src/apps/cortex/support/ILockable.h

   1 /*
   2  * Copyright (c) 1999-2000, Eric Moon.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions, and the following disclaimer.
  11  *
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions, and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * 3. The name of the author may not be used to endorse or promote products
  17  *    derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF TITLE, NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  23  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  24  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  26  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
  27  * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31
  32 // ILockable.h (Cortex)
  33 // * PURPOSE
  34 //   Simple interface by which an object's locking capabilites
  35 //   are declared/exposed.  Includes support for multiple lock
  36 //   modes (read/write) which objects can choose to support if
  37 //   they wish.
  38 //
  39 // * IMPLEMENTATION/USAGE
  40 //   Implementations are expected to follow the rules described
  41 //   in the MultiLock documentation (Be Developer Newsletter
  42 //   Vol.2 #36, Sep '98).  In brief: write locks can be nested
  43 //   (a thread holding the write lock may nest as many read or
  44 //   or write locks as it likes) but read locks may not (only one
  45 //   per thread.)
  46 //
  47 //   If using a simple BLocker to implement, ignore the mode.
  48 //
  49 // * HISTORY
  50 //   e.moon             26jul99         Moved Autolock into this file to
  51 //                                                                                      resolve header-naming conflict.
  52 //   e.moon             7jul99          Reworked slightly for Cortex.
  53 //   e.moon             13apr99         Begun (beDub)
  54
  55 #ifndef __ILockable_H__
  56 #define __ILockable_H__
  57
  58 #include <Debug.h>
  59
  60 #include "cortex_defs.h"
  61 __BEGIN_CORTEX_NAMESPACE
  62
  63 // the locking interface
  64
  65 class ILockable {
  66 public:
  67         ILockable() { }
  68         virtual ~ILockable() { }
  69 public:                                         // constants
  70         enum lock_t {
  71                 WRITE,
  72                 READ
  73         };
  74
  75 public:                                         // interface
  76         virtual bool lock(
  77                 lock_t type=WRITE,
  78                 bigtime_t timeout=B_INFINITE_TIMEOUT)=0;
  79
  80         virtual bool unlock(
  81                 lock_t type=WRITE)=0;
  82
  83         virtual bool isLocked(
  84                 lock_t type=WRITE) const=0;
  85 };
  86
  87
  88
  89 // a simple hands-free lock helper
  90
  91 class Autolock {
  92 public:                         // *** ctor/dtor
  93         virtual ~Autolock() {
  94                 ASSERT(m_target);
  95                 if(m_locked)
  96                         m_target->unlock();
  97         }
  98
  99         Autolock(ILockable& target) : m_target(&target) { init(); }
 100         Autolock(ILockable* target) : m_target( target) { init(); }
 101
 102         Autolock(const ILockable& target) :
 103                 m_target(const_cast<ILockable*>(&target)) { init(); }
 104         Autolock(const ILockable* target) :
 105                 m_target(const_cast<ILockable*>( target)) { init(); }
 106
 107 private:
 108         void init() {
 109                 ASSERT(m_target);
 110                 m_locked = m_target->lock();
 111         }
 112
 113         ILockable*                      m_target;
 114         bool                                            m_locked;
 115 };
 116
 117 __END_CORTEX_NAMESPACE
 118 #endif /*__ILockable_H__*/