用C代码实现环形缓冲区（ring buf）

本文主要是介绍用C代码实现环形缓冲区（ring buf），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

概述

因嵌入式项目需要，串口接收的数据有很高的周期性发送频率，原方式通过查询接收标志再接收会导致数据丢失和硬件buf溢出等问题，因此考虑开足够大的环形缓冲区（ring buf）实现，接收中断中仅实时的进行buf写操作，应用程序进行循环查询处理，将数据处理和数据接收解耦合，本文采用VS Code + Gcc编译器编写了测试验证程序，对ringbuf进行了测试，参考文章链接，并非照抄，而是在原文基础上进行了改进，并封装成单独的.c文件。

环境介绍

本文测试代码时在VS Code环境下进行了编写和调试，编译工具用的mingw64，详细配置方法就不做介绍了，主要介绍我遇到的一个问题：单个C程序可正常编译，但多个C程序编译报错（未定义的函数名），主要问题是launch.json 和 tasks.json 不对，参考文章，我的配置如下：

launch.json(没改）

 {// 使用 IntelliSense 了解相关属性。 // 悬停以查看现有属性的描述。// 欲了解更多信息，请访问: https://go.microsoft.com/fwlink/?linkid=830387"version": "0.2.0","configurations": []
}

tasks.json

该文件主要修改了 “$file"参数为："${cwd}\*.c”，以编译当前工程目录下的所有C文件

{"version": "2.0.0","tasks": [{"type": "cppbuild","label": "C/C++: gcc.exe 生成活动文件","command": "C:\\mingw64\\bin\\gcc.exe","args": ["-fdiagnostics-color=always","-g",//"${file}", //默认仅编译当前打开的单个文件"${cwd}\\*.c",//编译当前目录下的所有C文件"-o","${fileDirname}\\${fileBasenameNoExtension}.exe"],"options": {"cwd": "${fileDirname}"},"problemMatcher": ["$gcc"],"group": "build","detail": "编译器: C:\\mingw64\\bin\\gcc.exe"}]
}

注意

这2个文件不是自己编写的，生成方法如下：
打开项目文件夹->终端->配置默认生成任务->选择gcc,之后会自动生成，我们只需要修改部分内容即可

代码

三个文件，main.c为主程序，ringbuf.c和ringbuf.h

ringbuf.c

#include "ringbuf.h"/* ******************************************
* 环形缓冲区初始化函数 InitRingBuff函数参数说明：
*   参数1 buf ：指向ringbuf的结构体指针
*   参数2 size ：buf大小，单位字节
*   参数3 over_mode ：写入覆盖模式
*        0-   当buf满时阻塞写，并丢弃最新数据
*        1-   当buf满时覆盖写，并丢弃最早的数据
***************************************** */
void InitRingBuff(ringfifo *buf, unsigned int size,int over_mode)
{buf->pHead = (char *)malloc(size * sizeof(char));memset(buf->pHead, 0, size);buf->pValidRead = buf->pHead;buf->pValidWrite = buf->pHead;buf->pTail = buf->pHead + size;buf->used_space = 0;buf->free_space = size;buf->overwrite = over_mode; printf("pread is %d \t pwrite is %d \t used_space is %d \n",buf->pValidRead,buf->pValidWrite,buf->used_space);
}// 向缓冲区写数据
int WriteRingBuff(ringfifo *buf,char *pdata, unsigned int len)
{if (buf->pHead == NULL ){printf("WriteRingBuff: RingBuff is not Init!\n");return -2;}if (len > buf->pTail - buf->pHead){printf("WriteRingBuff: ring buf is too small\n");//每次写入数据不能超过buf总长度，否则认为buf开的不够return -1;}if ((len > buf->free_space) && (buf->overwrite != 1)){printf("WriteRingBuff: New add data is too long\n");//只有在覆盖模式才可写入超过剩余空间的数据，否则无法写入return -1;}// 若新增的数据长度大于写指针和尾指针之间的长度if (buf->pValidWrite + len > buf->pTail){int PreLen = buf->pTail - buf->pValidWrite;int LastLen = len - PreLen;memcpy(buf->pValidWrite, pdata, PreLen);memcpy(buf->pHead, pdata + PreLen, LastLen);buf->pValidWrite = buf->pHead + LastLen; // 新环形缓冲区尾地址}else{memcpy(buf->pValidWrite, pdata, len); // 将新数据内容添加到缓冲区buf->pValidWrite += len;              // 新的有效数据尾地址}if ((len > buf->free_space) && (buf->overwrite == 1))//覆盖写{buf->pValidRead = buf->pValidWrite;buf->used_space = buf->pTail - buf->pHead; buf->free_space = 0;}else{//未覆盖buf->used_space += len; buf->free_space -= len;}return 1;
}// 从缓冲区读数据
int ReadRingBuff(ringfifo *buf, char *pdata, unsigned int len)
{if (buf->pHead == NULL ){printf("ReadRingBuff: RingBuff is not Init!\n");return -2;}if (len > buf->used_space){printf("ReadRingBuff: Read data is too long\n");return -1;}if (len == 0){return 1;}if (buf->pValidRead + len > buf->pTail){int PreLen = buf->pTail - buf->pValidRead;int LastLen = len - PreLen;memcpy(pdata, buf->pValidRead, PreLen);memcpy(pdata + PreLen, buf->pHead, LastLen);buf->pValidRead = buf->pHead + LastLen;}else{memcpy(pdata, buf->pValidRead, len);buf->pValidRead += len;}buf->used_space -= len;buf->free_space +=len;return len;
}

ringbuf.h

#ifndef __RINGBUF_H_
#define __RINGBUF_H_#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>typedef struct
{char *pHead;       // 环形缓冲区首地址char *pValidRead;  // 已使用环形缓冲区首地址char *pValidWrite; // 已使用环形缓冲区尾地址char *pTail;       // 环形缓冲区尾地址unsigned int used_space;  //环形缓冲区有效数据个数unsigned int free_space; //环形缓冲区剩余空间int overwrite;// 1- overwrite
} ringfifo;void InitRingBuff(ringfifo *buf, unsigned int size,int over_mode);
int WriteRingBuff(ringfifo *buf,char *pdata, unsigned int len);
int ReadRingBuff(ringfifo *buf, char *pdata, unsigned int len);#endif

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "ringbuf.h"int main()
{char c;int len;int readLen = 1;char readBuffer[10];int i = 0;ringfifo buf1;int r;char* strbuff = (char*)malloc(100 * sizeof(char));buf1.overwrite = 1;InitRingBuff(&buf1,10,1);printf("Please enter a character,VER 0.4\n");while (1){fgets(strbuff,100,stdin);printf("strlen is %d\n",strlen(strbuff)-1);if(strlen(strbuff)>1){switch (*strbuff){case 'R':r = ReadRingBuff(&buf1,readBuffer, readLen);if (r > 0){for (i = 0; i < readLen; i++){printf("%c ", (char)readBuffer[i]);}printf("\n");printf("pread is %d \t pwrite is %d \t used_space is %d free space is %d BUF:",buf1.pValidRead,buf1.pValidWrite,buf1.used_space,buf1.free_space);for (i = 0; i < buf1.pTail - buf1.pHead; i++){printf("%c ", (char)*(buf1.pHead+i));}printf("\n");}break;default:WriteRingBuff(&buf1,strbuff, strlen(strbuff)-1);printf("pread is %d \t pwrite is %d \t used_space is %d free space is %d BUF:",buf1.pValidRead,buf1.pValidWrite,buf1.used_space,buf1.free_space);for (i = 0; i < buf1.pTail - buf1.pHead; i++){printf("%c ", (char)*(buf1.pHead+i));}printf("\n");break;}}};return 0;
}

测试说明

程序运行后输入除了”R“以外的任意字符，按回车后写入buf，输入R时从buf读取1个字节，初始化buf时需设置覆盖/阻塞模式，测试结果如下：

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