swait.c

来自「Porting the Simple Sockets Library Dr. C」· C语言 代码 · 共 78 行

/* Swait.c: this file contains code which allows one to wait until data
 *  is present at the Socket (this will block)
 *
 *  Returns: number of bytes of data awaiting perusal
 *	         or EOF if unable to "select" the socket
 */
#include <stdio.h>
#define SSLNEEDTIME
#include "sockets.h"

/* ---------------------------------------------------------------------
 * Source Code:
 */

#ifdef __PROTOTYPE__
int Swait(Socket *skt)
#else
int Swait(skt)
Socket *skt;
#endif
{
static char buf[PM_BIGBUF];
short  result;
int    ret;
fd_set emask;
fd_set rmask;
fd_set wmask;


/* sanity check */
if(!skt) {
	return -1;
	}

FD_ZERO(&rmask);
FD_SET(skt->skt,&rmask);
FD_ZERO(&wmask);
FD_ZERO(&emask);

/* test if something is available for reading on the socket.  This form
 * will block (sleep) until something arrives
 */
#ifdef SSLNOPEEK
result = select(skt->skt+1,rmask.fds_bits,wmask.fds_bits,emask.fds_bits,
         (struct timeval *) NULL);
#else
result = select(skt->skt+1, &rmask,&wmask,&emask, (struct timeval *) NULL);
#endif
if(result < 0) {
	return EOF;
	}

/* server sockets return the select result */
if(skt->type == PM_SERVER) {
	return result;
	}


#ifdef SSLNOPEEK

return 1;

#else /* #ifdef SSLNOPEEK ... #else ... #endif */

/* wait if message available from socket, return qty bytes avail */
if(FD_ISSET(skt->skt,&rmask)) {
	ret= recv(skt->skt,buf,PM_BIGBUF-1,MSG_PEEK);
	if(result == 1 && ret == 0) ret= EOF;
	return ret;
	}

/* socket is empty */
return 0;
#endif /* #ifdef SSLNOPEEK ... #else ... #endif */
}

/* --------------------------------------------------------------------- */