src/DiskIO/DiskIOStrategy.h

   1 /*
   2  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   3  * ----------------------------------------------------------
   4  *
   5  *  Squid is the result of efforts by numerous individuals from
   6  *  the Internet community; see the CONTRIBUTORS file for full
   7  *  details.   Many organizations have provided support for Squid's
   8  *  development; see the SPONSORS file for full details.  Squid is
   9  *  Copyrighted (C) 2001 by the Regents of the University of
  10  *  California; see the COPYRIGHT file for full details.  Squid
  11  *  incorporates software developed and/or copyrighted by other
  12  *  sources; see the CREDITS file for full details.
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License as published by
  16  *  the Free Software Foundation; either version 2 of the License, or
  17  *  (at your option) any later version.
  18  *
  19  *  This program is distributed in the hope that it will be useful,
  20  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  *  GNU General Public License for more details.
  23  *
  24  *  You should have received a copy of the GNU General Public License
  25  *  along with this program; if not, write to the Free Software
  26  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  27  *
  28  * Copyright (c) 2003 Robert Collins <robertc@squid-cache.org>
  29  */
  30
  31 #ifndef SQUID_DISKIOSTRATEGY_H
  32 #define SQUID_DISKIOSTRATEGY_H
  33
  34 #include "Store.h"
  35 #include "RefCount.h"
  36
  37 class DiskFile;
  38
  39 class ConfigOption;
  40
  41 class DiskIOStrategy
  42 {
  43
  44 public:
  45     virtual ~DiskIOStrategy() {}
  46
  47     /** Can the IO Strategy handle more requests ? */
  48     virtual bool shedLoad() = 0;
  49
  50     /** What is the current load? 999 = 99.9% */
  51     virtual int load() = 0;
  52
  53     /** Return a handle for performing IO operations */
  54     virtual RefCount<DiskFile> newFile(char const *path) = 0;
  55
  56     /** flush all IO operations  */
  57     virtual void sync() {}
  58
  59     /** whether the IO Strategy can use unlinkd */
  60     virtual bool unlinkdUseful() const = 0;
  61
  62     /** unlink a file by path */
  63     virtual void unlinkFile(char const *) = 0;
  64
  65     /** perform any pending callbacks */
  66     virtual int callback() { return 0; }
  67
  68     /** Init per-instance logic */
  69     virtual void init() {}
  70
  71     /** cachemgr output on the IO instance stats */
  72     virtual void statfs(StoreEntry & sentry)const {}
  73
  74     /** module specific options */
  75     virtual ConfigOption *getOptionTree() const { return NULL;}
  76 };
  77
  78 /* Because we need the DiskFile definition for newFile. */
  79 #include "DiskFile.h"
  80
  81 class SingletonIOStrategy : public DiskIOStrategy
  82 {
  83
  84 public:
  85     SingletonIOStrategy(DiskIOStrategy *anIO) : io(anIO) {}
  86
  87     virtual bool shedLoad() { return io->shedLoad(); }
  88
  89     virtual int load() { return io->load(); }
  90
  91     virtual RefCount<DiskFile> newFile (char const *path) {return io->newFile(path); }
  92
  93     virtual void sync() { io->sync(); }
  94
  95     virtual bool unlinkdUseful() const { return io->unlinkdUseful(); }
  96
  97     virtual void unlinkFile (char const *path) { io->unlinkFile(path); }
  98
  99     virtual int callback() { return io->callback(); }
 100
 101     virtual void init() { io->init(); }
 102
 103     virtual void statfs(StoreEntry & sentry)const { io->statfs(sentry); }
 104
 105     virtual ConfigOption *getOptionTree() const { return io->getOptionTree(); }
 106
 107 private:
 108     DiskIOStrategy *io;
 109 };
 110
 111 #endif /* SQUID_DISKIOSTRATEGY_H */