text: /* -*- Mode: C; tab-width: 4 -*-
   *
   * Copyright (c) 2003-2004, Apple Computer, Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1.  Redistributions of source code must retain the above copyright notice,
   *     this list of conditions and the following disclaimer.
   * 2.  Redistributions in binary form must reproduce the above copyright notice,
   *     this list of conditions and the following disclaimer in the documentation
   *     and/or other materials provided with the distribution.
   * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of its
   *     contributors may be used to endorse or promote products derived from this
   *     software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  
  /*! @header     DNS Service Discovery
   *
   * @discussion  This section describes the functions, callbacks, and data structures
   *              that make up the DNS Service Discovery API.
   *
   *              The DNS Service Discovery API is part of Bonjour, Apple's implementation
   *              of zero-configuration networking (ZEROCONF).
   *
   *              Bonjour allows you to register a network service, such as a
   *              printer or file server, so that it can be found by name or browsed
   *              for by service type and domain. Using Bonjour, applications can
   *              discover what services are available on the network, along with
   *              all the information -- such as name, IP address, and port --
   *              necessary to access a particular service.
   *
   *              In effect, Bonjour combines the functions of a local DNS server and
   *              AppleTalk. Bonjour allows applications to provide user-friendly printer
   *              and server browsing, among other things, over standard IP networks.
   *              This behavior is a result of combining protocols such as multicast and
   *              DNS to add new functionality to the network (such as multicast DNS).
   *
   *              Bonjour gives applications easy access to services over local IP
   *              networks without requiring the service or the application to support
   *              an AppleTalk or a Netbeui stack, and without requiring a DNS server
   *              for the local network.
   */
  
  
  /* _DNS_SD_H contains the mDNSResponder version number for this header file, formatted as follows:
   *   Major part of the build number * 10000 +
   *   minor part of the build number *   100
   * For example, Mac OS X 10.4.9 has mDNSResponder-108.4, which would be represented as
   * version 1080400. This allows C code to do simple greater-than and less-than comparisons:
   * e.g. an application that requires the DNSServiceGetProperty() call (new in mDNSResponder-126) can check:
   *
   *   #if _DNS_SD_H+0 >= 1260000
   *   ... some C code that calls DNSServiceGetProperty() ...
   *   #endif
   *
   * The version defined in this header file symbol allows for compile-time
   * checking, so that C code building with earlier versions of the header file
   * can avoid compile errors trying to use functions that aren't even defined
   * in those earlier versions. Similar checks may also be performed at run-time:
   *  => weak linking -- to avoid link failures if run with an earlier
   *     version of the library that's missing some desired symbol, or
   *  => DNSServiceGetProperty(DaemonVersion) -- to verify whether the running daemon
   *     ("system service" on Windows) meets some required minimum functionality level.
   */
  
  #ifndef _DNS_SD_H
  #define _DNS_SD_H 3200501
  
  #ifdef  __cplusplus
      extern "C" {
  #endif
  
  /* Set to 1 if libdispatch is supported
   * Note: May also be set by project and/or Makefile
   */
  #ifndef _DNS_SD_LIBDISPATCH
  #define _DNS_SD_LIBDISPATCH 0
  #endif /* ndef _DNS_SD_LIBDISPATCH */
  
  /* standard calling convention under Win32 is __stdcall */
  /* Note: When compiling Intel EFI (Extensible Firmware Interface) under MS Visual Studio, the */
  /* _WIN32 symbol is defined by the compiler even though it's NOT compiling code for Windows32 */
  #if defined(_WIN32) && !defined(EFI32) && !defined(EFI64)
  #define DNSSD_API __stdcall
  #else
  #define DNSSD_API
  #endif
  
  /* stdint.h does not exist on FreeBSD 4.x; its types are defined in sys/types.h instead */
  #if defined(__FreeBSD__) && (__FreeBSD__ < 5)
  #include <sys/types.h>
  
  /* Likewise, on Sun, standard integer types are in sys/types.h */
  #elif defined(__sun__)
  #include <sys/types.h>
  
  /* EFI does not have stdint.h, or anything else equivalent */
  #elif defined(EFI32) || defined(EFI64) || defined(EFIX64)
  #include "Tiano.h"
  #if !defined(_STDINT_H_)
  typedef UINT8       uint8_t;
  typedef INT8        int8_t;
  typedef UINT16      uint16_t;
  typedef INT16       int16_t;
  typedef UINT32      uint32_t;
  typedef INT32       int32_t;
  #endif
  /* Windows has its own differences */
  #elif defined(_WIN32)
  #include <windows.h>
  #define _UNUSED
  #ifndef _MSL_STDINT_H
  typedef UINT8       uint8_t;
  typedef INT8        int8_t;
  typedef UINT16      uint16_t;
  typedef INT16       int16_t;
  typedef UINT32      uint32_t;
  typedef INT32       int32_t;
  #endif
  
  /* All other Posix platforms use stdint.h */
  #else
  #include <stdint.h>
  #endif
  
  #if _DNS_SD_LIBDISPATCH
  #include <dispatch/dispatch.h>
  #endif
  
  /* DNSServiceRef, DNSRecordRef
   *
   * Opaque internal data types.
   * Note: client is responsible for serializing access to these structures if
   * they are shared between concurrent threads.
   */
  
  typedef struct _DNSServiceRef_t *DNSServiceRef;
  typedef struct _DNSRecordRef_t *DNSRecordRef;
  
  struct sockaddr;
  
  /*! @enum General flags
   * Most DNS-SD API functions and callbacks include a DNSServiceFlags parameter.
   * As a general rule, any given bit in the 32-bit flags field has a specific fixed meaning,
   * regardless of the function or callback being used. For any given function or callback,
   * typically only a subset of the possible flags are meaningful, and all others should be zero.
   * The discussion section for each API call describes which flags are valid for that call
   * and callback. In some cases, for a particular call, it may be that no flags are currently
   * defined, in which case the DNSServiceFlags parameter exists purely to allow future expansion.
   * In all cases, developers should expect that in future releases, it is possible that new flag
   * values will be defined, and write code with this in mind. For example, code that tests
   *     if (flags == kDNSServiceFlagsAdd) ...
   * will fail if, in a future release, another bit in the 32-bit flags field is also set.
   * The reliable way to test whether a particular bit is set is not with an equality test,
   * but with a bitwise mask:
   *     if (flags & kDNSServiceFlagsAdd) ...
   */
  enum
      {
      kDNSServiceFlagsMoreComing          = 0x1,
      /* MoreComing indicates to a callback that at least one more result is
       * queued and will be delivered following immediately after this one.
       * When the MoreComing flag is set, applications should not immediately
       * update their UI, because this can result in a great deal of ugly flickering
       * on the screen, and can waste a great deal of CPU time repeatedly updating
       * the screen with content that is then immediately erased, over and over.
       * Applications should wait until until MoreComing is not set, and then
       * update their UI when no more changes are imminent.
       * When MoreComing is not set, that doesn't mean there will be no more
       * answers EVER, just that there are no more answers immediately
       * available right now at this instant. If more answers become available
       * in the future they will be delivered as usual.
       */
  
      kDNSServiceFlagsAdd                 = 0x2,
      kDNSServiceFlagsDefault             = 0x4,
      /* Flags for domain enumeration and browse/query reply callbacks.
       * "Default" applies only to enumeration and is only valid in
       * conjunction with "Add". An enumeration callback with the "Add"
       * flag NOT set indicates a "Remove", i.e. the domain is no longer
       * valid.
       */
  
      kDNSServiceFlagsNoAutoRename        = 0x8,
      /* Flag for specifying renaming behavior on name conflict when registering
       * non-shared records. By default, name conflicts are automatically handled
       * by renaming the service. NoAutoRename overrides this behavior - with this
       * flag set, name conflicts will result in a callback. The NoAutorename flag
       * is only valid if a name is explicitly specified when registering a service
       * (i.e. the default name is not used.)
       */
  
      kDNSServiceFlagsShared              = 0x10,
      kDNSServiceFlagsUnique              = 0x20,
      /* Flag for registering individual records on a connected
       * DNSServiceRef. Shared indicates that there may be multiple records
       * with this name on the network (e.g. PTR records). Unique indicates that the
       * record's name is to be unique on the network (e.g. SRV records).
       */
  
      kDNSServiceFlagsBrowseDomains       = 0x40,
      kDNSServiceFlagsRegistrationDomains = 0x80,
      /* Flags for specifying domain enumeration type in DNSServiceEnumerateDomains.
       * BrowseDomains enumerates domains recommended for browsing, RegistrationDomains
       * enumerates domains recommended for registration.
       */
  
      kDNSServiceFlagsLongLivedQuery      = 0x100,
      /* Flag for creating a long-lived unicast query for the DNSServiceQueryRecord call. */
  
      kDNSServiceFlagsAllowRemoteQuery    = 0x200,
      /* Flag for creating a record for which we will answer remote queries
       * (queries from hosts more than one hop away; hosts not directly connected to the local link).
       */
  
      kDNSServiceFlagsForceMulticast      = 0x400,
      /* Flag for signifying that a query or registration should be performed exclusively via multicast
       * DNS, even for a name in a domain (e.g. foo.apple.com.) that would normally imply unicast DNS.
       */
  
      kDNSServiceFlagsForce               = 0x800,
      /* Flag for signifying a "stronger" variant of an operation.
       * Currently defined only for DNSServiceReconfirmRecord(), where it forces a record to
       * be removed from the cache immediately, instead of querying for a few seconds before
       * concluding that the record is no longer valid and then removing it. This flag should
       * be used with caution because if a service browsing PTR record is indeed still valid
       * on the network, forcing its removal will result in a user-interface flap -- the
       * discovered service instance will disappear, and then re-appear moments later.
       */
  
      kDNSServiceFlagsReturnIntermediates = 0x1000,
      /* Flag for returning intermediate results.
       * For example, if a query results in an authoritative NXDomain (name does not exist)
       * then that result is returned to the client. However the query is not implicitly
       * cancelled -- it remains active and if the answer subsequently changes
       * (e.g. because a VPN tunnel is subsequently established) then that positive
       * result will still be returned to the client.
       * Similarly, if a query results in a CNAME record, then in addition to following
       * the CNAME referral, the intermediate CNAME result is also returned to the client.
       * When this flag is not set, NXDomain errors are not returned, and CNAME records
       * are followed silently without informing the client of the intermediate steps.
       * (In earlier builds this flag was briefly calledkDNSServiceFlagsReturnCNAME)
       */
  
      kDNSServiceFlagsNonBrowsable        = 0x2000,
      /* A service registered with the NonBrowsable flag set can be resolved using
       * DNSServiceResolve(), but will not be discoverable using DNSServiceBrowse().
       * This is for cases where the name is actually a GUID; it is found by other means;
       * there is no end-user benefit to browsing to find a long list of opaque GUIDs.
       * Using the NonBrowsable flag creates SRV+TXT without the cost of also advertising
       * an associated PTR record.
       */
  
      kDNSServiceFlagsShareConnection     = 0x4000,
      /* For efficiency, clients that perform many concurrent operations may want to use a
       * single Unix Domain Socket connection with the background daemon, instead of having a
       * separate connection for each independent operation. To use this mode, clients first
       * call DNSServiceCreateConnection(&MainRef) to initialize the main DNSServiceRef.
       * For each subsequent operation that is to share that same connection, the client copies
       * the MainRef, and then passes the address of that copy, setting the ShareConnection flag
       * to tell the library that this DNSServiceRef is not a typical uninitialized DNSServiceRef;
       * it's a copy of an existing DNSServiceRef whose connection information should be reused.
       *
       * For example:
       *
       * DNSServiceErrorType error;
       * DNSServiceRef MainRef;
       * error = DNSServiceCreateConnection(&MainRef);
       * if (error) ...
       * DNSServiceRef BrowseRef = MainRef;  // Important: COPY the primary DNSServiceRef first...
       * error = DNSServiceBrowse(&BrowseRef, kDNSServiceFlagsShareConnection, ...); // then use the copy
       * if (error) ...
       * ...
       * DNSServiceRefDeallocate(BrowseRef); // Terminate the browse operation
       * DNSServiceRefDeallocate(MainRef);   // Terminate the shared connection
       *
       * Notes:
       *
       * 1. Collective kDNSServiceFlagsMoreComing flag
       * When callbacks are invoked using a shared DNSServiceRef, the
       * kDNSServiceFlagsMoreComing flag applies collectively to *all* active
       * operations sharing the same parent DNSServiceRef. If the MoreComing flag is
       * set it means that there are more results queued on this parent DNSServiceRef,
       * but not necessarily more results for this particular callback function. 
       * The implication of this for client programmers is that when a callback
       * is invoked with the MoreComing flag set, the code should update its
       * internal data structures with the new result, and set a variable indicating
       * that its UI needs to be updated. Then, later when a callback is eventually
       * invoked with the MoreComing flag not set, the code should update *all*
       * stale UI elements related to that shared parent DNSServiceRef that need
       * updating, not just the UI elements related to the particular callback
       * that happened to be the last one to be invoked.
       *
       * 2. Canceling operations and kDNSServiceFlagsMoreComing
       * Whenever you cancel any operation for which you had deferred UI updates
       * waiting because of a kDNSServiceFlagsMoreComing flag, you should perform
       * those deferred UI updates. This is because, after cancelling the operation,
       * you can no longer wait for a callback *without* MoreComing set, to tell
       * you do perform your deferred UI updates (the operation has been canceled,
       * so there will be no more callbacks). An implication of the collective
       * kDNSServiceFlagsMoreComing flag for shared connections is that this
       * guideline applies more broadly -- any time you cancel an operation on
       * a shared connection, you should perform all deferred UI updates for all
       * operations sharing that connection. This is because the MoreComing flag
       * might have been referring to events coming for the operation you canceled,
       * which will now not be coming because the operation has been canceled.
       *
       * 3. Only share DNSServiceRef's created with DNSServiceCreateConnection
       * Calling DNSServiceCreateConnection(&ref) creates a special shareable DNSServiceRef.
       * DNSServiceRef's created by other calls like DNSServiceBrowse() or DNSServiceResolve()
       * cannot be shared by copying them and using kDNSServiceFlagsShareConnection.
       *
       * 4. Don't Double-Deallocate
       * Calling DNSServiceRefDeallocate(ref) for a particular operation's DNSServiceRef terminates
       * just that operation. Calling DNSServiceRefDeallocate(ref) for the main shared DNSServiceRef
       * (the parent DNSServiceRef, originally created by DNSServiceCreateConnection(&ref))
       * automatically terminates the shared connection and all operations that were still using it.
       * After doing this, DO NOT then attempt to deallocate any remaining subordinate DNSServiceRef's.
       * The memory used by those subordinate DNSServiceRef's has already been freed, so any attempt
       * to do a DNSServiceRefDeallocate (or any other operation) on them will result in accesses
       * to freed memory, leading to crashes or other equally undesirable results.
       *
       * 5. Thread Safety
       * The dns_sd.h API does not presuppose any particular threading model, and consequently
       * does no locking of its own (which would require linking some specific threading library).
       * If client code calls API routines on the same DNSServiceRef concurrently
       * from multiple threads, it is the client's responsibility to use a mutext
       * lock or take similar appropriate precautions to serialize those calls.
       */
  
      kDNSServiceFlagsSuppressUnusable    = 0x8000,
  	/*
  	 * This flag is meaningful only in DNSServiceQueryRecord which suppresses unusable queries on the
  	 * wire. If "hostname" is a wide-area unicast DNS hostname (i.e. not a ".local." name)
  	 * but this host has no routable IPv6 address, then the call will not try to look up IPv6 addresses
  	 * for "hostname", since any addresses it found would be unlikely to be of any use anyway. Similarly,
  	 * if this host has no routable IPv4 address, the call will not try to look up IPv4 addresses for
  	 * "hostname".
  	 */
  
      kDNSServiceFlagsTimeout            = 0x10000,
  	/*
  	 * When kDNServiceFlagsTimeout is passed to DNSServiceQueryRecord or DNSServiceGetAddrInfo, the query is
  	 * stopped after a certain number of seconds have elapsed. The time at which the query will be stopped
  	 * is determined by the system and cannot be configured by the user. The query will be stopped irrespective
  	 * of whether a response was given earlier or not. When the query is stopped, the callback will be called
  	 * with an error code of kDNSServiceErr_Timeout and a NULL sockaddr will be returned for DNSServiceGetAddrInfo
  	 * and zero length rdata will be returned for DNSServiceQueryRecord.
  	 */
  
      kDNSServiceFlagsIncludeP2P          = 0x20000,
  	/*
  	 * Include P2P interfaces when kDNSServiceInterfaceIndexAny is specified.
  	 * By default, specifying kDNSServiceInterfaceIndexAny does not include P2P interfaces.
  	 */
  	kDNSServiceFlagsWakeOnResolve      = 0x40000
  	/*
  	 * This flag is meaningful only in DNSServiceResolve. When set, it tries to send a magic packet
  	 * to wake up the client.
  	 */
      };
  
  /* Possible protocols for DNSServiceNATPortMappingCreate(). */
  enum
      {
      kDNSServiceProtocol_IPv4 = 0x01,
      kDNSServiceProtocol_IPv6 = 0x02,
      /* 0x04 and 0x08 reserved for future internetwork protocols */
      
      kDNSServiceProtocol_UDP  = 0x10,
      kDNSServiceProtocol_TCP  = 0x20
      /* 0x40 and 0x80 reserved for future transport protocols, e.g. SCTP [RFC 2960]
       * or DCCP [RFC 4340]. If future NAT gateways are created that support port
       * mappings for these protocols, new constants will be defined here.
       */
      };
  
  /*
   * The values for DNS Classes and Types are listed in RFC 1035, and are available
   * on every OS in its DNS header file. Unfortunately every OS does not have the
   * same header file containing DNS Class and Type constants, and the names of
   * the constants are not consistent. For example, BIND 8 uses "T_A",
   * BIND 9 uses "ns_t_a", Windows uses "DNS_TYPE_A", etc.
   * For this reason, these constants are also listed here, so that code using
   * the DNS-SD programming APIs can use these constants, so that the same code
   * can compile on all our supported platforms.
   */
  
  enum
      {
      kDNSServiceClass_IN       = 1       /* Internet */
      };
  
  enum
      {
      kDNSServiceType_A          = 1,      /* Host address. */
      kDNSServiceType_NS         = 2,      /* Authoritative server. */
      kDNSServiceType_MD         = 3,      /* Mail destination. */
      kDNSServiceType_MF         = 4,      /* Mail forwarder. */
      kDNSServiceType_CNAME      = 5,      /* Canonical name. */
      kDNSServiceType_SOA        = 6,      /* Start of authority zone. */
      kDNSServiceType_MB         = 7,      /* Mailbox domain name. */
      kDNSServiceType_MG         = 8,      /* Mail group member. */
      kDNSServiceType_MR         = 9,      /* Mail rename name. */
      kDNSServiceType_NULL       = 10,     /* Null resource record. */
      kDNSServiceType_WKS        = 11,     /* Well known service. */
      kDNSServiceType_PTR        = 12,     /* Domain name pointer. */
      kDNSServiceType_HINFO      = 13,     /* Host information. */
      kDNSServiceType_MINFO      = 14,     /* Mailbox information. */
      kDNSServiceType_MX         = 15,     /* Mail routing information. */
      kDNSServiceType_TXT        = 16,     /* One or more text strings (NOT "zero or more..."). */
      kDNSServiceType_RP         = 17,     /* Responsible person. */
      kDNSServiceType_AFSDB      = 18,     /* AFS cell database. */
      kDNSServiceType_X25        = 19,     /* X_25 calling address. */
      kDNSServiceType_ISDN       = 20,     /* ISDN calling address. */
      kDNSServiceType_RT         = 21,     /* Router. */
      kDNSServiceType_NSAP       = 22,     /* NSAP address. */
      kDNSServiceType_NSAP_PTR   = 23,     /* Reverse NSAP lookup (deprecated). */
      kDNSServiceType_SIG        = 24,     /* Security signature. */
      kDNSServiceType_KEY        = 25,     /* Security key. */
      kDNSServiceType_PX         = 26,     /* X.400 mail mapping. */
      kDNSServiceType_GPOS       = 27,     /* Geographical position (withdrawn). */
      kDNSServiceType_AAAA       = 28,     /* IPv6 Address. */
      kDNSServiceType_LOC        = 29,     /* Location Information. */
      kDNSServiceType_NXT        = 30,     /* Next domain (security). */
      kDNSServiceType_EID        = 31,     /* Endpoint identifier. */
      kDNSServiceType_NIMLOC     = 32,     /* Nimrod Locator. */
      kDNSServiceType_SRV        = 33,     /* Server Selection. */
      kDNSServiceType_ATMA       = 34,     /* ATM Address */
      kDNSServiceType_NAPTR      = 35,     /* Naming Authority PoinTeR */
      kDNSServiceType_KX         = 36,     /* Key Exchange */
      kDNSServiceType_CERT       = 37,     /* Certification record */
      kDNSServiceType_A6         = 38,     /* IPv6 Address (deprecated) */
      kDNSServiceType_DNAME      = 39,     /* Non-terminal DNAME (for IPv6) */
      kDNSServiceType_SINK       = 40,     /* Kitchen sink (experimental) */
      kDNSServiceType_OPT        = 41,     /* EDNS0 option (meta-RR) */
      kDNSServiceType_APL        = 42,     /* Address Prefix List */
      kDNSServiceType_DS         = 43,     /* Delegation Signer */
      kDNSServiceType_SSHFP      = 44,     /* SSH Key Fingerprint */
      kDNSServiceType_IPSECKEY   = 45,     /* IPSECKEY */
      kDNSServiceType_RRSIG      = 46,     /* RRSIG */
      kDNSServiceType_NSEC       = 47,     /* Denial of Existence */
      kDNSServiceType_DNSKEY     = 48,     /* DNSKEY */
      kDNSServiceType_DHCID      = 49,     /* DHCP Client Identifier */
      kDNSServiceType_NSEC3      = 50,     /* Hashed Authenticated Denial of Existence */
      kDNSServiceType_NSEC3PARAM = 51,     /* Hashed Authenticated Denial of Existence */
  
      kDNSServiceType_HIP        = 55,     /* Host Identity Protocol */
  
      kDNSServiceType_SPF        = 99,     /* Sender Policy Framework for E-Mail */
      kDNSServiceType_UINFO      = 100,    /* IANA-Reserved */
      kDNSServiceType_UID        = 101,    /* IANA-Reserved */
      kDNSServiceType_GID        = 102,    /* IANA-Reserved */
      kDNSServiceType_UNSPEC     = 103,    /* IANA-Reserved */
  
      kDNSServiceType_TKEY       = 249,    /* Transaction key */
      kDNSServiceType_TSIG       = 250,    /* Transaction signature. */
      kDNSServiceType_IXFR       = 251,    /* Incremental zone transfer. */
      kDNSServiceType_AXFR       = 252,    /* Transfer zone of authority. */
      kDNSServiceType_MAILB      = 253,    /* Transfer mailbox records. */
      kDNSServiceType_MAILA      = 254,    /* Transfer mail agent records. */
      kDNSServiceType_ANY        = 255     /* Wildcard match. */
      };
  
  /* possible error code values */
  enum
      {
      kDNSServiceErr_NoError                   = 0,
      kDNSServiceErr_Unknown                   = -65537,  /* 0xFFFE FFFF */
      kDNSServiceErr_NoSuchName                = -65538,
      kDNSServiceErr_NoMemory                  = -65539,
      kDNSServiceErr_BadParam                  = -65540,
      kDNSServiceErr_BadReference              = -65541,
      kDNSServiceErr_BadState                  = -65542,
      kDNSServiceErr_BadFlags                  = -65543,
      kDNSServiceErr_Unsupported               = -65544,
      kDNSServiceErr_NotInitialized            = -65545,
      kDNSServiceErr_AlreadyRegistered         = -65547,
      kDNSServiceErr_NameConflict              = -65548,
      kDNSServiceErr_Invalid                   = -65549,
      kDNSServiceErr_Firewall                  = -65550,
      kDNSServiceErr_Incompatible              = -65551,  /* client library incompatible with daemon */
      kDNSServiceErr_BadInterfaceIndex         = -65552,
      kDNSServiceErr_Refused                   = -65553,
      kDNSServiceErr_NoSuchRecord              = -65554,
      kDNSServiceErr_NoAuth                    = -65555,
      kDNSServiceErr_NoSuchKey                 = -65556,
      kDNSServiceErr_NATTraversal              = -65557,
      kDNSServiceErr_DoubleNAT                 = -65558,
      kDNSServiceErr_BadTime                   = -65559,  /* Codes up to here existed in Tiger */
      kDNSServiceErr_BadSig                    = -65560,
      kDNSServiceErr_BadKey                    = -65561,
      kDNSServiceErr_Transient                 = -65562,
      kDNSServiceErr_ServiceNotRunning         = -65563,  /* Background daemon not running */
      kDNSServiceErr_NATPortMappingUnsupported = -65564,  /* NAT doesn't support NAT-PMP or UPnP */
      kDNSServiceErr_NATPortMappingDisabled    = -65565,  /* NAT supports NAT-PMP or UPnP but it's disabled by the administrator */
      kDNSServiceErr_NoRouter                  = -65566,  /* No router currently configured (probably no network connectivity) */
      kDNSServiceErr_PollingMode               = -65567,
      kDNSServiceErr_Timeout                   = -65568
  
      /* mDNS Error codes are in the range
       * FFFE FF00 (-65792) to FFFE FFFF (-65537) */
      };
  
  /* Maximum length, in bytes, of a service name represented as a */
  /* literal C-String, including the terminating NULL at the end. */
  
  #define kDNSServiceMaxServiceName 64
  
  /* Maximum length, in bytes, of a domain name represented as an *escaped* C-String */
  /* including the final trailing dot, and the C-String terminating NULL at the end. */
  
  #define kDNSServiceMaxDomainName 1009
  
  /*
   * Notes on DNS Name Escaping
   *   -- or --
   * "Why is kDNSServiceMaxDomainName 1009, when the maximum legal domain name is 256 bytes?"
   *
   * All strings used in the DNS-SD APIs are UTF-8 strings. Apart from the exceptions noted below,
   * the APIs expect the strings to be properly escaped, using the conventional DNS escaping rules:
   *
   *   '\\' represents a single literal '\' in the name
   *   '\.' represents a single literal '.' in the name
   *   '\ddd', where ddd is a three-digit decimal value from 000 to 255,
   *        represents a single literal byte with that value.
   *   A bare unescaped '.' is a label separator, marking a boundary between domain and subdomain.
   *
   * The exceptions, that do not use escaping, are the routines where the full
   * DNS name of a resource is broken, for convenience, into servicename/regtype/domain.
   * In these routines, the "servicename" is NOT escaped. It does not need to be, since
   * it is, by definition, just a single literal string. Any characters in that string
   * represent exactly what they are. The "regtype" portion is, technically speaking,
   * escaped, but since legal regtypes are only allowed to contain letters, digits,
   * and hyphens, there is nothing to escape, so the issue is moot. The "domain"
   * portion is also escaped, though most domains in use on the public Internet
   * today, like regtypes, don't contain any characters that need to be escaped.
   * As DNS-SD becomes more popular, rich-text domains for service discovery will
   * become common, so software should be written to cope with domains with escaping.
   *
   * The servicename may be up to 63 bytes of UTF-8 text (not counting the C-String
   * terminating NULL at the end). The regtype is of the form _service._tcp or
   * _service._udp, where the "service" part is 1-15 characters, which may be
   * letters, digits, or hyphens. The domain part of the three-part name may be
   * any legal domain, providing that the resulting servicename+regtype+domain
   * name does not exceed 256 bytes.
   *
   * For most software, these issues are transparent. When browsing, the discovered
   * servicenames should simply be displayed as-is. When resolving, the discovered
   * servicename/regtype/domain are simply passed unchanged to DNSServiceResolve().
   * When a DNSServiceResolve() succeeds, the returned fullname is already in
   * the correct format to pass to standard system DNS APIs such as res_query().
   * For converting from servicename/regtype/domain to a single properly-escaped
   * full DNS name, the helper function DNSServiceConstructFullName() is provided.
   *
   * The following (highly contrived) example illustrates the escaping process.
   * Suppose you have an service called "Dr. Smith\Dr. Johnson", of type "_ftp._tcp"
   * in subdomain "4th. Floor" of subdomain "Building 2" of domain "apple.com."
   * The full (escaped) DNS name of this service's SRV record would be:
   * Dr\.\032Smith\\Dr\.\032Johnson._ftp._tcp.4th\.\032Floor.Building\0322.apple.com.
   */
  
  
  /*
   * Constants for specifying an interface index
   *
   * Specific interface indexes are identified via a 32-bit unsigned integer returned
   * by the if_nametoindex() family of calls.
   *
   * If the client passes 0 for interface index, that means "do the right thing",
   * which (at present) means, "if the name is in an mDNS local multicast domain
   * (e.g. 'local.', '254.169.in-addr.arpa.', '{8,9,A,B}.E.F.ip6.arpa.') then multicast
   * on all applicable interfaces, otherwise send via unicast to the appropriate
   * DNS server." Normally, most clients will use 0 for interface index to
   * automatically get the default sensible behaviour.
   *
   * If the client passes a positive interface index, then for multicast names that
   * indicates to do the operation only on that one interface. For unicast names the
   * interface index is ignored unless kDNSServiceFlagsForceMulticast is also set.
   *
   * If the client passes kDNSServiceInterfaceIndexLocalOnly when registering
   * a service, then that service will be found *only* by other local clients
   * on the same machine that are browsing using kDNSServiceInterfaceIndexLocalOnly
   * or kDNSServiceInterfaceIndexAny.
   * If a client has a 'private' service, accessible only to other processes
   * running on the same machine, this allows the client to advertise that service
   * in a way such that it does not inadvertently appear in service lists on
   * all the other machines on the network.
   *
   * If the client passes kDNSServiceInterfaceIndexLocalOnly when browsing
   * then it will find *all* records registered on that same local machine.
   * Clients explicitly wishing to discover *only* LocalOnly services can
   * accomplish this by inspecting the interfaceIndex of each service reported
   * to their DNSServiceBrowseReply() callback function, and discarding those
   * where the interface index is not kDNSServiceInterfaceIndexLocalOnly.
   *
   * kDNSServiceInterfaceIndexP2P is meaningful only in Browse, QueryRecord,
   * and Resolve operations. It should not be used in other DNSService APIs.
   *
   * - If kDNSServiceInterfaceIndexP2P is passed to DNSServiceBrowse or
   *   DNSServiceQueryRecord, it restricts the operation to P2P.
   *
   * - If kDNSServiceInterfaceIndexP2P is passed to DNSServiceResolve, it is
   *   mapped internally to kDNSServiceInterfaceIndexAny, because resolving
   *   a P2P service may create and/or enable an interface whose index is not
   *   known a priori. The resolve callback will indicate the index of the
   *   interface via which the service can be accessed.
   *
   * If applications pass kDNSServiceInterfaceIndexAny to DNSServiceBrowse
   * or DNSServiceQueryRecord, they must set the kDNSServiceFlagsIncludeP2P flag
   * to include P2P. In this case, if a service instance or the record being queried 
   * is found over P2P, the resulting ADD event will indicate kDNSServiceInterfaceIndexP2P 
   * as the interface index.
   */
  
  #define kDNSServiceInterfaceIndexAny 0
  #define kDNSServiceInterfaceIndexLocalOnly ((uint32_t)-1)
  #define kDNSServiceInterfaceIndexUnicast   ((uint32_t)-2)
  #define kDNSServiceInterfaceIndexP2P       ((uint32_t)-3)
  
  typedef uint32_t DNSServiceFlags;
  typedef uint32_t DNSServiceProtocol;
  typedef int32_t  DNSServiceErrorType;
  
  
  /*********************************************************************************************
   *
   * Version checking
   *
   *********************************************************************************************/
  
  /* DNSServiceGetProperty() Parameters:
   *
   * property:        The requested property.
   *                  Currently the only property defined is kDNSServiceProperty_DaemonVersion.
   *
   * result:          Place to store result.
   *                  For retrieving DaemonVersion, this should be the address of a uint32_t.
   *
   * size:            Pointer to uint32_t containing size of the result location.
   *                  For retrieving DaemonVersion, this should be sizeof(uint32_t).
   *                  On return the uint32_t is updated to the size of the data returned.
   *                  For DaemonVersion, the returned size is always sizeof(uint32_t), but
   *                  future properties could be defined which return variable-sized results.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, or kDNSServiceErr_ServiceNotRunning
   *                  if the daemon (or "system service" on Windows) is not running.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceGetProperty
      (
      const char *property,  /* Requested property (i.e. kDNSServiceProperty_DaemonVersion) */
      void       *result,    /* Pointer to place to store result */
      uint32_t   *size       /* size of result location */
      );
  
  /*
   * When requesting kDNSServiceProperty_DaemonVersion, the result pointer must point
   * to a 32-bit unsigned integer, and the size parameter must be set to sizeof(uint32_t).
   *
   * On return, the 32-bit unsigned integer contains the version number, formatted as follows:
   *   Major part of the build number * 10000 +
   *   minor part of the build number *   100
   *
   * For example, Mac OS X 10.4.9 has mDNSResponder-108.4, which would be represented as
   * version 1080400. This allows applications to do simple greater-than and less-than comparisons:
   * e.g. an application that requires at least mDNSResponder-108.4 can check:
   *
   *   if (version >= 1080400) ...
   *
   * Example usage:
   *
   * uint32_t version;
   * uint32_t size = sizeof(version);
   * DNSServiceErrorType err = DNSServiceGetProperty(kDNSServiceProperty_DaemonVersion, &version, &size);
   * if (!err) printf("Bonjour version is %d.%d\n", version / 10000, version / 100 % 100);
   */
  
  #define kDNSServiceProperty_DaemonVersion "DaemonVersion"
  
  
  /*********************************************************************************************
   *
   * Unix Domain Socket access, DNSServiceRef deallocation, and data processing functions
   *
   *********************************************************************************************/
  
  /* DNSServiceRefSockFD()
   *
   * Access underlying Unix domain socket for an initialized DNSServiceRef.
   * The DNS Service Discovery implementation uses this socket to communicate between the client and
   * the mDNSResponder daemon. The application MUST NOT directly read from or write to this socket.
   * Access to the socket is provided so that it can be used as a kqueue event source, a CFRunLoop
   * event source, in a select() loop, etc. When the underlying event management subsystem (kqueue/
   * select/CFRunLoop etc.) indicates to the client that data is available for reading on the
   * socket, the client should call DNSServiceProcessResult(), which will extract the daemon's
   * reply from the socket, and pass it to the appropriate application callback. By using a run
   * loop or select(), results from the daemon can be processed asynchronously. Alternatively,
   * a client can choose to fork a thread and have it loop calling "DNSServiceProcessResult(ref);"
   * If DNSServiceProcessResult() is called when no data is available for reading on the socket, it
   * will block until data does become available, and then process the data and return to the caller.
   * When data arrives on the socket, the client is responsible for calling DNSServiceProcessResult(ref)
   * in a timely fashion -- if the client allows a large backlog of data to build up the daemon
   * may terminate the connection.
   *
   * sdRef:           A DNSServiceRef initialized by any of the DNSService calls.
   *
   * return value:    The DNSServiceRef's underlying socket descriptor, or -1 on
   *                  error.
   */
  
  int DNSSD_API DNSServiceRefSockFD(DNSServiceRef sdRef);
  
  
  /* DNSServiceProcessResult()
   *
   * Read a reply from the daemon, calling the appropriate application callback. This call will
   * block until the daemon's response is received. Use DNSServiceRefSockFD() in
   * conjunction with a run loop or select() to determine the presence of a response from the
   * server before calling this function to process the reply without blocking. Call this function
   * at any point if it is acceptable to block until the daemon's response arrives. Note that the
   * client is responsible for ensuring that DNSServiceProcessResult() is called whenever there is
   * a reply from the daemon - the daemon may terminate its connection with a client that does not
   * process the daemon's responses.
   *
   * sdRef:           A DNSServiceRef initialized by any of the DNSService calls
   *                  that take a callback parameter.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, otherwise returns
   *                  an error code indicating the specific failure that occurred.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceProcessResult(DNSServiceRef sdRef);
  
  
  /* DNSServiceRefDeallocate()
   *
   * Terminate a connection with the daemon and free memory associated with the DNSServiceRef.
   * Any services or records registered with this DNSServiceRef will be deregistered. Any
   * Browse, Resolve, or Query operations called with this reference will be terminated.
   *
   * Note: If the reference's underlying socket is used in a run loop or select() call, it should
   * be removed BEFORE DNSServiceRefDeallocate() is called, as this function closes the reference's
   * socket.
   *
   * Note: If the reference was initialized with DNSServiceCreateConnection(), any DNSRecordRefs
   * created via this reference will be invalidated by this call - the resource records are
   * deregistered, and their DNSRecordRefs may not be used in subsequent functions. Similarly,
   * if the reference was initialized with DNSServiceRegister, and an extra resource record was
   * added to the service via DNSServiceAddRecord(), the DNSRecordRef created by the Add() call
   * is invalidated when this function is called - the DNSRecordRef may not be used in subsequent
   * functions.
   *
   * Note: This call is to be used only with the DNSServiceRef defined by this API. It is
   * not compatible with dns_service_discovery_ref objects defined in the legacy Mach-based
   * DNSServiceDiscovery.h API.
   *
   * sdRef:           A DNSServiceRef initialized by any of the DNSService calls.
   *
   */
  
  void DNSSD_API DNSServiceRefDeallocate(DNSServiceRef sdRef);
  
  
  /*********************************************************************************************
   *
   * Domain Enumeration
   *
   *********************************************************************************************/
  
  /* DNSServiceEnumerateDomains()
   *
   * Asynchronously enumerate domains available for browsing and registration.
   *
   * The enumeration MUST be cancelled via DNSServiceRefDeallocate() when no more domains
   * are to be found.
   *
   * Note that the names returned are (like all of DNS-SD) UTF-8 strings,
   * and are escaped using standard DNS escaping rules.
   * (See "Notes on DNS Name Escaping" earlier in this file for more details.)
   * A graphical browser displaying a hierarchical tree-structured view should cut
   * the names at the bare dots to yield individual labels, then de-escape each
   * label according to the escaping rules, and then display the resulting UTF-8 text.
   *
   * DNSServiceDomainEnumReply Callback Parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceEnumerateDomains().
   *
   * flags:           Possible values are:
   *                  kDNSServiceFlagsMoreComing
   *                  kDNSServiceFlagsAdd
   *                  kDNSServiceFlagsDefault
   *
   * interfaceIndex:  Specifies the interface on which the domain exists. (The index for a given
   *                  interface is determined via the if_nametoindex() family of calls.)
   *
   * errorCode:       Will be kDNSServiceErr_NoError (0) on success, otherwise indicates
   *                  the failure that occurred (other parameters are undefined if errorCode is nonzero).
   *
   * replyDomain:     The name of the domain.
   *
   * context:         The context pointer passed to DNSServiceEnumerateDomains.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceDomainEnumReply)
      (
      DNSServiceRef                       sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      DNSServiceErrorType                 errorCode,
      const char                          *replyDomain,
      void                                *context
      );
  
  
  /* DNSServiceEnumerateDomains() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds
   *                  then it initializes the DNSServiceRef, returns kDNSServiceErr_NoError,
   *                  and the enumeration operation will run indefinitely until the client
   *                  terminates it by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           Possible values are:
   *                  kDNSServiceFlagsBrowseDomains to enumerate domains recommended for browsing.
   *                  kDNSServiceFlagsRegistrationDomains to enumerate domains recommended
   *                  for registration.
   *
   * interfaceIndex:  If non-zero, specifies the interface on which to look for domains.
   *                  (the index for a given interface is determined via the if_nametoindex()
   *                  family of calls.) Most applications will pass 0 to enumerate domains on
   *                  all interfaces. See "Constants for specifying an interface index" for more details.
   *
   * callBack:        The function to be called when a domain is found or the call asynchronously
   *                  fails.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is not invoked and the DNSServiceRef
   *                  is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceEnumerateDomains
      (
      DNSServiceRef                       *sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      DNSServiceDomainEnumReply           callBack,
      void                                *context  /* may be NULL */
      );
  
  
  /*********************************************************************************************
   *
   *  Service Registration
   *
   *********************************************************************************************/
  
  /* Register a service that is discovered via Browse() and Resolve() calls.
   *
   * DNSServiceRegisterReply() Callback Parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceRegister().
   *
   * flags:           When a name is successfully registered, the callback will be
   *                  invoked with the kDNSServiceFlagsAdd flag set. When Wide-Area
   *                  DNS-SD is in use, it is possible for a single service to get
   *                  more than one success callback (e.g. one in the "local" multicast
   *                  DNS domain, and another in a wide-area unicast DNS domain).
   *                  If a successfully-registered name later suffers a name conflict
   *                  or similar problem and has to be deregistered, the callback will
   *                  be invoked with the kDNSServiceFlagsAdd flag not set. The callback
   *                  is *not* invoked in the case where the caller explicitly terminates
   *                  the service registration by calling DNSServiceRefDeallocate(ref);
   *
   * errorCode:       Will be kDNSServiceErr_NoError on success, otherwise will
   *                  indicate the failure that occurred (including name conflicts,
   *                  if the kDNSServiceFlagsNoAutoRename flag was used when registering.)
   *                  Other parameters are undefined if errorCode is nonzero.
   *
   * name:            The service name registered (if the application did not specify a name in
   *                  DNSServiceRegister(), this indicates what name was automatically chosen).
   *
   * regtype:         The type of service registered, as it was passed to the callout.
   *
   * domain:          The domain on which the service was registered (if the application did not
   *                  specify a domain in DNSServiceRegister(), this indicates the default domain
   *                  on which the service was registered).
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceRegisterReply)
      (
      DNSServiceRef                       sdRef,
      DNSServiceFlags                     flags,
      DNSServiceErrorType                 errorCode,
      const char                          *name,
      const char                          *regtype,
      const char                          *domain,
      void                                *context
      );
  
  
  /* DNSServiceRegister() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds
   *                  then it initializes the DNSServiceRef, returns kDNSServiceErr_NoError,
   *                  and the registration will remain active indefinitely until the client
   *                  terminates it by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * interfaceIndex:  If non-zero, specifies the interface on which to register the service
   *                  (the index for a given interface is determined via the if_nametoindex()
   *                  family of calls.) Most applications will pass 0 to register on all
   *                  available interfaces. See "Constants for specifying an interface index" for more details.
   *
   * flags:           Indicates the renaming behavior on name conflict (most applications
   *                  will pass 0). See flag definitions above for details.
   *
   * name:            If non-NULL, specifies the service name to be registered.
   *                  Most applications will not specify a name, in which case the computer
   *                  name is used (this name is communicated to the client via the callback).
   *                  If a name is specified, it must be 1-63 bytes of UTF-8 text.
   *                  If the name is longer than 63 bytes it will be automatically truncated
   *                  to a legal length, unless the NoAutoRename flag is set,
   *                  in which case kDNSServiceErr_BadParam will be returned.
   *
   * regtype:         The service type followed by the protocol, separated by a dot
   *                  (e.g. "_ftp._tcp"). The service type must be an underscore, followed
   *                  by 1-15 characters, which may be letters, digits, or hyphens.
   *                  The transport protocol must be "_tcp" or "_udp". New service types
   *                  should be registered at <http://www.dns-sd.org/ServiceTypes.html>.
   *
   *                  Additional subtypes of the primary service type (where a service
   *                  type has defined subtypes) follow the primary service type in a
   *                  comma-separated list, with no additional spaces, e.g.
   *                      "_primarytype._tcp,_subtype1,_subtype2,_subtype3"
   *                  Subtypes provide a mechanism for filtered browsing: A client browsing
   *                  for "_primarytype._tcp" will discover all instances of this type;
   *                  a client browsing for "_primarytype._tcp,_subtype2" will discover only
   *                  those instances that were registered with "_subtype2" in their list of
   *                  registered subtypes.
   *
   *                  The subtype mechanism can be illustrated with some examples using the
   *                  dns-sd command-line tool:
   *
   *                  % dns-sd -R Simple _test._tcp "" 1001 &
   *                  % dns-sd -R Better _test._tcp,HasFeatureA "" 1002 &
   *                  % dns-sd -R Best   _test._tcp,HasFeatureA,HasFeatureB "" 1003 &
   *
   *                  Now:
   *                  % dns-sd -B _test._tcp             # will find all three services
   *                  % dns-sd -B _test._tcp,HasFeatureA # finds "Better" and "Best"
   *                  % dns-sd -B _test._tcp,HasFeatureB # finds only "Best"
   *
   *                  Subtype labels may be up to 63 bytes long, and may contain any eight-
   *                  bit byte values, including zero bytes. However, due to the nature of
   *                  using a C-string-based API, conventional DNS escaping must be used for
   *                  dots ('.'), commas (','), backslashes ('\') and zero bytes, as shown below:
   *                  
   *                  % dns-sd -R Test '_test._tcp,s\.one,s\,two,s\\three,s\000four' local 123
   *
   * domain:          If non-NULL, specifies the domain on which to advertise the service.
   *                  Most applications will not specify a domain, instead automatically
   *                  registering in the default domain(s).
   *
   * host:            If non-NULL, specifies the SRV target host name. Most applications
   *                  will not specify a host, instead automatically using the machine's
   *                  default host name(s). Note that specifying a non-NULL host does NOT
   *                  create an address record for that host - the application is responsible
   *                  for ensuring that the appropriate address record exists, or creating it
   *                  via DNSServiceRegisterRecord().
   *
   * port:            The port, in network byte order, on which the service accepts connections.
   *                  Pass 0 for a "placeholder" service (i.e. a service that will not be discovered
   *                  by browsing, but will cause a name conflict if another client tries to
   *                  register that same name). Most clients will not use placeholder services.
   *
   * txtLen:          The length of the txtRecord, in bytes. Must be zero if the txtRecord is NULL.
   *
   * txtRecord:       The TXT record rdata. A non-NULL txtRecord MUST be a properly formatted DNS
   *                  TXT record, i.e. <length byte> <data> <length byte> <data> ...
   *                  Passing NULL for the txtRecord is allowed as a synonym for txtLen=1, txtRecord="",
   *                  i.e. it creates a TXT record of length one containing a single empty string.
   *                  RFC 1035 doesn't allow a TXT record to contain *zero* strings, so a single empty
   *                  string is the smallest legal DNS TXT record.
   *                  As with the other parameters, the DNSServiceRegister call copies the txtRecord
   *                  data; e.g. if you allocated the storage for the txtRecord parameter with malloc()
   *                  then you can safely free that memory right after the DNSServiceRegister call returns.
   *
   * callBack:        The function to be called when the registration completes or asynchronously
   *                  fails. The client MAY pass NULL for the callback -  The client will NOT be notified
   *                  of the default values picked on its behalf, and the client will NOT be notified of any
   *                  asynchronous errors (e.g. out of memory errors, etc.) that may prevent the registration
   *                  of the service. The client may NOT pass the NoAutoRename flag if the callback is NULL.
   *                  The client may still deregister the service at any time via DNSServiceRefDeallocate().
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is never invoked and the DNSServiceRef
   *                  is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceRegister
      (
      DNSServiceRef                       *sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      const char                          *name,         /* may be NULL */
      const char                          *regtype,
      const char                          *domain,       /* may be NULL */
      const char                          *host,         /* may be NULL */
      uint16_t                            port,          /* In network byte order */
      uint16_t                            txtLen,
      const void                          *txtRecord,    /* may be NULL */
      DNSServiceRegisterReply             callBack,      /* may be NULL */
      void                                *context       /* may be NULL */
      );
  
  
  /* DNSServiceAddRecord()
   *
   * Add a record to a registered service. The name of the record will be the same as the
   * registered service's name.
   * The record can later be updated or deregistered by passing the RecordRef initialized
   * by this function to DNSServiceUpdateRecord() or DNSServiceRemoveRecord().
   *
   * Note that the DNSServiceAddRecord/UpdateRecord/RemoveRecord are *NOT* thread-safe
   * with respect to a single DNSServiceRef. If you plan to have multiple threads
   * in your program simultaneously add, update, or remove records from the same
   * DNSServiceRef, then it's the caller's responsibility to use a mutext lock
   * or take similar appropriate precautions to serialize those calls.
   *
   * Parameters;
   *
   * sdRef:           A DNSServiceRef initialized by DNSServiceRegister().
   *
   * RecordRef:       A pointer to an uninitialized DNSRecordRef. Upon succesfull completion of this
   *                  call, this ref may be passed to DNSServiceUpdateRecord() or DNSServiceRemoveRecord().
   *                  If the above DNSServiceRef is passed to DNSServiceRefDeallocate(), RecordRef is also
   *                  invalidated and may not be used further.
   *
   * flags:           Currently ignored, reserved for future use.
   *
   * rrtype:          The type of the record (e.g. kDNSServiceType_TXT, kDNSServiceType_SRV, etc)
   *
   * rdlen:           The length, in bytes, of the rdata.
   *
   * rdata:           The raw rdata to be contained in the added resource record.
   *
   * ttl:             The time to live of the resource record, in seconds.
   *                  Most clients should pass 0 to indicate that the system should
   *                  select a sensible default value.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, otherwise returns an
   *                  error code indicating the error that occurred (the RecordRef is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceAddRecord
      (
      DNSServiceRef                       sdRef,
      DNSRecordRef                        *RecordRef,
      DNSServiceFlags                     flags,
      uint16_t                            rrtype,
      uint16_t                            rdlen,
      const void                          *rdata,
      uint32_t                            ttl
      );
  
  
  /* DNSServiceUpdateRecord
   *
   * Update a registered resource record. The record must either be:
   *   - The primary txt record of a service registered via DNSServiceRegister()
   *   - A record added to a registered service via DNSServiceAddRecord()
   *   - An individual record registered by DNSServiceRegisterRecord()
   *
   * Parameters:
   *
   * sdRef:           A DNSServiceRef that was initialized by DNSServiceRegister()
   *                  or DNSServiceCreateConnection().
   *
   * RecordRef:       A DNSRecordRef initialized by DNSServiceAddRecord, or NULL to update the
   *                  service's primary txt record.
   *
   * flags:           Currently ignored, reserved for future use.
   *
   * rdlen:           The length, in bytes, of the new rdata.
   *
   * rdata:           The new rdata to be contained in the updated resource record.
   *
   * ttl:             The time to live of the updated resource record, in seconds.
   *                  Most clients should pass 0 to indicate that the system should
   *                  select a sensible default value.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, otherwise returns an
   *                  error code indicating the error that occurred.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceUpdateRecord
      (
      DNSServiceRef                       sdRef,
      DNSRecordRef                        RecordRef,     /* may be NULL */
      DNSServiceFlags                     flags,
      uint16_t                            rdlen,
      const void                          *rdata,
      uint32_t                            ttl
      );
  
  
  /* DNSServiceRemoveRecord
   *
   * Remove a record previously added to a service record set via DNSServiceAddRecord(), or deregister
   * an record registered individually via DNSServiceRegisterRecord().
   *
   * Parameters:
   *
   * sdRef:           A DNSServiceRef initialized by DNSServiceRegister() (if the
   *                  record being removed was registered via DNSServiceAddRecord()) or by
   *                  DNSServiceCreateConnection() (if the record being removed was registered via
   *                  DNSServiceRegisterRecord()).
   *
   * recordRef:       A DNSRecordRef initialized by a successful call to DNSServiceAddRecord()
   *                  or DNSServiceRegisterRecord().
   *
   * flags:           Currently ignored, reserved for future use.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, otherwise returns an
   *                  error code indicating the error that occurred.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceRemoveRecord
      (
      DNSServiceRef                 sdRef,
      DNSRecordRef                  RecordRef,
      DNSServiceFlags               flags
      );
  
  
  /*********************************************************************************************
   *
   *  Service Discovery
   *
   *********************************************************************************************/
  
  /* Browse for instances of a service.
   *
   * DNSServiceBrowseReply() Parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceBrowse().
   *
   * flags:           Possible values are kDNSServiceFlagsMoreComing and kDNSServiceFlagsAdd.
   *                  See flag definitions for details.
   *
   * interfaceIndex:  The interface on which the service is advertised. This index should
   *                  be passed to DNSServiceResolve() when resolving the service.
   *
   * errorCode:       Will be kDNSServiceErr_NoError (0) on success, otherwise will
   *                  indicate the failure that occurred. Other parameters are undefined if
   *                  the errorCode is nonzero.
   *
   * serviceName:     The discovered service name. This name should be displayed to the user,
   *                  and stored for subsequent use in the DNSServiceResolve() call.
   *
   * regtype:         The service type, which is usually (but not always) the same as was passed
   *                  to DNSServiceBrowse(). One case where the discovered service type may
   *                  not be the same as the requested service type is when using subtypes:
   *                  The client may want to browse for only those ftp servers that allow
   *                  anonymous connections. The client will pass the string "_ftp._tcp,_anon"
   *                  to DNSServiceBrowse(), but the type of the service that's discovered
   *                  is simply "_ftp._tcp". The regtype for each discovered service instance
   *                  should be stored along with the name, so that it can be passed to
   *                  DNSServiceResolve() when the service is later resolved.
   *
   * domain:          The domain of the discovered service instance. This may or may not be the
   *                  same as the domain that was passed to DNSServiceBrowse(). The domain for each
   *                  discovered service instance should be stored along with the name, so that
   *                  it can be passed to DNSServiceResolve() when the service is later resolved.
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceBrowseReply)
      (
      DNSServiceRef                       sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      DNSServiceErrorType                 errorCode,
      const char                          *serviceName,
      const char                          *regtype,
      const char                          *replyDomain,
      void                                *context
      );
  
  
  /* DNSServiceBrowse() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds
   *                  then it initializes the DNSServiceRef, returns kDNSServiceErr_NoError,
   *                  and the browse operation will run indefinitely until the client
   *                  terminates it by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           Currently ignored, reserved for future use.
   *
   * interfaceIndex:  If non-zero, specifies the interface on which to browse for services
   *                  (the index for a given interface is determined via the if_nametoindex()
   *                  family of calls.) Most applications will pass 0 to browse on all available
   *                  interfaces. See "Constants for specifying an interface index" for more details.
   *
   * regtype:         The service type being browsed for followed by the protocol, separated by a
   *                  dot (e.g. "_ftp._tcp"). The transport protocol must be "_tcp" or "_udp".
   *                  A client may optionally specify a single subtype to perform filtered browsing:
   *                  e.g. browsing for "_primarytype._tcp,_subtype" will discover only those
   *                  instances of "_primarytype._tcp" that were registered specifying "_subtype"
   *                  in their list of registered subtypes.
   *
   * domain:          If non-NULL, specifies the domain on which to browse for services.
   *                  Most applications will not specify a domain, instead browsing on the
   *                  default domain(s).
   *
   * callBack:        The function to be called when an instance of the service being browsed for
   *                  is found, or if the call asynchronously fails.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is not invoked and the DNSServiceRef
   *                  is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceBrowse
      (
      DNSServiceRef                       *sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      const char                          *regtype,
      const char                          *domain,    /* may be NULL */
      DNSServiceBrowseReply               callBack,
      void                                *context    /* may be NULL */
      );
  
  
  /* DNSServiceResolve()
   *
   * Resolve a service name discovered via DNSServiceBrowse() to a target host name, port number, and
   * txt record.
   *
   * Note: Applications should NOT use DNSServiceResolve() solely for txt record monitoring - use
   * DNSServiceQueryRecord() instead, as it is more efficient for this task.
   *
   * Note: When the desired results have been returned, the client MUST terminate the resolve by calling
   * DNSServiceRefDeallocate().
   *
   * Note: DNSServiceResolve() behaves correctly for typical services that have a single SRV record
   * and a single TXT record. To resolve non-standard services with multiple SRV or TXT records,
   * DNSServiceQueryRecord() should be used.
   *
   * DNSServiceResolveReply Callback Parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceResolve().
   *
   * flags:           Possible values: kDNSServiceFlagsMoreComing
   *
   * interfaceIndex:  The interface on which the service was resolved.
   *
   * errorCode:       Will be kDNSServiceErr_NoError (0) on success, otherwise will
   *                  indicate the failure that occurred. Other parameters are undefined if
   *                  the errorCode is nonzero.
   *
   * fullname:        The full service domain name, in the form <servicename>.<protocol>.<domain>.
   *                  (This name is escaped following standard DNS rules, making it suitable for
   *                  passing to standard system DNS APIs such as res_query(), or to the
   *                  special-purpose functions included in this API that take fullname parameters.
   *                  See "Notes on DNS Name Escaping" earlier in this file for more details.)
   *
   * hosttarget:      The target hostname of the machine providing the service. This name can
   *                  be passed to functions like gethostbyname() to identify the host's IP address.
   *
   * port:            The port, in network byte order, on which connections are accepted for this service.
   *
   * txtLen:          The length of the txt record, in bytes.
   *
   * txtRecord:       The service's primary txt record, in standard txt record format.
   *
   * context:         The context pointer that was passed to the callout.
   *
   * NOTE: In earlier versions of this header file, the txtRecord parameter was declared "const char *"
   * This is incorrect, since it contains length bytes which are values in the range 0 to 255, not -128 to +127.
   * Depending on your compiler settings, this change may cause signed/unsigned mismatch warnings.
   * These should be fixed by updating your own callback function definition to match the corrected
   * function signature using "const unsigned char *txtRecord". Making this change may also fix inadvertent
   * bugs in your callback function, where it could have incorrectly interpreted a length byte with value 250
   * as being -6 instead, with various bad consequences ranging from incorrect operation to software crashes.
   * If you need to maintain portable code that will compile cleanly with both the old and new versions of
   * this header file, you should update your callback function definition to use the correct unsigned value,
   * and then in the place where you pass your callback function to DNSServiceResolve(), use a cast to eliminate
   * the compiler warning, e.g.:
   *   DNSServiceResolve(sd, flags, index, name, regtype, domain, (DNSServiceResolveReply)MyCallback, context);
   * This will ensure that your code compiles cleanly without warnings (and more importantly, works correctly)
   * with both the old header and with the new corrected version.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceResolveReply)
      (
      DNSServiceRef                       sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      DNSServiceErrorType                 errorCode,
      const char                          *fullname,
      const char                          *hosttarget,
      uint16_t                            port,        /* In network byte order */
      uint16_t                            txtLen,
      const unsigned char                 *txtRecord,
      void                                *context
      );
  
  
  /* DNSServiceResolve() Parameters
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds
   *                  then it initializes the DNSServiceRef, returns kDNSServiceErr_NoError,
   *                  and the resolve operation will run indefinitely until the client
   *                  terminates it by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           Specifying kDNSServiceFlagsForceMulticast will cause query to be
   *                  performed with a link-local mDNS query, even if the name is an
   *                  apparently non-local name (i.e. a name not ending in ".local.")
   *
   * interfaceIndex:  The interface on which to resolve the service. If this resolve call is
   *                  as a result of a currently active DNSServiceBrowse() operation, then the
   *                  interfaceIndex should be the index reported in the DNSServiceBrowseReply
   *                  callback. If this resolve call is using information previously saved
   *                  (e.g. in a preference file) for later use, then use interfaceIndex 0, because
   *                  the desired service may now be reachable via a different physical interface.
   *                  See "Constants for specifying an interface index" for more details.
   *
   * name:            The name of the service instance to be resolved, as reported to the
   *                  DNSServiceBrowseReply() callback.
   *
   * regtype:         The type of the service instance to be resolved, as reported to the
   *                  DNSServiceBrowseReply() callback.
   *
   * domain:          The domain of the service instance to be resolved, as reported to the
   *                  DNSServiceBrowseReply() callback.
   *
   * callBack:        The function to be called when a result is found, or if the call
   *                  asynchronously fails.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is never invoked and the DNSServiceRef
   *                  is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceResolve
      (
      DNSServiceRef                       *sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      const char                          *name,
      const char                          *regtype,
      const char                          *domain,
      DNSServiceResolveReply              callBack,
      void                                *context  /* may be NULL */
      );
  
  
  /*********************************************************************************************
   *
   *  Querying Individual Specific Records
   *
   *********************************************************************************************/
  
  /* DNSServiceQueryRecord
   *
   * Query for an arbitrary DNS record.
   *
   * DNSServiceQueryRecordReply() Callback Parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceQueryRecord().
   *
   * flags:           Possible values are kDNSServiceFlagsMoreComing and
   *                  kDNSServiceFlagsAdd. The Add flag is NOT set for PTR records
   *                  with a ttl of 0, i.e. "Remove" events.
   *
   * interfaceIndex:  The interface on which the query was resolved (the index for a given
   *                  interface is determined via the if_nametoindex() family of calls).
   *                  See "Constants for specifying an interface index" for more details.
   *
   * errorCode:       Will be kDNSServiceErr_NoError on success, otherwise will
   *                  indicate the failure that occurred. Other parameters are undefined if
   *                  errorCode is nonzero.
   *
   * fullname:        The resource record's full domain name.
   *
   * rrtype:          The resource record's type (e.g. kDNSServiceType_PTR, kDNSServiceType_SRV, etc)
   *
   * rrclass:         The class of the resource record (usually kDNSServiceClass_IN).
   *
   * rdlen:           The length, in bytes, of the resource record rdata.
   *
   * rdata:           The raw rdata of the resource record.
   *
   * ttl:             If the client wishes to cache the result for performance reasons,
   *                  the TTL indicates how long the client may legitimately hold onto
   *                  this result, in seconds. After the TTL expires, the client should
   *                  consider the result no longer valid, and if it requires this data
   *                  again, it should be re-fetched with a new query. Of course, this
   *                  only applies to clients that cancel the asynchronous operation when
   *                  they get a result. Clients that leave the asynchronous operation
   *                  running can safely assume that the data remains valid until they
   *                  get another callback telling them otherwise.
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceQueryRecordReply)
      (
      DNSServiceRef                       sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      DNSServiceErrorType                 errorCode,
      const char                          *fullname,
      uint16_t                            rrtype,
      uint16_t                            rrclass,
      uint16_t                            rdlen,
      const void                          *rdata,
      uint32_t                            ttl,
      void                                *context
      );
  
  
  /* DNSServiceQueryRecord() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds
   *                  then it initializes the DNSServiceRef, returns kDNSServiceErr_NoError,
   *                  and the query operation will run indefinitely until the client
   *                  terminates it by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           kDNSServiceFlagsForceMulticast or kDNSServiceFlagsLongLivedQuery.
   *                  Pass kDNSServiceFlagsLongLivedQuery to create a "long-lived" unicast
   *                  query in a non-local domain. Without setting this flag, unicast queries
   *                  will be one-shot - that is, only answers available at the time of the call
   *                  will be returned. By setting this flag, answers (including Add and Remove
   *                  events) that become available after the initial call is made will generate
   *                  callbacks. This flag has no effect on link-local multicast queries.
   *
   * interfaceIndex:  If non-zero, specifies the interface on which to issue the query
   *                  (the index for a given interface is determined via the if_nametoindex()
   *                  family of calls.) Passing 0 causes the name to be queried for on all
   *                  interfaces. See "Constants for specifying an interface index" for more details.
   *
   * fullname:        The full domain name of the resource record to be queried for.
   *
   * rrtype:          The numerical type of the resource record to be queried for
   *                  (e.g. kDNSServiceType_PTR, kDNSServiceType_SRV, etc)
   *
   * rrclass:         The class of the resource record (usually kDNSServiceClass_IN).
   *
   * callBack:        The function to be called when a result is found, or if the call
   *                  asynchronously fails.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is never invoked and the DNSServiceRef
   *                  is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceQueryRecord
      (
      DNSServiceRef                       *sdRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      const char                          *fullname,
      uint16_t                            rrtype,
      uint16_t                            rrclass,
      DNSServiceQueryRecordReply          callBack,
      void                                *context  /* may be NULL */
      );
  
  
  /*********************************************************************************************
   *
   *  Unified lookup of both IPv4 and IPv6 addresses for a fully qualified hostname
   *
   *********************************************************************************************/
  
  /* DNSServiceGetAddrInfo
   *
   * Queries for the IP address of a hostname by using either Multicast or Unicast DNS.
   *
   * DNSServiceGetAddrInfoReply() parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceGetAddrInfo().
   *
   * flags:           Possible values are kDNSServiceFlagsMoreComing and
   *                  kDNSServiceFlagsAdd.
   *
   * interfaceIndex:  The interface to which the answers pertain.
   *
   * errorCode:       Will be kDNSServiceErr_NoError on success, otherwise will
   *                  indicate the failure that occurred.  Other parameters are
   *                  undefined if errorCode is nonzero.
   *
   * hostname:        The fully qualified domain name of the host to be queried for.
   *
   * address:         IPv4 or IPv6 address.
   *
   * ttl:             If the client wishes to cache the result for performance reasons,
   *                  the TTL indicates how long the client may legitimately hold onto
   *                  this result, in seconds. After the TTL expires, the client should
   *                  consider the result no longer valid, and if it requires this data
   *                  again, it should be re-fetched with a new query. Of course, this
   *                  only applies to clients that cancel the asynchronous operation when
   *                  they get a result. Clients that leave the asynchronous operation
   *                  running can safely assume that the data remains valid until they
   *                  get another callback telling them otherwise.
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceGetAddrInfoReply)
      (
      DNSServiceRef                    sdRef,
      DNSServiceFlags                  flags,
      uint32_t                         interfaceIndex,
      DNSServiceErrorType              errorCode,
      const char                       *hostname,
      const struct sockaddr            *address,
      uint32_t                         ttl,
      void                             *context
      );
  
  
  /* DNSServiceGetAddrInfo() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds then it
   *                  initializes the DNSServiceRef, returns kDNSServiceErr_NoError, and the query
   *                  begins and will last indefinitely until the client terminates the query
   *                  by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           kDNSServiceFlagsForceMulticast or kDNSServiceFlagsLongLivedQuery.
   *                  Pass kDNSServiceFlagsLongLivedQuery to create a "long-lived" unicast
   *                  query in a non-local domain. Without setting this flag, unicast queries
   *                  will be one-shot - that is, only answers available at the time of the call
   *                  will be returned. By setting this flag, answers (including Add and Remove
   *                  events) that become available after the initial call is made will generate
   *                  callbacks. This flag has no effect on link-local multicast queries.
   *
   * interfaceIndex:  The interface on which to issue the query.  Passing 0 causes the query to be
   *                  sent on all active interfaces via Multicast or the primary interface via Unicast.
   *
   * protocol:        Pass in kDNSServiceProtocol_IPv4 to look up IPv4 addresses, or kDNSServiceProtocol_IPv6
   *                  to look up IPv6 addresses, or both to look up both kinds. If neither flag is
   *                  set, the system will apply an intelligent heuristic, which is (currently)
   *                  that it will attempt to look up both, except:
   *
   *                   * If "hostname" is a wide-area unicast DNS hostname (i.e. not a ".local." name)
   *                     but this host has no routable IPv6 address, then the call will not try to
   *                     look up IPv6 addresses for "hostname", since any addresses it found would be
   *                     unlikely to be of any use anyway. Similarly, if this host has no routable
   *                     IPv4 address, the call will not try to look up IPv4 addresses for "hostname".
   *
   * hostname:        The fully qualified domain name of the host to be queried for.
   *
   * callBack:        The function to be called when the query succeeds or fails asynchronously.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceGetAddrInfo
      (
      DNSServiceRef                    *sdRef,
      DNSServiceFlags                  flags,
      uint32_t                         interfaceIndex,
      DNSServiceProtocol               protocol,
      const char                       *hostname,
      DNSServiceGetAddrInfoReply       callBack,
      void                             *context          /* may be NULL */
      );
  
  
  /*********************************************************************************************
   *
   *  Special Purpose Calls:
   *  DNSServiceCreateConnection(), DNSServiceRegisterRecord(), DNSServiceReconfirmRecord()
   *  (most applications will not use these)
   *
   *********************************************************************************************/
  
  /* DNSServiceCreateConnection()
   *
   * Create a connection to the daemon allowing efficient registration of
   * multiple individual records.
   *
   * Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. Deallocating
   *                  the reference (via DNSServiceRefDeallocate()) severs the
   *                  connection and deregisters all records registered on this connection.
   *
   * return value:    Returns kDNSServiceErr_NoError on success, otherwise returns
   *                  an error code indicating the specific failure that occurred (in which
   *                  case the DNSServiceRef is not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceCreateConnection(DNSServiceRef *sdRef);
  
  
  /* DNSServiceRegisterRecord
   *
   * Register an individual resource record on a connected DNSServiceRef.
   *
   * Note that name conflicts occurring for records registered via this call must be handled
   * by the client in the callback.
   *
   * DNSServiceRegisterRecordReply() parameters:
   *
   * sdRef:           The connected DNSServiceRef initialized by
   *                  DNSServiceCreateConnection().
   *
   * RecordRef:       The DNSRecordRef initialized by DNSServiceRegisterRecord(). If the above
   *                  DNSServiceRef is passed to DNSServiceRefDeallocate(), this DNSRecordRef is
   *                  invalidated, and may not be used further.
   *
   * flags:           Currently unused, reserved for future use.
   *
   * errorCode:       Will be kDNSServiceErr_NoError on success, otherwise will
   *                  indicate the failure that occurred (including name conflicts.)
   *                  Other parameters are undefined if errorCode is nonzero.
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
   typedef void (DNSSD_API *DNSServiceRegisterRecordReply)
      (
      DNSServiceRef                       sdRef,
      DNSRecordRef                        RecordRef,
      DNSServiceFlags                     flags,
      DNSServiceErrorType                 errorCode,
      void                                *context
      );
  
  
  /* DNSServiceRegisterRecord() Parameters:
   *
   * sdRef:           A DNSServiceRef initialized by DNSServiceCreateConnection().
   *
   * RecordRef:       A pointer to an uninitialized DNSRecordRef. Upon succesfull completion of this
   *                  call, this ref may be passed to DNSServiceUpdateRecord() or DNSServiceRemoveRecord().
   *                  (To deregister ALL records registered on a single connected DNSServiceRef
   *                  and deallocate each of their corresponding DNSServiceRecordRefs, call
   *                  DNSServiceRefDeallocate()).
   *
   * flags:           Possible values are kDNSServiceFlagsShared or kDNSServiceFlagsUnique
   *                  (see flag type definitions for details).
   *
   * interfaceIndex:  If non-zero, specifies the interface on which to register the record
   *                  (the index for a given interface is determined via the if_nametoindex()
   *                  family of calls.) Passing 0 causes the record to be registered on all interfaces.
   *                  See "Constants for specifying an interface index" for more details.
   *
   * fullname:        The full domain name of the resource record.
   *
   * rrtype:          The numerical type of the resource record (e.g. kDNSServiceType_PTR, kDNSServiceType_SRV, etc)
   *
   * rrclass:         The class of the resource record (usually kDNSServiceClass_IN)
   *
   * rdlen:           Length, in bytes, of the rdata.
   *
   * rdata:           A pointer to the raw rdata, as it is to appear in the DNS record.
   *
   * ttl:             The time to live of the resource record, in seconds.
   *                  Most clients should pass 0 to indicate that the system should
   *                  select a sensible default value.
   *
   * callBack:        The function to be called when a result is found, or if the call
   *                  asynchronously fails (e.g. because of a name conflict.)
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred (the callback is never invoked and the DNSRecordRef is
   *                  not initialized).
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceRegisterRecord
      (
      DNSServiceRef                       sdRef,
      DNSRecordRef                        *RecordRef,
      DNSServiceFlags                     flags,
      uint32_t                            interfaceIndex,
      const char                          *fullname,
      uint16_t                            rrtype,
      uint16_t                            rrclass,
      uint16_t                            rdlen,
      const void                          *rdata,
      uint32_t                            ttl,
      DNSServiceRegisterRecordReply       callBack,
      void                                *context    /* may be NULL */
      );
  
  
  /* DNSServiceReconfirmRecord
   *
   * Instruct the daemon to verify the validity of a resource record that appears
   * to be out of date (e.g. because TCP connection to a service's target failed.)
   * Causes the record to be flushed from the daemon's cache (as well as all other
   * daemons' caches on the network) if the record is determined to be invalid.
   * Use this routine conservatively. Reconfirming a record necessarily consumes
   * network bandwidth, so this should not be done indiscriminately.
   *
   * Parameters:
   *
   * flags:           Pass kDNSServiceFlagsForce to force immediate deletion of record,
   *                  instead of after some number of reconfirmation queries have gone unanswered.
   *
   * interfaceIndex:  Specifies the interface of the record in question.
   *                  The caller must specify the interface.
   *                  This API (by design) causes increased network traffic, so it requires
   *                  the caller to be precise about which record should be reconfirmed.
   *                  It is not possible to pass zero for the interface index to perform
   *                  a "wildcard" reconfirmation, where *all* matching records are reconfirmed.
   *
   * fullname:        The resource record's full domain name.
   *
   * rrtype:          The resource record's type (e.g. kDNSServiceType_PTR, kDNSServiceType_SRV, etc)
   *
   * rrclass:         The class of the resource record (usually kDNSServiceClass_IN).
   *
   * rdlen:           The length, in bytes, of the resource record rdata.
   *
   * rdata:           The raw rdata of the resource record.
   *
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceReconfirmRecord
      (
      DNSServiceFlags                    flags,
      uint32_t                           interfaceIndex,
      const char                         *fullname,
      uint16_t                           rrtype,
      uint16_t                           rrclass,
      uint16_t                           rdlen,
      const void                         *rdata
      );
  
  
  /*********************************************************************************************
   *
   *  NAT Port Mapping
   *
   *********************************************************************************************/
  
  /* DNSServiceNATPortMappingCreate
   *
   * Request a port mapping in the NAT gateway, which maps a port on the local machine
   * to an external port on the NAT. The NAT should support either the NAT-PMP or the UPnP IGD
   * protocol for this API to create a successful mapping.
   *
   * The port mapping will be renewed indefinitely until the client process exits, or
   * explicitly terminates the port mapping request by calling DNSServiceRefDeallocate().
   * The client callback will be invoked, informing the client of the NAT gateway's
   * external IP address and the external port that has been allocated for this client.
   * The client should then record this external IP address and port using whatever
   * directory service mechanism it is using to enable peers to connect to it.
   * (Clients advertising services using Wide-Area DNS-SD DO NOT need to use this API
   * -- when a client calls DNSServiceRegister() NAT mappings are automatically created
   * and the external IP address and port for the service are recorded in the global DNS.
   * Only clients using some directory mechanism other than Wide-Area DNS-SD need to use
   * this API to explicitly map their own ports.)
   *
   * It's possible that the client callback could be called multiple times, for example
   * if the NAT gateway's IP address changes, or if a configuration change results in a
   * different external port being mapped for this client. Over the lifetime of any long-lived
   * port mapping, the client should be prepared to handle these notifications of changes
   * in the environment, and should update its recorded address and/or port as appropriate.
   *
   * NOTE: There are two unusual aspects of how the DNSServiceNATPortMappingCreate API works,
   * which were intentionally designed to help simplify client code:
   *
   *  1. It's not an error to request a NAT mapping when the machine is not behind a NAT gateway.
   *     In other NAT mapping APIs, if you request a NAT mapping and the machine is not behind a NAT
   *     gateway, then the API returns an error code -- it can't get you a NAT mapping if there's no
   *     NAT gateway. The DNSServiceNATPortMappingCreate API takes a different view. Working out
   *     whether or not you need a NAT mapping can be tricky and non-obvious, particularly on
   *     a machine with multiple active network interfaces. Rather than make every client recreate
   *     this logic for deciding whether a NAT mapping is required, the PortMapping API does that
   *     work for you. If the client calls the PortMapping API when the machine already has a
   *     routable public IP address, then instead of complaining about it and giving an error,
   *     the PortMapping API just invokes your callback, giving the machine's public address
   *     and your own port number. This means you don't need to write code to work out whether
   *     your client needs to call the PortMapping API -- just call it anyway, and if it wasn't
   *     necessary, no harm is done:
   *
   *     - If the machine already has a routable public IP address, then your callback
   *       will just be invoked giving your own address and port.
   *     - If a NAT mapping is required and obtained, then your callback will be invoked
   *       giving you the external address and port.
   *     - If a NAT mapping is required but not obtained from the local NAT gateway,
   *       or the machine has no network connectivity, then your callback will be
   *       invoked giving zero address and port.
   *
   *  2. In other NAT mapping APIs, if a laptop computer is put to sleep and woken up on a new
   *     network, it's the client's job to notice this, and work out whether a NAT mapping
   *     is required on the new network, and make a new NAT mapping request if necessary.
   *     The DNSServiceNATPortMappingCreate API does this for you, automatically.
   *     The client just needs to make one call to the PortMapping API, and its callback will
   *     be invoked any time the mapping state changes. This property complements point (1) above.
   *     If the client didn't make a NAT mapping request just because it determined that one was
   *     not required at that particular moment in time, the client would then have to monitor
   *     for network state changes to determine if a NAT port mapping later became necessary.
   *     By unconditionally making a NAT mapping request, even when a NAT mapping not to be
   *     necessary, the PortMapping API will then begin monitoring network state changes on behalf of
   *     the client, and if a NAT mapping later becomes necessary, it will automatically create a NAT
   *     mapping and inform the client with a new callback giving the new address and port information.
   *
   * DNSServiceNATPortMappingReply() parameters:
   *
   * sdRef:           The DNSServiceRef initialized by DNSServiceNATPortMappingCreate().
   *
   * flags:           Currently unused, reserved for future use.
   *
   * interfaceIndex:  The interface through which the NAT gateway is reached.
   *
   * errorCode:       Will be kDNSServiceErr_NoError on success.
   *                  Will be kDNSServiceErr_DoubleNAT when the NAT gateway is itself behind one or
   *                  more layers of NAT, in which case the other parameters have the defined values.
   *                  For other failures, will indicate the failure that occurred, and the other
   *                  parameters are undefined.
   *
   * externalAddress: Four byte IPv4 address in network byte order.
   *
   * protocol:        Will be kDNSServiceProtocol_UDP or kDNSServiceProtocol_TCP or both.
   *
   * internalPort:    The port on the local machine that was mapped.
   *
   * externalPort:    The actual external port in the NAT gateway that was mapped.
   *                  This is likely to be different than the requested external port.
   *
   * ttl:             The lifetime of the NAT port mapping created on the gateway.
   *                  This controls how quickly stale mappings will be garbage-collected
   *                  if the client machine crashes, suffers a power failure, is disconnected
   *                  from the network, or suffers some other unfortunate demise which
   *                  causes it to vanish without explicitly removing its NAT port mapping.
   *                  It's possible that the ttl value will differ from the requested ttl value.
   *
   * context:         The context pointer that was passed to the callout.
   *
   */
  
  typedef void (DNSSD_API *DNSServiceNATPortMappingReply)
      (
      DNSServiceRef                    sdRef,
      DNSServiceFlags                  flags,
      uint32_t                         interfaceIndex,
      DNSServiceErrorType              errorCode,
      uint32_t                         externalAddress,   /* four byte IPv4 address in network byte order */
      DNSServiceProtocol               protocol,
      uint16_t                         internalPort,      /* In network byte order */
      uint16_t                         externalPort,      /* In network byte order and may be different than the requested port */
      uint32_t                         ttl,               /* may be different than the requested ttl */
      void                             *context
      );
  
  
  /* DNSServiceNATPortMappingCreate() Parameters:
   *
   * sdRef:           A pointer to an uninitialized DNSServiceRef. If the call succeeds then it
   *                  initializes the DNSServiceRef, returns kDNSServiceErr_NoError, and the nat
   *                  port mapping will last indefinitely until the client terminates the port
   *                  mapping request by passing this DNSServiceRef to DNSServiceRefDeallocate().
   *
   * flags:           Currently ignored, reserved for future use.
   *
   * interfaceIndex:  The interface on which to create port mappings in a NAT gateway. Passing 0 causes
   *                  the port mapping request to be sent on the primary interface.
   *
   * protocol:        To request a port mapping, pass in kDNSServiceProtocol_UDP, or kDNSServiceProtocol_TCP,
   *                  or (kDNSServiceProtocol_UDP | kDNSServiceProtocol_TCP) to map both.
   *                  The local listening port number must also be specified in the internalPort parameter.
   *                  To just discover the NAT gateway's external IP address, pass zero for protocol,
   *                  internalPort, externalPort and ttl.
   *
   * internalPort:    The port number in network byte order on the local machine which is listening for packets.
   *
   * externalPort:    The requested external port in network byte order in the NAT gateway that you would
   *                  like to map to the internal port. Pass 0 if you don't care which external port is chosen for you.
   *
   * ttl:             The requested renewal period of the NAT port mapping, in seconds.
   *                  If the client machine crashes, suffers a power failure, is disconnected from
   *                  the network, or suffers some other unfortunate demise which causes it to vanish
   *                  unexpectedly without explicitly removing its NAT port mappings, then the NAT gateway
   *                  will garbage-collect old stale NAT port mappings when their lifetime expires.
   *                  Requesting a short TTL causes such orphaned mappings to be garbage-collected
   *                  more promptly, but consumes system resources and network bandwidth with
   *                  frequent renewal packets to keep the mapping from expiring.
   *                  Requesting a long TTL is more efficient on the network, but in the event of the
   *                  client vanishing, stale NAT port mappings will not be garbage-collected as quickly.
   *                  Most clients should pass 0 to use a system-wide default value.
   *
   * callBack:        The function to be called when the port mapping request succeeds or fails asynchronously.
   *
   * context:         An application context pointer which is passed to the callback function
   *                  (may be NULL).
   *
   * return value:    Returns kDNSServiceErr_NoError on success (any subsequent, asynchronous
   *                  errors are delivered to the callback), otherwise returns an error code indicating
   *                  the error that occurred.
   *
   *                  If you don't actually want a port mapped, and are just calling the API
   *                  because you want to find out the NAT's external IP address (e.g. for UI
   *                  display) then pass zero for protocol, internalPort, externalPort and ttl.
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceNATPortMappingCreate
      (
      DNSServiceRef                    *sdRef,
      DNSServiceFlags                  flags,
      uint32_t                         interfaceIndex,
      DNSServiceProtocol               protocol,          /* TCP and/or UDP          */
      uint16_t                         internalPort,      /* network byte order      */
      uint16_t                         externalPort,      /* network byte order      */
      uint32_t                         ttl,               /* time to live in seconds */
      DNSServiceNATPortMappingReply    callBack,
      void                             *context           /* may be NULL             */
      );
  
  
  /*********************************************************************************************
   *
   *  General Utility Functions
   *
   *********************************************************************************************/
  
  /* DNSServiceConstructFullName()
   *
   * Concatenate a three-part domain name (as returned by the above callbacks) into a
   * properly-escaped full domain name. Note that callbacks in the above functions ALREADY ESCAPE
   * strings where necessary.
   *
   * Parameters:
   *
   * fullName:        A pointer to a buffer that where the resulting full domain name is to be written.
   *                  The buffer must be kDNSServiceMaxDomainName (1009) bytes in length to
   *                  accommodate the longest legal domain name without buffer overrun.
   *
   * service:         The service name - any dots or backslashes must NOT be escaped.
   *                  May be NULL (to construct a PTR record name, e.g.
   *                  "_ftp._tcp.apple.com.").
   *
   * regtype:         The service type followed by the protocol, separated by a dot
   *                  (e.g. "_ftp._tcp").
   *
   * domain:          The domain name, e.g. "apple.com.". Literal dots or backslashes,
   *                  if any, must be escaped, e.g. "1st\. Floor.apple.com."
   *
   * return value:    Returns kDNSServiceErr_NoError (0) on success, kDNSServiceErr_BadParam on error.
   *
   */
  
  DNSServiceErrorType DNSSD_API DNSServiceConstructFullName
      (
      char                            * const fullName,
      const char                      * const service,      /* may be NULL */
      const char                      * const regtype,
      const char                      * const domain
      );
  
  
  /*********************************************************************************************
   *
   *   TXT Record Construction Functions
   *
   *********************************************************************************************/
  
  /*
   * A typical calling sequence for TXT record construction is something like:
   *
   * Client allocates storage for TXTRecord data (e.g. declare buffer on the stack)
   * TXTRecordCreate();
   * TXTRecordSetValue();
   * TXTRecordSetValue();
   * TXTRecordSetValue();
   * ...
   * DNSServiceRegister( ... TXTRecordGetLength(), TXTRecordGetBytesPtr() ... );
   * TXTRecordDeallocate();
   * Explicitly deallocate storage for TXTRecord data (if not allocated on the stack)
   */
  
  
  /* TXTRecordRef
   *
   * Opaque internal data type.
   * Note: Represents a DNS-SD TXT record.
   */
  
  typedef union _TXTRecordRef_t { char PrivateData[16]; char *ForceNaturalAlignment; } TXTRecordRef;
  
  
  /* TXTRecordCreate()
   *
   * Creates a new empty TXTRecordRef referencing the specified storage.
   *
   * If the buffer parameter is NULL, or the specified storage size is not
   * large enough to hold a key subsequently added using TXTRecordSetValue(),
   * then additional memory will be added as needed using malloc().
   *
   * On some platforms, when memory is low, malloc() may fail. In this
   * case, TXTRecordSetValue() will return kDNSServiceErr_NoMemory, and this
   * error condition will need to be handled as appropriate by the caller.
   *
   * You can avoid the need to handle this error condition if you ensure
   * that the storage you initially provide is large enough to hold all
   * the key/value pairs that are to be added to the record.
   * The caller can precompute the exact length required for all of the
   * key/value pairs to be added, or simply provide a fixed-sized buffer
   * known in advance to be large enough.
   * A no-value (key-only) key requires  (1 + key length) bytes.
   * A key with empty value requires     (1 + key length + 1) bytes.
   * A key with non-empty value requires (1 + key length + 1 + value length).
   * For most applications, DNS-SD TXT records are generally
   * less than 100 bytes, so in most cases a simple fixed-sized
   * 256-byte buffer will be more than sufficient.
   * Recommended size limits for DNS-SD TXT Records are discussed in
   * <http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt>
   *
   * Note: When passing parameters to and from these TXT record APIs,
   * the key name does not include the '=' character. The '=' character
   * is the separator between the key and value in the on-the-wire
   * packet format; it is not part of either the key or the value.
   *
   * txtRecord:       A pointer to an uninitialized TXTRecordRef.
   *
   * bufferLen:       The size of the storage provided in the "buffer" parameter.
   *
   * buffer:          Optional caller-supplied storage used to hold the TXTRecord data.
   *                  This storage must remain valid for as long as
   *                  the TXTRecordRef.
   */
  
  void DNSSD_API TXTRecordCreate
      (
      TXTRecordRef     *txtRecord,
      uint16_t         bufferLen,
      void             *buffer
      );
  
  
  /* TXTRecordDeallocate()
   *
   * Releases any resources allocated in the course of preparing a TXT Record
   * using TXTRecordCreate()/TXTRecordSetValue()/TXTRecordRemoveValue().
   * Ownership of the buffer provided in TXTRecordCreate() returns to the client.
   *
   * txtRecord:           A TXTRecordRef initialized by calling TXTRecordCreate().
   *
   */
  
  void DNSSD_API TXTRecordDeallocate
      (
      TXTRecordRef     *txtRecord
      );
  
  
  /* TXTRecordSetValue()
   *
   * Adds a key (optionally with value) to a TXTRecordRef. If the "key" already
   * exists in the TXTRecordRef, then the current value will be replaced with
   * the new value.
   * Keys may exist in four states with respect to a given TXT record:
   *  - Absent (key does not appear at all)
   *  - Present with no value ("key" appears alone)
   *  - Present with empty value ("key=" appears in TXT record)
   *  - Present with non-empty value ("key=value" appears in TXT record)
   * For more details refer to "Data Syntax for DNS-SD TXT Records" in
   * <http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt>
   *
   * txtRecord:       A TXTRecordRef initialized by calling TXTRecordCreate().
   *
   * key:             A null-terminated string which only contains printable ASCII
   *                  values (0x20-0x7E), excluding '=' (0x3D). Keys should be
   *                  9 characters or fewer (not counting the terminating null).
   *
   * valueSize:       The size of the value.
   *
   * value:           Any binary value. For values that represent
   *                  textual data, UTF-8 is STRONGLY recommended.
   *                  For values that represent textual data, valueSize
   *                  should NOT include the terminating null (if any)
   *                  at the end of the string.
   *                  If NULL, then "key" will be added with no value.
   *                  If non-NULL but valueSize is zero, then "key=" will be
   *                  added with empty value.
   *
   * return value:    Returns kDNSServiceErr_NoError on success.
   *                  Returns kDNSServiceErr_Invalid if the "key" string contains
   *                  illegal characters.
   *                  Returns kDNSServiceErr_NoMemory if adding this key would
   *                  exceed the available storage.
   */
  
  DNSServiceErrorType DNSSD_API TXTRecordSetValue
      (
      TXTRecordRef     *txtRecord,
      const char       *key,
      uint8_t          valueSize,        /* may be zero */
      const void       *value            /* may be NULL */
      );
  
  
  /* TXTRecordRemoveValue()
   *
   * Removes a key from a TXTRecordRef. The "key" must be an
   * ASCII string which exists in the TXTRecordRef.
   *
   * txtRecord:       A TXTRecordRef initialized by calling TXTRecordCreate().
   *
   * key:             A key name which exists in the TXTRecordRef.
   *
   * return value:    Returns kDNSServiceErr_NoError on success.
   *                  Returns kDNSServiceErr_NoSuchKey if the "key" does not
   *                  exist in the TXTRecordRef.
   */
  
  DNSServiceErrorType DNSSD_API TXTRecordRemoveValue
      (
      TXTRecordRef     *txtRecord,
      const char       *key
      );
  
  
  /* TXTRecordGetLength()
   *
   * Allows you to determine the length of the raw bytes within a TXTRecordRef.
   *
   * txtRecord:       A TXTRecordRef initialized by calling TXTRecordCreate().
   *
   * return value:    Returns the size of the raw bytes inside a TXTRecordRef
   *                  which you can pass directly to DNSServiceRegister() or
   *                  to DNSServiceUpdateRecord().
   *                  Returns 0 if the TXTRecordRef is empty.
   */
  
  uint16_t DNSSD_API TXTRecordGetLength
      (
      const TXTRecordRef *txtRecord
      );
  
  
  /* TXTRecordGetBytesPtr()
   *
   * Allows you to retrieve a pointer to the raw bytes within a TXTRecordRef.
   *
   * txtRecord:       A TXTRecordRef initialized by calling TXTRecordCreate().
   *
   * return value:    Returns a pointer to the raw bytes inside the TXTRecordRef
   *                  which you can pass directly to DNSServiceRegister() or
   *                  to DNSServiceUpdateRecord().
   */
  
  const void * DNSSD_API TXTRecordGetBytesPtr
      (
      const TXTRecordRef *txtRecord
      );
  
  
  /*********************************************************************************************
   *
   *   TXT Record Parsing Functions
   *
   *********************************************************************************************/
  
  /*
   * A typical calling sequence for TXT record parsing is something like:
   *
   * Receive TXT record data in DNSServiceResolve() callback
   * if (TXTRecordContainsKey(txtLen, txtRecord, "key")) then do something
   * val1ptr = TXTRecordGetValuePtr(txtLen, txtRecord, "key1", &len1);
   * val2ptr = TXTRecordGetValuePtr(txtLen, txtRecord, "key2", &len2);
   * ...
   * memcpy(myval1, val1ptr, len1);
   * memcpy(myval2, val2ptr, len2);
   * ...
   * return;
   *
   * If you wish to retain the values after return from the DNSServiceResolve()
   * callback, then you need to copy the data to your own storage using memcpy()
   * or similar, as shown in the example above.
   *
   * If for some reason you need to parse a TXT record you built yourself
   * using the TXT record construction functions above, then you can do
   * that using TXTRecordGetLength and TXTRecordGetBytesPtr calls:
   * TXTRecordGetValue(TXTRecordGetLength(x), TXTRecordGetBytesPtr(x), key, &len);
   *
   * Most applications only fetch keys they know about from a TXT record and
   * ignore the rest.
   * However, some debugging tools wish to fetch and display all keys.
   * To do that, use the TXTRecordGetCount() and TXTRecordGetItemAtIndex() calls.
   */
  
  /* TXTRecordContainsKey()
   *
   * Allows you to determine if a given TXT Record contains a specified key.
   *
   * txtLen:          The size of the received TXT Record.
   *
   * txtRecord:       Pointer to the received TXT Record bytes.
   *
   * key:             A null-terminated ASCII string containing the key name.
   *
   * return value:    Returns 1 if the TXT Record contains the specified key.
   *                  Otherwise, it returns 0.
   */
  
  int DNSSD_API TXTRecordContainsKey
      (
      uint16_t         txtLen,
      const void       *txtRecord,
      const char       *key
      );
  
  
  /* TXTRecordGetValuePtr()
   *
   * Allows you to retrieve the value for a given key from a TXT Record.
   *
   * txtLen:          The size of the received TXT Record
   *
   * txtRecord:       Pointer to the received TXT Record bytes.
   *
   * key:             A null-terminated ASCII string containing the key name.
   *
   * valueLen:        On output, will be set to the size of the "value" data.
   *
   * return value:    Returns NULL if the key does not exist in this TXT record,
   *                  or exists with no value (to differentiate between
   *                  these two cases use TXTRecordContainsKey()).
   *                  Returns pointer to location within TXT Record bytes
   *                  if the key exists with empty or non-empty value.
   *                  For empty value, valueLen will be zero.
   *                  For non-empty value, valueLen will be length of value data.
   */
  
  const void * DNSSD_API TXTRecordGetValuePtr
      (
      uint16_t         txtLen,
      const void       *txtRecord,
      const char       *key,
      uint8_t          *valueLen
      );
  
  
  /* TXTRecordGetCount()
   *
   * Returns the number of keys stored in the TXT Record. The count
   * can be used with TXTRecordGetItemAtIndex() to iterate through the keys.
   *
   * txtLen:          The size of the received TXT Record.
   *
   * txtRecord:       Pointer to the received TXT Record bytes.
   *
   * return value:    Returns the total number of keys in the TXT Record.
   *
   */
  
  uint16_t DNSSD_API TXTRecordGetCount
      (
      uint16_t         txtLen,
      const void       *txtRecord
      );
  
  
  /* TXTRecordGetItemAtIndex()
   *
   * Allows you to retrieve a key name and value pointer, given an index into
   * a TXT Record. Legal index values range from zero to TXTRecordGetCount()-1.
   * It's also possible to iterate through keys in a TXT record by simply
   * calling TXTRecordGetItemAtIndex() repeatedly, beginning with index zero
   * and increasing until TXTRecordGetItemAtIndex() returns kDNSServiceErr_Invalid.
   *
   * On return:
   * For keys with no value, *value is set to NULL and *valueLen is zero.
   * For keys with empty value, *value is non-NULL and *valueLen is zero.
   * For keys with non-empty value, *value is non-NULL and *valueLen is non-zero.
   *
   * txtLen:          The size of the received TXT Record.
   *
   * txtRecord:       Pointer to the received TXT Record bytes.
   *
   * itemIndex:       An index into the TXT Record.
   *
   * keyBufLen:       The size of the string buffer being supplied.
   *
   * key:             A string buffer used to store the key name.
   *                  On return, the buffer contains a null-terminated C string
   *                  giving the key name. DNS-SD TXT keys are usually
   *                  9 characters or fewer. To hold the maximum possible
   *                  key name, the buffer should be 256 bytes long.
   *
   * valueLen:        On output, will be set to the size of the "value" data.
   *
   * value:           On output, *value is set to point to location within TXT
   *                  Record bytes that holds the value data.
   *
   * return value:    Returns kDNSServiceErr_NoError on success.
   *                  Returns kDNSServiceErr_NoMemory if keyBufLen is too short.
   *                  Returns kDNSServiceErr_Invalid if index is greater than
   *                  TXTRecordGetCount()-1.
   */
  
  DNSServiceErrorType DNSSD_API TXTRecordGetItemAtIndex
      (
      uint16_t         txtLen,
      const void       *txtRecord,
      uint16_t         itemIndex,
      uint16_t         keyBufLen,
      char             *key,
      uint8_t          *valueLen,
      const void       **value
      );
  
  #if _DNS_SD_LIBDISPATCH
  /*
  * DNSServiceSetDispatchQueue
  *
  * Allows you to schedule a DNSServiceRef on a serial dispatch queue for receiving asynchronous
  * callbacks.  It's the clients responsibility to ensure that the provided dispatch queue is running.
  *
  * A typical application that uses CFRunLoopRun or dispatch_main on its main thread will
  * usually schedule DNSServiceRefs on its main queue (which is always a serial queue)
  * using "DNSServiceSetDispatchQueue(sdref, dispatch_get_main_queue());"
  *
  * If there is any error during the processing of events, the application callback will
  * be called with an error code. For shared connections, each subordinate DNSServiceRef
  * will get its own error callback. Currently these error callbacks only happen
  * if the mDNSResponder daemon is manually terminated or crashes, and the error
  * code in this case is kDNSServiceErr_ServiceNotRunning. The application must call
  * DNSServiceRefDeallocate to free the DNSServiceRef when it gets such an error code.
  * These error callbacks are rare and should not normally happen on customer machines,
  * but application code should be written defensively to handle such error callbacks
  * gracefully if they occur.
  *
  * After using DNSServiceSetDispatchQueue on a DNSServiceRef, calling DNSServiceProcessResult
  * on the same DNSServiceRef will result in undefined behavior and should be avoided.
  *
  * Once the application successfully schedules a DNSServiceRef on a serial dispatch queue using
  * DNSServiceSetDispatchQueue, it cannot remove the DNSServiceRef from the dispatch queue, or use
  * DNSServiceSetDispatchQueue a second time to schedule the DNSServiceRef onto a different serial dispatch
  * queue. Once scheduled onto a dispatch queue a DNSServiceRef will deliver events to that queue until
  * the application no longer requires that operation and terminates it using DNSServiceRefDeallocate.
  *
  * service:         DNSServiceRef that was allocated and returned to the application, when the
  *                  application calls one of the DNSService API.
  *
  * queue:           dispatch queue where the application callback will be scheduled
  *
  * return value:    Returns kDNSServiceErr_NoError on success.
  *                  Returns kDNSServiceErr_NoMemory if it cannot create a dispatch source
  *                  Returns kDNSServiceErr_BadParam if the service param is invalid or the
  *                  queue param is invalid
  */
  
  DNSServiceErrorType DNSSD_API DNSServiceSetDispatchQueue
    (
    DNSServiceRef service,
    dispatch_queue_t queue
    );
  #endif //_DNS_SD_LIBDISPATCH
  
  #ifdef __APPLE_API_PRIVATE
  
  #define kDNSServiceCompPrivateDNS   "PrivateDNS"
  #define kDNSServiceCompMulticastDNS "MulticastDNS"
  
  #endif //__APPLE_API_PRIVATE
  
  /* Some C compiler cleverness. We can make the compiler check certain things for us,
   * and report errors at compile-time if anything is wrong. The usual way to do this would
   * be to use a run-time "if" statement or the conventional run-time "assert" mechanism, but
   * then you don't find out what's wrong until you run the software. This way, if the assertion
   * condition is false, the array size is negative, and the complier complains immediately.
   */
  
  struct CompileTimeAssertionChecks_DNS_SD
      {
      char assert0[(sizeof(union _TXTRecordRef_t) == 16) ? 1 : -1];
      };
  
  #ifdef  __cplusplus
      }
  #endif
  
  #endif  /* _DNS_SD_H */
  