Mask Update API

CCSDS Section 4: Mask vector update equations. More...

Functions
void	ccsds124_update_build (bitvector_t *build, const bitvector_t *input, const bitvector_t *prev_input, int new_mask_flag, size_t t)
	Update build vector (CCSDS Equation 6).
void	ccsds124_update_mask (bitvector_t *mask, const bitvector_t *input, const bitvector_t *prev_input, const bitvector_t *build_prev, int new_mask_flag)
	Update mask vector (CCSDS Equation 7).
void	ccsds124_compute_change (bitvector_t *change, const bitvector_t *mask, const bitvector_t *prev_mask, size_t t)
	Compute change vector (CCSDS Equation 8).

Detailed Description

CCSDS Section 4: Mask vector update equations.

These functions implement the core mask prediction logic that identifies which bits are predictable vs. unpredictable.

Function Documentation

ccsds124_compute_change()

void ccsds124_compute_change	(	bitvector_t *	change,
		const bitvector_t *	mask,
		const bitvector_t *	prev_mask,
		size_t	t
	)

Compute change vector (CCSDS Equation 8).

Dₜ = Mₜ XOR Mₜ₋₁. The caller sets prev_mask = mask before calling at t=0 so that D₀ = 0 (no change at initialization).

Parameters

[out]	change	Change vector Dₜ
[in]	mask	Current mask Mₜ
[in]	prev_mask	Previous mask Mₜ₋₁
[in]	t	Time index (unused, kept for API compatibility)

Definition at line 125 of file mask.c.

References bitvector_xor().

Referenced by ccsds124_compress_packet().

ccsds124_update_build()

void ccsds124_update_build	(	bitvector_t *	build,
		const bitvector_t *	input,
		const bitvector_t *	prev_input,
		int	new_mask_flag,
		size_t	t
	)

Update build vector (CCSDS Equation 6).

The build vector accumulates XOR differences between consecutive packets to track which bits have changed.

Parameters

[out]	build	Updated build vector Bₜ
[in]	input	Current input Iₜ
[in]	prev_input	Previous input Iₜ₋₁
[in]	new_mask_flag	ṗₜ flag (1 = reset build)
[in]	t	Time index (0 = first packet)

Definition at line 43 of file mask.c.

References bitvector_init(), bitvector_or(), bitvector_xor(), bitvector_zero(), and bitvector::length.

Referenced by ccsds124_compress_packet().

ccsds124_update_mask()

void ccsds124_update_mask	(	bitvector_t *	mask,
		const bitvector_t *	input,
		const bitvector_t *	prev_input,
		const bitvector_t *	build_prev,
		int	new_mask_flag
	)

Update mask vector (CCSDS Equation 7).

The mask vector identifies unpredictable bits (1 = unpredictable).

Parameters

[out]	mask	Updated mask vector Mₜ
[in]	input	Current input Iₜ
[in]	prev_input	Previous input Iₜ₋₁
[in]	build_prev	Previous build vector Bₜ₋₁
[in]	new_mask_flag	ṗₜ flag (1 = update from build)

Definition at line 85 of file mask.c.

References bitvector_init(), bitvector_or(), bitvector_xor(), and bitvector::length.

Referenced by ccsds124_compress_packet().