Line data    Source code

       1             : /*
       2             :    Unix SMB/CIFS implementation.
       3             : 
       4             :    very efficient functions to manage mapping a id (such as a fnum) to
       5             :    a pointer. This is used for fnum and search id allocation.
       6             : 
       7             :    Copyright (C) Andrew Tridgell 2004
       8             : 
       9             :    This code is derived from lib/idr.c in the 2.6 Linux kernel, which was
      10             :    written by Jim Houston jim.houston@ccur.com, and is
      11             :    Copyright (C) 2002 by Concurrent Computer Corporation
      12             : 
      13             :    This program is free software; you can redistribute it and/or modify
      14             :    it under the terms of the GNU General Public License as published by
      15             :    the Free Software Foundation; either version 2 of the License, or
      16             :    (at your option) any later version.
      17             : 
      18             :    This program is distributed in the hope that it will be useful,
      19             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      20             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      21             :    GNU General Public License for more details.
      22             : 
      23             :    You should have received a copy of the GNU General Public License
      24             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      25             : */
      26             : 
      27             : /*
      28             :   see the section marked "public interface" below for documentation
      29             : */
      30             : 
      31             : /**
      32             :  * @file
      33             :  */
      34             : 
      35             : #include "replace.h"
      36             : #include "samba_util.h" /* generate_random() */
      37             : #include "idtree.h"
      38             : #include "idtree_random.h"
      39             : 
      40             : /**
      41             :   allocate a new id randomly in the given range
      42             : */
      43      649065 : _PUBLIC_ int idr_get_new_random(struct idr_context *idp,
      44             :                                 void *ptr,
      45             :                                 int starting_id,
      46             :                                 int limit)
      47             : {
      48        3055 :         int id;
      49             : 
      50             :         /* first try a random starting point in the whole range, and if that fails,
      51             :            then start randomly in the bottom half of the range. This can only
      52             :            fail if the range is over half full, and finally fallback to any
      53             :            free id */
      54      655175 :         id = idr_get_new_above(
      55      649065 :                 idp, ptr, starting_id+(generate_random() % limit), limit);
      56      649065 :         if (id == -1) {
      57           0 :                 id = idr_get_new_above(
      58             :                         idp,
      59             :                         ptr,
      60           0 :                         starting_id+(generate_random()%(limit/2)),
      61             :                         limit);
      62             :         }
      63      649065 :         if (id == -1) {
      64           0 :                 id = idr_get_new_above(idp, ptr, starting_id, limit);
      65             :         }
      66             : 
      67      649065 :         return id;
      68             : }