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/* Implementation of a virtual FIFO */
#include "fifo.h"
#include <errno.h>
#include <string.h>
#define FIFO_IRQ_LO 0x01
#define FIFO_IRQ_HI 0x02
#define FIFO_IRQ_OFLOW 0x04
/* returns number of data bytes present in the fifo */
int fifo_available(struct fifo *fifo)
{
if (fifo->producer > fifo->consumer)
return fifo->producer - fifo->consumer;
else
return (fifo->size - fifo->consumer) + fifo->producer;
}
void fifo_check_water(struct fifo *fifo)
{
int avail = fifo_available(fifo);
if (avail <= fifo->watermark)
fifo->irq |= FIFO_IRQ_LO;
else
fifo->irq &= FIFO_IRQ_LO;
if (fifo->size - avail >= fifo->watermark)
fifo->irq |= FIFO_IRQ_HI;
else
fifo->irq &= FIFO_IRQ_HI;
}
void fifo_check_raise_int(struct fifo *fifo)
{
if (fifo->irq & fifo->irq_en)
fifo->callback(fifo, fifo->irq, fifo->cb_data);
}
u_int16_t fifo_data_put(struct fifo *fifo, u_int16_t len, u_int8_t *data)
{
if (len > fifo_available(fifo)) {
len = fifo_available(fifo);
fifo->irq |= FIFO_IRQ_OFLOW;
}
if (len + fifo->producer <= fifo->size) {
/* easy case */
memcpy(&fifo->data[fifo->producer], data, len);
fifo->producer += len;
} else {
/* difficult: wrap around */
u_int16_t chunk_len;
chunk_len = fifo->size - fifo->producer;
memcpy(&fifo->data[fifo->producer], data, chunk_len);
memcpy(&fifo->data[0], data + chunk_len, len - chunk_len);
fifo->producer = len - chunk_len;
}
fifo_check_water(fifo);
return len;
}
u_int16_t fifo_data_get(struct fifo *fifo, u_int16_t len, u_int8_t *data)
{
u_int16_t avail = fifo_available(fifo);
if (avail < len)
len = avail;
if (fifo->producer > fifo->consumer) {
/* easy case */
memcpy(data, &fifo->data[fifo->consumer], len);
} else {
/* difficult case: wrap */
u_int16_t chunk_len = fifo->size - fifo->consumer;
memcpy(data, &fifo->data[fifo->consumer], chunk_len);
memcpy(data+chunk_len, &fifo->data[0], len - chunk_len);
}
fifo_check_water(fifo);
return len;
}
int fifo_init(struct fifo *fifo, u_int16_t size,
void (*cb)(struct fifo *fifo, u_int8_t event, void *data), void *cb_data)
{
if (size > sizeof(fifo->data))
return -EINVAL;
memset(fifo->data, 0, sizeof(fifo->data));
fifo->size = size;
fifo->producer = fifo->consumer = 0;
fifo->watermark = 0;
fifo->callback = cb;
fifo->cb_data = cb_data;
return 0;
}
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