问可靠地检测计算机是否会进入休眠状态

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//
//  PDPowerManagement.h
//  Originally part of the Journler project: http://journler.phildow.net
//  Source code available at http://developers.phildow.net
//
//  Created by Philip Dow on 3/21/06.
//  Licensed under the LGPL: http://www.gnu.org/copyleft/lesser.html
//  You may modify and redistribute the code as needed.
//  Please keep this original notice intact.
//
//  Of course, I would appreciate a mentioning in your app's about box.
//  If you make improvements or additions to the code, please let me know.
//

#import <Cocoa/Cocoa.h>

//
// Be sure to include the IOKit Framework in your project

#import <mach/mach_port.h>
#import <mach/mach_interface.h>
#import <mach/mach_init.h>

#import <IOKit/pwr_mgt/IOPMLib.h>
#import <IOKit/IOMessage.h>

//
// Notifications
//
// The PDPowerManagementNotification will be sent to the default notification center
// with the shared instance of PDPowerManagement as the object. To make sure that a shared
// instance is available, call [PDPowerManagement sharedPowerManagement] somewhere in your code.
//
// The notification's user info dictionary will contain the PDPowerManagementMessage key with an
// NSNumber whose int value is either PDPowerManagementWillSleep or PDPowerManagementPoweredOn.

#define PDPowerManagementNotification   @"PDPowerManagementNotification"
#define PDPowerManagementMessage        @"PDPowerManagementMessage"
#define PDPowerManagementWillSleep      1
#define PDPowerManagementPoweredOn      3

//
// Disallowing Sleep
//
// There are two ways to disallow a power down. Either call setPermitSleep: with NO
// or implement the - (BOOL) shouldAllowIdleSleep:(id)sender delegate method and return NO as needed.
// At initialization _permitSleep is set to YES. With this value, the delegate method is
// always called if the delegate implements it. If _permitSleep is set to NO, the delegate
// method is never called. setPermitSleep: is thus a lazy way of always disallowing sleep.
//
// It must however be noted that it is not possible to cancel a sleep command that the user
// initiates. _permitSleep and the delegate method can only prevent an idle sleep. For
// more information: http://developer.apple.com/qa/qa2004/qa1340.html

@interface PDPowerManagement : NSObject {

    BOOL    _permitSleep;
    id      _delegate;

}

+ (id)sharedPowerManagement;

- (BOOL) permitSleep;
- (void) setPermitSleep:(BOOL)permitSleep;

- (id) delegate;
- (void) setDelegate:(id)delegate;

- (void) _postPMNotification:(NSInteger)message;
- (BOOL) _shouldAllowSleep;

@end

//
// Delegation
// You should implement: - (BOOL) shouldAllowIdleSleep:(id)sender
//
// If you set a delegate, before the computer is put to idle sleep the delegate's
// shouldAllowSleep: method will be called. Return NO to disallow the power down,
// return yes to permit it.

@interface NSObject (PDPowerManagementDelegate)

//
// return YES to permit a power down, NO to disallow it
- (BOOL) shouldAllowIdleSleep:(id)sender;

@end

//
//  PDPowerManagement.m
//  Journler
//
//  Created by Philip Dow on 3/21/06.
//  Copyright 2006 __MyCompanyName__. All rights reserved.
//

#import "PDPowerManagement.h"

@implementation PDPowerManagement

PDPowerManagement   *_self;
io_connect_t        root_port;

static void callback(void * x,io_service_t y,natural_t messageType,void * messageArgument)
{
    switch ( messageType ) {
        case kIOMessageSystemWillSleep:
            if ( [_self _shouldAllowSleep] ) {
                [_self _postPMNotification:PDPowerManagementWillSleep];
                IOAllowPowerChange(root_port,(long)messageArgument);
            }
            else
                IOCancelPowerChange(root_port,(long)messageArgument);
            break;
        case kIOMessageCanSystemSleep:
            IOAllowPowerChange(root_port,(long)messageArgument);
            break;
        case kIOMessageSystemHasPoweredOn:
            [_self _postPMNotification:PDPowerManagementPoweredOn];
            break;
    }

}

#pragma mark -

+ (id)sharedPowerManagement {
    static PDPowerManagement *sharedPowerManagement = nil;

    if (!sharedPowerManagement)
        sharedPowerManagement = [[PDPowerManagement allocWithZone:NULL] init];

    return sharedPowerManagement;
}


- (id)init
{

    if ( (self=[super init])!=nil )
        {
        IONotificationPortRef   notify;
        io_object_t             anIterator;

        root_port = IORegisterForSystemPower (0,&notify,callback,&anIterator);
        if ( root_port == IO_OBJECT_NULL ) {
            NSLog(@"IORegisterForSystemPower failed");
            return nil;
        }

        CFRunLoopAddSource(CFRunLoopGetCurrent(), IONotificationPortGetRunLoopSource(notify), kCFRunLoopDefaultMode);

        _permitSleep = YES;
        _self = self;

    }

    return self;
}

#pragma mark -

- (BOOL) permitSleep { return _permitSleep; }

- (void) setPermitSleep:(BOOL)permitSleep {
    _permitSleep = permitSleep;
}

- (id) delegate { return _delegate; }

- (void) setDelegate:(id)delegate {
    _delegate = delegate;
}

#pragma mark -

- (void) _postPMNotification:(NSInteger)message {

    NSNumber *dictionaryMessage;
    NSDictionary *userInfo;
    NSNotification *notification;


    // Useful for debugging
    /*
    switch ( message ) {

        case PDPowerManagementWillSleep:
            NSLog(@"Going to sleep now");
            break;
        case PDPowerManagementPoweredOn:
            NSLog(@"Just had a nice snooze");
            break;

    }
    */

    dictionaryMessage = [NSNumber numberWithInteger:message];
    userInfo = [NSDictionary dictionaryWithObjectsAndKeys:
            dictionaryMessage, PDPowerManagementMessage, nil];
    notification = [NSNotification notificationWithName:PDPowerManagementNotification
            object:self userInfo:userInfo];

    [[NSNotificationCenter defaultCenter] postNotification:notification];

}

- (BOOL) _shouldAllowSleep {

    if ( !_permitSleep )
        return NO;
    else {
        if ( _delegate && [_delegate respondsToSelector:@selector(shouldAllowIdleSleep:)] )
            return [_delegate shouldAllowIdleSleep:self];
        else
            return YES;
    }
}

@end