llfio_v2_xxx::process_handle Class Reference

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
enum	bitfield__flag : unsigned {   none = 0U , no_redirect_in_pipe = 1U << 1U , no_redirect_out_pipe = 1U << 2U , no_redirect_error_pipe = 1U << 3U ,   wait_on_close = 1U << 4U , release_pipes_on_close = 1U << 5U , no_multiplexable_pipes = 1U << 6U , no_redirect = no_redirect_in_pipe | no_redirect_out_pipe | no_redirect_error_pipe }
	The behaviour of theprocess handle. More...
using	path_type = handle::path_type
using	extent_type = handle::extent_type
using	size_type = handle::size_type
enum class	mode : unsigned char {   unchanged = 0 , none = 2 , attr_read = 4 , attr_write = 5 ,   read = 6 , write , append = 9 }
	The behaviour of the handle: does it read, read and write, or atomic append? More...
enum class	creation : unsigned char {   open_existing = 0 , only_if_not_exist , if_needed , truncate_existing ,   always_new }
	On opening, do we also create a new file or truncate an existing one? More...
enum class	caching : unsigned char {   unchanged = 0 , none , only_metadata , reads ,   reads_and_metadata , all , safety_barriers , temporary }
	What i/o on the handle may complete immediately due to kernel caching. More...

Public Member Functions
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.
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
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 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_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 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.

Protected Attributes
flag	_flags {flag::none}
pipe_handle	_in_pipe
pipe_handle	_out_pipe
pipe_handle	_error_pipe
union {
native_handle_type   _v
struct {
intptr_t   _padding0_
uint32_t   _padding1_
flag   flags
uint16_t   _padding2_
}   _
};

Detailed Description

A handle to this, or another, process.

Member Enumeration Documentation

bitfield__flag

enum llfio_v2_xxx::process_handle::bitfield__flag : unsigned

The behaviour of theprocess handle.

Enumerator
none	No flags.
no_redirect_in_pipe	Do not redirect the stdin for a launched process.
no_redirect_out_pipe	Do not redirect the stdout for a launched process.
no_redirect_error_pipe	Do not redirect the stderr for a launched process.
wait_on_close	Wait for the process to exit in .close()
release_pipes_on_close	Release the pipes in .close(). They are closed otherwise.
no_multiplexable_pipes	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)

caching

enum class 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).

  {
    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 class 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.

  {
    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 class 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)

  {
    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!!!
  };

Constructor & Destructor Documentation

process_handle() [1/4]

constexpr llfio_v2_xxx::process_handle::process_handle ( )

inlineconstexpr

Default constructor.

{}  // NOLINT

process_handle() [2/4]

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

inlineexplicitconstexprnoexcept

Construct a handle from a supplied native handle.

      : handle(std::move(h))
      , _flags(flags)
  {
  }

process_handle() [3/4]

constexpr llfio_v2_xxx::process_handle::process_handle ( handle &&  o, flag  flags = flag::none  )

inlineexplicitconstexprnoexcept

Explicit conversion from handle permitted.

      : handle(std::move(o))
      , _flags(flags)
  {
  }

~process_handle()

virtual llfio_v2_xxx::process_handle::~process_handle ( )

inlineoverridevirtual

  {
    (void) close_pipes();
    if(_v)
    {
      (void) process_handle::close();
      _v = {};
    }
  }

process_handle() [4/4]

constexpr llfio_v2_xxx::process_handle::process_handle ( process_handle &&  o )

inlineconstexprnoexcept

Move the handle.

      : handle(std::move(o))
      , _flags(o._flags)
      , _in_pipe(std::move(o._in_pipe))
      , _out_pipe(std::move(o._out_pipe))
      , _error_pipe(std::move(o._error_pipe))
  {
  }

Member Function Documentation

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); }

clone()

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

noexcept

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

Errors returnable

Any of the values POSIX dup() or DuplicateHandle() can return.

close()

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

overridevirtualnoexcept

Immediately close this handle, possibly closing the pipes, possibly blocking until a child process exits.

Reimplemented from llfio_v2_xxx::handle.

close_pipes()

result< void > llfio_v2_xxx::process_handle::close_pipes ( )

inlinenoexcept

Close or release all the pipes, depending on flag::release_pipes_on_close

  {
    if(!(_.flags & flag::release_pipes_on_close))
    {
      // Close the other's side's write pipes first, as closing its
      // read pipe may cause it to immediately exit
      if(_in_pipe.is_valid())
      {
        OUTCOME_TRY(_in_pipe.close());
      }
      if(_error_pipe.is_valid())
      {
        OUTCOME_TRY(_error_pipe.close());
      }
      if(_out_pipe.is_valid())
      {
        OUTCOME_TRY(_out_pipe.close());
      }
    }
    else
    {
      _in_pipe.release();
      _error_pipe.release();
      _out_pipe.release();
    }
    return success();
  }

current()

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

staticnoexcept

Return a process handle referring to the current process.

current_path()

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

overridevirtualnoexcept

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

noexcept

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() [1/2]

const pipe_handle & llfio_v2_xxx::process_handle::error_pipe ( ) const

inlinenoexcept

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

{ return _error_pipe; }

error_pipe() [2/2]

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.

{ return _error_pipe; }

flags()

flag llfio_v2_xxx::handle::flags ( ) const

inlinenoexceptinherited

The flags this handle was opened with.

{ return _.flags; }

in_pipe() [1/2]

const pipe_handle & llfio_v2_xxx::process_handle::in_pipe ( ) const

inlinenoexcept

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

{ return _in_pipe; }

in_pipe() [2/2]

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.

{ return _in_pipe; }

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;
  }

launch_process() [1/2]

static result< process_handle > llfio_v2_xxx::process_handle::launch_process ( path_view  path, span< path_view_component >  args, flag  flags = flag::wait_on_close  )

inlinestaticnoexcept

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

{ return launch_process(path, args, *current().environment(), flags); }

launch_process() [2/2]

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  )

staticnoexcept

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

Any of the values POSIX posix_spawn() or CreateProcess() can return.

native_handle()

native_handle_type llfio_v2_xxx::handle::native_handle ( ) const

inlinenoexceptinherited

The native handle used by this handle.

{ return _v; }

operator=()

process_handle & llfio_v2_xxx::process_handle::operator= ( process_handle &&  o )

inlinenoexcept

Move assignment of handle.

  {
    if(this == &o)
    {
      return *this;
    }
    this->~process_handle();
    new(this) process_handle(std::move(o));
    return *this;
  }

out_pipe() [1/2]

const pipe_handle & llfio_v2_xxx::process_handle::out_pipe ( ) const

inlinenoexcept

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

{ return _out_pipe; }

out_pipe() [2/2]

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.

{ return _out_pipe; }

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::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

Whatever POSIX fcntl() returns. On Windows nothing is changed on the handle.

Memory Allocations

No memory allocation.

Reimplemented from llfio_v2_xxx::handle.

{ return errc::operation_not_supported; }

swap() [1/2]

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);
  }

swap() [2/2]

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

inlinenoexcept

Swap with another instance.

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

try_wait()

template<class... Args>

bool llfio_v2_xxx::process_handle::try_wait ( Args &&...  args )

inlinenoexcept

try_wait_for()

template<class... Args, class Rep , class Period >

bool llfio_v2_xxx::process_handle::try_wait_for ( Args &&...  args, const std::chrono::duration< Rep, Period > &  duration  )

inlinenoexcept

try_wait_until()

template<class... Args, class Clock , class Duration >

bool llfio_v2_xxx::process_handle::try_wait_until ( Args &&...  args, const std::chrono::time_point< Clock, Duration > &  timeout  )

inlinenoexcept

wait()

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

noexcept

Waits until a process exits, returning its exit code.

Member Data Documentation

_flags

flag llfio_v2_xxx::process_handle::_flags {flag::none}

protected

{flag::none};

---

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

• include/llfio/v2.0/process_handle.hpp