第c++實現(xiàn)一個簡易的網(wǎng)絡緩沖區(qū)的實踐size_tused_size=m_write_index-m_read_index;//used_size表示已經(jīng)存儲的字節(jié)數(shù)

size_tremain_size=m_max_size-used_size;//remain_size表示剩余空間

size_texpand_size=m_max_size;

while(remain_sizeneed_size){//剩余空間不夠時擴展，用while表示直到擴展至夠用

expand_size*=m_expand_par;

remain_size=expand_size-used_size;

//cout"擴展長度中...總剩余總長度"remain_size""expand_sizeendl;

char*s1=newchar[expand_size]();//申請新的空間

memcpy(s1,m_s,m_max_size);

free(m_s);

m_s=s1;//將新空間掛載到緩沖區(qū)

m_max_size=expand_size;//更新緩沖區(qū)總長度

//cout"擴展結(jié)束，總長度為"m_max_sizeendl;

3.外部接口設計與實現(xiàn)

以讀緩沖區(qū)為例需要提供的接口有：向緩沖區(qū)寫入數(shù)據(jù)write_to_buffer(),向緩沖區(qū)讀取數(shù)據(jù)read_from_buffer()，得到能夠讀取的最大字節(jié)數(shù)readable_bytes()。

classBuffer{

public:

voidwrite_to_buffer(char*src);//從src中寫數(shù)據(jù)

size_treadable_bytes();//存儲數(shù)據(jù)的字節(jié)數(shù)

size_tread_from_buffer(char*dst,intbytes);//讀數(shù)據(jù)

size_tpop_bytes(size_tbytes);//丟棄數(shù)據(jù)

①寫入緩沖區(qū)write_to_buffer()

write_to_buffer()實現(xiàn)的思路如流程圖所示：

判斷剩余空間：

剩余空間不夠：調(diào)整數(shù)據(jù)至頭部、擴展緩沖區(qū)

剩余空間足夠：向下繼續(xù)

判斷當前空間：

當前空間不夠：調(diào)整數(shù)據(jù)至頭部

剩余空間足夠：向下繼續(xù)

存儲數(shù)據(jù)

根據(jù)流程圖實現(xiàn)起來邏輯非常清晰，src表示原始數(shù)據(jù)

voidBuffer::write_to_buffer(char*src)

size_tused_size=m_write_index-m_read_index;//used_size表示已經(jīng)存儲的字節(jié)數(shù)

size_tremain_size=m_max_size-used_size;//remain_size表示剩余空間

size_tcur_size=m_max_size-m_write_index;//cur_size表示當前能夠存儲的空間

size_tsize=init_random_write(src);

//printf("已經(jīng)使用%d,剩余總長度%d,剩余當前長度%d\n",used_size,remain_size,cur_size);

if(sizeremain_size){//剩余空間不夠

adjust_buffer();

expand_buffer(size);

elseif(sizecur_size){//剩余空間夠,當前存不下

adjust_buffer();

memcpy(m_s[m_write_index],src,size);//存儲數(shù)據(jù)

m_write_index+=size;

delete[]src;

//更新并打印log

//used_size=m_write_index-m_read_index;

//remain_size=m_max_size-used_size;

//cur_size=m_max_size-m_write_index;

//printf("已經(jīng)使用%d,剩余總長度%d,剩余當前長度%d\n",used_size,remain_size,cur_size);

流程圖中還出現(xiàn)隨機一段數(shù)據(jù)，這是用來調(diào)試的。隨機初始化一段長度為0~40，字符a~z的數(shù)據(jù)，并寫緩存區(qū)

staticintget_random_len(){

returnrand()%40;

staticintget_random_ala(){

returnrand()%26;

size_tBuffer::init_random_write(char**src)

intsize=get_random_len();

charala=get_random_ala();

*src=newchar[size];

cout"準備寫入的長度為"size"值全是"(unsignedchar)('a'+ala)endl;

for(inti=0;isize;i++){

(*src)[i]='a'+ala;

returnsize;

②讀取緩沖區(qū)read_from_buffer()

read_from_buffer(char*dst,intread_size)傳入需要拷貝到目的地址和需要讀取的字節(jié)數(shù)，需要注意的是需要讀取的字節(jié)數(shù)為-1表示全部讀取，函數(shù)返回實際讀取的字節(jié)數(shù)。實現(xiàn)如流程圖所示：

代碼如下

size_tBuffer::read_from_buffer(char*dst,intread_size)

size_tread_max=m_write_index-m_read_index;//read_max存儲的字節(jié)數(shù)

if(read_size==0||read_max==0)//讀取0字節(jié)和空緩存區(qū)時直接返回

return0;

if(read_size==-1){//全讀走

memcpy(dst,m_s[m_read_index],read_max);

m_read_index+=read_max;

cout"讀取了"read_max"個字節(jié)"endl;

elseif(read_size0){//讀取指定字節(jié)

if((size_t)read_sizeread_max)

read_size=read_max;

memcpy(dst,m_s[m_read_index],read_size);

m_read_index+=read_size;

cout"讀取了"read_size"個字節(jié)"endl;

returnread_size;//返回讀取的字節(jié)數(shù)

③丟棄數(shù)據(jù)pop_bytes

size_tpop_bytes(size_tsize)傳入需要丟棄的字節(jié)數(shù)，需要注意的是需要丟棄的字節(jié)數(shù)為-1表示全部丟棄；-2表示隨機丟棄0~40字節(jié)，函數(shù)返回實際丟棄的字節(jié)數(shù)。實現(xiàn)如流程圖所示：

size_tBuffer::pop_bytes(size_tsize)

size_tread_max=m_write_index-m_read_index;//存儲數(shù)據(jù)長度

//testrandom

if(size==-2)

size=get_random_len();

if(size==0||read_max==0)//緩沖區(qū)為空或丟棄0字節(jié)返回

return0;

if(size==-1){//全丟

m_read_index+=read_max;

cout"丟棄了"read_max"個字節(jié)"endl;

returnread_max;

if(size0){//丟棄指定字節(jié)

if(sizeread_max)

size=read_max;

m_read_index+=size;

cout"丟棄了"size"個字節(jié)"endl;

returnsize;

④其他接口

peek_read()和peek_write()返回讀寫指針的位置

size_tpeek_read();//指向準備讀的位置（調(diào)試用）

size_tpeek_write();//指向準備寫的位置（調(diào)試用）

size_tBuffer::peek_write()

returnm_write_index;

size_tBuffer::peek_read()

returnm_read_index;

4.完整代碼與測試

①完整代碼

Buffer.h

#pragmaonce

classBuffer{

public:

Buffer();//構(gòu)造

~Buffer();//析構(gòu)

intinit();//分配緩沖區(qū)

voidwrite_to_buffer(char*src);//寫數(shù)據(jù)

size_tpop_bytes(size_tbytes);//丟棄數(shù)據(jù)

size_tread_from_buffer(char*dst,intbytes);//讀數(shù)據(jù)

size_treadable_bytes();//得到存儲數(shù)據(jù)的字節(jié)數(shù)

size_tpeek_read();//指向準備讀的位置（調(diào)試用）

size_tpeek_write();//指向準備寫的位置（調(diào)試用）

private:

voidadjust_buffer();//調(diào)整數(shù)據(jù)位置至緩沖區(qū)頭

voidexpand_buffer(size_tneed_size);//擴展緩沖區(qū)長度

size_tinit_random_write(char**src);//隨機初始化一段數(shù)據(jù)（調(diào)試用）

private:

char*m_s;//緩沖區(qū)指針

size_tm_read_index;//讀指針位置

size_tm_write_index;//寫指針位置

size_tm_max_size;//緩沖區(qū)長度

size_tm_expand_par;//擴展因子

Buffer.cpp:

#include"Buffer.h"

#includeiostream

#includetime.h

usingnamespacestd;

inttotal_write=0;//記錄總寫入

inttotal_read=0;//記錄總讀取

staticintget_random_len(){

returnrand()%40;

staticintget_random_ala(){

returnrand()%26;

Buffer::Buffer()

:m_read_index(0),m_write_index(0),m_max_size(10),m_expand_par(2),m_s(nullptr)

Buffer::~Buffer()

delete[]m_s;

intBuffer::init()

m_s=newchar[m_max_size]();

if(m_s==nullptr){

cout"分配m_s失敗\n";

return-1;

return0;

size_tBuffer::read_from_buffer(char*dst,intread_size)

size_tread_max=m_write_index-m_read_index;//read_max存儲的字節(jié)數(shù)

if(read_size==0||read_max==0)//讀取0字節(jié)和空緩存區(qū)時直接返回

return0;

if(read_size==-1){//全讀走

memcpy(dst,m_s[m_read_index],read_max);

m_read_index+=read_max;

printf("讀取完成：\t讀取%d個字節(jié)\n",read_max);

total_read+=read_max;

elseif(read_size0){//讀取指定字節(jié)

if((size_t)read_sizeread_max)

read_size=read_max;

memcpy(dst,m_s[m_read_index],read_size);

m_read_index+=read_size;

printf("讀取完成：\t讀取%d個字節(jié)\n",read_size);

total_read+=read_size;

returnread_size;//返回讀取的字節(jié)數(shù)

size_tBuffer::readable_bytes()

returnm_write_index-m_read_index;

size_tBuffer::peek_write()

returnm_write_index;

size_tBuffer::peek_read()

returnm_read_index;

voidBuffer::write_to_buffer(char*src)

size_tused_size=m_write_index-m_read_index;//used_size表示已經(jīng)存儲的字節(jié)數(shù)

size_tremain_size=m_max_size-used_size;//remain_size表示剩余空間

size_tcur_size=m_max_size-m_write_index;//cur_size表示當前能夠存儲的空間

size_tsize=init_random_write(src);

//printf("已經(jīng)使用%d,剩余總長度%d,剩余當前長度%d\n",used_size,remain_size,cur_size);

if(sizeremain_size){//剩余空間不夠

adjust_buffer();

expand_buffer(size);

elseif(sizecur_size){//剩余空間夠,當前存不下

adjust_buffer();

memcpy(m_s[m_write_index],src,size);//存儲數(shù)據(jù)

m_write_index+=size;

delete[]src;

//更新并打印log

used_size=m_write_index-m_read_index;

remain_size=m_max_size-used_size;

cur_size=m_max_size-m_write_index;

printf("寫入完成：\t總存儲%d,剩余空間%d,剩余當前空間%d\n",used_size,remain_size,cur_size);

size_tBuffer::pop_bytes(size_tsize)

size_tread_max=m_write_index-m_read_index;//存儲數(shù)據(jù)長度

//testrandom

if(size==-2)

size=get_random_len();

if(size==0||read_max==0)//緩沖區(qū)為空或丟棄0字節(jié)返回

return0;

if(size==-1){//全丟

m_read_index+=read_max;

cout"丟棄了"read_max"個字節(jié)"endl;

total_read+=read_max;

returnread_max;

if(size0){//丟棄指定字節(jié)

if(sizeread_max)

size=read_max;

m_read_index+=size;

cout"丟棄了"size"個字節(jié)"endl;

total_read+=size;

returnsize;

size_tBuffer::init_random_write(char**src)

intsize=get_random_len();

total_write+=size;

*src=newchar[size];

charala=get_random_ala();

cout"隨機寫入:\t長度為"size"值全是"(unsignedchar)('a'+ala)endl;

for(inti=0;isize;i++){

(*src)[i]='a'+ala;

returnsize;

voidBuffer::adjust_buffer()

if(m_read_index==0)//數(shù)據(jù)已經(jīng)在頭部，直接返回

return;

intused_size=m_write_index-m_read_index;

if(used_size==0){//緩沖區(qū)為空，重置讀寫指針

m_write_index=0;

m_read_index=0;

else{

cout"調(diào)整前read_indexwrite_index"m_read_index""m_write_indexendl;

memcpy(m_s,m_s[m_read_index],used_size);//將數(shù)據(jù)拷貝至頭部

m_write_index-=m_read_index;//寫指針也前移

cout"調(diào)整了"used_size"個字節(jié)"endl;

m_read_index=0;//讀指針置0

cout"調(diào)整后read_indexwrite_index"m_read_index""m_write_indexendl;

voidBuffer::expand_buffer(size_tneed_size)//need_size需要寫入的字節(jié)數(shù)

size_tused_size=m_write_index-m_read_index;//used_size表示已經(jīng)存儲的字節(jié)數(shù)

size_tremain_size=m_max_size-used_size;//remain_size表示剩余空間

size_texpand_size=m_max_size;

while(remain_sizeneed_size){//剩余空間不夠時擴展，用while表示直到擴展至夠用

expand_size*=m_expand_par;

remain_size=expand_size-used_size;

cout"擴展長度中...總剩余總長度"remain_size""expand_sizeendl;

char*s1=newchar[expand_size]();//申請新的空間

memcpy(s1,m_s,m_max_size);

free(m_s);

m_s=s1;//將新空間掛載到緩沖區(qū)

m_max_size=expand_size;//更新緩沖區(qū)總長度

cout"擴展結(jié)束，總長度為"m_max_sizeendl;

②測試

intmain(){

srand((unsigned)time(NULL));//調(diào)試需要初始化隨機種子

Buffer*pbuffer=newBuffer();//創(chuàng)建Buffer對象

if(pbuffer-init()!=0)//init函數(shù)分配緩沖區(qū)

return0;

char*s=nullptr;//s是指向隨機數(shù)據(jù)的指針

char*read=newchar[1000];//讀取時將數(shù)據(jù)存儲到的指針read

size_tread_size=0;//本次讀取到的字節(jié)數(shù)

pbuffer-write_to_buffer(s);

read_size=pbuffer-read_from_buffer(read,-1);

pbuffer-write_to_buffer(s);

pbuffer-pop_bytes(-2);

read_size=read_size=pbuffer-read_from_buffer(read,0);

pbuffer-write_to_buffer(s);

cout"總寫入\t"total_writeendl;;

cout"總讀取\t"total_readendl;

cout"目前寫入"total_write-total_readendl;

cout"可讀取\t"pbuffer-readable_bytes()endl;

printf("write%dread%d\n",pbuffer-peek_write(),pbuffer-peek_read());

if(total_write-total_read!=pbuffer-readable_bytes()){//根據(jù)總寫入-總讀取和一共存儲的字節(jié)數(shù)判斷是否存儲正確

cout"error!!!"endl;

else

cout"testisok\n\n\n";

deletes;

delete[]read;

deletepbuffer;

return0;

隨機1000000次測試

intmain(){

srand((unsigned)time(NULL));//調(diào)試需要初始化隨機種子

Buffer*pbuffer=newBuffer();//創(chuàng)建Buffer對象

if(pbuffer-init()!=0)//init函數(shù)分配緩沖區(qū)

return0;

char*s=nullptr;//s是指向隨機數(shù)據(jù)的指針

char*read=newchar[1000];//讀取時將數(shù)據(jù)存儲到的指針read

size_tread_size=0;//本次讀取到的字節(jié)數(shù)

unsignedlonglongtime=0;//調(diào)試的循環(huán)次數(shù)

while(1){

pbuffer-write_to_buffer(s);

read_size=pbuffer-read_from_buffer(read,-1);

pbuffer-write_to_buffer(s);

pbuffer-write_to_buffer(s);

pbuffer-pop_bytes(-2);

read_size=read_size=pbuffer-read_from_buffer(read,0);

pbuffer-write_to_buffer(s);

pbuffer-pop_bytes(-2);

pbuffer-write_to_buffer(s);

read_size=pbuffer-read_from_buffer(read,-1);

pbuf