前面写了一系列文章都是关于网络底层机制封装的，后面要慢慢的将这些机制组装起来，实现一套可用的网络库。

既然是网络库，自然少不了对缓存的管理，本文实现一个带引用计数的buffer,作为packet的底层缓存组件.packet

的具体设计思路可见:

#ifndef _BUFFER_H#define _BUFFER_H/*        Copyright (C) <2012>  
     
          This program is free software: you can redistribute it and/or modify    it under the terms of the GNU General Public License as published by    the Free Software Foundation, either version 3 of the License, or    (at your option) any later version.    This program is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the    GNU General Public License for more details.    You should have received a copy of the GNU General Public License    along with this program.  If not, see 
      .*//** 带引用计数的buffer*/typedef struct buffer{    long ref_count;    unsigned long capacity;    unsigned long size;    struct buffer *next;    char   buf[0];}*buffer_t;buffer_t buffer_create_and_acquire(buffer_t,unsigned long);buffer_t buffer_acquire(buffer_t,buffer_t);void     buffer_release(buffer_t*);#endif
     

#include 
     
      #include 
      
       #include "buffer.h"static buffer_t buffer_create(unsigned long capacity){    unsigned long size = sizeof(struct buffer) + capacity;    buffer_t b = calloc(1,size);    if(b)    {        b->ref_count = 0;        b->size = 0;        b->capacity = capacity;    }    return b;}static void     buffer_destroy(buffer_t *b){    printf("buffer destroy\n");    if((*b)->next)        buffer_release(&(*b)->next);    free(*b);    *b = 0;}buffer_t buffer_create_and_acquire(buffer_t b,unsigned long capacity){    buffer_t nb = buffer_create(capacity);    return buffer_acquire(b,nb);}buffer_t buffer_acquire(buffer_t b1,buffer_t b2){    if(b1 == b2)        return b1;        if(b2)        ++b2->ref_count;    if(b1)        buffer_release(&b1);    return b2;}void buffer_release(buffer_t *b){    if(--(*b)->ref_count <= 0)        buffer_destroy(b);    *b = 0;}
      
     

测试用例如下:

buffer_t cur = 0;    buffer_t b1 = buffer_create_and_acquire(0,16);    buffer_t b2 = buffer_acquire(0,b1);    buffer_release(&b1);    buffer_release(&b2);    b1 = buffer_create_and_acquire(0,16); //b1指向bufferA    b1 = buffer_create_and_acquire(b1,16);//b1指向bufferB,bufferA计数减为0,被释放    buffer_release(&b1);    //创建3个buffer形成链表    b1 = buffer_create_and_acquire(0,16);    b1->next = buffer_create_and_acquire(0,16);    b1->next->next = buffer_create_and_acquire(0,16);    cur = b1;    while(cur)    {        cur = buffer_acquire(cur,cur->next);    }    //遍历结束,所有buffer的计数减为0,全部被释放