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// Copyright 2021 Nick Brassel (@tzarc)
// SPDX-License-Identifier: GPL-2.0-or-later
#include <stddef.h>
#include <timer.h>
#include <deferred_exec.h>
#ifndef MAX_DEFERRED_EXECUTORS
# define MAX_DEFERRED_EXECUTORS 8
#endif
typedef struct deferred_executor_t {
deferred_token token;
uint32_t trigger_time;
deferred_exec_callback callback;
void * cb_arg;
} deferred_executor_t;
static deferred_token current_token = 0;
static uint32_t last_deferred_exec_check = 0;
static deferred_executor_t executors[MAX_DEFERRED_EXECUTORS] = {0};
static inline bool token_can_be_used(deferred_token token) {
if (token == INVALID_DEFERRED_TOKEN) {
return false;
}
for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) {
if (executors[i].token == token) {
return false;
}
}
return true;
}
static inline deferred_token allocate_token(void) {
deferred_token first = ++current_token;
while (!token_can_be_used(current_token)) {
++current_token;
if (current_token == first) {
// If we've looped back around to the first, everything is already allocated (yikes!). Need to exit with a failure.
return INVALID_DEFERRED_TOKEN;
}
}
return current_token;
}
deferred_token defer_exec(uint32_t delay_ms, deferred_exec_callback callback, void *cb_arg) {
// Ignore queueing if it's a zero-time delay, or invalid callback
if (delay_ms == 0 || !callback) {
return INVALID_DEFERRED_TOKEN;
}
// Find an unused slot and claim it
for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) {
deferred_executor_t *entry = &executors[i];
if (entry->token == INVALID_DEFERRED_TOKEN) {
// Work out the new token value, dropping out if none were available
deferred_token token = allocate_token();
if (token == INVALID_DEFERRED_TOKEN) {
return false;
}
// Set up the executor table entry
entry->token = current_token;
entry->trigger_time = timer_read32() + delay_ms;
entry->callback = callback;
entry->cb_arg = cb_arg;
return current_token;
}
}
// None available
return INVALID_DEFERRED_TOKEN;
}
bool extend_deferred_exec(deferred_token token, uint32_t delay_ms) {
// Ignore queueing if it's a zero-time delay, or the token is not valid
if (delay_ms == 0 || token == INVALID_DEFERRED_TOKEN) {
return false;
}
// Find the entry corresponding to the token
for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) {
deferred_executor_t *entry = &executors[i];
if (entry->token == token) {
// Found it, extend the delay
entry->trigger_time = timer_read32() + delay_ms;
return true;
}
}
// Not found
return false;
}
bool cancel_deferred_exec(deferred_token token) {
// Ignore request if the token is not valid
if (token == INVALID_DEFERRED_TOKEN) {
return false;
}
// Find the entry corresponding to the token
for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) {
deferred_executor_t *entry = &executors[i];
if (entry->token == token) {
// Found it, cancel and clear the table entry
entry->token = INVALID_DEFERRED_TOKEN;
entry->trigger_time = 0;
entry->callback = NULL;
entry->cb_arg = NULL;
return true;
}
}
// Not found
return false;
}
void deferred_exec_task(void) {
uint32_t now = timer_read32();
// Throttle only once per millisecond
if (((int32_t)TIMER_DIFF_32(now, last_deferred_exec_check)) > 0) {
last_deferred_exec_check = now;
// Run through each of the executors
for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) {
deferred_executor_t *entry = &executors[i];
// Check if we're supposed to execute this entry
if (entry->token != INVALID_DEFERRED_TOKEN && ((int32_t)TIMER_DIFF_32(entry->trigger_time, now)) <= 0) {
// Invoke the callback and work work out if we should be requeued
uint32_t delay_ms = entry->callback(entry->trigger_time, entry->cb_arg);
// Update the trigger time if we have to repeat, otherwise clear it out
if (delay_ms > 0) {
// Intentionally add just the delay to the existing trigger time -- this ensures the next
// invocation is with respect to the previous trigger, rather than when it got to execution. Under
// normal circumstances this won't cause issue, but if another executor is invoked that takes a
// considerable length of time, then this ensures best-effort timing between invocations.
entry->trigger_time += delay_ms;
} else {
// If it was zero, then the callback is cancelling repeated execution. Free up the slot.
entry->token = INVALID_DEFERRED_TOKEN;
entry->trigger_time = 0;
entry->callback = NULL;
entry->cb_arg = NULL;
}
}
}
}
}
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