[Ace-users] Re: [ace-bugs] UUID_Generator

Douglas C. Schmidt schmidt at dre.vanderbilt.edu
Sat Sep 1 16:14:20 CDT 2007


Hi Wim,

> Hereby I sent you the source files, see attachments.

Great, thanks!

> Maybe it is better to rename the method get_timestamp to
> get_timestampAndClocksequence.

I've tweaked things a bit to ensure backwards compatibility with 
existing applications.  Can you please check out

http://www.dre.vanderbilt.edu/~schmidt/DOC_ROOT/ACE/ace/UUID.h
http://www.dre.vanderbilt.edu/~schmidt/DOC_ROOT/ACE/ace/UUID.cpp

and let me know if it's ok?  Also, could you please send me a brief
ChangeLog entry explaining what you've done and why.

Thanks very much,

        Doug

> Kind regards,
> 
> Wim van den Boogaard
> > Hi Wim,
> >
> > Thanks for using the PRF.
> >
> >
> >> ACE VERSION: 5.5.8 / 10
> >>
> >> HOST MACHINE and OPERATING SYSTEM:
> >>    WinXP
> >>
> >> TARGET MACHINE and OPERATING SYSTEM, if different from HOST:
> >> COMPILER NAME AND VERSION (AND PATCHLEVEL):
> >>
> >> THE $ACE_ROOT/ace/config.h FILE [if you use a link to a platform-
> >>    specific file, simply state which one]:
> >>    config-win32.h
> >>
> >>
> >> THE $ACE_ROOT/include/makeinclude/platform_macros.GNU FILE [if you
> >>    use a link to a platform-specific file, simply state which one
> >>    (unless this isn't used in this case, e.g., with Microsoft Visual
> >>    C++)]:
> >>
> >> CONTENTS OF $ACE_ROOT/bin/MakeProjectCreator/config/default.features
> >>    (used by MPC when you generate your own makefiles):
> >>     ---
> >>
> >> AREA/CLASS/EXAMPLE AFFECTED:
> >>
> >>    DOES THE PROBLEM AFFECT:
> >>        COMPILATION?
> >>        LINKING
> >>        EXECUTION
> >>                 OTHER (please specify)?
> >>
> >>    SYNOPSIS:
> >>        Double UUID generated in a multi threaded application.
> >>
> >>    DESCRIPTION:
> >>         The method UUID_Generator::generateUUID is not thread safe
> >> in respect to the combination uuid_state_.clockSequence
> >>         and timestamp.
> >>         The combination timestamp and clockSequence should be
> >> accessed in a thread safe manner. The method
> >>         UUID_Generator::get_timestamp returns the timestamp thread
> >> safe, but also modifies the uuid_state_.clockSequence.
> >>         The uuid_state_.clockSequence is accessed thread safe in
> >> UUID_Generator::generateUUID, but could have been modified
> >>         between the moment get_timestamp is being done and the
> >> moment it is being used.
> >>
> >>    REPEAT BY:
> >>
> >>    SAMPLE FIX/WORKAROUND:
> >>         Return the timestamp and clockSequence in a atomic manner
> >> via the get_timestamp method. I added an other argument
> >>         to the get_timestamp.
> >>         void get_timestamp(UUID_time& timestamp, ACE_UINT16& clockSequence);
> >>
> >>         Return the actual clockSequence in the get_timestamp method.
> >>
> >
> > Could you please send the code that implements this and we'll add it to ACE!
> >
> > Thanks,
> >
> >         Doug
> >
> >
> 
> //$Id: UUID.cpp 78180 2007-04-25 07:05:02Z johnnyw $
> 
> #include "ace/UUID.h"
> #include "ace/Guard_T.h"
> 
> #if !defined (__ACE_INLINE__)
> #include "ace/UUID.inl"
> #endif /* __ACE_INLINE__ */
> 
> #include "ace/Log_Msg.h"
> #include "ace/OS_NS_stdio.h"
> #include "ace/OS_NS_string.h"
> #include "ace/OS_NS_sys_time.h"
> #include "ace/OS_NS_netdb.h"
> #include "ace/OS_NS_unistd.h"
> #include "ace/ACE.h"
> 
> ACE_RCSID (ace,
>            UUID,
>            "$Id: UUID.cpp 78180 2007-04-25 07:05:02Z johnnyw $")
> 
> 
> ACE_BEGIN_VERSIONED_NAMESPACE_DECL
> 
> namespace ACE_Utils
> {
> 
>   UUID_node::UUID_node (void)
>   {
>     for (int i = 0; i < UUID_node::NODE_ID_SIZE; ++i)
>       {
>         nodeID_[i] = 0;
>       }
>   }
> 
>   UUID_node::NodeID&
>   UUID_node::nodeID (void)
>   {
>     return nodeID_;
>   }
> 
>   void
>   UUID_node::nodeID (NodeID& nodeID)
>   {
>     for (int i = 0; i < UUID_node::NODE_ID_SIZE; ++i)
>       {
>         nodeID_[i] = nodeID[i];
>       }
>   }
> 
>   UUID UUID::NIL_UUID;
> 
>   /// Construct a nil UUID. Such a UUID has every one of it's data
>   /// elements set to zero.
>   UUID::UUID(void)
>     : timeLow_ (0),
>       timeMid_ (0),
>       timeHiAndVersion_ (0),
>       clockSeqHiAndReserved_ (0),
>       clockSeqLow_ (0),
>       node_ (0),
>       node_release_ (true),
>       as_string_ (0)
>   {
>     ACE_NEW (node_,
>              UUID_node);
>   }
> 
>   /// Construct a UUID from a string representation of an UUID.
>   UUID::UUID (const ACE_CString& uuid_string)
>     : timeLow_ (0),
>       timeMid_ (0),
>       timeHiAndVersion_ (0),
>       clockSeqHiAndReserved_ (0),
>       clockSeqLow_ (0),
>       node_ (0),
>       node_release_ (true),
>       as_string_ (0)
>   {
>     ACE_NEW (node_,
>              UUID_node);
> 
>     this->from_string_i (uuid_string);
>   }
> 
>   UUID::UUID(const UUID &right)
>     : timeLow_ (right.timeLow_),
>       timeMid_ (right.timeMid_),
>       timeHiAndVersion_ (right.timeHiAndVersion_),
>       clockSeqHiAndReserved_ (right.clockSeqHiAndReserved_),
>       clockSeqLow_ (right.clockSeqLow_),
>       as_string_ (0)
>   {
>     ACE_NEW (node_,
>              UUID_node (*right.node_));
>   }
> 
>   UUID::~UUID (void)
>   {
>     if (node_release_)
>       delete node_;
> 
>     if (as_string_ != 0)
>       delete as_string_;
>   }
> 
>   const ACE_CString*
>   UUID::to_string (void)
>   {
>     /// Only compute the string representation once.
>     if (as_string_ == 0)
>       {
>         // Get a buffer exactly the correct size. Use the nil UUID as a
>         // gauge.  Don't forget the trailing nul.
>         size_t UUID_STRING_LENGTH = 36 + thr_id_.length () + pid_.length ();
>         char *buf = 0;
> 
>         if ((thr_id_.length () != 0) && (pid_.length () != 0))
>           {
>             UUID_STRING_LENGTH += 2; //for '-'
>             ACE_NEW_RETURN (buf,
>                             char[UUID_STRING_LENGTH + 1],
>                             0);
> 
>             ACE_OS::sprintf(buf,
>                             "%8.8x-%4.4x-%4.4x-%2.2x%2.2x-%2.2x%2.2x%2.2x%2.2x%2.2x%2.2x-%s-%s",
>                             this->timeLow_,
>                             this->timeMid_,
>                             this->timeHiAndVersion_,
>                             this->clockSeqHiAndReserved_,
>                             this->clockSeqLow_,
>                             (this->node_->nodeID ()) [0],
>                             (this->node_->nodeID ()) [1],
>                             (this->node_->nodeID ()) [2],
>                             (this->node_->nodeID ()) [3],
>                             (this->node_->nodeID ()) [4],
>                             (this->node_->nodeID ()) [5],
>                             thr_id_.c_str (),
>                             pid_.c_str ()
>                             );
>           }
>         else
>           {
>             ACE_NEW_RETURN (buf,
>                             char[UUID_STRING_LENGTH + 1],
>                             0);
> 
>             ACE_OS::sprintf (buf,
>                              "%8.8x-%4.4x-%4.4x-%2.2x%2.2x-%2.2x%2.2x%2.2x%2.2x%2.2x%2.2x",
>                              this->timeLow_,
>                              this->timeMid_,
>                              this->timeHiAndVersion_,
>                              this->clockSeqHiAndReserved_,
>                              this->clockSeqLow_,
>                              (this->node_->nodeID ()) [0],
>                              (this->node_->nodeID ()) [1],
>                              (this->node_->nodeID ()) [2],
>                              (this->node_->nodeID ()) [3],
>                              (this->node_->nodeID ()) [4],
>                              (this->node_->nodeID ()) [5]
>                              );
>           }
> 
>         // We allocated 'buf' above dynamically, so we shouldn't use
>         // ACE_NEW_RETURN here to avoid a possible memory leak.
>         ACE_NEW_NORETURN (this->as_string_,
>                           ACE_CString (buf, UUID_STRING_LENGTH));
> 
>         // we first free the dynamically allocated 'buf'.
>         delete [] buf;
> 
>         // then we test that ACE_NEW succeded for 'as_string_'
>         // if not, we return 0 (NULL) to indicate failure.
>         if( this->as_string_ == 0 )
>         {
>            return 0;
>         }
>       }
> 
>     return as_string_;
>   }
> 
>   void
>   UUID::from_string_i (const ACE_CString& uuid_string)
>   {
>     if (uuid_string.length() < NIL_UUID.to_string ()->length ())
>       {
>         ACE_ERROR ((LM_ERROR,
>                     "%N ACE_UUID::from_string_i - "
>                     "IllegalArgument(incorrect string length)\n"));
>         return;
>       }
> 
>     /// Special case for the nil UUID.
>     if (uuid_string == *NIL_UUID.to_string ())
>       {
>         bool copy_constructor_not_supported = false;
>         ACE_ASSERT (copy_constructor_not_supported);
>         //*this = NIL_UUID;
>         ACE_UNUSED_ARG (copy_constructor_not_supported);
>         return;
>       }
> 
>     unsigned int timeLow;
>     unsigned int timeMid;
>     unsigned int timeHiAndVersion;
>     unsigned int clockSeqHiAndReserved;
>     unsigned int clockSeqLow;
>     unsigned int node [UUID_node::NODE_ID_SIZE];
>     char thr_pid_buf [BUFSIZ];
> 
>     if (uuid_string.length() == NIL_UUID.to_string()->length())
>       {
>         // This might seem quite strange this being in ACE, but it
>         // seems to be a bit difficult to write a facade for ::sscanf
>         // because some compilers dont support vsscanf, including
>         // MSVC. It appears that most platforms support sscanf though
>         // so we need to use it directly.
>         const int nScanned =
> #if defined (ACE_HAS_TR24731_2005_CRT)
>           sscanf_s (
> #else
>           ::sscanf(
> #endif
>                    uuid_string.c_str(),
>                    "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x",
>                    &timeLow,
>                    &timeMid,
>                    &timeHiAndVersion,
>                    &clockSeqHiAndReserved,
>                    &clockSeqLow,
>                    &node[0],
>                    &node[1],
>                    &node[2],
>                    &node[3],
>                    &node[4],
>                    &node[5]
>                    );
> 
>         if (nScanned != 11)
>           {
>             ACE_DEBUG ((LM_DEBUG,
>                         "UUID::from_string_i - "
>                         "IllegalArgument(invalid string representation)\n"));
>             return;
>           }
>       }
>     else
>       {
>         const int nScanned =
> #if defined (ACE_HAS_TR24731_2005_CRT)
>           sscanf_s (uuid_string.c_str(),
>                     "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x-%s",
>                     &timeLow,
>                     &timeMid,
>                     &timeHiAndVersion,
>                     &clockSeqHiAndReserved,
>                     &clockSeqLow,
>                     &node[0],
>                     &node[1],
>                     &node[2],
>                     &node[3],
>                     &node[4],
>                     &node[5],
>                     thr_pid_buf,
>                     BUFSIZ
>                     );
> #else
>           ::sscanf (uuid_string.c_str(),
>                     "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x-%s",
>                     &timeLow,
>                     &timeMid,
>                     &timeHiAndVersion,
>                     &clockSeqHiAndReserved,
>                     &clockSeqLow,
>                     &node[0],
>                     &node[1],
>                     &node[2],
>                     &node[3],
>                     &node[4],
>                     &node[5],
>                     thr_pid_buf
>                     );
> #endif /* ACE_HAS_TR24731_2005_CRT */
> 
>         if (nScanned != 12)
>           {
>             ACE_DEBUG ((LM_DEBUG,
>                         "ACE_UUID::from_string_i - "
>                         "IllegalArgument(invalid string representation)\n"));
>             return;
>           }
>       }
> 
>     this->timeLow_ = static_cast<ACE_UINT32> (timeLow);
>     this->timeMid_ = static_cast<ACE_UINT16> (timeMid);
>     this->timeHiAndVersion_ = static_cast<ACE_UINT16> (timeHiAndVersion);
>     this->clockSeqHiAndReserved_ = static_cast<u_char> (clockSeqHiAndReserved);
>     this->clockSeqLow_ = static_cast<u_char> (clockSeqLow);
> 
>     UUID_node::NodeID nodeID;
>     for (int i = 0; i < UUID_node::NODE_ID_SIZE; ++i)
>       nodeID [i] = static_cast<u_char> (node[i]);
> 
>     this->node_->nodeID (nodeID);
> 
>     // Support varient 10- only
>     if ((this->clockSeqHiAndReserved_ & 0xc0) != 0x80 && (this->clockSeqHiAndReserved_ & 0xc0) != 0xc0)
>       {
>         ACE_DEBUG ((LM_DEBUG,
>                     "ACE_UUID::from_string_i - "
>                     "IllegalArgument(unsupported variant)\n"));
>         return;
>       }
> 
>     /// Support versions 1, 3, and 4 only
>     ACE_UINT16 V1 = this->timeHiAndVersion_;
> 
>     if ((V1 & 0xF000) != 0x1000 &&
>         (V1 & 0xF000) != 0x3000 &&
>       (V1 & 0xF000) != 0x4000)
>       {
>         ACE_DEBUG ((LM_DEBUG,
>                     "ACE_UUID::from_string_i - "
>                     "IllegalArgument(unsupported version)\n"));
>         return;
>       }
>     if ((this->clockSeqHiAndReserved_ & 0xc0) == 0xc0)
>       {
>         if (uuid_string.length() == NIL_UUID.to_string()->length())
>           {
>             ACE_DEBUG ((LM_DEBUG,
>                       "ACE_UUID::from_string_i - "
>                         "IllegalArgument (Missing Thread and Process Id)\n"));
>             return;
>           }
>         ACE_CString thr_pid_str (thr_pid_buf);
>         ssize_t pos = static_cast<ssize_t> (thr_pid_str.find ('-'));
>         if (pos == -1)
>           ACE_DEBUG ((LM_DEBUG,
>                       "ACE_UUID::from_string_i - "
>                       "IllegalArgument (Thread and Process Id format incorrect)\n"));
> 
>         this->thr_id_ = thr_pid_str.substr (0, pos);
>       this->pid_ = thr_pid_str.substr (pos+1, thr_pid_str.length ()-pos-1);
>       }
>   }
> 
>   UUID_Generator::UUID_Generator ()
>     : timeLast_ (0),
>       destroy_lock_ (true)
>   {
>     ACE_NEW (lock_,
>              ACE_SYNCH_MUTEX);
>   }
> 
>   UUID_Generator::~UUID_Generator()
>   {
>     if (destroy_lock_)
>       delete lock_;
>   }
> 
>   void
>   UUID_Generator::init (void)
>   {
>     ACE_OS::macaddr_node_t macaddress;
>     int result = ACE_OS::getmacaddress (&macaddress);
> 
>     UUID_node::NodeID nodeID;
>     if (result != -1)
>       {
> //         ACE_DEBUG ((LM_DEBUG,
> //                     "%02X-%02X-%02X-%02X-%02X-%02X\n",
> //                     macaddress.node [0],
> //                     macaddress.node [1],
> //                     macaddress.node [2],
> //                     macaddress.node [3],
> //                     macaddress.node [4],
> //                     macaddress.node [5]));
> 
>         ACE_OS::memcpy (&nodeID,
>                         macaddress.node,
>                         sizeof (nodeID));
>       }
>     else
>       {
>         nodeID [0] = static_cast<u_char> (ACE_OS::rand());
>         nodeID [1] = static_cast<u_char> (ACE_OS::rand());
>         nodeID [2] = static_cast<u_char> (ACE_OS::rand());
>         nodeID [3] = static_cast<u_char> (ACE_OS::rand());
>         nodeID [4] = static_cast<u_char> (ACE_OS::rand());
>         nodeID [5] = static_cast<u_char> (ACE_OS::rand());
>       }
> 
> 	ACE_UINT16 dummy;
>     this->get_timestamp (timeLast_,dummy);
> 
>     {
>       ACE_GUARD (ACE_SYNCH_MUTEX, ace_mon, *lock_);
>       uuid_state_.timestamp = timeLast_;
>       uuid_state_.node.nodeID (nodeID);
>     }
>   }
> 
> 
>   void
>   UUID_Generator::generateUUID (UUID& uuid,ACE_UINT16 version, u_char variant)
>   {
>     UUID_time timestamp;
> 	ACE_UINT16 clockSequence;
>     this->get_timestamp (timestamp,clockSequence);
> 
> 
>     // Construct a Version 1 UUID with the information in the arguements.
>     uuid.timeLow (static_cast<ACE_UINT32> (timestamp & 0xFFFFFFFF));
>     uuid.timeMid (static_cast<ACE_UINT16> ((timestamp >> 32) & 0xFFFF));
> 
> 
>     ACE_UINT16 tHAV = static_cast<ACE_UINT16> ((timestamp >> 48) & 0xFFFF);
>     tHAV |= (version << 12);
>     uuid.timeHiAndVersion (tHAV);
> 
>     u_char cseqHAV;
>     uuid.clockSeqLow (static_cast<u_char> (clockSequence & 0xFF));
>     cseqHAV = static_cast<u_char> ((clockSequence & 0x3f00) >> 8);
>     uuid_state_.timestamp = timestamp;
> 
>     cseqHAV |= variant;
>     uuid.clockSeqHiAndReserved (cseqHAV);
>     uuid.node (&(uuid_state_.node));
> 
>     if (variant == 0xc0)
>     {
>       ACE_Thread_ID thread_id;
>       char buf [BUFSIZ];
>       thread_id.to_string (buf);
>       uuid.thr_id (buf);
> 
>       ACE_OS::sprintf (buf,
>                        "%d",
>                        static_cast<int> (ACE_OS::getpid ()));
>       uuid.pid (buf);
>     }
>   }
> 
>   UUID*
>   UUID_Generator::generateUUID (ACE_UINT16 version, u_char variant)
>   {
>     UUID* uuid;
>     ACE_NEW_RETURN (uuid,
>                     UUID,
>                     0);
> 
>     this->generateUUID (*uuid, version, variant);
>     return uuid;
>   }
> 
>   /// Obtain a new timestamp. If UUID's are being generated too quickly
>   /// the clock sequence will be incremented
>   void
>   UUID_Generator::get_timestamp (UUID_time& timestamp,ACE_UINT16& clockSequence)
>   {
>     ACE_GUARD (ACE_SYNCH_MUTEX, mon, *lock_);
> 
>     this->get_systemtime(timestamp);
> 
>     // Account for the clock being set back. Increment the clock /
>     // sequence.
>     if (timestamp <= timeLast_)
>       uuid_state_.clockSequence = static_cast<u_char> ((uuid_state_.clockSequence + 1) & ACE_UUID_CLOCK_SEQ_MASK);
> 
>     // If the system time ticked since the last UUID was
>     // generated. Set / the clock sequence back.
>     else if (timestamp > timeLast_)
>       uuid_state_.clockSequence = 0;
> 
>     timeLast_ = timestamp;
> 	clockSequence = uuid_state_.clockSequence;
>   }
> 
>   /**
>    * ACE_Time_Value is in POSIX time, seconds since Jan 1, 1970. UUIDs use
>    * time in 100ns ticks since 15 October 1582. The difference is:
>    *   15 Oct 1582 - 1 Jan 1600: 17 days in Oct, 30 in Nov,  31 in Dec +
>    *       17 years and 4 leap days (1584, 88, 92 and 96)
>    *   1 Jan 1600 - 1 Jan 1900: 3 centuries + 73 leap days ( 25 in 17th cent.
>    *       and 24 each in 18th and 19th centuries)
>    *   1 Jan 1900 - 1 Jan 1970: 70 years + 17 leap days.
>    * This adds up, in days: (17+30+31+365*17+4)+(365*300+73)+(365*70+17) or
>    * 122192928000000000U (0x1B21DD213814000) 100 ns ticks.
>    */
>   void
>   UUID_Generator::get_systemtime (UUID_time & timestamp)
>   {
>     const UUID_time timeOffset =
> #if defined (ACE_LACKS_UNSIGNEDLONGLONG_T)
>       ACE_U_LongLong (ACE_INT64_LITERAL (0x1B21DD213814000));
> #elif defined (ACE_LACKS_LONGLONG_T)
>       ACE_U_LongLong (0x13814000u, 0x1B21DD2u);
> #else
>       ACE_UINT64_LITERAL (0x1B21DD213814000);
> #endif  /* ACE_LACKS_UNSIGNEDLONGLONG_T */
> 
>     /// Get the time of day, convert to 100ns ticks then add the offset.
>     ACE_Time_Value now = ACE_OS::gettimeofday();
>     ACE_UINT64 time;
>     now.to_usec (time);
>     time = time * 10;
>     timestamp = time + timeOffset;
> }
> 
>   ACE_SYNCH_MUTEX*
>   UUID_Generator::lock (void)
>   {
>     return this->lock_;
>   }
> 
>   void
>   UUID_Generator::lock (ACE_SYNCH_MUTEX* lock,
>                         bool release_lock)
>   {
>     if (this->destroy_lock_)
>       delete this->lock_;
> 
>     this->lock_ = lock;
>     this->destroy_lock_ = release_lock;
>   }
> 
> }
> 
> #if defined (ACE_HAS_EXPLICIT_STATIC_TEMPLATE_MEMBER_INSTANTIATION)
> template ACE_Singleton<ACE_Utils::UUID_Generator, ACE_SYNCH_MUTEX> *
>   ACE_Singleton<ACE_Utils::UUID_Generator, ACE_SYNCH_MUTEX>::singleton_;
> #endif /* ACE_HAS_EXPLICIT_STATIC_TEMPLATE_MEMBER_INSTANTIATION */
> 
> ACE_END_VERSIONED_NAMESPACE_DECL
> // -*- C++ -*-
> 
> //=============================================================================
> /**
>  *  @file  UUID.h
>  *
>  *  $Id: UUID.h 74958 2006-10-23 23:31:00Z ossama $
>  *
>  *  @author Andrew T. Finnel <andrew at activesol.net>
>  *  @author Yamuna Krishnmaurthy <yamuna at oomworks.com>
>  */
> //=============================================================================
> 
> #ifndef ACE_UUID_H
> #define ACE_UUID_H
> #include /**/ "ace/pre.h"
> 
> #include /**/ "ace/config-all.h"
> 
> #if !defined (ACE_LACKS_PRAGMA_ONCE)
> # pragma once
> #endif /* ACE_LACKS_PRAGMA_ONCE */
> 
> #include "ace/SString.h"
> #include "ace/Singleton.h"
> #include "ace/Synch_Traits.h"
> 
> ACE_BEGIN_VERSIONED_NAMESPACE_DECL
> 
> namespace ACE_Utils
> {
>   /// Class to hold a MAC address
>   class ACE_Export UUID_node
>   {
>   public:
> 
>     /// Constructor
>     UUID_node (void);
> 
>     enum {NODE_ID_SIZE = 6};
>     typedef u_char NodeID[NODE_ID_SIZE];
> 
>     NodeID& nodeID (void);
>     void nodeID (NodeID&);
> 
>     ///// Equality Operations
>     bool operator == (const UUID_node& right) const;
>     bool operator != (const UUID_node& right) const;
> 
>     ///// Relational Operations
>     //bool operator <  (const UUID_node& right) const;
> 
>   private:
>     NodeID nodeID_;
>   };
> 
> 
> 
>   /**
>    *  @class ACE_UUID
>    *
>    * ACE_UUID represents a Universally Unique IDentifier (UUID) as
>    * described in (the expired) INTERNET-DRAFT specification entitled
>    * UUIDs and GUIDs. All instances of UUID are of the time-based
>    * variety. That is, the version number part of the timeHiAndVersion
>    * field is 1.
>    *
>    * The default constructor creates a nil UUID.
>    *
>    * UUIDs have value semantics. In addition, they may be compared for
>    * ordering and equality.
>    *
>    * Additionally in this implementation provisions have been made to include
>    * process and thread ids to make the UUIDs more unique. The variant 0xc0
>    * has been added to facilitate this.
>    */
>   class ACE_Export UUID
>   {
>   public:
> 
>     /// Constructor
>     UUID (void);
> 
>     /// Constructs a UUID from a string representation.
>     UUID (const ACE_CString& uuidString);
> 
>     UUID (const UUID &right);
> 
>     // Destructor
>     ~UUID (void);
> 
>     ACE_UINT32 timeLow (void) const;
>     void timeLow (ACE_UINT32);
> 
>     ACE_UINT16 timeMid (void) const;
>     void timeMid (ACE_UINT16);
> 
>     ACE_UINT16 timeHiAndVersion (void) const;
>     void timeHiAndVersion (ACE_UINT16);
> 
>     u_char clockSeqHiAndReserved (void) const;
>     void clockSeqHiAndReserved (u_char);
> 
>     u_char clockSeqLow (void) const;
>     void clockSeqLow (u_char);
> 
>     UUID_node* node (void) const;
>     void node (UUID_node*);
> 
>     ACE_CString* thr_id (void);
>     void thr_id (char*);
> 
>     ACE_CString* pid (void);
>     void pid (char*);
> 
>     /// Returns a string representation of the UUID
>     const ACE_CString* to_string (void);
> 
>     /// Set the value using a string
>     void from_string (const ACE_CString& uuid_string);
> 
>     static UUID NIL_UUID;
> 
>     /// Equality Operations
>     bool operator== (const UUID &right) const;
>     bool operator!= (const UUID &right) const;
> 
>     /// Relational Operations
>     //bool operator<  (const UUID &right) const;
>     //bool operator>  (const UUID &right) const;
>     //bool operator<= (const UUID &right) const;
>     //bool operator>= (const UUID &right) const;
> 
>   private:
>     void from_string_i (const ACE_CString& uuidString);
> 
>     UUID& operator= (const UUID&);
> 
>     /// Data Members for Class Attributes
>     ACE_UINT32 timeLow_;
>     ACE_UINT16 timeMid_;
>     ACE_UINT16 timeHiAndVersion_;
>     u_char clockSeqHiAndReserved_;
>     u_char clockSeqLow_;
>     UUID_node* node_;
>     bool node_release_;
>     ACE_CString thr_id_;
>     ACE_CString pid_;
> 
>     /// The string representation of the UUID. This is created and
>     /// updated only on demand.
>     ACE_CString *as_string_;
>   };
> 
> 
>   /**
>    * @class ACE_UUID_Generator
>    *
>    * Singleton class that generates UUIDs.
>    *
>    */
>   class ACE_Export UUID_Generator
>   {
>   public:
> 
>     enum {ACE_UUID_CLOCK_SEQ_MASK = 0x3FFF};
> 
>     UUID_Generator();
>     ~UUID_Generator();
> 
>     void init (void);
> 
>     /// Format timestamp, clockseq, and nodeID into an UUID of the
>     /// specified version and variant. For generating UUID's with
>     /// thread and process ids use variant=0xc0
>     void generateUUID (UUID&, ACE_UINT16 version=0x0001, u_char variant=0x80);
> 
>     /// Format timestamp, clockseq, and nodeID into a VI UUID. For
>     /// generating UUID's with thread and process ids use variant=0xc0
>     UUID* generateUUID (ACE_UINT16 version=0x0001, u_char variant=0x80);
> 
>     /// Type to represent UTC as a count of 100 nanosecond intervals
>     /// since 00:00:00.00, 15 October 1582.
>     typedef ACE_UINT64 UUID_time;
> 
>     /// The locking strategy prevents multiple generators from accessing
>     /// the UUID_state at the same time. Get the locking strategy.
>     ACE_SYNCH_MUTEX* lock (void);
> 
>     /// Set a new locking strategy and return the old one.
>     void lock (ACE_SYNCH_MUTEX* lock,
>                bool release_lock);
> 
>   private:
> 
>     /// The system time when that last uuid was generated.
>     UUID_time timeLast_;
> 
>     /// Type to contain the UUID generator persistent state. This will
>     /// be kept in memory mapped shared memory
>     struct UUID_State
>     {
>       UUID_time timestamp;
>       UUID_node node;
>       ACE_UINT16 clockSequence;
>     };
> 
>     /// Obtain a UUID timestamp. Compensate for the fact that the time
>     /// obtained from getSystem time has a resolution less than 100ns.
>   void get_timestamp (UUID_time& timestamp, ACE_UINT16& clockSequence);
> 
>     /// Obtain the system time in UTC as a count of 100 nanosecond intervals
>     /// since 00:00:00.00, 15 October 1582 (the date of Gregorian reform to
>   /// the Christian calendar).
>     void get_systemtime( UUID_time& timeNow);
> 
>     /// The UUID generator persistent state.
>     UUID_State uuid_state_;
> 
>     ACE_SYNCH_MUTEX* lock_;
>     bool destroy_lock_;
>   };
> 
>   typedef ACE_Singleton<UUID_Generator, ACE_SYNCH_MUTEX> UUID_GENERATOR;
> 
> }
> 
> ACE_END_VERSIONED_NAMESPACE_DECL
> 
> #if defined (__ACE_INLINE__)
> #include "ace/UUID.inl"
> #endif /* __ACE_INLINE__ */
> 
> #include /**/ "ace/post.h"
> #endif // ACE_UUID_H



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