lib/libstand/splitfs.c

/*
 * Copyright (c) 2002 Maxim Sobolev
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "stand.h"

#define NTRIES      (3)
#define CONF_BUF    (512)
#define SEEK_BUF    (512)

struct split_file
{
    char  **filesv; /* Filenames */
    char  **descsv; /* Descriptions */
    int   filesc;   /* Number of parts */
    int   curfile;  /* Current file number */
    int   curfd;    /* Current file descriptor */
    off_t tot_pos;  /* Offset from the beginning of the sequence */
    off_t file_pos; /* Offset from the beginning of the slice */
};

static int  split_openfile(struct split_file *sf);
static int  splitfs_open(const char *path, struct open_file *f);
static int  splitfs_close(struct open_file *f);
static int  splitfs_read(struct open_file *f, void *buf, size_t size, size_t *resid);
static off_t    splitfs_seek(struct open_file *f, off_t offset, int where);
static int  splitfs_stat(struct open_file *f, struct stat *sb);

struct fs_ops splitfs_fsops = {
    "split",
    splitfs_open,
    splitfs_close,
    splitfs_read,
    null_write,
    splitfs_seek,
    splitfs_stat,
    null_readdir
};

static void
split_file_destroy(struct split_file *sf)
{
    int i;

    if (sf->filesc > 0) {
    for (i = 0; i < sf->filesc; i++) {
        free(sf->filesv[i]);
        free(sf->descsv[i]);
    }
    free(sf->filesv);
    free(sf->descsv);
    }
    free(sf);
}

static int
split_openfile(struct split_file *sf)
{
    int i;

    for (i = 0;; i++) {
    sf->curfd = open(sf->filesv[sf->curfile], O_RDONLY);
    if (sf->curfd >= 0)
        break;
    if ((sf->curfd == -1) && (errno != ENOENT))
        return (errno);
    if (i == NTRIES)
        return (EIO);
    printf("\nInsert disk labelled %s and press any key...",
        sf->descsv[sf->curfile]);
    getchar();
    putchar('\n');
    }
    sf->file_pos = 0;
    return (0);
}

static int
splitfs_open(const char *fname, struct open_file *f)
{
    char *buf, *confname, *cp;
    int conffd;
    struct split_file *sf;
    struct stat sb;

    /* Have to be in "just read it" mode */
    if (f->f_flags != F_READ)
    return(EPERM);

    /* If the name already ends in `.split', ignore it */
    if ((cp = strrchr(fname, '.')) && (!strcmp(cp, ".split")))
    return(ENOENT);

    /* Construct new name */
    confname = malloc(strlen(fname) + 7);
    sprintf(confname, "%s.split", fname);

    /* Try to open the configuration file */
    conffd = open(confname, O_RDONLY);
    free(confname);
    if (conffd == -1)
    return(ENOENT);

    if (fstat(conffd, &sb) < 0) {
    printf("splitfs_open: stat failed\n");
    close(conffd);
    return(ENOENT);
    }
    if (!S_ISREG(sb.st_mode)) {
    printf("splitfs_open: not a file\n");
    close(conffd);
    return(EISDIR);         /* best guess */
    }

    /* Allocate a split_file structure, populate it from the config file */
    sf = malloc(sizeof(struct split_file));
    bzero(sf, sizeof(struct split_file));
    buf = malloc(CONF_BUF);
    while (fgetstr(buf, CONF_BUF, conffd) > 0) {
    cp = buf;
    while ((*cp != '\0') && (isspace(*cp) == 0))
        cp++;
    if (*cp != '\0') {
        *cp = '\0';
        cp++;
    }
    while ((*cp != '\0') && (isspace(*cp) != 0))
        cp++;
    if (*cp == '\0')
        cp = buf;
    sf->filesc++;
    sf->filesv = realloc(sf->filesv, sizeof(*(sf->filesv)) * sf->filesc);
    sf->descsv = realloc(sf->descsv, sizeof(*(sf->descsv)) * sf->filesc);
    sf->filesv[sf->filesc - 1] = strdup(buf);
    sf->descsv[sf->filesc - 1] = strdup(cp);
    }
    free(buf);
    close(conffd);

    if (sf->filesc == 0) {
    split_file_destroy(sf);
    return(ENOENT);
    }
    errno = split_openfile(sf);
    if (errno != 0) {
    split_file_destroy(sf);
    return(ENOENT);
    }

    /* Looks OK, we'll take it */
    f->f_fsdata = sf;
    return (0);
}

static int
splitfs_close(struct open_file *f)
{
    int fd;
    struct split_file *sf;

    sf = (struct split_file *)f->f_fsdata;
    fd = sf->curfd;
    split_file_destroy(sf);
    return(close(fd));
}

static int
splitfs_read(struct open_file *f, void *buf, size_t size, size_t *resid)
{
    ssize_t nread;
    size_t totread;
    struct split_file *sf;

    sf = (struct split_file *)f->f_fsdata;
    totread = 0;
    do {
    nread = read(sf->curfd, buf, size - totread);

    /* Error? */
    if (nread == -1)
        return (errno);

    sf->tot_pos += nread;
    sf->file_pos += nread;
    totread += nread;
    buf = (char *)buf + nread;

    if (totread < size) {               /* EOF */
        if (sf->curfile == (sf->filesc - 1))    /* Last slice */
        break;

        /* Close previous slice */
        if (close(sf->curfd) != 0)
        return (errno);

        sf->curfile++;
        errno = split_openfile(sf);
        if (errno)
            return (errno);
    }
    } while (totread < size);

    if (resid != NULL)
    *resid = size - totread;

    return (0);
}

static off_t
splitfs_seek(struct open_file *f, off_t offset, int where)
{
    int nread;
    size_t resid;
    off_t new_pos, seek_by;
    struct split_file *sf;

    sf = (struct split_file *)f->f_fsdata;

    seek_by = offset;
    switch (where) {
    case SEEK_SET:
    seek_by -= sf->tot_pos;
    break;
    case SEEK_CUR:
    break;
    case SEEK_END:
    panic("splitfs_seek: SEEK_END not supported");
    break;
    default:
    errno = EINVAL;
    return (-1);
    }

    if (seek_by > 0) {
    /*
     * Seek forward - implemented using splitfs_read(), because otherwise we'll be
     * unable to detect that we have crossed slice boundary and hence
     * unable to do a long seek crossing that boundary.
     */
    void *tmp;

    tmp = malloc(SEEK_BUF);
    if (tmp == NULL) {
        errno = ENOMEM;
        return (-1);
    }

    nread = 0;
    for (; seek_by > 0; seek_by -= nread) {
        resid = 0;
        errno = splitfs_read(f, tmp, min(seek_by, SEEK_BUF), &resid);
        nread = min(seek_by, SEEK_BUF) - resid;
        if ((errno != 0) || (nread == 0))
        /* Error or EOF */
        break;
    }
    free(tmp);
    if (errno != 0)
        return (-1);
    }

    if (seek_by != 0) {
    /* Seek backward or seek past the boundary of the last slice */
    if (sf->file_pos + seek_by < 0)
        panic("splitfs_seek: can't seek past the beginning of the slice");
    new_pos = lseek(sf->curfd, seek_by, SEEK_CUR);
    if (new_pos < 0) {
        errno = EINVAL;
        return (-1);
    }
    sf->tot_pos += new_pos - sf->file_pos;
    sf->file_pos = new_pos;
    }

    return (sf->tot_pos);
}

static int
splitfs_stat(struct open_file *f, struct stat *sb)
{
    int result;
    struct split_file *sf = (struct split_file *)f->f_fsdata;

    /* stat as normal, but indicate that size is unknown */
    if ((result = fstat(sf->curfd, sb)) == 0)
    sb->st_size = -1;
    return (result);
}