1 files changed, 108 insertions, 0 deletions
diff --git a/firmware/src/os/fifo.c b/firmware/src/os/fifo.c
new file mode 100644
index 0000000..b0ec152
--- /dev/null
+++ b/firmware/src/os/fifo.c
@@ -0,0 +1,108 @@
+/* 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;
+}
+