關於C語言的下載函數的一些個人見解

#include

#include

#include

struct cfgmain

{

long size;

long Received;

char website[1000]; 想要一起學習C++的可以加裙三四零六五一六八七，裙內有各種資料滿足大家，歡迎加裙

}

int LoadWSA()

{

WSADATA wd;

if(WSAStartup(0x0101,&wd))

{

return -1;

}

return 0;

}

void downThread(char *url,int threadID,int rangeFrom,int rangeUntil,FILE *cfg,FILE *fp)

{

char *oriURL=url;

char *ReadWriteBuf=(char*)malloc(20000);

cfgmain cfgfile;

char bufferSend[65535];

char *bufferRecv=(char*)malloc(65535);

if(strstr(url,"http://"))

{

url=url+sizeof("http://");

}

int lengthOfWeb;

for(lengthOfWeb==0;lengthOfWeb

{

if(url[lengthOfWeb]=="/")

{

break;

}

}

char name[255];

memcpy(name,url,lengthOfWeb);

SOCKET sock=::socket(2,SOCK_STREAM,0);

struct hostent *h;

h=gethostbyname(name);

if(h==0)

{

printf("ThreadID :#%d ERROR:%d The thread will exit!
",threadID,WSAGetLastError());

return;

}

struct sockaddr_in saddr;

memcpy(&saddr.sin_addr,h->h_addr_list,h->h_length);

saddr.sin_port=htons(80);

saddr.sin_family=AF_INET;

if(connect(sock,(sockaddr*)&saddr,sizeof(sockaddr)))

{

printf("ThreadID :#%d ERROR:%d The thread will exit!
",threadID,WSAGetLastError());

return;

}

url=url+sizeof(h->h_length)+1;

unsigned int temp;

if(cfg==0)

{

sprintf(bufferSend,"GET /%s HTTP/1.1
Host: %s
Connection: close

",url,h->h_name);

}

else

{

fread(&cfgfile,1,sizeof(cfgmain),cfg);

rewind(cfg);

sprintf(bufferSend,"GET /%s HTTP/1.1
Host: %s
Connection: close
Accept-Range: %d-

",url,h->h_name,cfgfile.Received);

send(sock,bufferSend,strlen(bufferSend),0);

temp=recv(sock,bufferRecv,65535,0);

}

lengthOfWeb=0;

for(lengthOfWeb==0;lengthOfWeb

{

if(url[lengthOfWeb]=="
"&&url[lengthOfWeb+1]=="
"&&url[lengthOfWeb+2]=="
"&&url[lengthOfWeb+3]=="
")

{

break;

}

}

url=url+3;

char *oribufRecv=bufferRecv;

bufferRecv=bufferRecv+lengthOfWeb;

fwrite(bufferRecv,1,temp-lengthOfWeb,fp);

for(;;)

{

temp=recv(sock,oribufRecv,65535,0);

if(temp>=1)

{

fwrite(oribufRecv,1,temp,fp);

}

else

{

printf("Finish Downloading!
");

fclose(fp);

}

}

}

原理是透過http進行傳輸，至於監測http回應的數據的開始位置，我們用循環檢測，一旦檢測到兩個連續的0x0D 0x0A,我們就知道數據重這裡開始。然後進入循環不斷接受，一旦受到的數據包大小為0，證明伺服器已經斷開連接，也就是下載完畢

上述代碼都貼上了，僅供參考！

想要一起學習C++的可以加裙三四零六五一六八七，裙內有各種資料滿足大家，歡迎加裙

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