/*
* Copyright � 2007 Alistair Crooks.  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.
* 3. The name of the author may not be used to endorse or promote
*    products derived from this software without specific prior written
*    permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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/types.h>

#include <db.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

enum {
       BigEndian = 4321,
       LittleEndian = 1234
};

static struct stat      dbst;   /* stat info of database file */
static BTREEINFO        bt;     /* btree information */
static int              verbose; /* how chatty are we? */
static DB               *db;    /* data base operations struct */

/* perform the stat operation */
/* if this is the root, then just synthesise the data */
/* otherwise, retrieve the data, and be sure to fill in the size */
/* we use the mtime of the database file for each of the records */
static int
dbfs_getattr(const char *path, struct stat *st)
{
       int     res = 0;
       DBT     k;
       DBT     v;

       (void) memset(st, 0x0, sizeof(*st));
       if (strcmp(path, "/") == 0) {
               st->st_mode = S_IFDIR | 0755;
               st->st_nlink = 2;
       } else {
               k.size = strlen(k.data = __UNCONST(path + 1));
               if ((*db->seq)(db, &k, &v, R_CURSOR) != 0) {
                       return -ENOENT;
               }
               st->st_mode = S_IFREG | 0444;
               st->st_nlink = 1;
               st->st_size = v.size;
               st->st_mtime = dbst.st_mtime;
               st->st_atime = dbst.st_atime;
               st->st_ctime = dbst.st_ctime;
               st->st_uid = dbst.st_uid;
               st->st_gid = dbst.st_gid;
       }
       return res;
}

/* readdir operation */
/* run through the database file, returning records by key */
static int
dbfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
             off_t offset, struct fuse_file_info * fi)
{
       static int      ret;
       static DBT      k;
       int     flag;
       DBT     v;
       (void) fi;

       if (offset == 0) {
               (void) memset(&k, 0x0, sizeof(k));
               (void) filler(buf, ".", NULL, 0);
               (void) filler(buf, "..", NULL, 0);
               flag = R_FIRST;
               ret = 0;
       } else {
               flag = R_CURSOR;
       }
       if (ret != 0) {
               return 0;
       }
       for ( ; (ret = (*db->seq)(db, &k, &v, flag)) == 0 ; flag = R_NEXT) {
               if (filler(buf, k.data, NULL, 0) != 0) {
                       return 0;
               }
       }
       return 0;
}

/* open the file in the file system */
/* use seq method to get the record - get doesn't seem to work */
static int
dbfs_open(const char *path, struct fuse_file_info * fi)
{
       DBT     k;
       DBT     v;

       k.size = strlen(k.data = __UNCONST(path));
       if ((*db->get)(db, &k, &v, 0) != 0) {
               return -ENOENT;
       }

       if ((fi->flags & 3) != O_RDONLY) {
               return -EACCES;
       }
       return 0;
}

/* read the file's contents in the file system */
/* use seq method to get the record - get doesn't seem to work */
static int
dbfs_read(const char *path, char *buf, size_t size, off_t offset,
          struct fuse_file_info * fi)
{
       size_t  len;
       DBT     k;
       DBT     v;
       (void) fi;

       k.size = strlen(k.data = __UNCONST(path + 1));
       if ((*db->seq)(db, &k, &v, R_CURSOR) != 0) {
               return -ENOENT;
       }
       len = v.size;
       if (offset < len) {
               if (offset + size > len) {
                       size = len - offset;
               }
               (void) memcpy(buf, (char *) v.data + offset, size);
               buf[size - 1] = '\n';
       } else {
               size = 0;
       }
       return size;
}

/* fill in the statvfs struct */
static int
dbfs_statfs(const char *path, struct statvfs *st)
{
       (void) memset(st, 0x0, sizeof(*st));
       st->f_blocks = dbst.st_size / dbst.st_blksize;
       st->f_bsize = st->f_frsize = st->f_iosize = dbst.st_blksize;
       st->f_owner = dbst.st_uid;
       st->f_files = 1;
       return 0;
}

/* operations struct */
static struct fuse_operations dbfs_oper = {
       .getattr = dbfs_getattr,
       .readdir = dbfs_readdir,
       .open = dbfs_open,
       .read = dbfs_read,
       .statfs = dbfs_statfs
};

int
main(int argc, char **argv)
{
       int     i;

       while ((i = getopt(argc, argv, "v")) != -1) {
               switch(i) {
               case 'v':
                       verbose = 1;
                       break;
               }
       }
       if (stat(argv[optind], &dbst) != 0) {
               err(EXIT_FAILURE, "can't stat `%s'", argv[optind]);
       }
       bt.lorder = LittleEndian;
       if ((db = dbopen(argv[optind], O_RDONLY, 0666, DB_BTREE, &bt)) == NULL) {
               bt.lorder = BigEndian;
               db = dbopen(argv[optind], O_RDONLY, 0666, DB_BTREE, &bt);
               if (verbose) {
                       printf("Database not little endian - trying big endian now\n");
               }
       }
       if (db == NULL) {
               err(EXIT_FAILURE, "can't open db `%s'", argv[optind]);
       }
       return fuse_main(argc, argv, &dbfs_oper);
}

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