the null_file class implements the /dev/null behavior More...

#include <null_file.hpp>

Inheritance diagram for libdar::null_file:

Collaboration diagram for libdar::null_file:

Public Member Functions
	null_file (gf_mode m)

	null_file (const null_file &ref)=default

	null_file (null_file &&ref) noexcept=default

null_file &	operator= (const null_file &ref)=default

null_file &	operator= (null_file &&ref) noexcept=default

virtual bool	skippable (skippability direction, const infinint &amount) override
	whether the implementation is able to skip More...

virtual bool	skip (const infinint &pos) override
	skip at the absolute position More...

virtual bool	skip_to_eof () override
	skip to the end of file

virtual bool	skip_relative (signed int x) override

virtual bool	truncatable (const infinint &pos) const override
	whether the implementation is able to truncate to the given position

virtual infinint	get_position () const override
	get the current read/write position

Public Member Functions inherited from libdar::generic_file
	generic_file (gf_mode m)
	main constructor

	generic_file (const generic_file &ref)
	copy constructor

	generic_file (generic_file &&ref) noexcept
	move constructor

generic_file &	operator= (const generic_file &ref)
	assignment operator

generic_file &	operator= (generic_file &&ref) noexcept
	move operator

	~generic_file () noexcept(false)
	virtual destructor, More...

void	terminate ()
	destructor-like call, except that it is allowed to throw exceptions

bool	operator== (generic_file &ref)

bool	operator!= (generic_file &ref)

gf_mode	get_mode () const
	retreive the openning mode for this object

void	read_ahead (const infinint &amount)

void	ignore_read_ahead (bool mode)

virtual U_I	read (char *a, U_I size) override
	read data from the generic_file inherited from proto_generic_file

virtual void	write (const char *a, U_I size) override
	write data to the generic_file inherited from proto_generic_file

void	write (const std::string &arg)
	write a string to the generic_file More...

S_I	read_back (char &a)
	skip back one char, read on char and skip back one char

S_I	read_forward (char &a)
	read one char

virtual bool	skip_relative (S_I x)=0
	skip relatively to the current position

virtual void	truncate (const infinint &pos)
	truncate file at the given offset More...

virtual void	copy_to (generic_file &ref)
	copy all data from current position to the object in argument

virtual void	copy_to (generic_file &ref, const infinint &crc_size, crc *&value)
	copy all data from the current position to the object in argument and computes a CRC value of the transmitted data More...

U_32	copy_to (generic_file &ref, U_32 size)
	small copy (up to 4GB) with CRC calculation

infinint	copy_to (generic_file &ref, infinint size)
	copy the given amount to the object in argument

bool	diff (generic_file &f, const infinint &me_read_ahead, const infinint &you_read_ahead, const infinint &crc_size, crc *&value)
	compares the contents with the object in argument More...

bool	diff (generic_file &f, const infinint &me_read_ahead, const infinint &you_read_ahead, const infinint &crc_size, crc *&value, infinint &err_offset)

void	reset_crc (const infinint &width)
	reset CRC on read or writen data More...

bool	crc_status () const
	to known whether CRC calculation is activated or not

crc *	get_crc ()
	get CRC of the transfered date since last reset More...

void	sync_write ()
	write any pending data

void	flush_read ()
	be ready to read at current position, reseting all pending data for reading, cached and in compression engine for example

Public Member Functions inherited from libdar::proto_generic_file
	proto_generic_file (const proto_generic_file &ref)=default
	copy constructor

	proto_generic_file (proto_generic_file &&ref) noexcept=default
	move constructor

proto_generic_file &	operator= (const proto_generic_file &ref)=default
	assignment operator

proto_generic_file &	operator= (proto_generic_file &&ref) noexcept=default
	move operator

virtual	~proto_generic_file () noexcept(false)
	virtual destructor More...

Public Member Functions inherited from libdar::thread_cancellation
	thread_cancellation ()
	the constructor

	thread_cancellation (const thread_cancellation &ref)=default
	copy constructor

	thread_cancellation (thread_cancellation &&ref) noexcept=default
	move constructor

thread_cancellation &	operator= (const thread_cancellation &ref)=default
	assignment operator

thread_cancellation &	operator= (thread_cancellation &&ref) noexcept=default
	move operator

virtual	~thread_cancellation () noexcept(false)
	the destructor

void	check_self_cancellation () const
	Checkpoint test : whether the current libdar call must abort or not. More...

void	block_delayed_cancellation (bool mode)

Protected Member Functions
virtual void	inherited_read_ahead (const infinint &amount) override
	tells the object that several calls to read() will follow to probably obtain at least the given amount of data More...

virtual U_I	inherited_read (char *a, U_I size) override
	implementation of read() operation More...

virtual void	inherited_write (const char *a, U_I siz) override
	implementation of the write() operation More...

virtual void	inherited_truncate (const infinint &pos) override
	truncate file at the give offset More...

virtual void	inherited_sync_write () override
	write down any pending data More...

virtual void	inherited_flush_read () override
	reset internal engine, flush caches in order to read the data at current position More...

virtual void	inherited_terminate () override
	destructor-like call, except that it is allowed to throw exceptions More...

Protected Member Functions inherited from libdar::generic_file
void	set_mode (gf_mode x)

bool	is_terminated () const

Private Member Functions
void	set_offset (const infinint &x)

bool	set_rel_offset (signed int x)

Private Attributes
infinint	offset

infinint	max_offset

Additional Inherited Members
Public Types inherited from libdar::generic_file
enum	skippability { skip_backward , skip_forward }

Static Public Member Functions inherited from libdar::thread_cancellation
static U_I	count ()
	method for debugging/control purposes

Detailed Description

the null_file class implements the /dev/null behavior

this is a generic_file implementation that emulate the comportment of the /dev/null special file. all that is writen to is lost, and nothing can be read from it (empty file). This is a completed implementation all call are consistent.

Definition at line 49 of file null_file.hpp.

Member Function Documentation

◆ inherited_flush_read()

virtual void libdar::null_file::inherited_flush_read ( )

inlineoverrideprotectedvirtual

reset internal engine, flush caches in order to read the data at current position

Note: when the object relies on external object or system object to fetch the data from for reading, when a call to (inherited_)flush_read() occurs, the current object must not assume that any previously read data is still valid if it has internal buffers or the like and it should flush them asap. This call must not propagate the flush_read to any other gneric_file object it could rely on

Implements libdar::generic_file.

Definition at line 87 of file null_file.hpp.

◆ inherited_read()

virtual U_I libdar::null_file::inherited_read	(	char *	a,
		U_I	size
	)

inlineoverrideprotectedvirtual

implementation of read() operation

Parameters

[in,out]	a	where to put the data to read
[in]	size	says how much data to read

Returns: the exact amount of data read and put into 'a'

Note: read as much byte as requested, up to end of file stays blocked if not enough data is available and EOF not yet met. May return less data than requested only if EOF as been reached. in other worlds, EOF is reached when returned data is stricly less than the requested data Any problem shall be reported by throwing an exception.

Implements libdar::generic_file.

Definition at line 69 of file null_file.hpp.

References libdar::thread_cancellation::check_self_cancellation().

◆ inherited_read_ahead()

virtual void libdar::null_file::inherited_read_ahead ( const infinint & amount )

inlineoverrideprotectedvirtual

tells the object that several calls to read() will follow to probably obtain at least the given amount of data

Parameters

[in] amount is the maximum expected amount of data that is known to be read

Note: this call may be implemented as a do-nothing call, its presence is only to allow optimization when possible, like in multi-threaded environment

Implements libdar::generic_file.

Definition at line 67 of file null_file.hpp.

◆ inherited_sync_write()

virtual void libdar::null_file::inherited_sync_write ( )

inlineoverrideprotectedvirtual

write down any pending data

Note: called after sanity checks from generic_file::sync_write() this method's role is to write down any data pending for writing in the current object it has not to be propagated to other gneric_file object this object could rely on

Implements libdar::generic_file.

Definition at line 86 of file null_file.hpp.

◆ inherited_terminate()

virtual void libdar::null_file::inherited_terminate ( )

inlineoverrideprotectedvirtual

destructor-like call, except that it is allowed to throw exceptions

Note: this method must never be called directly but using terminate() instead, generic_file class manages it to never be called more than once

Implements libdar::generic_file.

Definition at line 88 of file null_file.hpp.

◆ inherited_truncate()

virtual void libdar::null_file::inherited_truncate ( const infinint & pos )

inlineoverrideprotectedvirtual

truncate file at the give offset

Note: if pos is greater than the current file size, this call may do nothing (not even enlarging the file); this call should always fail on a read-only generic_file; implementation must throw exception if truncate is not possible for other reason than read/write access mode

Implements libdar::generic_file.

Definition at line 85 of file null_file.hpp.

◆ inherited_write()

virtual void libdar::null_file::inherited_write	(	const char *	a,
		U_I	size
	)

inlineoverrideprotectedvirtual

implementation of the write() operation

Parameters

[in]	a	what data to write
[in]	size	amount of data to write

Note: must either write all data or report an error by throwing an exception

Implements libdar::generic_file.

Definition at line 77 of file null_file.hpp.

References libdar::thread_cancellation::check_self_cancellation().

◆ skip()

virtual bool libdar::null_file::skip ( const infinint & pos )

inlineoverridevirtual

skip at the absolute position

Parameters

[in] pos the offset in byte where next read/write operation must start

Returns: true if operation was successfull and false if the requested position is not valid (after end of file)

Note: if requested position is not valid the reading/writing cursor must be set to the closest valid position

Implements libdar::generic_file.

Definition at line 60 of file null_file.hpp.

◆ skippable()

virtual bool libdar::null_file::skippable	(	skippability	direction,
		const infinint &	amount
	)

inlineoverridevirtual

whether the implementation is able to skip

Note: the capability to skip does not mean that skip_relative() or skip() will succeed, but rather that the inherited class implementation does not by construction forbid the requested skip (like inherited class providing a generic_file interface of an anonymous pipe for example)

Implements libdar::generic_file.

Definition at line 59 of file null_file.hpp.

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

null_file.hpp

Public Member Functions

Protected Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ inherited_flush_read()

◆ inherited_read()

◆ inherited_read_ahead()

◆ inherited_sync_write()

◆ inherited_terminate()

◆ inherited_truncate()

◆ inherited_write()

◆ skip()

◆ skippable()