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Diffstat (limited to '')
| -rw-r--r-- | agents/virt/common/fdops.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/agents/virt/common/fdops.c b/agents/virt/common/fdops.c new file mode 100644 index 0000000..329e9b7 --- /dev/null +++ b/agents/virt/common/fdops.c @@ -0,0 +1,202 @@ +/* + Copyright Red Hat, Inc. 2002-2003 + + This program is free software; you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by the + Free Software Foundation; either version 2, or (at your option) any + later version. + + This program is distributed in the hope that it will be useful, but + WITHOUT ANY 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; see the file COPYING. If not, write to the + Free Software Foundation, Inc., 675 Mass Ave, Cambridge, + MA 02139, USA. +*/ +/** @file + * Wrapper functions around read/write/select to retry in the event + * of interrupts. + */ + +#include "config.h" + +#include <unistd.h> +#include <sys/types.h> +#include <fcntl.h> +#include <errno.h> + +#include "fdops.h" + +/** + * This is a wrapper around select which will retry in the case we receive + * EINTR. This is necessary for _read_retry, since it wouldn't make sense + * to have _read_retry terminate if and only if two EINTRs were received + * in a row - one during the read() call, one during the select call... + * + * See select(2) for description of parameters. + */ +int +_select_retry(int fdmax, fd_set * rfds, fd_set * wfds, fd_set * xfds, + struct timeval *timeout) +{ + int rv; + + while (1) { + rv = select(fdmax, rfds, wfds, xfds, timeout); + if (rv == -1) { + /* return on EBADF/EINVAL/ENOMEM; continue on EINTR/EAGAIN/ENOMEM */ + if (errno == EINTR || errno == EAGAIN || errno == ENOMEM) + continue; + } + return rv; + } +} + +/** + * Retries a write in the event of a non-blocked interrupt signal. + * + * @param fd File descriptor to which we are writing. + * @param buf Data buffer to send. + * @param count Number of bytes in buf to send. + * @param timeout (struct timeval) telling us how long we should retry. + * @return The number of bytes written to the file descriptor, + * or -1 on error (with errno set appropriately). + */ +ssize_t +_write_retry(int fd, void *buf, int count, struct timeval * timeout) +{ + int n, total = 0, remain = count, rv = 0; + fd_set wfds, xfds; + char *tmp_buf = (char *)buf; + + while (total < count) { + + /* Create the write FD set of 1... */ + FD_ZERO(&wfds); + FD_SET(fd, &wfds); + FD_ZERO(&xfds); + FD_SET(fd, &xfds); + + /* wait for the fd to be available for writing */ + rv = _select_retry(fd + 1, NULL, &wfds, &xfds, timeout); + if (rv == -1) + return -1; + else if (rv == 0) { + errno = ETIMEDOUT; + return -1; + } + + if (FD_ISSET(fd, &xfds)) { + errno = EPIPE; + return -1; + } + + /* + * Attempt to write to fd + */ + n = write(fd, tmp_buf + total, remain); + + /* + * When we know our fd was select()ed and we receive 0 bytes + * when we write, the fd was closed. + */ + if ((n == 0) && (rv == 1)) { + errno = EPIPE; + return -1; + } + + if (n == -1) { + if ((errno == EAGAIN) || (errno == EINTR)) { + /* + * Not ready? + */ + continue; + } + + /* Other errors: EIO, EINVAL, etc */ + return -1; + } + + total += n; + remain -= n; + } + + return total; +} + +/** + * Retry reads until we (a) time out or (b) get our data. Of course, if + * timeout is NULL, it'll wait forever. + * + * @param sockfd File descriptor we want to read from. + * @param buf Preallocated buffer into which we will read data. + * @param count Number of bytes to read. + * @param timeout (struct timeval) describing how long we should retry. + * @return The number of bytes read on success, or -1 on failure. + Note that we will always return (count) or (-1). + */ +ssize_t +_read_retry(int sockfd, void *buf, int count, struct timeval * timeout) +{ + int n, total = 0, remain = count, rv = 0; + fd_set rfds, xfds; + char *tmp_buf = (char *)buf; + + while (total < count) { + FD_ZERO(&rfds); + FD_SET(sockfd, &rfds); + FD_ZERO(&xfds); + FD_SET(sockfd, &xfds); + + /* + * Select on the socket, in case it closes while we're not + * looking... + */ + rv = _select_retry(sockfd + 1, &rfds, NULL, &xfds, timeout); + if (rv == -1) + return -1; + else if (rv == 0) { + errno = ETIMEDOUT; + return -1; + } + + if (FD_ISSET(sockfd, &xfds)) { + errno = EPIPE; + return -1; + } + + /* + * Attempt to read off the socket + */ + n = read(sockfd, tmp_buf + total, remain); + + /* + * When we know our socket was select()ed and we receive 0 bytes + * when we read, the socket was closed. + */ + if ((n == 0) && (rv == 1)) { + errno = EPIPE; + return -1; + } + + if (n == -1) { + if ((errno == EAGAIN) || (errno == EINTR)) { + /* + * Not ready? Wait for data to become available + */ + continue; + } + + /* Other errors: EPIPE, EINVAL, etc */ + return -1; + } + + total += n; + remain -= n; + } + + return total; +} |