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Annotation of driverkit/libDriver/User/NXConditionLock.m, revision 1.1.1.1

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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