sdl

package
v0.4.0 Latest Latest
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 Go to latest Published: Sep 2, 2026 License: Apache-2.0 Imports: 4 Imported by: 0

Documentation

Overview

Package sdl provides shared data link primitives used by both TM (tmdl) and TC (tcdl) Space Data Link Protocol implementations.

It contains generic channel buffers, multiplexers, service interfaces, and manager types that are parameterized by frame type, avoiding code duplication between the TM downlink and TC uplink packages.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrNoFramesAvailable indicates there are no frames to retrieve.
	ErrNoFramesAvailable = errors.New("no frames available")

	// ErrBufferFull indicates the channel buffer is full.
	ErrBufferFull = errors.New("channel buffer full")

	// ErrNoChannels indicates no channels are registered on the multiplexer.
	ErrNoChannels = errors.New("no channels registered")

	// ErrServiceNotFound indicates the requested service was not found.
	ErrServiceNotFound = errors.New("service not found for specified key")

	// ErrMasterChannelNotFound indicates the requested master channel was not found.
	ErrMasterChannelNotFound = errors.New("master channel not found for specified SCID")

	// ErrNoMasterChannels indicates no master channels are registered.
	ErrNoMasterChannels = errors.New("no master channels registered")
)

Functions

This section is empty.

Types

type Channel 

type Channel[F any] struct {
	ID uint8
	// contains filtered or unexported fields
}

Channel is a generic thread-safe FIFO frame buffer. F is the frame type (e.g., *TMTransferFrame or *TCTransferFrame).

func NewChannel 

func NewChannel[F any](id uint8, bufferSize int) *Channel[F]

NewChannel creates a new channel with the given ID and buffer capacity.

func (*Channel[F]) Add 

func (ch *Channel[F]) Add(f F) error

Add stores a new frame in the channel buffer.

func (*Channel[F]) HasFrames 

func (ch *Channel[F]) HasFrames() bool

HasFrames checks if there are frames available.

func (*Channel[F]) Len 

func (ch *Channel[F]) Len() int

Len returns the number of frames currently buffered.

func (*Channel[F]) Next 

func (ch *Channel[F]) Next() (F, error)

Next retrieves and removes the oldest frame from the buffer.

type Counter added in v0.3.0 

type Counter interface {
	~uint8 | ~uint16 | ~uint32 | ~uint64
}

Counter is a frame count field. The protocols use widths from eight bits (TM, TC) through twenty-four (AOS) up to USLP's managed maximum of fifty-six, carried in whichever unsigned type holds them.

type GapCounter added in v0.3.0 

type GapCounter[C Counter] struct {
	// contains filtered or unexported fields
}

GapCounter tracks one wrapping frame count and reports how many frames went missing between one it saw and the next. It is safe for concurrent use.

The zero value is not usable; construct with NewGapCounter, which needs the mask.

func NewGapCounter added in v0.3.0 

func NewGapCounter[C Counter](mask C) *GapCounter[C]

NewGapCounter returns a counter for a field of the given mask, which must be all ones up to the field width, 0xFF for eight bits, 0xFFFFFF for twenty-four, up to 0xFFFFFFFFFFFFFF for USLP's 56-bit maximum.

func (*GapCounter[C]) LastGap added in v0.3.0 

func (g *GapCounter[C]) LastGap() int

LastGap returns the gap reported by the most recent Track, across all channels.

func (*GapCounter[C]) Reset added in v0.3.0 

func (g *GapCounter[C]) Reset()

Reset forgets every channel, so the next frame on each is treated as a first frame again.

func (*GapCounter[C]) Track added in v0.3.0 

func (g *GapCounter[C]) Track(channel uint8, count C) int

Track records a frame count seen on a channel and returns the gap before it: how many frames are missing between the last one tracked on that channel and this one.

The first frame on a channel reports a gap of zero. There is nothing to compare it against, and reporting the distance from an assumed zero would invent a loss that did not happen. A receiver joining a pass in progress would report a gap of however far the counter had already run.

func (*GapCounter[C]) TrackWithCycle added in v0.3.0 

func (g *GapCounter[C]) TrackWithCycle(channel uint8, count C, cycle uint8, cycleMask uint8) int

TrackWithCycle records a frame count together with the cycle counter some protocols pair it with, and returns the gap before it. AOS is the one that needs this: when the VC frame count usage flag is set, the signaling field carries a four-bit VC frame count cycle that increments each time the 24-bit count wraps (CCSDS 732.0-B-4 4.1.2.5.5.3), and the pair behaves as one 28-bit count. cycleMask is the cycle field's width in the same all-ones form as the count mask: 0xF for AOS's four bits.

The combined count (cycle bits above the count bits) must fit in C. Do not mix Track and TrackWithCycle on the same channel: the two disagree about the modulus, so a gap computed across the switch would be wrong.

type MCMultiplexer 

type MCMultiplexer[F any] struct {
	// contains filtered or unexported fields
}

MCMultiplexer handles weighted round-robin scheduling across master channels, keyed by Spacecraft ID (uint16). A MCMultiplexer is safe for concurrent use.

func NewMCMultiplexer 

func NewMCMultiplexer[F any]() *MCMultiplexer[F]

NewMCMultiplexer creates a new master channel multiplexer.

func (*MCMultiplexer[F]) Add 

func (m *MCMultiplexer[F]) Add(mc MCSource[F], priority int)

Add registers a master channel with a priority weight. Priority must be at least 1; values below 1 are clamped to 1.

func (*MCMultiplexer[F]) HasPending 

func (m *MCMultiplexer[F]) HasPending() bool

HasPending checks if any master channel has pending frames.

func (*MCMultiplexer[F]) Len 

func (m *MCMultiplexer[F]) Len() int

Len returns the number of registered master channels.

func (*MCMultiplexer[F]) Next 

func (m *MCMultiplexer[F]) Next() (F, error)

Next selects the next frame for transmission using weighted round-robin.

type MCSource 

type MCSource[F any] interface {
	SCID() uint16
	GetNextFrame() (F, error)
	HasPendingFrames() bool
}

MCSource is the interface that master channels must implement to participate in physical-channel multiplexing.

type MasterChanneler 

type MasterChanneler[F any] interface {
	AddFrame(frame F) error
	GetNextFrame() (F, error)
	HasPendingFrames() bool
}

MasterChanneler is the interface that master channels must implement to be used with ServiceManager. F is the frame type.

type Multiplexer 

type Multiplexer[F any] struct {
	// contains filtered or unexported fields
}

Multiplexer handles frame scheduling from multiple channels using weighted round-robin. F is the frame type.

A Multiplexer is safe for concurrent use. Its own scheduling state (the cursor and the remaining weight) is guarded here; the channels it draws from carry their own locks.

func NewMultiplexer 

func NewMultiplexer[F any]() *Multiplexer[F]

NewMultiplexer initializes a new multiplexer.

func (*Multiplexer[F]) AddChannel 

func (mux *Multiplexer[F]) AddChannel(ch *Channel[F], priority int)

AddChannel registers a channel with a priority weight. Priority must be at least 1; values below 1 are clamped to 1.

func (*Multiplexer[F]) HasPending 

func (mux *Multiplexer[F]) HasPending() bool

HasPending checks if any channel has pending frames.

func (*Multiplexer[F]) Len 

func (mux *Multiplexer[F]) Len() int

Len returns the number of registered channels.

func (*Multiplexer[F]) Next 

func (mux *Multiplexer[F]) Next() (F, error)

Next selects the next frame for transmission based on weighted round-robin.

type PacketSizer 

type PacketSizer func(data []byte) int

PacketSizer returns the total length in bytes of the packet starting at data[0], or -1 if the data is too short to determine length. Used by packet services to find packet boundaries within frame data.

type Service 

type Service interface {
	Send(data []byte) error
	Receive() ([]byte, error)
	Flush() error
}

Service defines the interface for all Space Data Link services.

type ServiceManager 

type ServiceManager[S comparable, F any] struct {
	// contains filtered or unexported fields
}

ServiceManager manages services and master channels generically. S is the service type key, F is the frame type. A ServiceManager is safe for concurrent use.

func NewServiceManager 

func NewServiceManager[S comparable, F any]() *ServiceManager[S, F]

NewServiceManager creates a new ServiceManager.

func (*ServiceManager[S, F]) AddFrameToMasterChannel 

func (m *ServiceManager[S, F]) AddFrameToMasterChannel(scid uint16, frame F) error

AddFrameToMasterChannel routes a frame to the specified Master Channel.

func (*ServiceManager[S, F]) FlushService 

func (m *ServiceManager[S, F]) FlushService(vcid uint8, serviceType S) error

FlushService flushes the specified service.

func (*ServiceManager[S, F]) GetNextFrameFromMasterChannel 

func (m *ServiceManager[S, F]) GetNextFrameFromMasterChannel(scid uint16) (F, error)

GetNextFrameFromMasterChannel retrieves the next frame from the Master Channel's multiplexer.

func (*ServiceManager[S, F]) HasPendingFramesInMasterChannel 

func (m *ServiceManager[S, F]) HasPendingFramesInMasterChannel(scid uint16) bool

HasPendingFramesInMasterChannel checks if a Master Channel has pending frames.

func (*ServiceManager[S, F]) ReceiveData 

func (m *ServiceManager[S, F]) ReceiveData(vcid uint8, serviceType S) ([]byte, error)

ReceiveData receives data from the specified service type for a given VCID.

func (*ServiceManager[S, F]) RegisterMasterChannel 

func (m *ServiceManager[S, F]) RegisterMasterChannel(scid uint16, mc MasterChanneler[F])

RegisterMasterChannel registers a Master Channel.

func (*ServiceManager[S, F]) RegisterVirtualService 

func (m *ServiceManager[S, F]) RegisterVirtualService(vcid uint8, serviceType S, service Service)

RegisterVirtualService registers a service for a specific VCID and service type.

func (*ServiceManager[S, F]) SendData 

func (m *ServiceManager[S, F]) SendData(vcid uint8, serviceType S, data []byte) error

SendData sends data using the specified service type for a given VCID.

Source Files

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