Detailed Description

Find packet boundaries in a raw CCSDS-SPP byte-stream.

See also: ccsds_spp.h, ccsds_spp::PacketizerStatic, ccsds_spp::Dispatch.

This helper object finds CCSDS-SPP packet boundaries in an incoming byte-stream. The byte-stream can be written directly to this object, or passively pulled from any Readable source. In either case, delimited SPP frames are available by reading from this object. Reads are backed by an internal buffer.

Note that SPP provides few mechanisms for detecting errors. Packet desynchronization is resolved using a timeout (default one second) that discards any trailing data. If more robust error-detection is required, please consider using the CCSDS AOS space data-link protocol

See also: ccsds_aos.h.

Definition at line 98 of file ccsds_spp.h.

#include <ccsds_spp.h>

Inheritance diagram for satcat5::ccsds_spp::Packetizer:

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Collaboration diagram for satcat5::ccsds_spp::Packetizer:

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Public Member Functions
satcat5::io::Writeable *	bypass ()
	Direct write-access to the internal buffer.

satcat5::io::Writeable *	packet ()
	Write-access with CCSDS-SPP packetization.

satcat5::io::EventListener *	listen ()
	Access the event-listener used for read/pull mode.

satcat5::io::Counter &	counter ()
	Access the internal statistics counters.

void	flush ()
	Reset partial packets and synchronization state. More...

void	reset ()
	Full reset of buffer and synchronization state. More...

void	set_timeout (unsigned timeout_msec)
	If sync is lost, rely on idle periods to resync.

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

void	set_callback (satcat5::io::EventListener *callback) override
	Update registered callback for data_rcvd() events. 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().

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

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

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

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

virtual void	write_abort ()
	If possible, abort the current partially-written packet. 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;`

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

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

Protected Member Functions
	Packetizer (u8 buff, unsigned rxbytes, unsigned rxpkt, satcat5::io::Readable src=nullptr)
	Child class must provide a working buffer. More...

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

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

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...

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

Protected Attributes
satcat5::io::BufferedCopy	m_copy
	Push-pull adapter.

satcat5::io::PacketBuffer	m_buff
	Output buffer.

unsigned	m_rem
	Bytes remaining in current packet.

unsigned	m_timeout
	User-configurable resync timeout.

u8	m_wridx
	Packet header write pointer.

u16	m_sreg
	Packet header working buffer.

friend	LimitedWrite

friend	WriteableBroadcast

friend	WriteableRedirect

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

unsigned	m_trem

unsigned	m_tnext

Constructor & Destructor Documentation

◆ Packetizer()

Packetizer::Packetizer	(	u8 *	buff,
		unsigned	rxbytes,
		unsigned	rxpkt,
		satcat5::io::Readable *	src = `nullptr`
	)

protected

Child class must provide a working buffer.

Child class may provide a Readable source or null.

Definition at line 43 of file ccsds_spp.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.

◆ flush()

void Packetizer::flush ( )

Reset partial packets and synchronization state.

Discards incomplete partials, but retains complete packets.

Definition at line 59 of file ccsds_spp.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 Packetizer::get_write_space ( ) const

overridevirtual

How many bytes can be written without blocking?

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

Implements satcat5::io::Writeable.

Definition at line 55 of file ccsds_spp.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.

◆ reset()

void Packetizer::reset ( )

Full reset of buffer and synchronization state.

Discards ALL buffer contents, including complete packets.

Definition at line 67 of file ccsds_spp.cc.

◆ set_callback()

void ReadableRedirect::set_callback ( satcat5::io::EventListener * callback )

overridevirtualinherited

Update registered callback for data_rcvd() events.

Child objects of io::Readable SHOULD usually leave this method as-is.

Reimplemented from satcat5::io::Readable.

Definition at line 331 of file io_readable.cc.

◆ write_abort()

void Writeable::write_abort ( )

virtualinherited

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 in satcat5::port::Mailmap, satcat5::io::PacketBuffer, satcat5::io::MultiWriter, satcat5::io::WriteableRedirect, satcat5::io::ArrayWrite, satcat5::io::CounterInline, satcat5::io::ChecksumRxCommon, satcat5::io::ChecksumTxCommon, satcat5::io::WriteableBroadcast, satcat5::eth::SwitchPort, satcat5::io::HdlcEncoder::ByteStuff, and satcat5::io::FileWriter.

Definition at line 186 of file io_writeable.cc.

◆ write_bytes()

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

virtualinherited

Write 0 or more bytes from a buffer.

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

Reimplemented in satcat5::port::MailmapAligned, satcat5::port::Mailmap, satcat5::io::PacketBuffer, satcat5::io::MultiWriter, satcat5::io::MultiPacket::Overwriter, satcat5::io::NullWrite, satcat5::io::WriteableRedirect, satcat5::io::LimitedWrite, satcat5::io::CounterInline, satcat5::io::WriteableBroadcast, and satcat5::io::FileWriter.

Definition at line 170 of file io_writeable.cc.

◆ write_finalize()

bool Writeable::write_finalize ( )

virtualinherited

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 in satcat5::port::Mailmap, satcat5::io::PacketBuffer, satcat5::io::MultiWriterBypass, satcat5::io::MultiWriter, satcat5::io::WriteableRedirect, satcat5::io::ArrayWrite, satcat5::io::WriteableThrottle, satcat5::io::CounterInline, satcat5::io::WriteableBroadcastAny, satcat5::io::WriteableBroadcast, satcat5::eth::SwitchPort, satcat5::eth::ChecksumRx, satcat5::eth::ChecksumTx, satcat5::crc16::XmodemRx, satcat5::crc16::XmodemTx, satcat5::crc16::KermitRx, satcat5::crc16::KermitTx, satcat5::io::SlipEncoder, satcat5::io::HdlcEncoder::ByteStuff, satcat5::io::CobsEncoder, satcat5::coap::Connection, satcat5::test::EthernetInterface, satcat5::io::BufferedTee, satcat5::io::WritePcapInterface, satcat5::io::WritePcap, satcat5::io::FileWriter, and satcat5::util::ChatPrinter.

Definition at line 185 of file io_writeable.cc.

◆ write_next()

void Packetizer::write_next ( u8 data )

overrideprotectedvirtual

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 77 of file ccsds_spp.cc.

◆ write_overflow()

void Writeable::write_overflow ( )

protectedvirtualinherited

Optional error handling for write overflow.

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

Reimplemented in satcat5::port::Mailmap, satcat5::io::PacketBuffer, satcat5::io::MultiWriter, satcat5::io::WriteableRedirect, satcat5::io::ArrayWrite, satcat5::io::ChecksumTxCommon, satcat5::io::WriteableBroadcast, satcat5::io::SlipDecoder, satcat5::io::SlipEncoder, satcat5::io::HdlcDecoder, satcat5::io::CobsDecoder, and satcat5::io::CobsEncoder.

Definition at line 187 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

Protected Attributes

Private Member Functions

Private Attributes

Constructor & Destructor Documentation

◆ Packetizer()

Member Function Documentation

◆ copy_and_finalize()

◆ copy_to()

◆ flush()

◆ get_read_ready()

◆ get_write_space()

◆ read_bytes()

◆ read_consume()

◆ read_finalize()

◆ read_next()

◆ read_notify()

◆ read_str()

◆ read_u8()

◆ read_underflow()

◆ request_poll()

◆ reset()

◆ set_callback()

◆ write_abort()

◆ write_bytes()

◆ write_finalize()

◆ write_next()

◆ write_overflow()

◆ write_str()

◆ write_u8()

Member Data Documentation

◆ m_callback