xrootd/XrdSys/XrdSysXSLock.hh

0001 #ifndef __SYS_XSLOCK_HH__
0002 #define __SYS_XSLOCK_HH__
0003 /******************************************************************************/
0004 /*                                                                            */
0005 /*                       X r d S y s X S L o c k . h h                        */
0006 /*                                                                            */
0007 /* (c) 2003 by the Board of Trustees of the Leland Stanford, Jr., University  */
0008 /*                            All Rights Reserved                             */
0009 /*   Produced by Andrew Hanushevsky for Stanford University under contract    */
0010 /*              DE-AC02-76-SFO0515 with the Department of Energy              */
0011 /*                                                                            */
0012 /* This file is part of the XRootD software suite.                            */
0013 /*                                                                            */
0014 /* XRootD is free software: you can redistribute it and/or modify it under    */
0015 /* the terms of the GNU Lesser General Public License as published by the     */
0016 /* Free Software Foundation, either version 3 of the License, or (at your     */
0017 /* option) any later version.                                                 */
0018 /*                                                                            */
0019 /* XRootD is distributed in the hope that it will be useful, but WITHOUT      */
0020 /* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or      */
0021 /* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public       */
0022 /* License for more details.                                                  */
0023 /*                                                                            */
0024 /* You should have received a copy of the GNU Lesser General Public License   */
0025 /* along with XRootD in a file called COPYING.LESSER (LGPL license) and file  */
0026 /* COPYING (GPL license).  If not, see <http://www.gnu.org/licenses/>.        */
0027 /*                                                                            */
0028 /* The copyright holder's institutional names and contributor's names may not */
0029 /* be used to endorse or promote products derived from this software without  */
0030 /* specific prior written permission of the institution or contributor.       */
0031 /******************************************************************************/
0032
0033 #include <cerrno>
0034 #include "XrdSys/XrdSysPthread.hh"
0035
0036 // These are valid usage options
0037 //
0038 enum XrdSysXS_Type {xs_None = 0, xs_Shared = 1, xs_Exclusive = 2};
0039
0040 // This class implements the shared lock. Any number of readers are allowed
0041 // by requesting a shared lock. Only one exclusive writer is allowed by
0042 // requesting an exclusive lock. Up/downgrading is not supported.
0043 //
0044 class XrdSysXSLock
0045 {
0046 public:
0047
0048 void        Lock(const XrdSysXS_Type usage);
0049
0050 void      UnLock(const XrdSysXS_Type usage=xs_None);
0051
0052           XrdSysXSLock() : cur_usage(xs_None), cur_count(0), exc_wait(0),
0053                            shr_wait(0), toggle(0), WantShr(0), WantExc(0) {}
0054          ~XrdSysXSLock();
0055
0056 private:
0057
0058 XrdSysXS_Type cur_usage;
0059 int           cur_count;
0060 int           exc_wait;
0061 int           shr_wait;
0062 int           toggle;
0063
0064 XrdSysMutex       LockContext;
0065 XrdSysSemaphore   WantShr;
0066 XrdSysSemaphore   WantExc;
0067 };
0068 #endif