/**
* \file
*   Ring Buffer library
*/

#include "mqtt/ringbuf.h"


/**
* \brief init a RINGBUF object
* \param r pointer to a RINGBUF object
* \param buf pointer to a byte array
* \param size size of buf
* \return 0 if successfull, otherwise failed
*/
I16 ICACHE_FLASH_ATTR RINGBUF_Init(RINGBUF *r, U8* buf, I32 size)
{
  if (r == NULL || buf == NULL || size < 2) return -1;

  r->p_o = r->p_r = r->p_w = buf;
  r->fill_cnt = 0;
  r->size = size;

  return 0;
}
/**
* \brief put a character into ring buffer
* \param r pointer to a ringbuf object
* \param c character to be put
* \return 0 if successfull, otherwise failed
*/
I16 ICACHE_FLASH_ATTR RINGBUF_Put(RINGBUF *r, U8 c)
{
  if (r->fill_cnt >= r->size)return -1; // ring buffer is full, this should be atomic operation


  r->fill_cnt++;              // increase filled slots count, this should be atomic operation


  *r->p_w++ = c;              // put character into buffer

  if (r->p_w >= r->p_o + r->size)     // rollback if write pointer go pass
    r->p_w = r->p_o;          // the physical boundary

  return 0;
}
/**
* \brief get a character from ring buffer
* \param r pointer to a ringbuf object
* \param c read character
* \return 0 if successfull, otherwise failed
*/
I16 ICACHE_FLASH_ATTR RINGBUF_Get(RINGBUF *r, U8* c)
{
  if (r->fill_cnt <= 0)return -1;     // ring buffer is empty, this should be atomic operation


  r->fill_cnt--;                // decrease filled slots count


  *c = *r->p_r++;               // get the character out

  if (r->p_r >= r->p_o + r->size)       // rollback if write pointer go pass
    r->p_r = r->p_o;            // the physical boundary

  return 0;
}