XrdPosixCallBack.hh

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00001 #ifndef __POSIX_CALLBACK_HH__
00002 #define __POSIX_CALLBACK_HH__
00003 /******************************************************************************/
00004 /*                                                                            */
00005 /*                   X r d P o s i x C a l l B a c k . h h                    */
00006 /*                                                                            */
00007 /* (c) 2010 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 // This abstract class defines the callback interface for file open() calls.
00034 // It is passed when using the XrdPosixXrootd::Open() call. When passed, the
00035 // open request will be done in the background. When a callback object is
00036 // supplied, Open() will *always* return -1. However, if started successfully,
00037 // Open() will return -1 with errno set to EINPROGRESS. Otherwise, errno will
00038 // contain the reason the Open() request immediately failed. Upon completion,
00039 // the callback's Compete() method is invoked.  The Result parameter will either
00040 // be a non-negative file descriptor or -errno indicating that the Open()
00041 // failed. Note that the caller is responsible for deleting the callback object
00042 // after it has been invoked. Note that callbacks will be executed in a
00043 // separate thread unless open() is called with O_SYNC or maxThreads is zero.
00044 // WARNING: If O_SYNC or maxThreads is zero, then the callback must *not*
00045 //          issue any filesystem calls using the supplied file descriptor.
00046 //          Ignoring this will produce undetermined results including possible
00047 //          deadlock. Synchrnous callbacks are only meant to support private
00048 //          thread management.
00049 
00050 class XrdPosixCallBack
00051 {
00052 public:
00053 
00054 virtual void Complete(int Result) = 0;
00055 
00056              XrdPosixCallBack() {}
00057 virtual     ~XrdPosixCallBack() {}
00058 };
00059 #endif

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