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Commit b30523d

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CFHostSample: Version 3.0, 2017年03月14日
Rewritten in Swift. The main program is a simple command line tool that accepts parameters, creates query objects, runs them, and prints the results. The various query classes are each a simple wrapper around CFHost; each has extensive comments explaining how to use the class and how the class works internally. Signed-off-by: Liu Lantao <liulantao@gmail.com>
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‎CFHostSample/CFHostSample.xcodeproj/project.pbxproj‎

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/*
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Copyright (C) 2017 Apple Inc. All Rights Reserved.
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See LICENSE.txt for this sample’s licensing information
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Abstract:
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Resolves a DNS name to a list of IP addresses.
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*/
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@import Foundation;
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NS_ASSUME_NONNULL_BEGIN
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@protocol QHostAddressQueryDelegate;
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/// This class uses CFHost to query a DNS name for its addresses. To do this:
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///
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/// 1. Create the `QHostAddressQuery` object with the name in question.
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///
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/// 2. Set a delegate.
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///
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/// 3. Call `start()`.
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///
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/// 4. Wait for `-hostAddressQuery:didCompleteWithAddresses:` or `-hostAddressQuery:didCompleteWithError:`
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/// to be called.
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///
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/// CFHost, and hence this class, is run loop based. The class remembers the run loop on which you
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/// call `start()` and delivers the delegate callbacks on that run loop.
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@interface QHostAddressQuery : NSObject
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/// Creates an instance to query the specified DNS name for its addresses.
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///
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/// - Parameter name: The DNS name to query.
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- (instancetype)initWithName:(NSString *)name NS_DESIGNATED_INITIALIZER;
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- (instancetype)init NS_UNAVAILABLE;
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/// The DNS name to query.
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@property (nonatomic, copy, readonly) NSString * name;
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/// You must set this to learn about the results of your query.
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@property (nonatomic, weak, readwrite) id<QHostAddressQueryDelegate> delegate;
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/// Starts the query process.
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///
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/// The query remembers the thread that called this method and calls any delegate
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/// callbacks on that thread.
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///
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/// - Important: For the query to make progress, this thread must run its run loop in
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/// the default run loop mode.
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///
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/// - Warning: It is an error to start a query that's running.
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- (void)start;
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/// Cancels a running query.
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///
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/// If you successfully cancel a query, no delegate callback for that query will be
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/// called.
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///
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/// If the query is running, you must call this from the thread that called `start()`.
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///
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/// - Note: It is acceptable to call this on a query that's not running; it does nothing
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// in that case.
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- (void)cancel;
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@end
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/// The delegate protocol for the HostAddressQuery class.
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@protocol QHostAddressQueryDelegate <NSObject>
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@required
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/// Called when the query completes successfully.
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///
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/// This is called on the same thread that called `start()`.
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///
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/// - Parameters:
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/// - addresses: The addresses for the DNS name. This has some important properties:
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/// - It will not be empty.
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/// - Each element is an `NSData` value that contains some flavour of `sockaddr`
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/// - It can contain any combination of IPv4 and IPv6 addresses
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/// - The addresses are sorted, with the most preferred first
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/// - query: The query that completed.
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- (void)hostAddressQuery:(QHostAddressQuery *)query didCompleteWithAddresses:(NSArray<NSData *> *)addresses;
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/// Called when the query completes with an error.
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///
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/// This is called on the same thread that called `start()`.
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///
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/// - Parameters:
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/// - error: An error describing the failure.
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/// - query: The query that completed.
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///
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/// - Important: In most cases the error will be in domain `kCFErrorDomainCFNetwork`
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/// with a code of `kCFHostErrorUnknown` (aka `CFNetworkErrors.cfHostErrorUnknown`),
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/// and the user info dictionary will contain an element with the `kCFGetAddrInfoFailureKey`
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/// key whose value is an NSNumber containing an `EAI_XXX` value (from `<netdb.h>`).
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- (void)hostAddressQuery:(QHostAddressQuery *)query didCompleteWithError:(NSError *)error;
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@end
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NS_ASSUME_NONNULL_END
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/*
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Copyright (C) 2017 Apple Inc. All Rights Reserved.
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See LICENSE.txt for this sample’s licensing information
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Abstract:
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Resolves a DNS name to a list of IP addresses.
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*/
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#import "QHostAddressQuery.h"
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NS_ASSUME_NONNULL_BEGIN
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@interface QHostAddressQuery ()
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/// The underlying CFHost object that does the resolution.
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@property (nonatomic, strong, readwrite, nullable) CFHostRef host __attribute__ (( NSObject ));
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/// The run loop on which the CFHost object is scheduled; this is set in `start()`
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/// and cleared when the query stops (either via `cancel()` or by completing).
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@property (nonatomic, strong, readwrite, nullable) NSRunLoop * targetRunLoop;
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@end
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NS_ASSUME_NONNULL_END
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@implementation QHostAddressQuery
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- (instancetype)initWithName:(NSString *)name {
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NSParameterAssert(name != nil);
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self = [super init];
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if (self != nil) {
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self->_name = [name copy];
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self->_host = CFHostCreateWithName(nil, (__bridge CFStringRef) self->_name);
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}
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return self;
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}
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- (instancetype)init {
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abort();
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}
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- (void)start {
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NSParameterAssert(self.targetRunLoop == nil);
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self.targetRunLoop = NSRunLoop.currentRunLoop;
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CFHostClientContext context = {
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.info = (void *) CFBridgingRetain(self)
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};
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BOOL success = CFHostSetClient(self.host, HostClientCallBack, &context) != false;
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assert(success);
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CFHostScheduleWithRunLoop(self.host, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
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CFStreamError streamError;
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success = CFHostStartInfoResolution(self.host, kCFHostAddresses, &streamError) != false;
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if ( ! success ) {
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[self stopWithStreamError:&streamError notify:NO];
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}
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}
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/// Our CFHost callback function for our host; this just extracts the object from the `info`
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/// pointer and calls methods on it.
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static void HostClientCallBack(CFHostRef theHost, CFHostInfoType typeInfo, const CFStreamError * __nullable error, void * __nullable info) {
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#pragma unused(theHost)
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#pragma unused(typeInfo)
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QHostAddressQuery * obj = (__bridge QHostAddressQuery *) info;
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assert([obj isKindOfClass:[QHostAddressQuery class]]);
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if ( (error == NULL) || ( (error->domain == 0) && (error->error == 0) ) ) {
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[obj stopWithStreamError:NULL notify:YES];
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} else {
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[obj stopWithStreamError:error notify:YES];
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}
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}
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/// Stops the query with the supplied error, notifying the delegate if `notify` is true.
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- (void)stopWithStreamError:(nullable const CFStreamError *)streamError notify:(BOOL)notify {
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NSError * error = nil;
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if (streamError != NULL) {
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// Convert a CFStreamError to a NSError. This is less than ideal. I only handle a
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// limited number of error domains, and I can't use a switch statement because
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// some of the `kCFStreamErrorDomainXxx` values are not a constant. Wouldn't it be
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// nice if there was a public API to do this mapping <rdar://problem/5845848>
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// or a CFHost API that used CFError <rdar://problem/6016542>.
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if (streamError->domain == kCFStreamErrorDomainPOSIX) {
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error = [NSError errorWithDomain:NSPOSIXErrorDomain code:streamError->error userInfo:nil];
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} else if (streamError->domain == kCFStreamErrorDomainMacOSStatus) {
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error = [NSError errorWithDomain:NSOSStatusErrorDomain code:streamError->error userInfo:nil];
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} else if (streamError->domain == kCFStreamErrorDomainNetServices) {
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error = [NSError errorWithDomain:(__bridge NSString *) kCFErrorDomainCFNetwork code:streamError->error userInfo:nil];
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} else if (streamError->domain == kCFStreamErrorDomainNetDB) {
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error = [NSError errorWithDomain:(__bridge NSString *) kCFErrorDomainCFNetwork code:kCFHostErrorUnknown userInfo:@{
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(__bridge NSString *) kCFGetAddrInfoFailureKey: @(streamError->error)
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}];
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} else {
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// If it's something we don't understand, we just assume it comes from
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// CFNetwork.
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error = [NSError errorWithDomain:(__bridge NSString *) kCFErrorDomainCFNetwork code:streamError->error userInfo:nil];
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}
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}
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[self stopWithError:error notify:notify];
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}
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/// Stops the query with the supplied error, notifying the delegate if `notify` is true.
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- (void)stopWithError:(nullable NSError *)error notify:(BOOL)notify {
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NSParameterAssert(NSRunLoop.currentRunLoop == self.targetRunLoop);
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self.targetRunLoop = nil;
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CFHostSetClient(self.host, nil, nil);
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CFHostUnscheduleFromRunLoop(self.host, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
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CFHostCancelInfoResolution(self.host, kCFHostAddresses);
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CFRelease( (__bridge CFTypeRef) self );
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id<QHostAddressQueryDelegate> strongDelegate = self.delegate;
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if (notify && (strongDelegate != nil) ) {
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if (error != nil) {
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[strongDelegate hostAddressQuery:self didCompleteWithError:error];
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} else {
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NSArray<NSData *> * addresses = (__bridge NSArray<NSData *> *) CFHostGetAddressing(self.host, NULL);
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[strongDelegate hostAddressQuery:self didCompleteWithAddresses:addresses];
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}
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}
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}
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- (void)cancel {
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if (self.targetRunLoop != nil) {
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[self stopWithError:[NSError errorWithDomain:NSCocoaErrorDomain code:NSUserCancelledError userInfo:nil] notify:NO];
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}
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}
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@end
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/*
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Copyright (C) 2017 Apple Inc. All Rights Reserved.
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See LICENSE.txt for this sample’s licensing information
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Abstract:
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Resolves an IP address to a list of DNS names.
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*/
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@import Foundation;
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NS_ASSUME_NONNULL_BEGIN
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@protocol QHostNameQueryDelegate;
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/// This class uses CFHost to query an IP address for its DNS names. To do this:
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///
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/// 1. Create the `QHostNameQuery` object with the name in question.
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///
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/// 2. Set a delegate.
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///
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/// 3. Call `start()`.
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///
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/// 4. Wait for `-hostNameQuery:didCompleteWithNames:` or `-hostNameQuery:didCompleteWithError:`
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/// to be called.
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///
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/// CFHost, and hence this class, is run loop based. The class remembers the run loop on which you
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/// call `start()` and delivers the delegate callbacks on that run loop.
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///
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/// - Important: Reverse DNS queries are notoriously unreliable. Specifically, you must not
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/// assume that:
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///
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/// - Every IP address has a valid reverse DNS name
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/// - The reverse DNS name is unique
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/// - There's any correlation between the forward and reverse DNS mappings
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///
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/// Unless you have domain specific knowledge (for example, you're working in an enterprise
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/// environment where you know how the DNS is set up), reverse DNS queries are generally not
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/// useful for anything other than logging.
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@interface QHostNameQuery : NSObject
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/// Creates an instance to query the specified IP address for its DNS name.
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///
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/// - Parameter address: The IP address to query, as a `NSData` value containing some flavour of `sockaddr`.
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- (instancetype)initWithAddress:(NSData *)address NS_DESIGNATED_INITIALIZER;
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- (instancetype)init NS_UNAVAILABLE;
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/// The IP address to query, as a `NSData` value containing some flavour of `sockaddr`.
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@property (nonatomic, copy, readonly) NSData * address;
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/// You must set this to learn about the results of your query.
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@property (nonatomic, weak, readwrite) id<QHostNameQueryDelegate> delegate;
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/// Starts the query process.
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///
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/// The query remembers the thread that called this method and calls any delegate
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/// callbacks on that thread.
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///
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/// - Important: For the query to make progress, this thread must run its run loop in
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/// the default run loop mode.
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///
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/// - Warning: It is an error to start a query that's running.
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- (void)start;
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/// Cancels a running query.
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///
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/// If you successfully cancel a query, no delegate callback for that query will be
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/// called.
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///
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/// If the query is running, you must call this from the thread that called `start()`.
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///
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/// - Note: It is acceptable to call this on a query that's not running; it does nothing
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// in that case.
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- (void)cancel;
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@end
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/// The delegate protocol for the HostNameQuery class.
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@protocol QHostNameQueryDelegate <NSObject>
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@required
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/// Called when the query completes successfully.
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///
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/// This is called on the same thread that called `start()`.
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///
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/// - Parameters:
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/// - names: The DNS names for the IP address.
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/// - query: The query that completed.
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- (void)hostNameQuery:(QHostNameQuery *)query didCompleteWithNames:(NSArray<NSString *> *)names;
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/// Called when the query completes with an error.
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///
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/// This is called on the same thread that called `start()`.
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///
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/// - Parameters:
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/// - error: An error describing the failure.
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/// - query: The query that completed.
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///
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/// - Important: In most cases the error will be in domain `kCFErrorDomainCFNetwork`
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/// with a code of `kCFHostErrorUnknown` (aka `CFNetworkErrors.cfHostErrorUnknown`),
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/// and the user info dictionary will contain an element with the `kCFGetAddrInfoFailureKey`
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/// key whose value is an NSNumber containing an `EAI_XXX` value (from `<netdb.h>`).
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- (void)hostNameQuery:(QHostNameQuery *)query didCompleteWithError:(NSError *)error;
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@end
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NS_ASSUME_NONNULL_END

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