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struct rt_ringbuffer
{
    rt_uint8_t *buffer_ptr;
    rt_uint16_t read_mirror : 1;
    rt_uint16_t read_index : 15;
    rt_uint16_t write_mirror : 1;
    rt_uint16_t write_index : 15;
    rt_int16_t buffer_size;
};

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void rt_ringbuffer_init(struct rt_ringbuffer *rb,
                        rt_uint8_t           *pool,
                        rt_int16_t            size)
{
    RT_ASSERT(rb != RT_NULL);
    RT_ASSERT(size > 0);

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

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

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/**
 * @brief Put a block of data into the ring buffer. If the capacity of ring buffer is insufficient, it will discard out-of-range data.
 *
 * @param rb            A pointer to the ring buffer object.
 * @param ptr           A pointer to the data buffer.
 * @param length        The size of data in bytes.
 *
 * @return Return the data size we put into the ring buffer.
 */
rt_size_t rt_ringbuffer_put(struct rt_ringbuffer *rb,
                            const rt_uint8_t     *ptr,
                            rt_uint16_t           length)
{
    rt_uint16_t size;

    RT_ASSERT(rb != RT_NULL);

    /* whether has enough space */
    size = rt_ringbuffer_space_len(rb);

    /* no space */
    if (size == 0)
        return 0;

    /* drop some data */
    if (size < length)
        length = size;

    if (rb->buffer_size - rb->write_index > length)
    {
        /* read_index - write_index = empty space */
        rt_memcpy(&rb->buffer_ptr[rb->write_index], ptr, length);
        /* this should not cause overflow because there is enough space for
         * length of data in current mirror */
        rb->write_index += length;
        return length;
    }

    rt_memcpy(&rb->buffer_ptr[rb->write_index],
           &ptr[0],
           rb->buffer_size - rb->write_index);
    rt_memcpy(&rb->buffer_ptr[0],
           &ptr[rb->buffer_size - rb->write_index],
           length - (rb->buffer_size - rb->write_index));

    /* we are going into the other side of the mirror */
    rb->write_mirror = ~rb->write_mirror;
    rb->write_index = length - (rb->buffer_size - rb->write_index);

    return length;
}
RTM_EXPORT(rt_ringbuffer_put);

/**
 * @brief Put a block of data into the ring buffer. If the capacity of ring buffer is insufficient, it will overwrite the existing data in the ring buffer.
 *
 * @param rb            A pointer to the ring buffer object.
 * @param ptr           A pointer to the data buffer.
 * @param length        The size of data in bytes.
 *
 * @return Return the data size we put into the ring buffer.
 */
rt_size_t rt_ringbuffer_put_force(struct rt_ringbuffer *rb,
                            const rt_uint8_t     *ptr,
                            rt_uint16_t           length)
{
    rt_uint16_t space_length;

    RT_ASSERT(rb != RT_NULL);

    space_length = rt_ringbuffer_space_len(rb);

    if (length > rb->buffer_size)
    {
        ptr = &ptr[length - rb->buffer_size];
        length = rb->buffer_size;
    }

    if (rb->buffer_size - rb->write_index > length)
    {
        /* read_index - write_index = empty space */
        rt_memcpy(&rb->buffer_ptr[rb->write_index], ptr, length);
        /* this should not cause overflow because there is enough space for
         * length of data in current mirror */
        rb->write_index += length;

        if (length > space_length)
            rb->read_index = rb->write_index;

        return length;
    }

    rt_memcpy(&rb->buffer_ptr[rb->write_index],
           &ptr[0],
           rb->buffer_size - rb->write_index);
    rt_memcpy(&rb->buffer_ptr[0],
           &ptr[rb->buffer_size - rb->write_index],
           length - (rb->buffer_size - rb->write_index));

    /* we are going into the other side of the mirror */
    rb->write_mirror = ~rb->write_mirror;
    rb->write_index = length - (rb->buffer_size - rb->write_index);

    if (length > space_length)
    {
        if (rb->write_index <= rb->read_index)
            rb->read_mirror = ~rb->read_mirror;
        rb->read_index = rb->write_index;
    }

    return length;
}
RTM_EXPORT(rt_ringbuffer_put_force);

/**
 * @brief Get data from the ring buffer.
 *
 * @param rb            A pointer to the ring buffer.
 * @param ptr           A pointer to the data buffer.
 * @param length        The size of the data we want to read from the ring buffer.
 *
 * @return Return the data size we read from the 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_ASSERT(rb != RT_NULL);

    /* whether has enough data  */
    size = rt_ringbuffer_data_len(rb);

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

    /* less data */
    if (size < length)
        length = size;

    if (rb->buffer_size - rb->read_index > length)
    {
        /* copy all of data */
        rt_memcpy(ptr, &rb->buffer_ptr[rb->read_index], length);
        /* this should not cause overflow because there is enough space for
         * length of data in current mirror */
        rb->read_index += length;
        return length;
    }

    rt_memcpy(&ptr[0],
           &rb->buffer_ptr[rb->read_index],
           rb->buffer_size - rb->read_index);
    rt_memcpy(&ptr[rb->buffer_size - rb->read_index],
           &rb->buffer_ptr[0],
           length - (rb->buffer_size - rb->read_index));

    /* we are going into the other side of the mirror */
    rb->read_mirror = ~rb->read_mirror;
    rb->read_index = length - (rb->buffer_size - rb->read_index);

    return length;
}
RTM_EXPORT(rt_ringbuffer_get);

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rt_inline enum rt_ringbuffer_state rt_ringbuffer_status(struct rt_ringbuffer *rb)
{
    if (rb->read_index == rb->write_index)
    {
        if (rb->read_mirror == rb->write_mirror)
            return RT_RINGBUFFER_EMPTY;
        else
            return RT_RINGBUFFER_FULL;
    }
    return RT_RINGBUFFER_HALFFULL;
}

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struct kfifo {
 unsigned char *buffer; /* the buffer holding the data */
 unsigned int size; /* the size of the allocated buffer */
 unsigned int in; /* data is added at offset (in % size) */
 unsigned int out; /* data is extracted from off. (out % size) */
 spinlock_t *lock; /* protects concurrent modifications */
};

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struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
    int gfp_mask, spinlock_t *lock)
{
 struct kfifo *fifo;

 /* size must be a power of 2 */
 BUG_ON(size & (size - 1));

 fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
 if (!fifo)
  return ERR_PTR(-ENOMEM);

 fifo->buffer = buffer;
 fifo->size = size;
 fifo->in = fifo->out = 0;
 fifo->lock = lock;

 return fifo;
}

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/*
 * __kfifo_put - puts some data into the FIFO, no locking version
 * @fifo: the fifo to be used.
 * @buffer: the data to be added.
 * @len: the length of the data to be added.
 *
 * This function copies at most 'len' bytes from the 'buffer' into
 * the FIFO depending on the free space, and returns the number of
 * bytes copied.
 *
 * Note that with only one concurrent reader and one concurrent
 * writer, you don't need extra locking to use these functions.
 */
unsigned int __kfifo_put(struct kfifo *fifo,
    unsigned char *buffer, unsigned int len)
{
 unsigned int l;

 len = min(len, fifo->size - fifo->in + fifo->out);

 /* first put the data starting from fifo->in to buffer end */
 l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
 memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);

 /* then put the rest (if any) at the beginning of the buffer */
 memcpy(fifo->buffer, buffer + l, len - l);

 fifo->in += len;

 return len;
}
EXPORT_SYMBOL(__kfifo_put);

unsigned int __kfifo_get(struct kfifo *fifo,
    unsigned char *buffer, unsigned int len)
{
 unsigned int l;

 len = min(len, fifo->in - fifo->out);

 /* first get the data from fifo->out until the end of the buffer */
 l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
 memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);

 /* then get the rest (if any) from the beginning of the buffer */
 memcpy(buffer + l, fifo->buffer, len - l);

 fifo->out += len;

 return len;
}
EXPORT_SYMBOL(__kfifo_get);

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static inline unsigned int __kfifo_len(struct kfifo *fifo)
{
 return fifo->in - fifo->out;
}

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struct __kfifo {
 unsigned int in;
 unsigned int out;
 unsigned int mask;
 unsigned int esize;
 void  *data;
};