DNSSDObjects/DNSSDBrowser.m

/*
    File:       DNSSDBrowser.m
 
    Contains:   Uses the low-level DNS-SD API to browse for Bonjour services.
 
    Written by: DTS
 
    Copyright:  Copyright (c) 2011 Apple Inc. All Rights Reserved.
 
    Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple Inc.
                ("Apple") in consideration of your agreement to the following
                terms, and your use, installation, modification or
                redistribution of this Apple software constitutes acceptance of
                these terms.  If you do not agree with these terms, please do
                not use, install, modify or redistribute this Apple software.
 
                In consideration of your agreement to abide by the following
                terms, and subject to these terms, Apple grants you a personal,
                non-exclusive license, under Apple's copyrights in this
                original Apple software (the "Apple Software"), to use,
                reproduce, modify and redistribute the Apple Software, with or
                without modifications, in source and/or binary forms; provided
                that if you redistribute the Apple Software in its entirety and
                without modifications, you must retain this notice and the
                following text and disclaimers in all such redistributions of
                the Apple Software. Neither the name, trademarks, service marks
                or logos of Apple Inc. may be used to endorse or promote
                products derived from the Apple Software without specific prior
                written permission from Apple.  Except as expressly stated in
                this notice, no other rights or licenses, express or implied,
                are granted by Apple herein, including but not limited to any
                patent rights that may be infringed by your derivative works or
                by other works in which the Apple Software may be incorporated.
 
                The Apple Software is provided by Apple on an "AS IS" basis. 
                APPLE MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
                WITHOUT LIMITATION THE IMPLIED WARRANTIES OF NON-INFRINGEMENT,
                MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, REGARDING
                THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN
                COMBINATION WITH YOUR PRODUCTS.
 
                IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT,
                INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
                TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
                DATA, OR PROFITS; OR BUSINESS INTERRUPTION) ARISING IN ANY WAY
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                OF CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR
                OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF
                SUCH DAMAGE.
 
*/
 
#import "DNSSDBrowser.h"
 
#include <dns_sd.h>
 
#pragma mark * DNSSDBrowser
 
@interface DNSSDBrowser ()
 
// private properties
 
@property (assign, readwrite) DNSServiceRef      sdRef;
 
// forward declarations
 
- (void)stopWithError:(NSError *)error notify:(BOOL)notify;
 
@end
 
@implementation DNSSDBrowser
 
@synthesize domain = domain_;
@synthesize type = type_;
 
@synthesize delegate = delegate_;
 
@synthesize sdRef = sdRef_;
 
- (id)initWithDomain:(NSString *)domain type:(NSString *)type
    // See comment in header.
{
    // domain may be nil or empty
    assert( ! [domain hasPrefix:@"."] );
    assert(type != nil);
    assert([type length] != 0);
    assert( ! [type hasPrefix:@"."] );
    self = [super init];
    if (self != nil) {
        if ( ([domain length] != 0) && ! [domain hasSuffix:@"."] ) {
            domain = [domain stringByAppendingString:@"."];
        }
        if ( ! [type hasSuffix:@"."] ) {
            type = [type stringByAppendingString:@"."];
        }
        self->domain_ = [domain copy];
        self->type_ = [type copy];
    }
    return self;
}
 
- (void)dealloc
{
    if (self->sdRef_ != NULL) {
        DNSServiceRefDeallocate(self->sdRef_);
    }
    [self->domain_ release];
    [self->type_ release];
    [super dealloc];
}
 
- (void)browseReplyWithFlags:(DNSServiceFlags)flags domain:(NSString *)domain type:(NSString *)type name:(NSString *)name
    // Called when DNS-SD tells us that a service has been discovered or lost.
{
    BOOL            moreComing;
    DNSSDService *   service;
    
    assert(domain != nil);
    assert(type   != nil);
    assert(name   != nil);
    
    moreComing = (flags & kDNSServiceFlagsMoreComing) != 0;
    
    service = [[[DNSSDService alloc] initWithDomain:domain type:type name:name] autorelease];
    assert(service != nil);
    
    if (flags & kDNSServiceFlagsAdd) {
        if ([self.delegate respondsToSelector:@selector(dnssdBrowser:didAddService:moreComing:)]) {
            [self.delegate dnssdBrowser:self didAddService:service moreComing:moreComing];
        }
    } else {
        if ([self.delegate respondsToSelector:@selector(dnssdBrowser:didRemoveService:moreComing:)]) {
            [self.delegate dnssdBrowser:self didRemoveService:service moreComing:moreComing];
        }
    }
}
 
static void BrowseReplyCallback(
    DNSServiceRef                       sdRef,
    DNSServiceFlags                     flags,
    uint32_t                            interfaceIndex,
    DNSServiceErrorType                 errorCode,
    const char                          *serviceName,
    const char                          *regtype,
    const char                          *replyDomain,
    void                                *context
)
    // Called by DNS-SD when something happens with the browse operation.
{
    DNSSDBrowser *    obj;
    #pragma unused(interfaceIndex)
 
    assert([NSThread isMainThread]);        // because sdRef dispatches to the main queue
    
    obj = (DNSSDBrowser *) context;
    assert([obj isKindOfClass:[DNSSDBrowser class]]);
    assert(sdRef == obj->sdRef_);
    #pragma unused(sdRef)
    
    if (errorCode == kDNSServiceErr_NoError) {
        [obj browseReplyWithFlags:flags domain:[NSString stringWithUTF8String:replyDomain] type:[NSString stringWithUTF8String:regtype] name:[NSString stringWithUTF8String:serviceName]];
    } else {
        [obj stopWithError:[NSError errorWithDomain:NSNetServicesErrorDomain code:errorCode userInfo:nil] notify:YES];
    }
}
 
- (void)startBrowse
    // See comment in header.
{
    NSString *              domain;
    DNSServiceErrorType     errorCode;
    
    if (self.sdRef == NULL) {
        domain = self.domain;
        if (domain == nil) {
            domain = @"";
        }
        
        errorCode = DNSServiceBrowse(&self->sdRef_, 0, kDNSServiceInterfaceIndexAny, [self.type UTF8String], [domain UTF8String], BrowseReplyCallback, self);
        if (errorCode == kDNSServiceErr_NoError) {
            errorCode = DNSServiceSetDispatchQueue(self.sdRef, dispatch_get_main_queue());
        }
        if (errorCode == kDNSServiceErr_NoError) {
            if ([self.delegate respondsToSelector:@selector(dnssdBrowserWillBrowse:)]) {
                [self.delegate dnssdBrowserWillBrowse:self];
            }
        } else {
            [self stopWithError:[NSError errorWithDomain:NSNetServicesErrorDomain code:errorCode userInfo:nil] notify:YES];
        }
    }
}
 
- (void)stopWithError:(NSError *)error notify:(BOOL)notify
    // An internal bottleneck for shutting down the object.
{
    if (notify) {
        if (error != nil) {
            if ([self.delegate respondsToSelector:@selector(dnssdBrowser:didNotBrowse:)]) {
                [self.delegate dnssdBrowser:self didNotBrowse:error];
            }
        }
    }
    if (self.sdRef != NULL) {
        DNSServiceRefDeallocate(self.sdRef);
        self.sdRef = NULL;
    }
    if (notify) {
        if ([self.delegate respondsToSelector:@selector(dnssdBrowserDidStopBrowse:)]) {
            [self.delegate dnssdBrowserDidStopBrowse:self];
        }
    }
}
 
- (void)stop
    // See comment in header.
{
    [self stopWithError:nil notify:NO];
}
 
@end