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Annotation of driverkit/libDriver/User/NXConditionLock.m, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: /*     Copyright (c) 1991 NeXT Computer, Inc.  All rights reserved. 
        !            25:  *
        !            26:  * NXConditionLock.m. Lock object with exported condition variable, 
        !            27:  *     user version.
        !            28:  *
        !            29:  * HISTORY
        !            30:  * 01-Aug-91    Doug Mitchell at NeXT
        !            31:  *      Created. 
        !            32:  */
        !            33: 
        !            34: 
        !            35: #import <machkit/NXLock.h>
        !            36: #import <mach/cthreads.h>
        !            37: 
        !            38: @implementation NXConditionLock 
        !            39: 
        !            40: /*
        !            41:  * _priv instance variable points to one of these.
        !            42:  */
        !            43: typedef struct {
        !            44:        struct mutex            m;
        !            45:        struct condition        c;
        !            46:        int                             locked;
        !            47:        int                     conditionVar;
        !            48: } conditionlock_priv_t;
        !            49: 
        !            50: - init
        !            51: {
        !            52:        conditionlock_priv_t *priv;
        !            53: 
        !            54:        [super init];
        !            55:        priv = _priv = malloc(sizeof(conditionlock_priv_t));
        !            56:        mutex_init(&priv->m);
        !            57:        condition_init(&priv->c);
        !            58:        priv->locked = 0;
        !            59:        priv->conditionVar = 0;
        !            60:        return self;
        !            61: }
        !            62: 
        !            63: - initWith : (int)condition
        !            64: {
        !            65:        conditionlock_priv_t *priv;
        !            66: 
        !            67:        [self init];
        !            68:        priv = _priv;
        !            69:        priv->conditionVar = condition;
        !            70:        return self;
        !            71: }
        !            72: 
        !            73: - (int) condition
        !            74: {
        !            75:        conditionlock_priv_t *priv = _priv;
        !            76: 
        !            77:        return priv->conditionVar;
        !            78: }
        !            79: 
        !            80: - free 
        !            81: {
        !            82:        conditionlock_priv_t *priv = _priv;
        !            83: 
        !            84:        mutex_clear(&priv->m);
        !            85:        condition_clear(&priv->c);
        !            86:        free(priv);
        !            87:        return [super free];
        !            88: }
        !            89: 
        !            90: // enter critical region, regardless of conditionVar
        !            91: - lock
        !            92: {
        !            93:        conditionlock_priv_t *priv = _priv;
        !            94: 
        !            95:        mutex_lock(&priv->m);
        !            96:        while (priv->locked)
        !            97:                condition_wait(&priv->c, &priv->m);     // block nicely
        !            98:        priv->locked = TRUE;
        !            99:        mutex_unlock(&priv->m);
        !           100:        return self;
        !           101: }
        !           102: 
        !           103: // leave critical region, regardless of conditionVar
        !           104: - unlock       // leave critical region, regardless of conditionVar
        !           105: {
        !           106:        conditionlock_priv_t *priv = _priv;
        !           107: 
        !           108:        mutex_lock(&priv->m);
        !           109:        priv->locked = FALSE;
        !           110:        mutex_unlock(&priv->m);
        !           111:        condition_broadcast(&priv->c);  // let everyone check conditionVar
        !           112:        return self;
        !           113: }
        !           114: 
        !           115: // enter critical section only upon condition
        !           116: - lockWhen : (int)value        // enter critical section only upon condition
        !           117: {
        !           118:        conditionlock_priv_t *priv = _priv;
        !           119: 
        !           120:        mutex_lock(&priv->m);
        !           121:        while(priv->locked || priv->conditionVar != value)
        !           122:                condition_wait(&priv->c, &priv->m);
        !           123:        priv->locked = TRUE;
        !           124:        mutex_unlock(&priv->m);
        !           125:        return self;
        !           126: }
        !           127: 
        !           128: // leave critical section, establishing condition 'value'
        !           129: - unlockWith : (int)value 
        !           130: {
        !           131:        conditionlock_priv_t *priv = _priv;
        !           132: 
        !           133:        mutex_lock(&priv->m);
        !           134:        priv->conditionVar = value;
        !           135:        priv->locked = FALSE;
        !           136:        mutex_unlock(&priv->m);
        !           137:        condition_broadcast(&priv->c);  // let everyone check condition
        !           138:        return self;
        !           139: }
        !           140: 
        !           141: @end

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