利用pack和unpack互相轉化php和c的語言結構

在實際開發中,有時會遇到PHP和C語言結搆的互相轉化問題,這時候PHP的函數pack和unpack就能幫上大忙了.
pack()將數據打包成二進制串
unpack()從字串中的二進制串轉化成指定的格式.
詳細格式可於官方瀏覽:
http://hk.php.net/manual/en/function.pack.php
例如架構為:

typedef struct _BorrowInfo
{
char mobile[32];
char area[8];
int   type;
int   ret
} BorrowInfo

將PHP變量轉成結搆

$type=100;
$mobile="13901234567";
$ret=0;
$area="BJ";
$returnstr=sprintf("%-32s,$mobile).sprintf("%-8s,$area).pack("l",$type).pack("l",$ret);

將結搆轉成php變量,對于字符型變量可以直接取得.

$moible=substr($returnstr,0,32);
$area=substr($returnstr,32,8);
$farray=unpack("nint",substr($returnstr,40,4));
$type=$farray['int']; //RET變量也可以向type類似取得

需要注意的事,C語言結搆由于內存對齊方式和機器字節順序問題,需要對代碼進行微調,才能正常使用.
比如將結搆體搆體的手機號設為25位,則整個結搆sizeof后是44字節,而不是41字節,切記.否則用PHP轉成的結搆C語言是解析不了的.

SERVER C

/*server.c*/
#include
#include
#include
#include
#include
#include
#include
#include
#include

main(){
     int sock;
     struct sockaddr_in server,client;
     int recvd,snd;
     int structlength;
     char * server_ip = "128.168.10.1";/*server ip address*/
     int port = 8888;
     char recvbuf[2000],sendbuf[2000];    
     char str1[]="I have received:\n";
     memset((char *)&server,0,sizeof(server));
     server.sin_family = AF_INET;
     server.sin_addr.s_addr = inet_addr(server_ip);
     server.sin_port = htons(port);
     memset((char *)&client,0,sizeof(client));
     client.sin_family = AF_INET;
     client.sin_addr.s_addr = htonl(INADDR_ANY);
     client.sin_port = htons(port);
     if((sock = socket (AF_INET,SOCK_DGRAM,0)) < 0 ){
         printf("socket create error!\n");
         exit(1);
     }
     structlength = sizeof(server);
     if( bind(sock,(struct sockaddr *) &server,structlength) < 0){
         printf("socket bind error!\n");
         perror("bind");
         exit(1);
     }
     while(1){
         structlength = sizeof(client);
         printf("waiting.......\n");
         recvd = recvfrom(sock,recvbuf,sizeof(recvbuf),0,
             (struct sockaddr *) & client,&structlength);
         if(recvd < 0){
             perror("recvfrom");
             exit(EXIT_FAILURE);    
         }
         else{
             printf("received:%s\n",recvbuf);
             memset(sendbuf,0,strlen(sendbuf));
             memcpy(sendbuf,str1,strlen(str1));
             snd = sendto(sock,sendbuf,strlen(str1),0,
             (struct sockaddr *) &client,structlength);
             if(snd < 0){
             perror("sendto");
             exit(1);
             }
             printf("sendok!\n");
         }  
     }
     close(sock);
}

CLIENT PHP

$server_ip="128.168.10.1";
$port = 8888;
$sock=@socket_create(AF_INET,SOCK_DGRAM,0);
if(!$sock){
     echo "socket create failure";
}
if($buf=="")
     $buf="hello,how are you!\n";
if(!@socket_sendto($sock,$buf,strlen($buf),0,"128.168.10.1",8888))
{
     echo "send error\n";
     socket_close($sock);
     exit();
}
$buf="";
$msg="";
if(!@socket_recvfrom($sock,$msg,256,0,&$server_ip,&$port))
{
     echo "recvieve error!";
     socket_close($sock);
     exit();
}
echo trim($msg)."\n";
socket_close($sock);