环形缓冲区算法

1万 · 2024-11-15 13:04

在嵌入式开发中离不开设备通信，而在通信中稳定性最高的莫过于环形缓冲区算法，当读取速度大于写入速度时，在环形缓冲区的支持下不会丢掉任何一个字节(硬件问题除外)。下面我分享一段由我原创的Ringbuffer代码。

C文件：

/**
  ******************************************************************************
  * @file cx_ringbuff.c
  * @author  CX
  * @version V1.0.0.2
  * @date 2016-07-13
  * @brief 1.0.0.2 期望帧逻辑优化
         修改匹配期望帧任务的条件
         增加匹配期望帧函数
         1.0.0.1 优化耦合性
         优化读取逻辑
         增加多缓冲区支持
      1.0.0.0 主体架构搭建，完成读写环形结构化
  ******************************************************************************
  * @Attention
  *
  * 项目：None
  * 官网 : None
  * 实验室：None
  *
  ******************************************************************************
  */

#include "cx_ringbuff.h"

/* 除了必须的缓冲区外没有向外部模块公开一个变量，实现高内聚，低耦合 */
RingBuff_Typedef  RingBuffStruct;

/**
* @brief 缓冲区实例化
* @param rb_ptr 缓冲区结构体地址
* @retval  None
* @notice  None
*/
void RingBuff_New(RingBuff_Typedef* rb_ptr)
{
rb_ptr->Readpos = rb_ptr->RxBuff;
rb_ptr->Writepos = rb_ptr->RxBuff;
rb_ptr->ReadRetStateStruct.Readstate = Fail;
rb_ptr->ReadRetStateStruct.ptr = NULL;
rb_ptr->RingbufCount = 0;
memset(rb_ptr->RxBuff, 0, MaxBuffSize);
}

/**
  * @brief 定位函数
  * @param rb_ptr 缓冲区结构体地址,addr 当前读写地址
  * @retval  addr+1 or 0
  * @notice  None
  */
unsigned char* NextDataAddrHandle(RingBuff_Typedef* rb_ptr, unsigned char* addr)
{
return (addr + 1) == (rb_ptr->RxBuff + MaxBuffSize) ? rb_ptr->RxBuff : (addr + 1);
}

/**
  * @brief 读字节函数
  * @param rb_ptr 缓冲区结构体地址
  * @retval  data
  * @notice  None
  */
ReadRetState_Typedef* ReadDataFromRingbuff(RingBuff_Typedef* rb_ptr)
{
if (rb_ptr->RingbufCount > 0)
{
      rb_ptr->ReadRetStateStruct.ptr = rb_ptr->Readpos;
      rb_ptr->ReadRetStateStruct.Readstate = Success;
      rb_ptr->Readpos = NextDataAddrHandle(rb_ptr, rb_ptr->Readpos);
      rb_ptr->RingbufCount--;
      return &rb_ptr->ReadRetStateStruct;
}
rb_ptr->ReadRetStateStruct.Readstate = Fail;
rb_ptr->ReadRetStateStruct.ptr = NULL;
return &rb_ptr->ReadRetStateStruct;
}

/**
  * @brief 写字节函数
  * @param rb_ptr 缓冲区结构体地址,data 写入数据
  * @retval  None
  * @notice  None
  */
void WriteDataToRingbuff(RingBuff_Typedef* rb_ptr, unsigned char data)
{
*(rb_ptr->Writepos) = data;
rb_ptr->Writepos = NextDataAddrHandle(rb_ptr,rb_ptr->Writepos);
rb_ptr->RingbufCount++;
}

/**
  * @brief 读指定包长函数
  * @param rb_ptr 缓冲区结构体地址,head 包头,length 包长
  * @retval  读取状态及数据包地址
  * @notice  length为整个数据包长即头置尾
*/
ReadRetState_Typedef* ReadEfectiveFrameFixLength(RingBuff_Typedef* rb_ptr, unsigned char head, unsigned char length)
{
unsigned char count = rb_ptr->RingbufCount;             //标记触发前有效数据大小
if (count < length)
{
      rb_ptr->ReadRetStateStruct.Readstate = Fail;
      rb_ptr->ReadRetStateStruct.ptr = NULL;
      return &rb_ptr->ReadRetStateStruct;
}
while (count >= length)
{
      rb_ptr->ReadRetStateStruct = *ReadDataFromRingbuff(rb_ptr);
      count--;
      if (rb_ptr->ReadRetStateStruct.Readstate == Success && *rb_ptr->ReadRetStateStruct.ptr == head)
      {
         return &rb_ptr->ReadRetStateStruct;
      }
}
rb_ptr->ReadRetStateStruct.Readstate = Fail;
rb_ptr->ReadRetStateStruct.ptr = NULL;
return &rb_ptr->ReadRetStateStruct;
}

/**
  * @brief 读期望帧
  * @param rb_ptr 缓冲区结构体地址,str 期望帧
  * @retval  读取状态
  * @notice  None
*/
ReadRetState_Enum ReadEfectiveFrame(RingBuff_Typedef* rb_ptr, const char* str)
{
unsigned char count = rb_ptr->RingbufCount;                //标记触发前有效数据大小
unsigned char length = strlen(str);
unsigned char i = 0;
if (count < length)
{
      return Fail;
}
while (count >= length)
{
      rb_ptr->ReadRetStateStruct = *ReadDataFromRingbuff(rb_ptr);
      count--;
      if (rb_ptr->ReadRetStateStruct.Readstate == Success && *rb_ptr->ReadRetStateStruct.ptr == *(str + i))
      {
         count++;
         i++;
      }
      else
      {
         i = 0;
      }
      if (i == length)
      {
         return Success;
      }
}
return Fail;
}

/**
  * @brief 匹配期望帧
  * @param rb_ptr 缓冲区结构体地址,str 期望帧所在注册表地址, ExpectFrameCount 期望帧注册表的个数
  * @retval  读取状态
  * @notice  None
*/
ReadRetState_Typedef* MatchExpectFrame(RingBuff_Typedef* rb_ptr, const char** str, unsigned char ExpectFrameCount)
{
unsigned char Retcount = rb_ptr->RingbufCount;
unsigned char* RetPos = rb_ptr->Readpos;

unsigned char i = 0;
for (i = 0; i < ExpectFrameCount; i++)
{
      if (ReadEfectiveFrame(rb_ptr, *(str + i)) == Success)
      {
         rb_ptr->ReadRetStateStruct.pos = i;
         rb_ptr->ReadRetStateStruct.Readstate = Success;
         return &rb_ptr->ReadRetStateStruct;
      }
      else
      {
         rb_ptr->RingbufCount = Retcount;
         rb_ptr->Readpos = RetPos;
      }
}
rb_ptr->ReadRetStateStruct.Readstate = Fail;
return &rb_ptr->ReadRetStateStruct;
}

/******************** (C)COPYRIGHT(2016) YFTC  END OF FILE **********************/
H文件
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#ifndef __CX_RINGBUFF_H
#define __CX_RINGBUFF_H

#include "stdlib.h"
#include "string.h"

#define       MaxBuffSize       256       //缓冲区大小可任意设置，但最好为2^X

typedef enum
{
Success = 1,
Fail = !Success,
}ReadRetState_Enum;

typedef struct
{
ReadRetState_Enum Readstate;             //读状态
unsigned char* ptr;                      //读取字节地址
unsigned char  pos;                      //期望帧在注册表中位置
}ReadRetState_Typedef;

typedef struct
{
unsigned char* Writepos;                   //写入地址
unsigned char* Readpos;                   //读取地址
unsigned char RingbufCount;                //有效未读数据大小
ReadRetState_Typedef ReadRetStateStruct; //读缓冲相关
unsigned char RxBuff[MaxBuffSize];       //数据缓存区
}RingBuff_Typedef;

void RingBuff_New(RingBuff_Typedef* rb_ptr);
unsigned char* NextDataAddrHandle(RingBuff_Typedef* rb_ptr,unsigned char* addr);
ReadRetState_Typedef* ReadDataFromRingbuff(RingBuff_Typedef* rb_ptr);
void WriteDataToRingbuff(RingBuff_Typedef* rb_ptr,unsigned char data);
ReadRetState_Typedef* ReadEfectiveFrameFixLength(RingBuff_Typedef* rb_ptr, unsigned char head, unsigned char length);
ReadRetState_Enum ReadEfectiveFrame(RingBuff_Typedef* rb_ptr, const char* str);
ReadRetState_Typedef* MatchExpectFrame(RingBuff_Typedef* rb_ptr, const char** str, unsigned char ExpectFrameCount);

#endif

以上就是我所编写的Ringbuffer源码。
从.H文件中可看到Ringbuff的数据结构，当中有读写地址以及有效未读数据大小，以及读状态等。