet the requirements from state_requirements().

  {
    (void) storage;
    (void) _h;
    (void) _visitor;
    (void) d;
    return nullptr;
  }

construct_and_init_io_operation() [1/5]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct_and_init_io_operation ( span< byte >  storage, byte_io_handle *  _h, io_operation_state_visitor *  _visitor, registered_buffer_type &&  b, deadline  d, io_request< buffers_type >  reqs  )

inlinevirtualnoexcept

Combines .construct() with .init_io_operation() in a single call for improved efficiency.

  {
    io_operation_state *state = construct(storage, _h, _visitor, std::move(b), d, std::move(reqs));
    if(state != nullptr)
    {
      init_io_operation(state);
    }
    return state;
  }

construct_and_init_io_operation() [2/5]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct_and_init_io_operation ( span< byte >  storage, byte_io_handle *  _h, io_operation_state_visitor *  _visitor, registered_buffer_type &&  b, deadline  d, io_request< const_buffers_type >  reqs  )

inlinevirtualnoexcept

Combines .construct() with .init_io_operation() in a single call for improved efficiency.

  {
    io_operation_state *state = construct(storage, _h, _visitor, std::move(b), d, std::move(reqs));
    if(state != nullptr)
    {
      init_io_operation(state);
    }
    return state;
  }

construct_and_init_io_operation() [3/5]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct_and_init_io_operation ( span< byte >  storage, byte_io_handle *  _h, io_operation_state_visitor *  _visitor, registered_buffer_type &&  b, deadline  d, io_request< const_buffers_type >  reqs, barrier_kind  kind  )

inlinevirtualnoexcept

Combines .construct() with .init_io_operation() in a single call for improved efficiency.

  {
    io_operation_state *state = construct(storage, _h, _visitor, std::move(b), d, std::move(reqs), kind);
    if(state != nullptr)
    {
      init_io_operation(state);
    }
    return state;
  }

construct_and_init_io_operation() [4/5]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct_and_init_io_operation ( span< byte >  storage, byte_socket_handle *  _h, io_operation_state_visitor *  _visitor, deadline  d, const ip::address &  addr  )

inlinevirtualnoexcept

Combines .construct() with .init_io_operation() in a single call for improved efficiency.

  {
    io_operation_state *state = construct(storage, _h, _visitor, d, addr);
    if(state != nullptr)
    {
      init_io_operation(state);
    }
    return state;
  }

construct_and_init_io_operation() [5/5]

virtual io_operation_state * llfio_v2_xxx::byte_io_multiplexer::construct_and_init_io_operation ( span< byte >  storage, listening_byte_socket_handle *  _h, io_operation_state_visitor *  _visitor, deadline  d, std::pair< byte_socket_handle, ip::address > &  req  )

inlinevirtualnoexcept

Combines .construct() with .init_io_operation() in a single call for improved efficiency.

  {
    io_operation_state *state = construct(storage, _h, _visitor, d, req);
    if(state != nullptr)
    {
      init_io_operation(state);
    }
    return state;
  }

current_path()

virtual result< path_type > llfio_v2_xxx::handle::current_path ( ) const

virtualnoexceptinherited

Returns the current path of the open handle as said by the operating system. Note that you are NOT guaranteed that any path refreshed bears any resemblance to the original, some operating systems will return some different path which still reaches the same inode via some other route e.g. hardlinks, dereferenced symbolic links, etc. Windows and Linux correctly track changes to the specific path the handle was opened with, not getting confused by other hard links. MacOS nearly gets it right, but under some circumstances e.g. renaming may switch to a different hard link's path which is almost certainly a bug.

If LLFIO was not able to determine the current path for this open handle e.g. the inode has been unlinked, it returns an empty path. Be aware that FreeBSD can return an empty (deleted) path for file inodes no longer cached by the kernel path cache, LLFIO cannot detect the difference. FreeBSD will also return any path leading to the inode if it is hard linked. FreeBSD does implement path retrieval for directory inodes correctly however, and see algorithm::cached_parent_handle_adapter<T> for a handle adapter which makes use of that.

On Linux if /proc is not mounted, this call fails with an error. All APIs in LLFIO which require the use of current_path() can be told to not use it e.g. flag::disable_safety_unlinks. It is up to you to detect if current_path() is not working, and to change how you call LLFIO appropriately.

On Windows, you will almost certainly get back a path of the form \!!\Device\HarddiskVolume10\Users\ned\.... See path_view for what all the path prefix sequences mean, but to summarise the \!!\ prefix is LLFIO-only and will not be accepted by other Windows APIs. Pass LLFIO derived paths through the function to_win32_path() to Win32-ise them. This function is also available on Linux where it does nothing, so you can use it in portable code.

Warning

This call is expensive, it always asks the kernel for the current path, and no checking is done to ensure what the kernel returns is accurate or even sensible. Be aware that despite these precautions, paths are unstable and can change randomly at any moment. Most code written to use absolute file systems paths is racy, so don't do it, use path_handle to fix a base location on the file system and work from that anchor instead!

Memory Allocations\n At least one malloc for the path_type, likely several more.

See also

algorithm::cached_parent_handle_adapter<T> which overrides this with an implementation based on retrieving the current path of a cached handle to the parent directory. On platforms with instability or failure to retrieve the correct current path for regular files, the cached parent handle adapter works around the problem by taking advantage of directory inodes not having the same instability problems on any platform.

Reimplemented in llfio_v2_xxx::process_handle.

do_byte_io_handle_allocate_registered_buffer()

result< byte_io_multiplexer::registered_buffer_type > llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_allocate_registered_buffer ( byte_io_handle *  h, size_t &  bytes  )

inlinevirtualnoexcept

Implements byte_io_handle::allocate_registered_buffer()

{
  return h->_do_allocate_registered_buffer(bytes);
}

do_byte_io_handle_deregister() [1/2]

virtual result< void > llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_deregister ( byte_io_handle *  )

inlinevirtualnoexcept

Implements byte_io_handle deregistration.

{ return success(); }

do_byte_io_handle_deregister() [2/2]

virtual result< void > llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_deregister ( listening_byte_socket_handle *  )

inlinevirtualnoexcept

Implements listening_byte_socket_handle deregistration.

{ return errc::operation_not_supported; }

do_byte_io_handle_max_buffers()

size_t llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_max_buffers ( const byte_io_handle *  h ) const

inlinevirtualnoexcept

Implements byte_io_handle::max_buffers()

{
  return h->_do_max_buffers();
}

do_byte_io_handle_register() [1/2]

virtual result< uint8_t > llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_register ( byte_io_handle *  )

inlinevirtualnoexcept

Implements byte_io_handle registration. The bottom two bits of the returned value are set into _v.behaviour's _multiplexer_state_bit0 and _multiplexer_state_bit

{ return (uint8_t) 0; }

do_byte_io_handle_register() [2/2]

virtual result< uint8_t > llfio_v2_xxx::byte_io_multiplexer::do_byte_io_handle_register ( listening_byte_socket_handle *  )

inlinevirtualnoexcept

Implements listening_byte_socket_handle registration. The bottom two bits of the returned value are set into _v.behaviour's _multiplexer_state_bit0 and _multiplexer_state_bit

{ return errc::operation_not_supported; }

flags()

flag llfio_v2_xxx::handle::flags ( ) const

inlinenoexceptinherited

The flags this handle was opened with.

{ return _.flags; }

flush_inited_io_operations()

virtual result< void > llfio_v2_xxx::byte_io_multiplexer::flush_inited_io_operations ( )

inlinevirtualnoexcept

Flushes any previously initiated i/o, if necessary for this i/o multiplexer.

{ return success(); }

handle() [1/4]

constexpr llfio_v2_xxx::handle::handle ( )

inlineconstexpr

Todo:

Why is io_result<buffers_type> not a standard layout type?

      : _v()
  {
  }  // NOLINT

handle() [2/4]

llfio_v2_xxx::handle::handle ( const handle &  )

delete

Todo:

Why is io_result<buffers_type> not a standard layout type?

handle() [3/4]

constexpr llfio_v2_xxx::handle::handle ( handle &&  o )

inlineconstexprnoexcept

Todo:

Why is io_result<buffers_type> not a standard layout type?

      : _v(std::move(o._v))
  {
    o._v = native_handle_type();
  }

handle() [4/4]

constexpr llfio_v2_xxx::handle::handle ( native_handle_type  h, flag  flags = flag::none  )

inlineexplicitconstexprnoexcept

Todo:

Why is io_result<buffers_type> not a standard layout type?

      : _v(std::move(h), /* special move constructor to work around a constexpr bug in clang*/ uint16_t(flags))
  {
  }

is_allocation()

bool llfio_v2_xxx::handle::is_allocation ( ) const

inlinenoexceptinherited

True if a memory allocation.

{ return _v.is_allocation(); }

is_append_only()

bool llfio_v2_xxx::handle::is_append_only ( ) const

inlinenoexceptinherited

True if the handle is append only.

{ return _v.is_append_only(); }

is_directory()

bool llfio_v2_xxx::handle::is_directory ( ) const

inlinenoexceptinherited

True if a directory.

{ return _v.is_directory(); }

is_http_socket()

bool llfio_v2_xxx::handle::is_http_socket ( ) const

inlinenoexceptinherited

True if a HTTP socket.

{ return _v.is_http_socket(); }

is_kernel_handle()

bool llfio_v2_xxx::handle::is_kernel_handle ( ) const

inlinenoexceptinherited

True if native_handle() is a valid kernel handle.

{ return _v.is_kernel_handle(); }

is_multiplexable()

bool llfio_v2_xxx::handle::is_multiplexable ( ) const

inlinenoexceptinherited

True if multiplexable.

{ return !!(_.flags & flag::multiplexable); }

is_multiplexer()

bool llfio_v2_xxx::handle::is_multiplexer ( ) const

inlinenoexceptinherited

True if a multiplexer like BSD kqueues, Linux epoll or Windows IOCP.

{ return _v.is_multiplexer(); }

is_nonblocking()

bool llfio_v2_xxx::handle::is_nonblocking ( ) const

inlinenoexceptinherited

True if nonblocking.

{ return _v.is_nonblocking(); }

is_path()

bool llfio_v2_xxx::handle::is_path ( ) const

inlinenoexceptinherited

True if a path or a directory.

{ return _v.is_path(); }

is_pipe()

bool llfio_v2_xxx::handle::is_pipe ( ) const

inlinenoexceptinherited

True if a pipe.

{ return _v.is_pipe(); }

is_process()

bool llfio_v2_xxx::handle::is_process ( ) const

inlinenoexceptinherited

True if a process.

{ return _v.is_process(); }

is_readable()

bool llfio_v2_xxx::handle::is_readable ( ) const

inlinenoexceptinherited

True if the handle is readable.

{ return _v.is_readable(); }

is_regular()

bool llfio_v2_xxx::handle::is_regular ( ) const

inlinenoexceptinherited

True if a regular file or device.

{ return _v.is_regular(); }

is_section()

bool llfio_v2_xxx::handle::is_section ( ) const

inlinenoexceptinherited

True if a memory section.

{ return _v.is_section(); }

is_seekable()

bool llfio_v2_xxx::handle::is_seekable ( ) const

inlinenoexceptinherited

True if seekable.

{ return _v.is_seekable(); }

is_socket()

bool llfio_v2_xxx::handle::is_socket ( ) const

inlinenoexceptinherited

True if a socket.

{ return _v.is_socket(); }

is_symlink()

bool llfio_v2_xxx::handle::is_symlink ( ) const

inlinenoexceptinherited

True if a symlink.

{ return _v.is_symlink(); }

is_tls_socket()

bool llfio_v2_xxx::handle::is_tls_socket ( ) const

inlinenoexceptinherited

True if a TLS socket.

{ return _v.is_tls_socket(); }

is_valid()

bool llfio_v2_xxx::handle::is_valid ( ) const

inlinenoexceptinherited

True if the handle is valid (and usually open)

{ return _v.is_valid(); }

is_writable()

bool llfio_v2_xxx::handle::is_writable ( ) const

inlinenoexceptinherited

True if the handle is writable.

{ return _v.is_writable(); }

kernel_caching()

caching llfio_v2_xxx::handle::kernel_caching ( ) const

inlinenoexceptinherited

Kernel cache strategy used by this handle.

  {
    const bool safety_barriers = !!(_v.behaviour & native_handle_type::disposition::safety_barriers);
    const bool cache_metadata = !!(_v.behaviour & native_handle_type::disposition::cache_metadata);
    const bool cache_reads = !!(_v.behaviour & native_handle_type::disposition::cache_reads);
    const bool cache_writes = !!(_v.behaviour & native_handle_type::disposition::cache_writes);
    const bool cache_temporary = !!(_v.behaviour & native_handle_type::disposition::cache_temporary);
    if(cache_temporary)
    {
      return caching::temporary;
    }
    if(cache_metadata && cache_reads && cache_writes)
    {
      return safety_barriers ? caching::safety_barriers : caching::all;
    }
    if(cache_metadata && cache_reads)
    {
      return caching::reads_and_metadata;
    }
    if(cache_reads)
    {
      return caching::reads;
    }
    if(cache_metadata)
    {
      return caching::only_metadata;
    }
    return caching::none;
  }

native_handle()

native_handle_type llfio_v2_xxx::handle::native_handle ( ) const

inlinenoexceptinherited

The native handle used by this handle.

{ return _v; }

QUICKCPPLIB_BITFIELD_BEGIN_T()

llfio_v2_xxx::handle::QUICKCPPLIB_BITFIELD_BEGIN_T ( flag  , uint16_t    )

inlineinherited

Bitwise flags which can be specified.

< No flags

Unlinks the file on handle close. On POSIX, this simply unlinks whatever is pointed to by path() upon the call of close() if and only if the inode matches. On Windows, if you are on Windows 10 1709 or later, exactly the same thing occurs. If on previous editions of Windows, the file entry does not disappears but becomes unavailable for anyone else to open with an errc::resource_unavailable_try_again error return. Because this is confusing, unless the win_disable_unlink_emulation flag is also specified, this POSIX behaviour is somewhat emulated by LLFIO on older Windows by renaming the file to a random name on close() causing it to appear to have been unlinked immediately.

Some kernel caching modes have unhelpfully inconsistent behaviours in getting your data onto storage, so by default unless this flag is specified LLFIO adds extra fsyncs to the following operations for the caching modes specified below: truncation of file length either explicitly or during file open. closing of the handle either explicitly or in the destructor.

Additionally on Linux only to prevent loss of file metadata: On the parent directory whenever a file might have been created. On the parent directory on file close.

This only occurs for these kernel caching modes: caching::none caching::reads caching::reads_and_metadata caching::safety_barriers

file_handle::unlink() could accidentally delete the wrong file if someone has renamed the open file handle since the time it was opened. To prevent this occuring, where the OS doesn't provide race free unlink-by-open-handle we compare the inode of the path we are about to unlink with that of the open handle before unlinking.

Warning

This does not prevent races where in between the time of checking the inode and executing the unlink a third party changes the item about to be unlinked. Only operating systems with a true race-free unlink syscall are race free.

Ask the OS to disable prefetching of data. This can improve random i/o performance.

Ask the OS to maximise prefetching of data, possibly prefetching the entire file into kernel cache. This can improve sequential i/o performance.

< See the documentation for unlink_on_first_close

Microsoft Windows NTFS, having been created in the late 1980s, did not originally implement extents-based storage and thus could only represent sparse files via efficient compression of intermediate zeros. With NTFS v3.0 (Microsoft Windows 2000), a proper extents-based on-storage representation was added, thus allowing only 64Kb extent chunks written to be stored irrespective of whatever the maximum file extent was set to.

For various historical reasons, extents-based storage is disabled by default in newly created files on NTFS, unlike in almost every other major filing system. You have to explicitly "opt in" to extents-based storage.

As extents-based storage is nearly cost free on NTFS, LLFIO by default opts in to extents-based storage for any empty file it creates. If you don't want this, you can specify this flag to prevent that happening.

Filesystems tend to be embarrassingly parallel for operations performed to different inodes. Where LLFIO performs i/o to multiple inodes at a time, it will use OpenMP or the Parallelism or Concurrency standard library extensions to usually complete the operation in constant rather than linear time. If you don't want this default, you can disable default using this flag.

Microsoft Windows NTFS has the option, when creating a directory, to set whether leafname lookup will be case sensitive. This is the only way of getting exact POSIX semantics on Windows without resorting to editing the system registry, however it also affects all code doing lookups within that directory, so we must default it to off.

Create the handle in a way where i/o upon it can be multiplexed with other i/o on the same initiating thread of execution i.e. you can perform more than one read concurrently, without using threads. The blocking operations .read() and .write() may have to use a less efficient, but cancellable, blocking implementation for handles created in this way. On Microsoft Windows, this creates handles with OVERLAPPED semantics. On POSIX, this creates handles with nonblocking semantics for non-file handles such as pipes and sockets, however for file, directory and symlink handles it does not set nonblocking, as it is non-portable.

< Using insane POSIX byte range locks

< This is an inode created with no representation on the filing system

                                              {
  none = uint16_t(0),  //!< No flags
  /*! Unlinks the file on handle close. On POSIX, this simply unlinks whatever is pointed
  to by `path()` upon the call of `close()` if and only if the inode matches. On Windows,
  if you are on Windows 10 1709 or later, exactly the same thing occurs. If on previous
  editions of Windows, the file entry does not disappears but becomes unavailable for
  anyone else to open with an `errc::resource_unavailable_try_again` error return. Because this is confusing, unless the
  `win_disable_unlink_emulation` flag is also specified, this POSIX behaviour is
  somewhat emulated by LLFIO on older Windows by renaming the file to a random name on `close()`
  causing it to appear to have been unlinked immediately.
  */
  unlink_on_first_close = uint16_t(1U << 0U),
 
  /*! Some kernel caching modes have unhelpfully inconsistent behaviours
  in getting your data onto storage, so by default unless this flag is
  specified LLFIO adds extra fsyncs to the following operations for the
  caching modes specified below:
  * truncation of file length either explicitly or during file open.
  * closing of the handle either explicitly or in the destructor.
 
  Additionally on Linux only to prevent loss of file metadata:
  * On the parent directory whenever a file might have been created.
  * On the parent directory on file close.
 
  This only occurs for these kernel caching modes:
  * caching::none
  * caching::reads
  * caching::reads_and_metadata
  * caching::safety_barriers
  */
  disable_safety_barriers = uint16_t(1U << 2U),
  /*! `file_handle::unlink()` could accidentally delete the wrong file if someone has
  renamed the open file handle since the time it was opened. To prevent this occuring,
  where the OS doesn't provide race free unlink-by-open-handle we compare the inode of
  the path we are about to unlink with that of the open handle before unlinking.
  \warning This does not prevent races where in between the time of checking the inode
  and executing the unlink a third party changes the item about to be unlinked. Only
  operating systems with a true race-free unlink syscall are race free.
  */
  disable_safety_unlinks = uint16_t(1U << 3U),
  /*! Ask the OS to disable prefetching of data. This can improve random
  i/o performance.
  */
  disable_prefetching = uint16_t(1U << 4U),
  /*! Ask the OS to maximise prefetching of data, possibly prefetching the entire file
  into kernel cache. This can improve sequential i/o performance.
  */
  maximum_prefetching = uint16_t(1U << 5U),
 
  win_disable_unlink_emulation = uint16_t(1U << 9U),  //!< See the documentation for `unlink_on_first_close`
  /*! Microsoft Windows NTFS, having been created in the late 1980s, did not originally
  implement extents-based storage and thus could only represent sparse files via
  efficient compression of intermediate zeros. With NTFS v3.0 (Microsoft Windows 2000),
  a proper extents-based on-storage representation was added, thus allowing only 64Kb
  extent chunks written to be stored irrespective of whatever the maximum file extent
  was set to.
 
  For various historical reasons, extents-based storage is disabled by default in newly
  created files on NTFS, unlike in almost every other major filing system. You have to
  explicitly "opt in" to extents-based storage.
 
  As extents-based storage is nearly cost free on NTFS, LLFIO by default opts in to
  extents-based storage for any empty file it creates. If you don't want this, you
  can specify this flag to prevent that happening.
  */
  win_disable_sparse_file_creation = uint16_t(1U << 10U),
  /*! Filesystems tend to be embarrassingly parallel for operations performed to different
  inodes. Where LLFIO performs i/o to multiple inodes at a time, it will use OpenMP or
  the Parallelism or Concurrency standard library extensions to usually complete the
  operation in constant rather than linear time. If you don't want this default, you can
  disable default using this flag.
  */
  disable_parallelism = uint16_t(1U << 11U),
  /*! Microsoft Windows NTFS has the option, when creating a directory, to set whether
  leafname lookup will be case sensitive. This is the only way of getting exact POSIX
  semantics on Windows without resorting to editing the system registry, however it also
  affects all code doing lookups within that directory, so we must default it to off.
  */
  win_create_case_sensitive_directory = uint16_t(1U << 12U),
 
  /*! Create the handle in a way where i/o upon it can be multiplexed with other i/o
  on the same initiating thread of execution i.e. you can perform more than one read
  concurrently, without using threads. The blocking operations `.read()` and `.write()`
  may have to use a less efficient, but cancellable, blocking implementation for handles created
  in this way. On Microsoft Windows, this creates handles with `OVERLAPPED` semantics.
  On POSIX, this creates handles with nonblocking semantics for non-file handles such
  as pipes and sockets, however for file, directory and symlink handles it does not set
  nonblocking, as it is non-portable.
  */
  multiplexable = uint16_t(1U << 13U),
 
  // NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!
 
  byte_lock_insanity = uint16_t(1U << 14U),  //!< Using insane POSIX byte range locks
  anonymous_inode = uint16_t(1U << 15U)      //!< This is an inode created with no representation on the filing system
  } QUICKCPPLIB_BITFIELD_END(flag)

release()

virtual native_handle_type llfio_v2_xxx::handle::release ( )

inlinevirtualnoexceptinherited

Release the native handle type managed by this handle.

Reimplemented in llfio_v2_xxx::map_handle, and llfio_v2_xxx::mapped_file_handle.

  {
    native_handle_type ret(std::move(_v));
    return ret;
  }

requires_aligned_io()

bool llfio_v2_xxx::handle::requires_aligned_io ( ) const

inlinenoexceptinherited

True if requires aligned i/o.

{ return _v.requires_aligned_io(); }

set_append_only()

virtual result< void > llfio_v2_xxx::handle::set_append_only ( bool  enable )

virtualnoexceptinherited

EXTENSION: Changes whether this handle is append only or not.

Warning

On Windows this is implemented as a bit of a hack to make it fast like on POSIX, so make sure you open the handle for read/write originally. Note unlike on POSIX the append_only disposition will be the only one toggled, seekable and readable will remain turned on.

Errors returnable\n Whatever POSIX fcntl() returns. On Windows nothing is changed on the handle.

Memory Allocations\n No memory allocation.

Reimplemented in llfio_v2_xxx::process_handle.

swap()

void llfio_v2_xxx::handle::swap ( handle &  o )

inlinenoexceptinherited

Swap with another instance.

  {
    handle temp(std::move(*this));
    *this = std::move(o);
    o = std::move(temp);
  }

---

The documentation for this class was generated from the following files:

• include/llfio/v2.0/byte_io_multiplexer.hpp
• include/llfio/v2.0/byte_io_handle.hpp