XrdSysXSLock.hh

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00001 #ifndef __SYS_XSLOCK_HH__
00002 #define __SYS_XSLOCK_HH__
00003 /******************************************************************************/
00004 /*                                                                            */
00005 /*                       X r d S y s X S L o c k . h h                        */
00006 /*                                                                            */
00007 /* (c) 2003 by the Board of Trustees of the Leland Stanford, Jr., University  */
00008 /*                            All Rights Reserved                             */
00009 /*   Produced by Andrew Hanushevsky for Stanford University under contract    */
00010 /*              DE-AC02-76-SFO0515 with the Department of Energy              */
00011 /*                                                                            */
00012 /* This file is part of the XRootD software suite.                            */
00013 /*                                                                            */
00014 /* XRootD is free software: you can redistribute it and/or modify it under    */
00015 /* the terms of the GNU Lesser General Public License as published by the     */
00016 /* Free Software Foundation, either version 3 of the License, or (at your     */
00017 /* option) any later version.                                                 */
00018 /*                                                                            */
00019 /* XRootD is distributed in the hope that it will be useful, but WITHOUT      */
00020 /* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or      */
00021 /* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public       */
00022 /* License for more details.                                                  */
00023 /*                                                                            */
00024 /* You should have received a copy of the GNU Lesser General Public License   */
00025 /* along with XRootD in a file called COPYING.LESSER (LGPL license) and file  */
00026 /* COPYING (GPL license).  If not, see <http://www.gnu.org/licenses/>.        */
00027 /*                                                                            */
00028 /* The copyright holder's institutional names and contributor's names may not */
00029 /* be used to endorse or promote products derived from this software without  */
00030 /* specific prior written permission of the institution or contributor.       */
00031 /******************************************************************************/
00032 
00033 #include <errno.h>
00034 #include "XrdSys/XrdSysPthread.hh"
00035 
00036 // These are valid usage options
00037 //
00038 enum XrdSysXS_Type {xs_None = 0, xs_Shared = 1, xs_Exclusive = 2};
00039 
00040 // This class implements the shared lock. Any number of readers are allowed
00041 // by requesting a shared lock. Only one exclusive writer is allowed by
00042 // requesting an exclusive lock. Up/downgrading is not supported.
00043 //
00044 class XrdSysXSLock
00045 {
00046 public:
00047 
00048 void        Lock(const XrdSysXS_Type usage);
00049 
00050 void      UnLock(const XrdSysXS_Type usage=xs_None);
00051 
00052           XrdSysXSLock() : cur_usage(xs_None), cur_count(0), exc_wait(0),
00053                            shr_wait(0), toggle(0), WantShr(0), WantExc(0) {}
00054          ~XrdSysXSLock();
00055 
00056 private:
00057 
00058 XrdSysXS_Type cur_usage;
00059 int           cur_count;
00060 int           exc_wait;
00061 int           shr_wait;
00062 int           toggle;
00063 
00064 XrdSysMutex       LockContext;
00065 XrdSysSemaphore   WantShr;
00066 XrdSysSemaphore   WantExc;
00067 };
00068 #endif

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