Detailed Description

Remote-control override of an I/O device.

For any I/O device with a io::Readable / io::Writeable interface, this class allows automatic switching between normal passthrough operation and remote control by another device. While in remote control mode, passthrough commands are blocked.

The io::Override object is attached to the I/O device on creation. From that point, users should not access the I/O device directly. Instead, read and write calls pass through the io::Override object to the underlying I/O device.

cfg::Uart my_uart(&cfgbus, 123);        // Example UART object
io::Override local(&my_uart, &my_uart); // Attach override
local.write_str("Local data");          // Passthrough to UART
local.write_finalize();                 // Passthrough to UART
if (local.get_read_ready()) {...}       // Passthrough to UART

The remote-control interface is attached later. Any buffered I/O stream can be used, such as io::PacketBuffer or net::Tpipe.

Remote-control mode is activated whenever data appears in the remote-control buffer, or by direct call to set_override. Once the object is in remote mode, the remote interface has exclusive control. Local passthrough calls are blocked, and received data is copied to the remote interface buffer.

io::PacketBufferHeap remote;            // Remote control
local.set_remote(&remote, &remote);     // Attach remote
local.write_str("In normal mode, local data is accepted.");
local.write_finalize();                 // Accepted
remote.write_str("Remote data activates override mode.");
remote.write_finalize();                // Accepted
local.write_str("In remote mode, local data is blocked.");
local.write_finalize();                 // Blocked

The system returns to normal operation after a period of inactivity (default 30 seconds) or by another direct call to set_override.

Definition at line 54 of file io_override.h.

#include <io_override.h>

Inheritance diagram for satcat5::io::Override:

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Collaboration diagram for satcat5::io::Override:

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Public Member Functions
	Override (satcat5::io::Writeable dst, satcat5::io::Readable src, satcat5::io::CopyMode mode=CopyMode::PACKET)
	Attach to the underlying I/O device. More...

void	set_callback (satcat5::io::EventListener *callback) override
	Override set_callback() to set the internal variable only.

bool	is_remote () const
	Is this block in local or remote mode?

void	set_override (bool remote)
	Manually set local or remote mode.

void	set_remote (satcat5::io::Writeable tx, satcat5::io::Readable rx)
	Attach the remote-control interface.

void	set_timeout (unsigned msec)
	Set timeout for automatic return to local mode. More...

unsigned	get_read_ready () const override
	How many bytes can be read without blocking? More...

bool	read_bytes (unsigned nbytes, void *dst) override
	Read 0 or more bytes into a buffer. More...

bool	read_consume (unsigned nbytes) override
	Read and discard 0 or more bytes. More...

void	read_finalize () override
	Consume any remaining bytes in this frame, if applicable. More...

u8	read_u8 ()
	One of many functions for reading integer/floating point values, see details. More...

unsigned	read_str (unsigned dst_size, char *dst)
	Safely read a null-terminated input string. More...

template<class T >
bool	read_obj (T &t)
	Templated wrapper for any object with the following method: `bool read_from(satcat5::io::Readable* rd);`

unsigned	copy_to (satcat5::io::Writeable *dst)
	Copy data to a Writeable object, without finalizing. More...

bool	copy_and_finalize (satcat5::io::Writeable *dst, satcat5::io::CopyMode mode=CopyMode::PACKET)
	Copy data to a Writeable object, then finalize. More...

void	request_poll ()
	Call this method to request polling at a later time. More...

void	request_cancel ()
	Call this method to cancel a previous request_poll().

unsigned	get_write_space () const override
	How many bytes can be written without blocking? More...

void	write_abort () override
	If possible, abort the current partially-written packet. More...

void	write_bytes (unsigned nbytes, const void *src) override
	Write 0 or more bytes from a buffer. More...

bool	write_finalize () override
	Mark end of frame and release temporary working data. More...

void	write_u8 (u8 data)
	One of many functions for writing integer/floating point values, see details. More...

void	write_str (const char *str)
	Write the contents of a null-terminated string. More...

template<class T >
void	write_obj (const T &obj)
	Templated wrapper for any object with the following method: `void write_to(satcat5::io::Writeable* wr) const;`

Static Public Member Functions
static unsigned	count_ondemand ()
	Count queued objects of this type (i.e., non-idle).

Protected Member Functions
void	data_rcvd (satcat5::io::Readable *src) override
	The data_rcvd() callback is polled whenever data is available. More...

void	data_unlink (satcat5::io::Readable *src) override
	Unlink this EventListener from the designated source, because the designated Readable object is being destroyed. More...

void	timer_event () override
	Child class MUST override this method.

void	watchdog_reset ()

u8	read_next () override
	Read the next byte from the underlying buffer or device. More...

void	read_underflow () override
	Optional error handling for read underflow. More...

void	read_src (satcat5::io::Readable *src)
	Children may reset the source object as needed.

void	read_notify ()
	Attempt notification by calling `m_callback->data_rcvd()`. More...

void	write_next (u8 data) override
	Write the next byte to the underlying buffer or device. More...

void	write_overflow () override
	Optional error handling for write overflow. More...

void	write_dst (satcat5::io::Writeable *dst)

void	timer_once (unsigned msec)
	Configure a one-time notification after X milliseconds.

void	timer_every (unsigned msec)
	Configure a repeating notification every X milliseconds.

void	timer_stop ()
	Stop all future notifications.

unsigned	timer_interval () const
	Accessor for recurring timer interval, if one is set.

unsigned	timer_remaining () const
	Accessor for time to next event, if one is set.

Static Protected Member Functions
static unsigned	count_timer ()
	Count all objects of this type, including idle timers.

Protected Attributes
satcat5::io::Readable *	m_dev_rd

satcat5::io::Readable *	m_ovr_rd

satcat5::io::Writeable *	m_dev_wr

satcat5::io::Writeable *	m_ovr_wr

const satcat5::io::CopyMode	m_mode

bool	m_remote

unsigned	m_timeout

friend	WriteableRedirect

friend	LimitedWrite

friend	WriteableBroadcast

Private Member Functions
void	poll_demand ()
	Event handler for on-demand polling.

void	query (unsigned elapsed_msec)

Private Attributes
satcat5::io::Readable *	m_src

satcat5::io::EventListener *	m_callback
	Pointer to the callback object, or NULL. More...

satcat5::poll::OnDemand *	m_next

bool	m_idle

satcat5::io::Writeable *	m_dst

unsigned	m_trem

unsigned	m_tnext

Constructor & Destructor Documentation

◆ Override()

Override::Override	(	satcat5::io::Writeable *	dst,
		satcat5::io::Readable *	src,
		satcat5::io::CopyMode	mode = `CopyMode::PACKET`
	)

Attach to the underlying I/O device.

Parameters

src	Data source to be read.
dst	Destination to be written.
mode	Set data-streaming mode.

Definition at line 13 of file io_override.cc.

Member Function Documentation

◆ copy_and_finalize()

bool Readable::copy_and_finalize	(	satcat5::io::Writeable *	dst,
		satcat5::io::CopyMode	mode = `CopyMode::PACKET`
	)

inherited

Copy data to a Writeable object, then finalize.

As copy_to(), but also calls read_finalize() and/or write_finalize() depending on the input/output mode.

In packet mode (the default), call both read_finalize() and write_finalize() if the operation copies all available data. Use this mode whenever the input is packetized.

In byte-stream mode, call write_finalize() if the operation copies any data, but never call read_finalize(). Use this mode for inputs that do not delimit packet boundaries.

Parameters

dst	The destination object.
mode	Select packet mode or stream mode.

Returns: True if the output was finalized successfully.

Definition at line 234 of file io_readable.cc.

◆ copy_to()

unsigned Readable::copy_to ( satcat5::io::Writeable * dst )

inherited

Copy data to a Writeable object, without finalizing.

Copy the contents of this Readable to a Writeable object, stopping at end-of-input, end-of-frame, or the capacity of the destination buffer (whichever comes first). This method does not call read_finalize or write_finalize(). To automatically make finalize calls,

See also: copy_and_finalize.

Returns: The number of bytes copied.

Definition at line 214 of file io_readable.cc.

◆ data_rcvd()

void Override::data_rcvd ( satcat5::io::Readable * src )

overrideprotectedvirtual

The data_rcvd() callback is polled whenever data is available.

A pointer is provided to assist handlers with multiple sources. Child objects of io::EventListener MUST override this method.

Implements satcat5::io::EventListener.

Definition at line 62 of file io_override.cc.

◆ data_unlink()

void Override::data_unlink ( satcat5::io::Readable * src )

overrideprotectedvirtual

Unlink this EventListener from the designated source, because the designated Readable object is being destroyed.

Child objects of io::EventListener MAY override this method if action is required.

Reimplemented from satcat5::io::EventListener.

Definition at line 76 of file io_override.cc.

◆ get_read_ready()

unsigned ReadableRedirect::get_read_ready ( ) const

overridevirtualinherited

How many bytes can be read without blocking?

Child objects of io::Readable MUST override this method.

Implements satcat5::io::Readable.

Definition at line 336 of file io_readable.cc.

◆ get_write_space()

unsigned WriteableRedirect::get_write_space ( ) const

overridevirtualinherited

How many bytes can be written without blocking?

Child objects of io::Writeable MUST override this method.

Implements satcat5::io::Writeable.

Definition at line 236 of file io_writeable.cc.

◆ read_bytes()

bool ReadableRedirect::read_bytes	(	unsigned	nbytes,
		void *	dst
	)

overridevirtualinherited

Read 0 or more bytes into a buffer.

Child objects of io::Readable MAY override this method for improved performance.

Reimplemented from satcat5::io::Readable.

Definition at line 339 of file io_readable.cc.

◆ read_consume()

bool ReadableRedirect::read_consume ( unsigned nbytes )

overridevirtualinherited

Read and discard 0 or more bytes.

Child objects of io::Readable MAY override this method for improved performance.

Reimplemented from satcat5::io::Readable.

Definition at line 342 of file io_readable.cc.

◆ read_finalize()

void ReadableRedirect::read_finalize ( )

overridevirtualinherited

Consume any remaining bytes in this frame, if applicable.

Child objects of io::Readable SHOULD override this method if they support framing.

Reimplemented from satcat5::io::Readable.

Definition at line 345 of file io_readable.cc.

◆ read_next()

u8 ReadableRedirect::read_next ( )

overrideprotectedvirtualinherited

Read the next byte from the underlying buffer or device.

Child objects of io::Readable MUST override this method.

Implements satcat5::io::Readable.

Definition at line 348 of file io_readable.cc.

◆ read_notify()

void Readable::read_notify ( )

protectedinherited

Attempt notification by calling m_callback->data_rcvd().

Child objects of io::Readable MAY call this to override default notifications.

Definition at line 254 of file io_readable.cc.

◆ read_str()

unsigned Readable::read_str	(	unsigned	dst_size,
		char *	dst
	)

inherited

Safely read a null-terminated input string.

The input is always consumed up to the end-of-input or the first zero byte, whichever comes first.

Returns: The length of the output string, which may be truncated as needed to fit in the provided buffer.

Definition at line 179 of file io_readable.cc.

◆ read_u8()

u8 Readable::read_u8 ( )

inherited

One of many functions for reading integer/floating point values, see details.

Several functions are provided for reading and writing scalar types to/from io::Readable and io::Writeable instances. Since there are many of these that are frequently inherited, they are hidden from documentation. These functions follow a shared template:

read_ or write_ prefix.
u for unsigned, s for signed, f for floating-point.
Data-type width in bits.
- Available widths for ints: 8/16/24/32/48/64.
- Available widths for floats: 32/64.
l suffix if little-endian, no suffix if big-endian.

Example: write_s48l is "Write 48 bits (6 bytes) to this io::Writeable as a signed value in little-endian order".

Definition at line 44 of file io_readable.cc.

◆ read_underflow()

void ReadableRedirect::read_underflow ( )

overrideprotectedvirtualinherited

Optional error handling for read underflow.

Child objects of io::Readable MAY override this method.

Reimplemented from satcat5::io::Readable.

Definition at line 351 of file io_readable.cc.

◆ request_poll()

void satcat5::poll::OnDemand::request_poll ( )

inherited

Call this method to request polling at a later time.

Safe to stack requests, but only one call to poll().

Definition at line 208 of file polling.cc.

◆ set_timeout()

void Override::set_timeout ( unsigned msec )

Set timeout for automatic return to local mode.

A timeout of zero disables this function.

Definition at line 56 of file io_override.cc.

◆ write_abort()

void WriteableRedirect::write_abort ( )

overridevirtualinherited

If possible, abort the current partially-written packet.

Child objects of io::Writeable SHOULD override this method if it is practical to prevent in-progress data from being relayed downstream.

Reimplemented from satcat5::io::Writeable.

Definition at line 239 of file io_writeable.cc.

◆ write_bytes()

void WriteableRedirect::write_bytes	(	unsigned	nbytes,
		const void *	src
	)

overridevirtualinherited

Write 0 or more bytes from a buffer.

Child objects of io::Writeable MAY override write_bytes as needed for performance.

Reimplemented from satcat5::io::Writeable.

Definition at line 242 of file io_writeable.cc.

◆ write_finalize()

bool WriteableRedirect::write_finalize ( )

overridevirtualinherited

Mark end of frame and release temporary working data.

Child objects of io::Writeable SHOULD override this method to mark frame bounds.

Returns: True if successful, false on error.

Reimplemented from satcat5::io::Writeable.

Definition at line 245 of file io_writeable.cc.

◆ write_next()

void WriteableRedirect::write_next ( u8 data )

overrideprotectedvirtualinherited

Write the next byte to the underlying buffer or device.

Child objects of io::Writeable MUST override this method.

Implements satcat5::io::Writeable.

Definition at line 248 of file io_writeable.cc.

◆ write_overflow()

void WriteableRedirect::write_overflow ( )

overrideprotectedvirtualinherited

Optional error handling for write overflow.

Child objects of io::Writeable MAY override this method for error handling.

Reimplemented from satcat5::io::Writeable.

Definition at line 251 of file io_writeable.cc.

◆ write_str()

void Writeable::write_str ( const char * str )

inherited

Write the contents of a null-terminated string.

Note: Null-termination is not copied to the output.

Definition at line 180 of file io_writeable.cc.

◆ write_u8()

void Writeable::write_u8 ( u8 data )

inherited

One of many functions for writing integer/floating point values, see details.

Several functions are provided for reading and writing scalar types to/from io::Readable and io::Writeable instances. Since there are many of these that are frequently inherited, they are hidden from documentation. These functions follow a shared template:

read_ or write_ prefix.
u for unsigned, s for signed, f for floating-point.
Data-type width in bits.
- Available widths for ints: 8/16/24/32/48/64.
- Available widths for floats: 32/64.
l suffix if little-endian, no suffix if big-endian.

Example: write_s48l is "Write 48 bits (6 bytes) to this io::Writeable as a signed value in little-endian order".

Definition at line 20 of file io_writeable.cc.

Member Data Documentation

◆ m_callback

satcat5::io::EventListener* satcat5::io::Readable::m_callback

privateinherited

Pointer to the callback object, or NULL.

This can only be modified through the set_callback(...) method.

Definition at line 199 of file io_readable.h.

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

Detailed Description

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Private Member Functions

Private Attributes

Constructor & Destructor Documentation

◆ Override()

Member Function Documentation

◆ copy_and_finalize()

◆ copy_to()

◆ data_rcvd()

◆ data_unlink()

◆ get_read_ready()

◆ get_write_space()

◆ read_bytes()

◆ read_consume()

◆ read_finalize()

◆ read_next()

◆ read_notify()

◆ read_str()

◆ read_u8()

◆ read_underflow()

◆ request_poll()

◆ set_timeout()

◆ write_abort()

◆ write_bytes()

◆ write_finalize()

◆ write_next()

◆ write_overflow()

◆ write_str()

◆ write_u8()

Member Data Documentation

◆ m_callback