[paraslash.git] / fd.c

/*
 * Copyright (C) 2006-2007 Andre Noll <maan@systemlinux.org>
 *
 *     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 of the License, 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; if not, write to the Free Software
 *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 */

/** \file fd.c helper functions for file descriptor handling */

#include "para.h"
#include <sys/mman.h>
#include <fcntl.h>
#include <sys/select.h>

#include "error.h"
/**
 * check whether a file exists
 *
 * \param fn the file name
 *
 * \return Non-zero iff file exists.
 */
int file_exists(const char *fn)
{
        struct stat statbuf;

        return !stat(fn, &statbuf);
}

/**
 * paraslash's wrapper for select(2)
 *
 * It calls select(2) (with no exceptfds) and starts over if select() was
 * interrupted by a signal.
 *
 * \param n the highest-numbered descriptor in any of the two sets, plus 1
 * \param readfds fds that should be checked for readability
 * \param writefds fds that should be checked for writablility
 * \param timeout_tv upper bound on the amount of time elapsed before select()
 * returns
 *
 * \return The return value of the underlying select() call.
 *
 * All arguments are passed verbatim to select(2).
 * \sa select(2) select_tut(2)
 */
int para_select(int n, fd_set *readfds, fd_set *writefds,
                struct timeval *timeout_tv)
{
        int ret, err;
        do {
                ret = select(n, readfds, writefds, NULL, timeout_tv);
                err = errno;
        } while (ret < 0 && err == EINTR);
        if (ret < 0)
                PARA_CRIT_LOG("select error: %s, max_fileno: %d\n",
                        strerror(err), n);
        return ret;
}

/**
 * set a file descriptor to non-blocking mode
 *
 * \param fd The file descriptor
 *
 * \returns 1 on success, -E_F_GETFL, -E_F_SETFL, on errors.
 */
int mark_fd_nonblock(int fd)
{
        int flags = fcntl(fd, F_GETFL);
        if (flags < 0)
                return -E_F_GETFL;
        if (fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK) < 0)
                return -E_F_SETFL;
        return 1;
}

/**
 * set a file descriptor in a fd_set
 *
 * \param fd the file descriptor to be set
 * \param fds the file descriptor set
 * \param max_fileno highest-numbered file descriptor
 *
 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
 * return, \a max_fileno contains the maximum of the old_value and \a fd.
 *
 * \sa para_select
*/
void para_fd_set(int fd, fd_set *fds, int *max_fileno)
{

        if (fd < 0 || fd >= FD_SETSIZE) {
                PARA_EMERG_LOG("fatal: tried to add invalid fd %d\n", fd);
                exit(EXIT_FAILURE);
        }
#if 0
        {
                int flags = fcntl(fd, F_GETFL);
                if (!(flags & O_NONBLOCK)) {
                        PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
                        exit(EXIT_FAILURE);
                }
        }
#endif
        FD_SET(fd, fds);
        *max_fileno = PARA_MAX(*max_fileno, fd);
}

/**
 * paraslash's wrapper for fread(3)
 *
 * \param dest destination pointer
 * \param nbytes size of one element
 * \param nmemb number of elements to write
 * \param stream the input stream
 *
 * \return negative on errors, zero on end of file, and the number of bytes
 * (not elements) read on success.
 *
 * \sa fread(3)
 */
__must_check int para_fread(void *dest, size_t nbytes, size_t nmemb, FILE *stream)
{
        size_t res = fread(dest, nbytes, nmemb, stream);
        if (res == nmemb)
                return nbytes * nmemb;
        if (feof(stream))
                return 0;
        return -E_FREAD;
}
/**
* paraslash's wrapper for fgets(3)
* \param line pointer to the buffer to store the line
* \param size the size of the buffer given by \a line
* \param f the stream to read from
*
* \return Unlike the standard fgets() function, an integer value
* is returned. On success, this function returns 1. On errors, -E_FGETS
* is returned. A zero return value indicates an end of file condition.
*/
__must_check int para_fgets(char *line, int size, FILE *f)
{
again:
        if (fgets(line, size, f))
                return 1;
        if (feof(f))
                return 0;
        if (!ferror(f))
                return -E_FGETS;
        if (errno != EINTR) {
                PARA_ERROR_LOG("%s\n", strerror(errno));
                return -E_FGETS;
        }
        clearerr(f);
        goto again;
}

/**
 * paralash's wrapper for fseek(3)
 *
 * \param stream stream to seek
 * \param offset added to the position specified by whence
 * \param whence \p SEEK_SET, \p SEEK_CUR, or \p SEEK_END
 *
 * \return positive on success, -E_FSEEK on errors.
 *
 * \sa fseek(3)
 */
int para_fseek(FILE *stream, long offset, int whence)
{
        int ret = fseek(stream, offset, whence);
        return ret < 0? -E_FSEEK : 1;
}

/**
 * *paraslash's wrapper for mmap
 *
 * \param length number of bytes to mmap
 * \param prot either PROT_NONE or the bitwise OR of one or more of
 * PROT_EXEC PROT_READ PROT_WRITE
 * \param flags exactly one of MAP_SHARED and MAP_PRIVATE
 * \param fd the file to mmap from
 * \param offset mmap start
 *
 * \return This function either returns a valid pointer to the mapped area
 * or calls exit() on errors.
 */
void *para_mmap(size_t length, int prot, int flags, int fd, off_t offset)
{
        void *ret = mmap(NULL, length, prot, flags, fd, offset);
        if (ret != MAP_FAILED)
                return ret;
        PARA_EMERG_LOG("mmap failed: %s", strerror(errno));
        exit(EXIT_FAILURE);
}