A handle to this, or another, process. More...

#include "process_handle.hpp"

Inheritance diagram for llfio_v2_xxx::process_handle:

Classes
struct	_byte_array_deleter

Public Types
using	path_type = handle::path_type

using	extent_type = handle::extent_type

using	size_type = handle::size_type

enum	mode : unsigned char { unchanged = 0, mode::none = 2, mode::attr_read = 4, mode::attr_write = 5, mode::read = 6, mode::write = 7, mode::append = 9 }
	The behaviour of the handle: does it read, read and write, or atomic append? More...

enum	creation : unsigned char { creation::open_existing = 0, creation::only_if_not_exist, creation::if_needed, creation::truncate_existing, creation::always_new }
	On opening, do we also create a new file or truncate an existing one? More...

enum	caching : unsigned char { unchanged = 0, caching::none = 1, caching::only_metadata = 2, caching::reads = 3, caching::reads_and_metadata = 5, caching::all = 6, caching::safety_barriers = 7, caching::temporary = 8 }
	What i/o on the handle may complete immediately due to kernel caching. More...

Public Member Functions
	QUICKCPPLIB_BITFIELD_BEGIN (flag)
	The behaviour of theprocess handle. More...

	QUICKCPPLIB_BITFIELD_END (flag)

constexpr	process_handle ()
	Default constructor.

constexpr	process_handle (native_handle_type h, flag flags=flag::none) noexcept
	Construct a handle from a supplied native handle.

constexpr	process_handle (handle &&o, flag flags=flag::none) noexcept
	Explicit conversion from handle permitted.

	process_handle (const process_handle &)=delete
	No copy construction (use clone())

process_handle &	operator= (const process_handle &o)=delete
	No copy assignment.

constexpr	process_handle (process_handle &&o) noexcept
	Move the handle.

process_handle &	operator= (process_handle &&o) noexcept
	Move assignment of handle.

void	swap (process_handle &o) noexcept
	Swap with another instance.

pipe_handle &	in_pipe () noexcept

const pipe_handle &	in_pipe () const noexcept
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

pipe_handle &	error_pipe () noexcept

const pipe_handle &	error_pipe () const noexcept
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

pipe_handle &	out_pipe () noexcept

const pipe_handle &	out_pipe () const noexcept
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

result< void >	close_pipes () noexcept
	Close or release all the pipes, depending on `flag::release_pipes_on_close`

bool	is_running () const noexcept
	Returns true if the process is currently running.

virtual result< path_type >	current_path () const noexcept override

virtual result< void >	close () noexcept override
	Immediately close this handle, possibly closing the pipes, possibly blocking until a child process exits.

result< process_handle >	clone () const noexcept

virtual result< void >	set_append_only (bool) noexcept override
	EXTENSION: Changes whether this handle is append only or not. More...

std::unique_ptr< span< path_view_component >, _byte_array_deleter >	environment () const noexcept

result< intptr_t >	wait (deadline d={}) const noexcept

template<class... Args>
bool	try_wait (Args &&... args) noexcept

template<class... Args, class Rep , class Period >
bool	try_wait_for (Args &&... args, const std::chrono::duration< Rep, Period > &duration) noexcept

template<class... Args, class Clock , class Duration >
bool	try_wait_until (Args &&... args, const std::chrono::time_point< Clock, Duration > &timeout) noexcept

void	swap (handle &o) noexcept
	Swap with another instance.

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.

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_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.

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.

flag	flags () const noexcept
	The flags this handle was opened with.

native_handle_type	native_handle () const noexcept
	The native handle used by this handle.

Static Public Member Functions
static const process_handle &	current () noexcept

static result< process_handle >	launch_process (path_view path, span< path_view_component > args, span< path_view_component > env= *current().environment(), flag flags=flag::wait_on_close) noexcept

static result< process_handle >	launch_process (path_view path, span< path_view_component > args, flag flags=flag::wait_on_close) noexcept
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Static Protected Member Functions
static constexpr void	_set_caching (native_handle_type &nativeh, caching caching) noexcept

Protected Attributes
flag	_flags {flag::none}

pipe_handle	_in_pipe

pipe_handle	_out_pipe

pipe_handle	_error_pipe

native_handle_type	_v

Detailed Description

A handle to this, or another, process.

Member Enumeration Documentation

◆ caching

enum llfio_v2_xxx::handle::caching : unsigned char

stronginherited

What i/o on the handle may complete immediately due to kernel caching.

Enumerator
none	No caching whatsoever, all reads and writes come from storage (i.e. `O_DIRECT\|O_SYNC`). Align all i/o to 4Kb boundaries for this to work. `disable_safety_barriers` can be used here.
only_metadata	Cache reads and writes of metadata but avoid caching data (`O_DIRECT`), thus i/o here does not affect other cached data for other handles. Align all i/o to 4Kb boundaries for this to work.
reads	Cache reads only. Writes of data and metadata do not complete until reaching storage (`O_SYNC`). `disable_safety_barriers` can be used here.
reads_and_metadata	Cache reads and writes of metadata, but writes of data do not complete until reaching storage (`O_DSYNC`). `disable_safety_barriers` can be used here.
all	Cache reads and writes of data and metadata so they complete immediately, sending writes to storage at some point when the kernel decides (this is the default file system caching on a system).
safety_barriers	Cache reads and writes of data and metadata so they complete immediately, but issue safety barriers at certain points. See documentation for `disable_safety_barriers`.
temporary	Cache reads and writes of data and metadata so they complete immediately, only sending any updates to storage on last handle close in the system or if memory becomes tight as this file is expected to be temporary (Windows and FreeBSD only).

                      : unsigned char  // bit 0 set means safety barriers enabled
   {
     unchanged = 0,
     none = 1,                //!< No caching whatsoever, all reads and writes come from storage (i.e. <tt>O_DIRECT|O_SYNC</tt>). Align all i/o to 4Kb boundaries for this to work. <tt>disable_safety_barriers</tt> can be used here.
     only_metadata = 2,       //!< Cache reads and writes of metadata but avoid caching data (<tt>O_DIRECT</tt>), thus i/o here does not affect other cached data for other handles. Align all i/o to 4Kb boundaries for this to work.
     reads = 3,               //!< Cache reads only. Writes of data and metadata do not complete until reaching storage (<tt>O_SYNC</tt>). <tt>disable_safety_barriers</tt> can be used here.
     reads_and_metadata = 5,  //!< Cache reads and writes of metadata, but writes of data do not complete until reaching storage (<tt>O_DSYNC</tt>). <tt>disable_safety_barriers</tt> can be used here.
     all = 6,                 //!< Cache reads and writes of data and metadata so they complete immediately, sending writes to storage at some point when the kernel decides (this is the default file system caching on a system).
     safety_barriers = 7,     //!< Cache reads and writes of data and metadata so they complete immediately, but issue safety barriers at certain points. See documentation for <tt>disable_safety_barriers</tt>.
     temporary = 8            //!< Cache reads and writes of data and metadata so they complete immediately, only sending any updates to storage on last handle close in the system or if memory becomes tight as this file is expected to be temporary (Windows and FreeBSD only).
                              // NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!
   };

◆ creation

enum llfio_v2_xxx::handle::creation : unsigned char

stronginherited

On opening, do we also create a new file or truncate an existing one?

Enumerator
open_existing	Filesystem entry must already exist.
only_if_not_exist	Filesystem entry must NOT exist, and is atomically created by the success of this operation.
if_needed	If filesystem entry exists that is used, else one is created.
truncate_existing	Filesystem entry must already exist. It is atomically truncated on open, leaving creation date and unique identifier unmodified.
always_new	If filesystem entry exists, it is atomically replaced with a new inode, else a new entry is created.

                       : unsigned char
   {
     open_existing = 0,  //!< Filesystem entry must already exist
     only_if_not_exist,  //!< Filesystem entry must NOT exist, and is atomically created by the success of this operation
     if_needed,          //!< If filesystem entry exists that is used, else one is created
     truncate_existing,  //!< Filesystem entry must already exist. It is atomically truncated on open, leaving creation date and unique identifier unmodified.
     always_new          //!< If filesystem entry exists, it is atomically replaced with a new inode, else a new entry is created.
                         // NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!
   };

◆ mode

enum llfio_v2_xxx::handle::mode : unsigned char

stronginherited

The behaviour of the handle: does it read, read and write, or atomic append?

Enumerator
none	No ability to read or write anything, but can synchronise (SYNCHRONIZE or 0)
attr_read	Ability to read attributes (FILE_READ_ATTRIBUTES\|SYNCHRONIZE or O_RDONLY)
attr_write	Ability to read and write attributes (FILE_READ_ATTRIBUTES\|FILE_WRITE_ATTRIBUTES\|SYNCHRONIZE or O_RDONLY)
read	Ability to read (READ_CONTROL\|FILE_READ_DATA\|FILE_READ_ATTRIBUTES\|FILE_READ_EA\|SYNCHRONISE or O_RDONLY)
write	Ability to read and write (READ_CONTROL\|FILE_READ_DATA\|FILE_READ_ATTRIBUTES\|FILE_READ_EA\|FILE_WRITE_DATA\|FILE_WRITE_ATTRIBUTES\|FILE_WRITE_EA\|FILE_APPEND_DATA\|SYNCHRONISE or O_RDWR)
append	All mainstream OSs and CIFS guarantee this is atomic with respect to all other appenders (FILE_APPEND_DATA\|SYNCHRONISE or O_APPEND)

                   : unsigned char  // bit 0 set means writable
   {
     unchanged = 0,
     none = 2,        //!< No ability to read or write anything, but can synchronise (SYNCHRONIZE or 0)
     attr_read = 4,   //!< Ability to read attributes (FILE_READ_ATTRIBUTES|SYNCHRONIZE or O_RDONLY)
     attr_write = 5,  //!< Ability to read and write attributes (FILE_READ_ATTRIBUTES|FILE_WRITE_ATTRIBUTES|SYNCHRONIZE or O_RDONLY)
     read = 6,        //!< Ability to read (READ_CONTROL|FILE_READ_DATA|FILE_READ_ATTRIBUTES|FILE_READ_EA|SYNCHRONISE or O_RDONLY)
     write = 7,       //!< Ability to read and write (READ_CONTROL|FILE_READ_DATA|FILE_READ_ATTRIBUTES|FILE_READ_EA|FILE_WRITE_DATA|FILE_WRITE_ATTRIBUTES|FILE_WRITE_EA|FILE_APPEND_DATA|SYNCHRONISE or O_RDWR)
     append = 9       //!< All mainstream OSs and CIFS guarantee this is atomic with respect to all other appenders (FILE_APPEND_DATA|SYNCHRONISE or O_APPEND)
                      // NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!
   };

Member Function Documentation

◆ clone()

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

inlinenoexcept

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

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

◆ current()

static const process_handle& llfio_v2_xxx::process_handle::current ( )

inlinestaticnoexcept

Return a process handle referring to the current process.

◆ current_path()

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

inlineoverridevirtualnoexcept

Returns the current path of the binary the process is executing.

Note: If the current path cannot be retrieved on this platform (i.e. invariant to concurrent filesystem modification), an empty path is returned. This includes the current process.

Reimplemented from llfio_v2_xxx::handle.

◆ environment()

std::unique_ptr<span<path_view_component>, _byte_array_deleter> llfio_v2_xxx::process_handle::environment ( ) const

inlinenoexcept

Retrieves the current environment of the process.

Note: If the current environment cannot be retrieved on this platform, a null pointer is returned.

◆ error_pipe()

pipe_handle& llfio_v2_xxx::process_handle::error_pipe ( )

inlinenoexcept

A pipe with which one can read what another process writes to stderr, or by which this process can write to stderr.

138 { return _error_pipe; }

◆ in_pipe()

pipe_handle& llfio_v2_xxx::process_handle::in_pipe ( )

inlinenoexcept

A pipe with which one can read what another process writes to stdout, or by which this process can read from stdin. Therefore always read-only.

132 { return _in_pipe; }

◆ launch_process()

static result<process_handle> llfio_v2_xxx::process_handle::launch_process	(	path_view	path,
		span< path_view_component >	args,
		span< path_view_component >	env = `*current().environment()`,
		flag	flags = `flag::wait_on_close`
	)

inlinestaticnoexcept

Create a new process launching the binary at path.

Parameters

path	The absolute path to the binary to launch.
args	An array of arguments to pass to the process.
env	An array of environment variables to set for the process, which defaults to the current process' environment.
flags	Any additional custom behaviours.

This is the only handle creation function in LLFIO which requires an absolute path. This is because no platform implements race-free process launch, and worse, there is no way of non-intrusively emulating race-free process launch either. So we accept the inevitable, launching child processes is always racy with respect to concurrent filesystem modification.

Errors returnable\n Any of the values POSIX posix_spawn() or CreateProcess() can return.

◆ out_pipe()

pipe_handle& llfio_v2_xxx::process_handle::out_pipe ( )

inlinenoexcept

A pipe with which one can write what another process reads from stdin, or by which this process can write to stdout. Therefore always write-only.

144 { return _out_pipe; }

◆ QUICKCPPLIB_BITFIELD_BEGIN()

llfio_v2_xxx::process_handle::QUICKCPPLIB_BITFIELD_BEGIN ( flag )

inline

The behaviour of theprocess handle.

< No flags

< Do not redirect the stdin for a launched process

< Do not redirect the stdout for a launched process

< Do not redirect the stderr for a launched process

< Wait for the process to exit in .close()

< Release the pipes in .close(). They are closed otherwise.

< Do not create any redirected pipes as multiplexable

                                   {none = 0U,                          //!< No flags
                                    no_redirect_in_pipe = 1U << 1U,     //!< Do not redirect the `stdin` for a launched process
                                    no_redirect_out_pipe = 1U << 2U,    //!< Do not redirect the `stdout` for a launched process
                                    no_redirect_error_pipe = 1U << 3U,  //!< Do not redirect the `stderr` for a launched process
  
                                    wait_on_close = 1U << 4U,           //!< Wait for the process to exit in `.close()`
                                    release_pipes_on_close = 1U << 5U,  //!< Release the pipes in `.close()`. They are closed otherwise.
                                    no_multiplexable_pipes = 1U << 6U,  //!< Do not create any redirected pipes as multiplexable
  
                                    // NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!
                                    no_redirect = no_redirect_in_pipe | no_redirect_out_pipe | no_redirect_error_pipe} QUICKCPPLIB_BITFIELD_END(flag);

◆ set_append_only()

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

inlineoverridevirtualnoexcept

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 from llfio_v2_xxx::handle.

195 { return errc::operation_not_supported; }

◆ wait()

result<intptr_t> llfio_v2_xxx::process_handle::wait ( deadline d = {} ) const

inlinenoexcept

Waits until a process exits, returning its exit code.

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

include/llfio/v2.0/process_handle.hpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ caching

◆ creation

◆ mode

Member Function Documentation

◆ clone()

◆ current()

◆ current_path()

◆ environment()

◆ error_pipe()

◆ in_pipe()

◆ launch_process()

◆ out_pipe()

◆ QUICKCPPLIB_BITFIELD_BEGIN()

◆ set_append_only()

◆ wait()