tabs/kernel/util/fifo.c
2020-01-09 12:06:45 +01:00

60 lines
No EOL
1.3 KiB
C

#ifndef UTIL_FIFO_C
#define UTIL_FIFO_C
#define FIFO_INITIAL_SIZE 128
#define FIFO_QUEUE_EMPTY -1
#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>
#include "../memory.c"
typedef struct fifo_struct {
int num_elems;
int max_elems;
uint8_t* head;
uint8_t* curr_elem;
} fifo;
fifo* fifo_new() {
fifo* ret = alloc(sizeof(fifo));
void* head = alloc(sizeof(uint8_t) * FIFO_INITIAL_SIZE);
ret->num_elems = 0;
ret->max_elems = FIFO_INITIAL_SIZE;
ret->head = head;
ret->curr_elem = head;
return ret;
}
void fifo_optimize(fifo* queue) {
if (queue->head == queue->curr_elem) {
// resize, not implemented yet (blocked by reallocarray)
} else {
// move all items to the beginning of the list
for(int i = 0; i < queue->num_elems; i++) {
queue->head[i] = queue->curr_elem[i];
}
queue->curr_elem = queue->head;
}
}
void fifo_enqueue(fifo* queue, uint8_t value) {
if (queue->num_elems == queue->max_elems) {
fifo_optimize(queue);
}
queue->curr_elem[queue->num_elems] = value;
queue->num_elems++;
}
int16_t fifo_dequeue(fifo* queue) {
if (queue->num_elems <= 0) {
return FIFO_QUEUE_EMPTY;
}
uint8_t ret = queue->curr_elem[0];
queue->curr_elem++;
queue->num_elems--;
return ret;
}
#endif //UTIL_FIFO_C