/*
 * File      : ringbuffer.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2012, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rt-thread.org/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2012-09-30     Bernard      first version.
 */

#include <rtthread.h>
#include <rtdevice.h>
#include <string.h>

void rt_ringbuffer_init(struct rt_ringbuffer* rb, rt_uint8_t *pool, rt_uint16_t size)
{
	RT_ASSERT(rb != RT_NULL);

	/* initialize read and write index */
	rb->read_index = rb->write_index = 0;

	/* set buffer pool and size */
	rb->buffer_ptr = pool;
	rb->buffer_size = RT_ALIGN_DOWN(size, RT_ALIGN_SIZE);
}
RTM_EXPORT(rt_ringbuffer_init);

rt_size_t rt_ringbuffer_put(struct rt_ringbuffer* rb, const rt_uint8_t *ptr, rt_uint16_t length)
{
	rt_uint16_t size;
	rt_uint16_t mask;
	rt_uint16_t write_position;
	
	RT_ASSERT(rb != RT_NULL);

	mask = rb->buffer_size - 1;
	/* whether has enough space */
	size = rb->buffer_size - (rb->write_index - rb->read_index);

	/* no space */
	if (size == 0) return 0;
	/* drop some data */
	if (size < length) length = size;

	write_position = (rb->write_index & mask);
	if (rb->buffer_size - write_position> length)
	{
		/* read_index - write_index = empty space */
		memcpy(&rb->buffer_ptr[write_position], ptr, length);
	}
	else
	{
		memcpy(&rb->buffer_ptr[write_position], ptr, rb->buffer_size - write_position);
		memcpy(&rb->buffer_ptr[0], &ptr[rb->buffer_size - write_position],
				length - (rb->buffer_size - write_position));
	}
	rb->write_index += length;

	return length;
}
RTM_EXPORT(rt_ringbuffer_put);

/**
 * put a character into ring buffer
 */
rt_size_t rt_ringbuffer_putchar(struct rt_ringbuffer* rb, const rt_uint8_t ch)
{
	rt_uint16_t mask;

	RT_ASSERT(rb != RT_NULL);
	/* whether has enough space */
	mask = rb->buffer_size - 1;
	
	/* whether has enough space */
	if (rb->write_index - rb->read_index == rb->buffer_size) return 0;

	/* put character */
	rb->buffer_ptr[rb->write_index & mask] = ch;
	rb->write_index += 1;

	return 1;
}
RTM_EXPORT(rt_ringbuffer_putchar);

/**
 *  get data from ring buffer
 */
rt_size_t rt_ringbuffer_get(struct rt_ringbuffer* rb, rt_uint8_t *ptr, rt_uint16_t length)
{
	rt_size_t size;
	rt_uint16_t mask;
	rt_uint16_t read_position;

	RT_ASSERT(rb != RT_NULL);
	/* whether has enough data  */
	mask = rb->buffer_size - 1;
	size = rb->write_index - rb->read_index;

	/* no data */
	if (size == 0) return 0;
	/* less data */
	if (size < length) length = size;

	read_position = rb->read_index & mask;
	if (rb->buffer_size - read_position >= length)
	{
		/* copy all of data */
		memcpy(ptr, &rb->buffer_ptr[read_position], length);
	}
	else
	{
		/* copy first and second */
		memcpy(ptr, &rb->buffer_ptr[read_position], rb->buffer_size - read_position);
		memcpy(&ptr[rb->buffer_size - read_position], &rb->buffer_ptr[0],
			   length - rb->buffer_size + read_position);
	}
	rb->read_index += length;

	return length;
}
RTM_EXPORT(rt_ringbuffer_get);

/**
 * get a character from a ringbuffer
 */
rt_size_t rt_ringbuffer_getchar(struct rt_ringbuffer* rb, rt_uint8_t *ch)
{
	rt_uint16_t mask;

	RT_ASSERT(rb != RT_NULL);
	
	/* ringbuffer is empty */
	if (rb->read_index == rb->write_index) return 0;

	mask = rb->buffer_size - 1;

	/* put character */
	*ch = rb->buffer_ptr[rb->read_index & mask];
	rb->read_index += 1;

	return 1;
}
RTM_EXPORT(rt_ringbuffer_getchar);