recv.c

一款类linux的操作系统源码

/*
 *  Roadrunner/pk
 *    Copyright (C) 1989-2002  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT 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, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <errno.h>
#include <fs.h>
#if _DEBUG
#include <stdio.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <sys/intr.h>
#include <sys/socket.h>

ssize_t
recv(int s, void *msg, size_t len, int flags)
{
    socket_t socket;
    buf_t b;
    char *buf;
    int pos, request;

    if (s < 0 || s >= FILES)
	return EINVAL;

    if (filetab[s].type != FT_SOCKET)
	return ENOTSOCK;

    socket = (socket_t) filetab[s].data;
    if (socket->state != SS_CONNECTING && socket->state != SS_CONNECTED)
	return ENOTCONN;

    for (request = len; socket->rcv_cc < request;) {
	disable;

	/* Check connection state */
	if (socket->state < SS_CONNECTED) {
	    enable;
	    return ENOTCONN;
	} else if (socket->state > SS_CONNECTED) {
	    enable;
	    return EINTR;
	}
	current->state = PS_SOCKET;
	insq(current, &(socket->rcvr));
	proc_transfer();	       /* enables interrupts */
    }
    disable;

    for (buf = (char *) msg, pos = 0;;) {
	/* Take data from packet at head of receive queue */
	b = socket->rcvq.h;
	if (b == NULL) {
#if _DEBUG
	    kprintf("recv: receive queue empty\n");
#endif
	    enable;
	    return EINTR;
	}
	/* Check whether packet has more data than requested */
	if (blen(b) >= len) {
	    bcopy(bstart(b), buf + pos, len);
	    bstart(b) += len;
	    blen(b) -= len;
	    socket->rcv_cc -= len;

	    /* Check whether packet had exactly the amount requested */
	    if (blen(b) == 0) {
		bdeq(&(socket->rcvq));
		_bfree(b);
	    }
	    break;
	}
	/* Packet does not contain enough to satify the entire request */
	bcopy(bstart(b), buf + pos, blen(b));
	len -= blen(b);
	pos += blen(b);
	socket->rcv_cc -= blen(b);
	bdeq(&(socket->rcvq));
	_bfree(b);
    }
    enable;
    return request;
}