edge_ring.c File Reference

The tap's edge words and their ring. More...

#include "edge_ring.h"
#include <string.h>

Macros
#define	HALF   (1u << (EDGE_COUNT_BITS - 1u))
	Half the counter range: the limit of a wrap-safe distance.

Functions
uint32_t	edge_word (uint32_t count, bool level)
	The word the program pushes for an edge at counter value count.
uint32_t	edge_word_count (uint32_t word)
	A word's 31-bit count and level.
bool	edge_word_level (uint32_t word)
	The word's level after the edge.
uint64_t	edge_tick (uint32_t count, uint64_t est)
	The tick of the counter value count nearest est, with a counter that started at 0 and counts down.
void	edge_ring_init (edge_ring_t *r)
	Start reading a ring from slot 0, as after the DMA channel restarts.
size_t	edge_ring_take (edge_ring_t *r, const uint32_t *ring, uint32_t size, uint32_t wr, uint64_t est, tone_edge_t *out, size_t max, bool *overrun)
	Take the words in ring ( size words, a power of two) written since the last call, wr being the slot the DMA writes next, as edges stamped against est (the present tick, edge_tick()).

Detailed Description

The tap's edge words and their ring.

See edge_ring.h.

SPDX-License-Identifier: MIT

Function Documentation

edge_ring_init()

void edge_ring_init

(

edge_ring_t *

r

)

Start reading a ring from slot 0, as after the DMA channel restarts.

The ring holds only zero words at that moment, so a lap before the first read shows as a word in its last slot.

Parameters

r	Reader state to initialise.

edge_ring_take()

size_t edge_ring_take	(	edge_ring_t *	r,
		const uint32_t *	ring,
		uint32_t	size,
		uint32_t	wr,
		uint64_t	est,
		tone_edge_t *	out,
		size_t	max,
		bool *	overrun )

Take the words in ring ( size words, a power of two) written since the last call, wr being the slot the DMA writes next, as edges stamped against est (the present tick, edge_tick()).

At most max edges go to out; words past that stay in the ring for the next call.

Returns the edges written. *overrun is set when the DMA lapped the reader: nothing is returned, the reader is moved after the newest word, and the caller ends the beep under way (tone_flush()).

Parameters

r	Reader state.
ring	Ring of edge words.
size	Ring size in words, a power of two.
wr	Slot the DMA writes next.
est	Estimate of the present tick.
out	Receives the edges.
max	Most edges taken in this call.
overrun	Set to true when the DMA lapped the reader; may be NULL.

Returns

Number of edges written to out.

edge_tick()

uint64_t edge_tick	(	uint32_t	count,
		uint64_t	est )

The tick of the counter value count nearest est, with a counter that started at 0 and counts down.

Ticks before the start do not exist: the result is at least 0.

Parameters

count	Counter value of the edge, 31 bits.
est	Estimate of the present tick.

Returns

The 64-bit tick of the edge.

edge_word()

uint32_t edge_word	(	uint32_t	count,
		bool	level )

The word the program pushes for an edge at counter value count.

Parameters

count	Counter value at the edge; the low 31 bits are used.
level	Level after the edge: true for a rise.

Returns

The edge word.

edge_word_count()

uint32_t edge_word_count

(

uint32_t

word

)

A word's 31-bit count and level.

Parameters

word	Edge word.

Returns

The count, 0 to 2^31 - 1.

edge_word_level()

bool edge_word_level

(

uint32_t

word

)

The word's level after the edge.

Parameters

word	Edge word.

Returns

true for a rise.