/******************************************************************************
 * @brief 环形缓冲区管理(参考linux/kfifo)
 *
 * Copyright (c) 2016~2020, <morro_luo@163.com>
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs: 
 * Date Author Notes 
 * 2016年05月30日 Morro 初版完成
 ******************************************************************************/
#include "ringbuffer.h"
#include <string.h>
#include <stddef.h>

#define min(a,b) ( (a) < (b) )? (a):(b) 
 
/*
 *@brief 构造一个空环形缓冲区
 *@param[in] r - 环形缓冲区管理器
 *@param[in] buf - 数据缓冲区
 *@param[in] len - buf长度(必须是2的N次幂)
 *@retval bool
 */
bool ring_buf_init(ring_buf_t *r,unsigned char *buf, unsigned int len)
{
 r->buf = buf;
 r->size = len;
 r->front = r->rear = 0;
 return buf != NULL && (len & len -1) == 0;
}

/*
 *@brief 清空环形缓冲区 
 *@param[in] r - 待清空的环形缓冲区
 *@retval none
 */
void ring_buf_clr(ring_buf_t *r)
{
 r->front = r->rear = 0;
}

/*
 *@brief 获取环形缓冲区数据长度
 *@retval 环形缓冲区中有效字节数 
 */
unsigned int ring_buf_len(ring_buf_t *r)
{
 return r->rear - r->front;
}

/*
 *@brief 将指定长度的数据放到环形缓冲区中 
 *@param[in] buf - 数据缓冲区
 * len - 缓冲区长度 
 *@retval 实际放到中的数据 
 */
unsigned int ring_buf_put(ring_buf_t *r,unsigned char *buf,unsigned int len)
{
 unsigned int i;
 unsigned int left;
 left = r->size + r->front - r->rear;
 len = min(len , left);
 i = min(len, r->size - (r->rear & r->size - 1)); 
 memcpy(r->buf + (r->rear & r->size - 1), buf, i); 
 memcpy(r->buf, buf + i, len - i);
 r->rear += len; 
 return len;
 
}

/*
 *@brief 从环形缓冲区中读取指定长度的数据 
 *@param[in] len - 读取长度 
 *@param[out] buf - 输出数据缓冲区
 *@retval 实际读取长度 
 */
unsigned int ring_buf_get(ring_buf_t *r,unsigned char *buf,unsigned int len)
{
 unsigned int i;
 unsigned int left; 
 left = r->rear - r->front;
 len = min(len , left); 
 i = min(len, r->size - (r->front & r->size - 1));
 memcpy(buf, r->buf + (r->front & r->size - 1), i); 
 memcpy(buf + i, r->buf, len - i); 
 r->front += len;
 return len;
}