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 65class ILockable { 66public: 67 ILockable() { } 68 virtual ~ILockable() { } 69public: // constants 70 enum lock_t { 71 WRITE, 72 READ 73 }; 74 75public: // 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 91class Autolock { 92public: // *** 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 107private: 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__*/ 119