160 lines
4.1 KiB
C
160 lines
4.1 KiB
C
/*
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* The Qubes OS Project, http://www.qubes-os.org
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*
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* Copyright (C) 2010 Rafal Wojtczuk <rafal@invisiblethingslab.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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#include "libvchan.h"
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#include <xenctrl.h>
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#include <string.h>
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/**
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\return How much data is immediately available for reading
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*/
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int libvchan_data_ready(struct libvchan *ctrl)
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{
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return *ctrl->rd_prod - *ctrl->rd_cons;
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}
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/**
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\return How much space is available for writing, without blocking
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*/
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int libvchan_buffer_space(struct libvchan *ctrl)
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{
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return ctrl->wr_ring_size - (*ctrl->wr_prod - *ctrl->wr_cons);
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}
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static int do_notify(struct libvchan *ctrl)
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{
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return xc_evtchn_notify(ctrl->evfd, ctrl->evport);
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}
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/// returns nonzero if the peer has closed connection
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int libvchan_is_eof(struct libvchan *ctrl)
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{
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if (ctrl->is_server) {
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if (ctrl->ring->client_closed)
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return -1;
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} else {
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if (ctrl->ring->server_closed) {
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ctrl->ring->client_closed = 1;
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do_notify(ctrl);
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return -1;
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}
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}
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return 0;
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}
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/// waits for the peer to do any action
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/**
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\return -1 return value means peer has closed
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*/
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int libvchan_wait(struct libvchan *ctrl)
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{
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int ret;
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ret = xc_evtchn_pending(ctrl->evfd);
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if (ret!=-1 && xc_evtchn_unmask(ctrl->evfd, ctrl->evport))
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return -1;
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if (ret!=-1 && libvchan_is_eof(ctrl))
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return -1;
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return ret;
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}
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/**
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may sleep (only if no buffer space available);
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may write less data than requested;
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returns the amount of data processed, -1 on error or peer close
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*/
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int libvchan_write(struct libvchan *ctrl, char *data, int size)
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{
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int avail, avail_contig;
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int real_idx;
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while ((avail = libvchan_buffer_space(ctrl)) == 0)
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if (libvchan_wait(ctrl) < 0)
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return -1;
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if (avail > size)
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avail = size;
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real_idx = (*ctrl->wr_prod) & (ctrl->wr_ring_size - 1);
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avail_contig = ctrl->wr_ring_size - real_idx;
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if (avail_contig < avail)
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avail = avail_contig;
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memcpy(ctrl->wr_ring + real_idx, data, avail);
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*ctrl->wr_prod += avail;
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if (do_notify(ctrl) < 0)
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return -1;
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return avail;
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}
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/**
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may sleep (only if no data is available for reading);
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may return less data than requested;
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returns the amount of data processed, -1 on error or peer close
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*/
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int libvchan_read(struct libvchan *ctrl, char *data, int size)
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{
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int avail, avail_contig;
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int real_idx;
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while ((avail = libvchan_data_ready(ctrl)) == 0)
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if (libvchan_wait(ctrl) < 0)
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return -1;
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if (avail > size)
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avail = size;
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real_idx = (*ctrl->rd_cons) & (ctrl->rd_ring_size - 1);
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avail_contig = ctrl->rd_ring_size - real_idx;
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if (avail_contig < avail)
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avail = avail_contig;
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memcpy(data, ctrl->rd_ring + real_idx, avail);
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*ctrl->rd_cons += avail;
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if (do_notify(ctrl) < 0)
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return -1;
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return avail;
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}
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/**
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Wait fot the writes to finish, then notify the peer of closing
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On server side, it waits for the peer to acknowledge
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*/
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int libvchan_close(struct libvchan *ctrl)
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{
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while (*ctrl->wr_prod != *ctrl->wr_cons)
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if (libvchan_wait(ctrl) < 0)
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return -1;
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if (ctrl->is_server) {
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ctrl->ring->server_closed = 1;
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do_notify(ctrl);
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while (!ctrl->ring->client_closed
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&& libvchan_wait(ctrl) == 0);
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} else {
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ctrl->ring->client_closed = 1;
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do_notify(ctrl);
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}
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return 0;
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}
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/// The fd to use for select() set
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int libvchan_fd_for_select(struct libvchan *ctrl)
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{
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return ctrl->evfd;
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}
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/// Unmasks event channel; must be called before calling select(), and only then
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void libvchan_prepare_to_select(struct libvchan *ctrl)
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{
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xc_evtchn_unmask(ctrl->evfd, ctrl->evport);
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}
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