/** @file databasehelpers.cc
 * @brief Helper functions for database handling
 */
/* Copyright 2002-2019 Olly Betts
 * Copyright 2008 Lemur Consulting Ltd
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */

#include <config.h>

#include "databasehelpers.h"

#include "backends.h"

#include "glass/glass_defs.h"

#include "io_utils.h"
#include "omassert.h"
#include "posixy_wrapper.h"

#include <algorithm>
#include <cstring>
#include <string>
#include <sys/types.h>
#include "safesysstat.h"
#include "safeunistd.h"

using namespace std;

int
test_if_single_file_db(const struct stat& sb,
		       const string& path,
		       int* fd_ptr)
{
    Assert(fd_ptr);
#if defined XAPIAN_HAS_GLASS_BACKEND
    if (!S_ISREG(sb.st_mode)) return BACKEND_UNKNOWN;
    // Look at the size as a clue - if it's less than GLASS_MIN_BLOCKSIZE then
    // it's not a single-file glass database.  For a larger file, we peek at
    // the start of the file to determine what it is.
    if (sb.st_size < GLASS_MIN_BLOCKSIZE)
	return BACKEND_UNKNOWN;
    int fd = posixy_open(path.c_str(), O_RDONLY|O_BINARY);
    if (fd != -1) {
	char magic_buf[14];
	// FIXME: Don't duplicate magic check here...
	if (io_read(fd, magic_buf, 14) == 14 &&
	    lseek(fd, 0, SEEK_SET) == 0 &&
	    memcmp(magic_buf, "\x0f\x0dXapian Glass", 14) == 0) {
	    *fd_ptr = fd;
	    return BACKEND_GLASS;
	}
	::close(fd);
    }
#else
    (void)sb;
    (void)path;
    (void)fd_ptr;
#endif
    return BACKEND_UNKNOWN;
}
