环形缓冲
/** * Copyright (c) 2008, ×××研发中心 * All rights reserved. ** 名 称： * 摘 要： * 作 者：test * 版 本：1.0 * 时 间：08.08.27 16:21:55 */#include <stdio.h>#include <string.h>#include <stdlib.h>#include <iostream>#include <pthread.h>#include <time.h>#define INITBUFSIZE 10 /*环型缓冲区初始单元个数*/#define UNITSIZE 200/*每单元大小*/using namespace std;/*global data*//*Cirbuf chain 写进程可能很快 以至于不只有1个或2个环形缓冲，可能有多个*/struct Cirbuf* packetCirbuf;/*环形缓冲的一个单元*/struct CirUnit{ int flag; /*0 表明可写,1表明可读*/ char unit;};/*环形缓冲*/struct Cirbuf{ struct Cirbuf * newBuf; /*point to new Cirbuf*/ int readPoint; /*for reading thread*/ int writePoint; /*for writing thread*/ int bufSize; /*buf char array's size*/ struct CirUnit *buf; /*point to unit array*/};struct Cirbuf* GetNewCirbuf(int bufSize,struct Cirbuf* oldBuf){ if(bufSize>30000) { printf("oh my god,the bufSize is out of my league,I cannot handle it,exit"); exit(1); } struct Cirbuf* newBuf = new Cirbuf(); printf("new buffer %d\n",bufSize); usleep(1000000); if(oldBuf != NULL) oldBuf->newBuf = newBuf; newBuf->newBuf = NULL; newBuf->readPoint = newBuf->writePoint = 0; newBuf->bufSize = bufSize; newBuf->buf = new CirUnit; memset(newBuf->buf,0,sizeof(CirUnit)*bufSize); /*初始化单元为0*/ return newBuf;}int FreeCirbuf(struct Cirbuf* bufPoint){ delete bufPoint->buf; delete bufPoint; printf("delete buffer \n"); return 1;}void DoWrite(struct Cirbuf* latestBuf,char flag){ latestBuf->buf.unit = flag; printf("write %d \n",flag);}void DoRead(){ printf("read %d \n",packetCirbuf->buf.unit);}extern "C" void* ReadThread(void *arg){ while(1) { usleep(200000); if(packetCirbuf->buf.flag == 0) { if(packetCirbuf->newBuf != NULL) { /*表明readthread已经处理完旧的缓冲区并且已经有新的缓冲区，这时应该释放旧缓冲*/ struct Cirbuf *temp = packetCirbuf; packetCirbuf = packetCirbuf->newBuf; FreeCirbuf(temp); continue; } /* delay*/ pthread_cond_t mycond = PTHREAD_COND_INITIALIZER; pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; struct timespec ts; int rv; ts.tv_sec = 0; ts.tv_nsec = 50000; /* 500,00 nanoseconds = 50 ms */ pthread_mutex_lock(&mymutex); rv = pthread_cond_timedwait(&mycond, &mymutex, &ts); pthread_mutex_unlock(&mymutex); continue; } DoRead(); packetCirbuf->buf.flag = 0; if(++packetCirbuf->readPoint == packetCirbuf->bufSize) packetCirbuf->readPoint = 0; } return NULL;}extern "C" void* WriteThread(void *arg){ struct Cirbuf* latestBuf; /*进写进程后，初始化latestBuf指针 使其指向packetCirbuf，这时的packetCirbuf是由主线程函数创建的初始buf*/ latestBuf = packetCirbuf; if(latestBuf == NULL) { cout << "packet capture buffer NULL error" << endl; exit(0); } /*进入循环*/ char test=0; while(1) { usleep(100000); if (latestBuf->buf.flag == 1) { /*we need a larger buf*/ latestBuf = GetNewCirbuf(latestBuf->bufSize * 2,latestBuf); } else { DoWrite(latestBuf,test++); latestBuf->buf.flag = 1; if(++latestBuf->writePoint == latestBuf->bufSize) latestBuf->writePoint = 0; } if(test == 127) break; } return NULL;}int main(int argc, char *argv[]){ pthread_t threadNum; packetCirbuf = GetNewCirbuf(INITBUFSIZE,NULL); pthread_create(&threadNum,NULL,WriteThread,NULL); pthread_create(&threadNum,NULL,ReadThread,NULL); pthread_join(threadNum,NULL); pthread_join(threadNum,NULL); FreeCirbuf(packetCirbuf);}见到的一个不错的环形缓冲。
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