< draft-mealling-uuid-urn-00.txt		draft-mealling-uuid-urn-01.txt >
	Network Working Group M. Mealling		Network Working Group P. Leach
	Internet-Draft VeriSign, Inc.		Internet-Draft Microsoft
	Expires: April 1, 2003 P. Leach		Expires: April 2, 2004 M. Mealling
	Microsoft		VeriSign, Inc.
	R. Salz		R. Salz
	Datapower Technology, Inc.		DataPower Technology, Inc.
	October 2002		October 3, 2003
	A UUID URN Namespace		A UUID URN Namespace
	draft-mealling-uuid-urn-00.txt		draft-mealling-uuid-urn-01.txt
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.		all provisions of Section 10 of RFC2026.
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2002). All Rights Reserved.		Copyright (C) The Internet Society (2003). All Rights Reserved.
	Abstract		Abstract
	This specification defines a Uniform Resource Name namespace for		This specification defines a Uniform Resource Name namespace for
	UUIDs ( (Universally Unique IDentifier), also known as GUIDs		UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
	(Globally Unique IDentifier). A UUID is 128 bits long, and if		Unique IDentifier). A UUID is 128 bits long, and can provide a
	generated according to the one of the mechanisms in this document, is		guarantee of uniqueness across space and time. UUIDs were originally
	either guaranteed to be different from all other UUIDs/GUIDs		used in the Network Computing System (NCS) [1] and later in the Open
	generated until 3400 A.D. or extremely likely to be different		Software Foundation's (OSF) Distributed Computing Environment [2].
	(depending on the mechanism chosen). UUIDs were originally used in
	the Network Computing System (NCS) [1] and later in the Open Software
	Foundation's (OSF) Distributed Computing Environment [2].
	This specification is derived from the latter specification with the		This specification is derived from the latter specification with the
	kind permission of the OSF. The original version of this document		kind permission of the OSF (now known as The Open Group). Earlier
	was written by Paul Leach and Rich Salz but was unpublished for		versions of this document never left draft stage; this document
	several years. This is an updated version incorporated as part of		incorporates that information here.
	the URN registration document.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Namespace Registration Template . . . . . . . . . . . . . . 4		3. Namespace Registration Template . . . . . . . . . . . . . . 3
	4. Specification . . . . . . . . . . . . . . . . . . . . . . . 7		4. Specification . . . . . . . . . . . . . . . . . . . . . . . 6
	4.1 Format . . . . . . . . . . . . . . . . . . . . . . . . . . . 7		4.1 Format . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	4.1.1 Variant . . . . . . . . . . . . . . . . . . . . . . . . . . 7		4.1.1 Variant . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	4.1.2 UUID Layout . . . . . . . . . . . . . . . . . . . . . . . . 8		4.1.2 Layout and byte order . . . . . . . . . . . . . . . . . . . 6
	4.1.3 Version . . . . . . . . . . . . . . . . . . . . . . . . . . 9		4.1.3 Version . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	4.1.4 Timestamp . . . . . . . . . . . . . . . . . . . . . . . . . 10		4.1.4 Timestamp . . . . . . . . . . . . . . . . . . . . . . . . . 8
	4.1.5 Clock sequence . . . . . . . . . . . . . . . . . . . . . . . 10		4.1.5 Clock sequence . . . . . . . . . . . . . . . . . . . . . . . 8
	4.1.6 Node . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11		4.1.6 Node . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
	4.1.7 Nil UUID . . . . . . . . . . . . . . . . . . . . . . . . . . 11		4.1.7 Nil UUID . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	4.2 Algorithms for creating a time-based UUID . . . . . . . . . 12		4.2 Algorithms for creating a time-based UUID . . . . . . . . . 10
	4.2.1 Basic algorithm . . . . . . . . . . . . . . . . . . . . . . 12		4.2.1 Basic algorithm . . . . . . . . . . . . . . . . . . . . . . 10
	4.2.2 Reading stable storage . . . . . . . . . . . . . . . . . . . 13		4.2.2 Generation details . . . . . . . . . . . . . . . . . . . . . 12
	4.2.3 System clock resolution . . . . . . . . . . . . . . . . . . 13		4.3 Algorithm for creating a name-based UUID . . . . . . . . . . 13
	4.2.4 Writing stable storage . . . . . . . . . . . . . . . . . . . 14		4.4 Algorithms for creating a UUID from truly random or
	4.2.5 Sharing state across processes . . . . . . . . . . . . . . . 14		pseudo-random numbers . . . . . . . . . . . . . . . . . . . 14
	4.2.6 UUID Generation details . . . . . . . . . . . . . . . . . . 14		4.5 Node IDs that do not identify the host . . . . . . . . . . . 15
	4.3 Algorithm for creating a name-based UUID . . . . . . . . . . 15		5. Community Considerations . . . . . . . . . . . . . . . . . . 16
	5. Algorithms for creating a UUID from truly random or		6. Security Considerations . . . . . . . . . . . . . . . . . . 17
	pseudo-random numbers . . . . . . . . . . . . . . . . . . . 16		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 17
	6. Byte order of UUIDs . . . . . . . . . . . . . . . . . . . . 17		Normative References . . . . . . . . . . . . . . . . . . . . 17
	7. Node IDs when no IEEE 802 network card is available . . . . 17		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 18
	8. Obtaining IEEE 802 addresses . . . . . . . . . . . . . . . . 19		A. Appendix A - Sample Implementation . . . . . . . . . . . . . 18
	9. Community Considerations . . . . . . . . . . . . . . . . . . 19		B. Appendix B - Sample output of utest . . . . . . . . . . . . 29
	10. Security Considerations . . . . . . . . . . . . . . . . . . 20		C. Appendix C - Some name space IDs . . . . . . . . . . . . . . 29
	11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20		Intellectual Property and Copyright Statements . . . . . . . 31
	Normative References . . . . . . . . . . . . . . . . . . . . 20
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 21
	A. Appendix A - UUID Sample Implementation . . . . . . . . . . 21
	B. Appendix B - Sample output of utest . . . . . . . . . . . . 33
	C. Appendix C - Some name space IDs . . . . . . . . . . . . . . 33
	Full Copyright Statement . . . . . . . . . . . . . . . . . . 35
	1. Introduction		1. Introduction
	This specification defines a Uniform Resource Name (URN) [4]		This specification defines a Uniform Resource Name namespace for
	namespace for UUIDs (Universally Unique IDentifiers), also known as		UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
	GUIDs (Globally Unique IDentifiers). A UUID is 128 bits long, and if		Unique IDentifier). A UUID is 128 bits long, and requires no central
	generated according to the one of the mechanisms in this document, is		registration process.
	either guaranteed to be different from all other UUIDs/GUIDs
	generated until 3400 A.D. or extremely likely to be different
	(depending on the mechanism chosen).
	It is extremely important to note that most of the text in this		The information here is meant to be a concise guide for those wishing
	document originated with Paul Leach and Rich Salz. It has been		to implement services using UUIDs as URNs. Nothing in this document
	modified in order to be compliant with URN namespace registration		should be construed to mean that it supersedes the DCE standards that
	procedures. Nothing in this document should be construed to mean		defined UUIDs to begin with.
	that it supercedes the DCE standards that defined UUIDs to begin
	with. The information here is simply meant as a concise guide for
	those wishing to implement services using UUIDs as URNs.
	2. Motivation		2. Motivation
	One of the main reasons for using UUIDs is that no centralized		One of the main reasons for using UUIDs is that no centralized
	authority is required to administer them (beyond the one that		authority is required to administer them (although one format uses
	allocates IEEE 802.1 node identifiers). As a result, generation on		IEEE 802.1 node identifiers, others do not). As a result, generation
	demand can be completely automated, and they can be used for a wide		on demand can be completely automated, and they can be used for a
	variety of purposes. The UUID generation algorithm described here		wide variety of purposes. The UUID generation algorithm described
	supports very high allocation rates: 10 million per second per		here supports very high allocation rates: 10 million per second per
	machine if you need it, so that they could even be used as		machine if necessary, so that they could even be used as transaction
	transaction IDs.		IDs.
	UUIDs are fixed-size (128-bits) which is reasonably small relative to		UUIDs are of a fixed size (128-bits) which is reasonably small
	other alternatives. This fixed, relatively small size lends itself		relative to other alternatives. This lends itself well to sorting,
	well to sorting, ordering, and hashing of all sorts, storing in		ordering, and hashing of all sorts, storing in databases, simple
	databases, simple allocation, and ease of programming in general.		allocation, and ease of programming in general.
	Since UUIDs are unique and persistent given correct time settings,		Since UUIDs are unique and persistent, they make excellent Uniform
	they make excellent Uniform Resource Names. The unique ability to		Resource Names. The unique ability to generate a new UUID without a
	generate new UUIDs without a registration process allows for UUIDs to		registration process allows for UUIDs to be one of the URNs with the
	be one the URN with the lowest minting cost.		lowest minting cost.
	3. Namespace Registration Template		3. Namespace Registration Template
	Namespace ID: UUID		Namespace ID: UUID
	Registration Information:		Registration Information:
	Registration date: 2002-10-01		Registration date: 2003-10-01
	Declared registrant of the namespace:		Declared registrant of the namespace:
	JTC 1/SC6 (ASN.1 Rapporteur Group)		JTC 1/SC6 (ASN.1 Rapporteur Group)
	Declaration of syntactic structure:		Declaration of syntactic structure:
	A UUID is an identifier that is unique across both space and time,		A UUID is an identifier that is unique across both space and time,
	with respect to the space of all UUIDs. To be precise, the UUID		with respect to the space of all UUIDs. Since a UUID is a fixed
	consists of a finite bit space. Thus the time value used for		size and contains a time field, it is possible for values to
	constructing a UUID is limited and will roll over in the future		rollover (around A.D. 3400, depending on the specific algorithm
	(approximately at A.D. 3400, based on the specified algorithm).		used). A UUID can be used for multiple purposes, from tagging
	A UUID can be used for multiple purposes, from tagging objects		objects with an extremely short lifetime, to reliably identifying
	with an extremely short lifetime, to reliably identifying very		very persistent objects across a network.
	persistent objects across a network.
	The internal representation of a UUID is a specfic sequence of		The internal representation of a UUID is a specific sequence of
	bits in memory. In order to accurately represent a UUID as a URN		bits in memory, as described in Section 4. In order to accurately
	it is necessary to convert the bit sequence to a string		represent a UUID as a URN, it is necessary to convert the bit
	representation. The exact sequence and meaning of this bit		sequence to a string representation.
	sequence is covered in Section 4
	Each field is treated as an integer and has its value printed as a		Each field is treated as an integer and has its value printed as a
	zero-filled hexadecimal digit string with the most significant		zero-filled hexadecimal digit string with the most significant
	digit first. The hexadecimal values a to f inclusive are output		digit first. The hexadecimal values a through f are output as
	as lower case characters, and are case insensitive on input. The		lower case characters, and are case insensitive on input.
	sequence is the same as the UUID constructed type.
	The formal definition of the UUID string representation is		The formal definition of the UUID string representation is
	provided by the following extended BNF:		provided by the following extended BNF:
	UUID = <time_low> "-" <time_mid> "-"		UUID = <time_low> "-" <time_mid> "-"
	<time_high_and_version> "-"		<time_high_and_version> "-"
	<clock_seq_and_reserved>		<clock_seq_and_reserved>
	<clock_seq_low> "-" <node>		<clock_seq_low> "-" <node>
	time_low = 4*<hexOctet>		time_low = 4*<hexOctet>
	time_mid = 2*<hexOctet>		time_mid = 2*<hexOctet>
	time_high_and_version = 2*<hexOctet>		time_high_and_version = 2*<hexOctet>
	clock_seq_and_reserved = <hexOctet>		clock_seq_and_reserved = <hexOctet>
	clock_seq_low = <hexOctet>		clock_seq_low = <hexOctet>
	node = 6*<hexOctet		node = 6*<hexOctet
	hexOctet = <hexDigit> <hexDigit>		hexOctet = <hexDigit> <hexDigit>
	hexDigit =		hexDigit =
	"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"		"0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
	| "a" | "b" | "c" | "d" | "e" | "f"		| "a" | "b" | "c" | "d" | "e" | "f"
	| "A" | "B" | "C" | "D" | "E" | "F"		| "A" | "B" | "C" | "D" | "E" | "F"
	The following is an example of the string representation of a UUID		The following is an example of the string representation of a UUID
	as a URN:		as a URN:
	urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6		urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
	Relevant ancillary documentation:		Relevant ancillary documentation:
	[2]		[2]
	Identifier uniqueness considerations:		Identifier uniqueness considerations:
	Due to the combination of spacial and temporal components and the		This document specifies three algorithms to generate UUIDs: the
	fact that spatial uniqueness is maintained via 802.1 MAC		first leverages the unique values of 802.1 MAC addresses to
	addresses, all UUIDs that are generated according to the standards		guarantee uniqueness, the second another uses pseudo-random number
	and techniques mentioned in this document are unique from all		generators, and the third uses cryptographic hashing and
	other UUIDs that have been or will be assigned.		application-provided text strings. As a result, it is possible to
			guarantee that UUIDs generated according to the mechanisms here
			will be unique from all other UUIDs that have been or will be
			assigned.
	Identifier persistence considerations:		Identifier persistence considerations:
	UUIDs are inherently very difficult to resolve in a global sense.		UUIDs are inherently very difficult to resolve in a global sense.
	This, coupled with the fact that UUIDs are temporally unique		This, coupled with the fact that UUIDs are temporally unique
	within their spatial context, ensures that UUIDs will remain as		within their spatial context, ensures that UUIDs will remain as
	persistent as possible.		persistent as possible.
	Process of identifier assignment:		Process of identifier assignment:
	The generation of UUIDs does not require that a registration		Generating a UUID does not require that it be a registration
	authority be contacted for each identifier. Instead, it requires		authority be contacted. One algorithm requires a unique value over
	a unique value over space for each UUID generator. This spatially		space for each generator. This value is typically an IEEE 802
	unique value is specified as an IEEE 802 address, which is usually		address, usually already available on network-connected hosts. The
	already available to network-connected systems. This 48-bit		address can be assigned from an address block obtained from the
	address can be assigned based on an address block obtained through		IEEE registration authority. If no such address is available, or
	the IEEE registration authority. This section of the UUID		privacy concerns make its use undesirable, Section 4.5 specifies
	specification assumes the availability of an IEEE 802 address to a		two alternatives; another approach is to use version 3 or version
	system desiring to generate a UUID, but if one is not available		4 UUIDs as defined below.
	Section 7 specifies a way to generate a probabilistically unique
	one that can not conflict with any properly assigned IEEE 802
	address.
	Process for identifier resolution:		Process for identifier resolution:
	Due to UUIDs not being globally resolvable, this value is not		Since UUIDs are not globally resolvable, this is not applicable.
	applicable.
	Rules for Lexical Equivalence:		Rules for Lexical Equivalence:
	Consider each field of the UUID to be an unsigned integer as shown		Consider each field of the UUID to be an unsigned integer as shown
	in the table in section 3.1. Then, to compare a pair of UUIDs,		in the table in section Section 4.1.2. Then, to compare a pair of
	arithmetically compare the corresponding fields from each UUID in		UUIDs, arithmetically compare the corresponding fields from each
	order of significance and according to their data type. Two UUIDs		UUID in order of significance and according to their data type.
	are equal if and only if all the corresponding fields are equal.		Two UUIDs are equal if and only if all the corresponding fields
			are equal.
	Note: as a practical matter, on many systems comparison of two		As an implementation note, on many systems equality comparison can
	UUIDs for equality can be performed simply by comparing the 128		be performed by doing the appropriate byte-order canonicalization,
	bits of their in-memory representation considered as a 128 bit		and then treating the two UUIDs as 128-bit unsigned integers.
	unsigned integer. Here, it is presumed that by the time the in-
	memory representation is obtained the appropriate byte-order
	canonicalizations have been carried out.
	Two UUIDs allocated according to the same variant can also be		UUIDs as defined in this document can also be ordered
	ordered lexicographically. For the UUID variant herein defined,		lexicographically. For a pair of UUIDs, the first one follows the
	the first of two UUIDs follows the second if the most significant		second if the most significant field in which the UUIDs differ is
	field in which the UUIDs differ is greater for the first UUID.		greater for the first UUID. The second precedes the first if the
	The first of a pair of UUIDs precedes the second if the most		most significant field in which the UUIDs differ is greater for
	significant field in which the UUIDs differ is greater for the		the second UUID.
	second UUID.
	Conformance with URN Syntax:		Conformance with URN Syntax:
	The string representation of a UUID produces a string that is		The string representation of a UUID is fully compatible with the
	fully compatible with the URN syntax. When converting from an		URN syntax. When converting from an bit-oriented, in-memory
	bit-oriented, in-memory representation of a UUID into a URN, care		representation of a UUID into a URN, care must be taken to
	must be taken to strictly adhere to the byte order issues		strictly adhere to the byte order issues mentioned in the string
	mentioned in the string representation section.		representation section.
	Validation mechanism:		Validation mechanism:
	Appart from determining if the timestamp portion of the UUID is in		Apart from determining if the timestamp portion of the UUID is in
	the future and thus no yet assignable, there is no mechanism for		the future and therefore not yet assignable, there is no mechanism
	determining if a UUID is 'valid' in any real sense.		for determining if a UUID is 'valid' in any real sense.
	Scope:		Scope:
	UUIDs are global in scope.		UUIDs are global in scope.
	4. Specification		4. Specification
	4.1 Format		4.1 Format
	In its most general form, all that can be said of the UUID format is		In its most general form, all that can be said of the UUID format is
	that a UUID is 16 octets, and that some bits of octet 8 of the UUID		that a UUID is 16 octets, and that some bits of the eight octet --
	called the variant field (specified in the next section) determine		the variant field specified below -- determine finer structure.
	finer structure.
	4.1.1 Variant		4.1.1 Variant
	The variant field determines the layout of the UUID. That is, the		The variant field determines the layout of the UUID. That is, the
	interpretation of all other bits in the UUID depends on the setting		interpretation of all other bits in the UUID depends on the setting
	of the bits in the variant field. The variant field consists of a		of the bits in the variant field. As such, it could more accurately
	variable number of the msbs of octet 8 of the UUID.		be called a type field; we retain the original term for
			compatibility. The variant field consists of a variable number of the
			most significant bits of the eighth octet of the UUID.
	The following table lists the contents of the variant field.		The following table lists the contents of the variant field, where
			the letter "x" indicates a "don't-care" value.
	Msb0 Msb1 Msb2 Description		Msb0 Msb1 Msb2 Description
	0 - - Reserved, NCS backward compatibility.		0 x x Reserved, NCS backward compatibility.
	1 0 - The variant specified in this document.		1 0 x The variant specified in this document.
	1 1 0 Reserved, Microsoft Corporation backward		1 1 0 Reserved, Microsoft Corporation backward
	compatibility		compatibility
	1 1 1 Reserved for future definition.		1 1 1 Reserved for future definition.
	Other UUID variants may not interoperate with the UUID variant		Interoperability (in any form) with variants other than the one
	specified in this document, where interoperability is defined as the		defined here is not guaranteed. This is unlikely to be an issue in
	applicability of operations such as string conversion and lexical		practice.
	ordering across different systems. However, UUIDs allocated
	according to the stricture of different variants, though they may
	define different interpretations of the bits outside the variant
	field, will not result in duplicate UUID allocation, because of the
	differing values of the variant field itself.
	The remaining fields described below (version, timestamp, etc.) are		4.1.2 Layout and byte order
	defined only for the UUID variant noted above.		To minimize confusion about bit assignments within octets, the UUID
			record definition is defined only in terms of fields that are
			integral numbers of octets. The fields are presented with the most
			significant one first.
	4.1.2 UUID Layout		Field Data Type Octet Note
			#
	The following table gives the format of a UUID for the variant		time_low unsigned 32 0-3 The low field of the
	specified herein. The UUID consists of a record of 16 octets. To		bit integer timestamp
	minimize confusion about bit assignments within octets, the UUID
	record definition is defined only in terms of fields that are
	integral numbers of octets. The fields are in order of significance
	for comparison purposes, with "time_low" the most significant, and
	"node" the least significant.
	Field Data Type Octet Note		time_mid unsigned 16 4-5 The middle field of the
	#		bit integer timestamp
	time_low unsigned 32 0-3 The low field of the		time_hi_and_version unsigned 16 6-7 The high field of the
	bit integer timestamp.		bit integer timestamp multiplexed
			with the version number
	time_mid unsigned 16 4-5 The middle field of the		clock_seq_hi_and_rese unsigned 8 8 The high field of the
	bit integer timestamp.		rved bit integer clock sequence
			multiplexed with the
			variant
	time_hi_and_version unsigned 16 6-7 The high field of the		clock_seq_low unsigned 8 9 The low field of the
	bit integer timestamp multiplexed		bit integer clock sequence
	with the version number.
	clock_seq_hi_and_rese unsigned 8 8 The high field of the		node unsigned 48 10-15 The spatially unique
	rved bit integer clock sequence		bit integer node identifier
	multiplexed with the
	variant.
	clock_seq_low unsigned 8 9 The low field of the		In the absence of explicit application or presentation protocol
	bit integer clock sequence.		specification to the contrary, a UUID is encoded as a 128-bit object,
			as follows: the fields are encoded as 16 octets, with the sizes and
			order of the fields defined above, and with each field encoded with
			the Most Significant Byte first (this is known as network byte
			order).
	node unsigned 48 10-15 The spatially unique		0 1 2 3
	bit integer node identifier.		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| time_low |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| time_mid | time_hi_and_version |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|clk_seq_hi_res | clk_seq_low | node (0-1) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| node (2-5) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	4.1.3 Version		4.1.3 Version
	The version number is in the most significant 4 bits of the time		The version number is in the most significant four bits of the time
	stamp (time_hi_and_version).		stamp (time_hi_and_version).
	The following table lists currently defined versions of the UUID.		The following table lists the currently-defined versions for this
			UUID variant.
	Msb0 Msb1 Msb2 Msb3 Version Description		Msb0 Msb1 Msb2 Msb3 Version Description
	0 0 0 1 1 The time-based version		0 0 0 1 1 The time-based version
	specified in this		specified in this document.
	document.
	0 0 1 0 2 Reserved for DCE		0 0 1 0 2 DCE Security version, with
	Security version, with		embedded POSIX UIDs.
	embedded POSIX UIDs.
	0 0 1 1 3 The name-based version		0 0 1 1 3 The name-based version
	specified in this document		specified in this document.
	0 1 0 0 4 The randomly or pseudo-		0 1 0 0 4 The randomly or pseudo-
	randomly generated		randomly generated version
	version specified in		specified in this document.
	this document
			The version is more accurately a sub-type; again, we retain the term
			for compatibility.
	4.1.4 Timestamp		4.1.4 Timestamp
	The timestamp is a 60 bit value. For UUID version 1, this is		The timestamp is a 60-bit value. For UUID version 1, this is
	represented by Coordinated Universal Time (UTC) as a count of 100-		represented by Coordinated Universal Time (UTC) as a count of
	nanosecond intervals since 00:00:00.00, 15 October 1582 (the date of		100-nanosecond intervals since 00:00:00.00, 15 October 1582 (the date
	Gregorian reform to the Christian calendar).		of Gregorian reform to the Christian calendar).
	For systems that do not have UTC available, but do have local time,		For systems that do not have UTC available, but do have the local
	they MAY use local time instead of UTC, as long as they do so		time, they may use that instead of UTC, as long as they do so
	consistently throughout the system. This is NOT RECOMMENDED,		consistently throughout the system. This is not recommended however,
	however, and it should be noted that all that is needed to generate		particularly since all that is needed to generate UTC from local time
	UTC, given local time, is a time zone offset.		is a time zone offset.
	For UUID version 3, it is a 60 bit value constructed from a name.		For UUID version 3, the timestamp is a 60-bit value constructed from
			a name as described in Section 4.3.
	For UUID version 4, it is a randomly or pseudo-randomly generated 60		For UUID version 4, it is a randomly or pseudo-randomly generated
	bit value.		60-bit value, as described in Section 4.4.
	4.1.5 Clock sequence		4.1.5 Clock sequence
	For UUID version 1, the clock sequence is used to help avoid		For UUID version 1, the clock sequence is used to help avoid
	duplicates that could arise when the clock is set backwards in time		duplicates that could arise when the clock is set backwards in time
	or if the node ID changes.		or if the node ID changes.
	If the clock is set backwards, or even might have been set backwards		If the clock is set backwards, or even might have been set backwards
	(e.g., while the system was powered off), and the UUID generator can		(e.g., while the system was powered off), and the UUID generator can
	not be sure that no UUIDs were generated with timestamps larger than		not be sure that no UUIDs were generated with timestamps larger than
	the value to which the clock was set, then the clock sequence has to		the value to which the clock was set, then the clock sequence has to
	be changed. If the previous value of the clock sequence is known, it		be changed. If the previous value of the clock sequence is known, it
	can be just incremented; otherwise it should be set to a random or		can be just incremented; otherwise it should be set to a random or
	high-quality pseudo random value.		high-quality pseudo random value.
	Similarly, if the node ID changes (e.g. because a network card has		Similarly, if the node ID changes (e.g. because a network card has
	been moved between machines), setting the clock sequence to a random		been moved between machines), setting the clock sequence to a random
	number minimizes the probability of a duplicate due to slight		number minimizes the probability of a duplicate due to slight
	differences in the clock settings of the machines. (If the value of		differences in the clock settings of the machines. (If the value of
	clock sequence associated with the changed node ID were known, then		clock sequence associated with the changed node ID were known, then
	the clock sequence could just be incremented, but that is unlikely.)		the clock sequence could just be incremented, but that is unlikely.)
	The clock sequence MUST be originally (i.e., once in the lifetime of		The clock sequence MUST be originally (i.e., once in the lifetime of
	a system) initialized to a random number to minimize the correlation		a system) initialized to a random number to minimize the correlation
	across systems. This provides maximum protection against node		across systems. This provides maximum protection against node
	identifiers that may move or switch from system to system rapidly.		identifiers that may move or switch from system to system rapidly.
	The initial value MUST NOT be correlated to the node identifier.		The initial value MUST NOT be correlated to the node identifier.
	For UUID version 3, it is a 14 bit value constructed from a name.		For UUID version 3, it is a 14-bit value constructed from a name as
			described in Section 4.3.
	For UUID version 4, it is a randomly or pseudo-randomly generated 14		For UUID version 4, it is a randomly or pseudo-randomly generated
	bit value.		14-bit value as described in Section 4.4.
	4.1.6 Node		4.1.6 Node
	For UUID version 1, the node field consists of the IEEE address,		For UUID version 1, the node field consists of the IEEE address,
	usually the host address. For systems with multiple IEEE 802		usually the host address. For systems with multiple IEEE 802
	addresses, any available address can be used. The lowest addressed		addresses, any available address can be used. The lowest addressed
	octet (octet number 10) contains the global/local bit and the		octet (octet number 10) contains the global/local bit and the
	unicast/multicast bit, and is the first octet of the address		unicast/multicast bit, and is the first octet of the address
	transmitted on an 802.3 LAN.		transmitted on an 802.3 LAN.
	For systems with no IEEE address, a randomly or pseudo-randomly		For systems with no IEEE address, a randomly or pseudo-randomly
	generated value may be used (see section 4). The multicast bit must		generated value may be used; see Section 4.5. The multicast bit must
	be set in such addresses, in order that they will never conflict with		be set in such addresses, in order that they will never conflict with
	addresses obtained from network cards.		addresses obtained from network cards.
	For UUID version 3, the node field is a 48 bit value constructed from		For UUID version 3, the node field is a 48-bit value constructed from
	a name.		a name as described in Section 4.3.
	For UUID version 4, the node field is a randomly or pseudo-randomly		For UUID version 4, the node field is a randomly or pseudo-randomly
	generated 48 bit value.		generated 48-bit value as described in Section 4.4.
	4.1.7 Nil UUID		4.1.7 Nil UUID
	The nil UUID is special form of UUID that is specified to have all		The nil UUID is special form of UUID that is specified to have all
	128 bits set to 0 (zero).		128 bits set to zero.
	4.2 Algorithms for creating a time-based UUID		4.2 Algorithms for creating a time-based UUID
	Various aspects of the algorithm for creating a version 1 UUID are		Various aspects of the algorithm for creating a version 1 UUID are
	discussed in the following sections. UUID generation requires a		discussed in the following sections.
	guarantee of uniqueness within the node ID for a given variant and
	version. Interoperability is provided by complying with the
	specified data structure.
	4.2.1 Basic algorithm		4.2.1 Basic algorithm
	The following algorithm is simple, correct, and inefficient:		The following algorithm is simple, correct, and inefficient:
	o Obtain a system wide global lock		o Obtain a system-wide global lock
	o From a system wide shared stable store (e.g., a file), read the		o From a system-wide shared stable store (e.g., a file), read the
	UUID generator state: the values of the time stamp, clock		UUID generator state: the values of the time stamp, clock
	sequence, and node ID used to generate the last UUID.		sequence, and node ID used to generate the last UUID.
	o Get the current time as a 60 bit count of 100-nanosecond intervals		o Get the current time as a 60-bit count of 100-nanosecond intervals
	since 00:00:00.00, 15 October 1582		since 00:00:00.00, 15 October 1582
	o Get the current node ID		o Get the current node ID
	o If the state was unavailable (non-existent or corrupted), or the		o If the state was unavailable (e.g., non-existent or corrupted), or
	saved node ID is different than the current node ID, generate a		the saved node ID is different than the current node ID, generate
	random clock sequence value		a random clock sequence value
	o If the state was available, but the saved time stamp is later than		o If the state was available, but the saved time stamp is later than
	the current time stamp, increment the clock sequence value		the current time stamp, increment the clock sequence value
	o Format a UUID from the current time stamp, clock sequence, and
	node ID values according to the structure in section 3.1 (see
	section 3.2.6 for more details)
	o Save the state (current time stamp, clock sequence, and node ID)		o Save the state (current time stamp, clock sequence, and node ID)
	back to the stable store		back to the stable store
	o Release the system wide global lock		o Release the global lock
			o Format a UUID from the current time stamp, clock sequence, and
			node ID values according to the steps in Section 4.2.2.
	If UUIDs do not need to be frequently generated, the above algorithm		If UUIDs do not need to be frequently generated, the above algorithm
	may be perfectly adequate. For higher performance requirements,		may be perfectly adequate. For higher performance requirements,
	however, issues with the basic algorithm include:		however, issues with the basic algorithm include:
	o Reading the state from stable storage each time is inefficient		o Reading the state from stable storage each time is inefficient
	o The resolution of the system clock may not be 100-nanoseconds		o The resolution of the system clock may not be 100-nanoseconds
	o Writing the state to stable storage each time is inefficient		o Writing the state to stable storage each time is inefficient
	o Sharing the state across process boundaries may be inefficient		o Sharing the state across process boundaries may be inefficient
	Each of these issues can be addressed in a modular fashion by local		Each of these issues can be addressed in a modular fashion by local
	improvements in the functions that read and write the state and read		improvements in the functions that read and write the state and read
	the clock. We address each of them in turn in the following		the clock. We address each of them in turn in the following sections.
	sections.
	4.2.2 Reading stable storage		4.2.1.1 Reading stable storage
	The state only needs to be read from stable storage once at boot		The state only needs to be read from stable storage once at boot
	time, if it is read into a system wide shared volatile store (and		time, if it is read into a system-wide shared volatile store (and
	updated whenever the stable store is updated).		updated whenever the stable store is updated).
	If an implementation does not have any stable store available, then		If an implementation does not have any stable store available, then
	it can always say that the values were unavailable. This is the		it can always say that the values were unavailable. This is the least
	least desirable implementation, because it will increase the		desirable implementation, because it will increase the frequency of
	frequency of creation of new clock sequence numbers, which increases		creation of new clock sequence numbers, which increases the
	the probability of duplicates.		probability of duplicates.
	If the node ID can never change (e.g., the net card is inseparable		If the node ID can never change (e.g., the net card is inseparable
	from the system), or if any change also reinitializes the clock		from the system), or if any change also reinitializes the clock
	sequence to a random value, then instead of keeping it in stable		sequence to a random value, then instead of keeping it in stable
	store, the current node ID may be returned.		store, the current node ID may be returned.
	4.2.3 System clock resolution		4.2.1.2 System clock resolution
	The time stamp is generated from the system time, whose resolution		The time stamp is generated from the system time, whose resolution
	may be less than the resolution of the UUID time stamp.		may be less than the resolution of the UUID time stamp.
	If UUIDs do not need to be frequently generated, the time stamp can		If UUIDs do not need to be frequently generated, the time stamp can
	simply be the system time multiplied by the number of 100-nanosecond		simply be the system time multiplied by the number of 100-nanosecond
	intervals per system time interval.		intervals per system time interval.
	If a system overruns the generator by requesting too many UUIDs		If a system overruns the generator by requesting too many UUIDs
	within a single system time interval, the UUID service MUST either:		within a single system time interval, the UUID service MUST either:
	return an error, or stall the UUID generator until the system clock		return an error, or stall the UUID generator until the system clock
	catches up.		catches up.
	A high resolution time stamp can be simulated by keeping a count of		A high resolution time stamp can be simulated by keeping a count of
	how many UUIDs have been generated with the same value of the system		how many UUIDs have been generated with the same value of the system
	time, and using it to construction the low-order bits of the time		time, and using it to construction the low-order bits of the time
	stamp. The count will range between zero and the number of 100-		stamp. The count will range between zero and the number of
	nanosecond intervals per system time interval.		100-nanosecond intervals per system time interval.
	Note: if the processors overrun the UUID generation frequently,		Note: if the processors overrun the UUID generation frequently,
	additional node identifiers can be allocated to the system, which		additional node identifiers can be allocated to the system, which
	will permit higher speed allocation by making multiple UUIDs		will permit higher speed allocation by making multiple UUIDs
	potentially available for each time stamp value.		potentially available for each time stamp value.
	4.2.4 Writing stable storage		4.2.1.3 Writing stable storage
	The state does not always need to be written to stable store every		The state does not always need to be written to stable store every
	time a UUID is generated. The timestamp in the stable store can be		time a UUID is generated. The timestamp in the stable store can be
	periodically set to a value larger than any yet used in a UUID; as		periodically set to a value larger than any yet used in a UUID; as
	long as the generated UUIDs have time stamps less than that value,		long as the generated UUIDs have time stamps less than that value,
	and the clock sequence and node ID remain unchanged, only the shared		and the clock sequence and node ID remain unchanged, only the shared
	volatile copy of the state needs to be updated. Furthermore, if the		volatile copy of the state needs to be updated. Furthermore, if the
	time stamp value in stable store is in the future by less than the		time stamp value in stable store is in the future by less than the
	typical time it takes the system to reboot, a crash will not cause a		typical time it takes the system to reboot, a crash will not cause a
	reinitialization of the clock sequence.		reinitialization of the clock sequence.
	4.2.5 Sharing state across processes		4.2.1.4 Sharing state across processes
	If it is too expensive to access shared state each time a UUID is		If it is too expensive to access shared state each time a UUID is
	generated, then the system wide generator can be implemented to		generated, then the system-wide generator can be implemented to
	allocate a block of time stamps each time it is called, and a per-		allocate a block of time stamps each time it is called, and a
	process generator can allocate from that block until it is exhausted.		per-process generator can allocate from that block until it is
			exhausted.
	4.2.6 UUID Generation details		4.2.2 Generation details
	UUIDs are generated according to the following algorithm:		Version 1 UUIDs are generated according to the following algorithm:
	o Determine the values for the UTC-based timestamp and clock		o Determine the values for the UTC-based timestamp and clock
	sequence to be used in the UUID, as described above.		sequence to be used in the UUID, as described in Section 4.2.1.
	o For the purposes of this algorithm, consider the timestamp to be a		o For the purposes of this algorithm, consider the timestamp to be a
	60-bit unsigned integer and the clock sequence to be a 14-bit		60-bit unsigned integer and the clock sequence to be a 14-bit
	unsigned integer. Sequentially number the bits in a field,		unsigned integer. Sequentially number the bits in a field,
	starting from 0 (zero) for the least significant bit.		starting with zero for the least significant bit.
	o Set the time_low field equal to the least significant 32-bits		o Set the time_low field equal to the least significant 32 bits
	(bits numbered 0 to 31 inclusive) of the time stamp in the same		(bits zero through 31) of the time stamp in the same order of
	order of significance.		significance.
	o Set the time_mid field equal to the bits numbered 32 to 47		o Set the time_mid field equal to bits 32 through 47 from the time
	inclusive of the time stamp in the same order of significance.		stamp in the same order of significance.
	o Set the 12 least significant bits (bits numbered 0 to 11		o Set the 12 least significant bits (bits zero through 11) of the
	inclusive) of the time_hi_and_version field equal to the bits		time_hi_and_version field equal to bits 48 through 59 from the
	numbered 48 to 59 inclusive of the time stamp in the same order of		time stamp in the same order of significance.
	significance.
	o Set the 4 most significant bits (bits numbered 12 to 15 inclusive)		o Set the four most significant bits (bits 12 through 15) of the
	of the time_hi_and_version field to the 4-bit version number		time_hi_and_version field to the four-bit version number
	corresponding to the UUID version being created, as shown in the		corresponding to the UUID version being created, as shown in the
	table in section 3.1.3.		table above.
	o Set the clock_seq_low field to the 8 least significant bits (bits		o Set the clock_seq_low field to the eight least significant bits
	numbered 0 to 7 inclusive) of the clock sequence in the same order		(bits zero through seven) of the clock sequence in the same order
	of significance.		of significance.
	o Set the 6 least significant bits (bits numbered 0 to 5 inclusive)		o Set the six least significant bits (bits zero through five) of the
	of the clock_seq_hi_and_reserved field to the 6 most significant		clock_seq_hi_and_reserved field to the six most significant bits
	bits (bits numbered 8 to 13 inclusive) of the clock sequence in		(bits eight through 13) of the clock sequence in the same order of
	the same order of significance.		significance.
	o Set the 2 most significant bits (bits numbered 6 and 7) of the		o Set the two most significant bits (bits six and seven) of the
	clock_seq_hi_and_reserved to 0 and 1, respectively.		clock_seq_hi_and_reserved to zero and one, respectively.
	o Set the node field to the 48-bit IEEE address in the same order of		o Set the node field to the 48-bit IEEE address in the same order of
	significance as the address.		significance as the address.
	4.3 Algorithm for creating a name-based UUID		4.3 Algorithm for creating a name-based UUID
	The version 3 UUID is meant for generating UUIDs from "names" that		The version 3 UUID is meant for generating UUIDs from "names" that
	are drawn from, and unique within, some "name space". Some examples		are drawn from, and unique within, some "name space." The concept of
	of names (and, implicitly, name spaces) might be DNS names, URLs, ISO		name and name space should be broadly construed, and not limited to
	Object IDs (OIDs), reserved words in a programming language, or X.500		textual names. For example, some name spaces are the domain name
	Distinguished Names (DNs); thus, the concept of name and name space		system, URLs, ISO Object IDs (OIDs), X.500 Distinguished Names (DNs),
	should be broadly construed, and not limited to textual names. The		and reserved words in a programming language. The mechanisms or
	mechanisms or conventions for allocating names from, and ensuring		conventions for allocating names from, and ensuring their uniqueness
	their uniqueness within, their name spaces are beyond the scope of		within, their name spaces are beyond the scope of this specification.
	this specification.
	The requirements for such UUIDs are as follows:		The requirements for version 3 UUIDs are as follows:
	o The UUIDs generated at different times from the same name in the		o The UUIDs generated at different times from the same name in the
	same namespace MUST be equal		same namespace MUST be equal
	o The UUIDs generated from two different names in the same namespace		o The UUIDs generated from two different names in the same namespace
	should be different (with very high probability)		should be different (with very high probability)
	o The UUIDs generated from the same name in two different namespaces		o The UUIDs generated from the same name in two different namespaces
	should be different with (very high probability)		should be different with (very high probability)
	o If two UUIDs that were generated from names are equal, then they		o If two UUIDs that were generated from names are equal, then they
	were generated from the same name in the same namespace (with very		were generated from the same name in the same namespace (with very
	high probability).		high probability).
	The algorithm for generating the a UUID from a name and a name space		The algorithm for generating the a UUID from a name and a name space
	are as follows:		are as follows:
	o Allocate a UUID to use as a "name space ID" for all UUIDs		o Allocate a UUID to use as a "name space ID" for all UUIDs
	generated from names in that name space		generated from names in that name space; see Appendix C for some
			pre-defined values
	o Convert the name to a canonical sequence of octets (as defined by		o Convert the name to a canonical sequence of octets (as defined by
	the standards or conventions of its name space); put the name		the standards or conventions of its name space); put the name
	space ID in network byte order		space ID in network byte order
	o Compute the MD5 [3] hash of the name space ID concatenated with		o Compute the MD5 [3] hash of the name space ID concatenated with
	the name		the name
	o Set octets 0-3 of time_low field to octets 0-3 of the MD5 hash		o Set octets zero through three of the time_low field to octets zero
			through three of the MD5 hash
	o Set octets 0-1 of time_mid field to octets 4-5 of the MD5 hash		o Set octets zero and one of the time_mid field to octets four and
			five of the MD5 hash
	o Set octets 0-1 of time_hi_and_version field to octets 6-7 of the		o Set octets zero and one of the time_hi_and_version field to octets
	MD5 hash		six and seven of the MD5 hash
	o Set the clock_seq_hi_and_reserved field to octet 8 of the MD5 hash		o Set the four most significant bits (bits 12 through 15) of the
			time_hi_and_version field to the four-bit version number from
			Section 4.1.3.
	o Set the clock_seq_low field to octet 9 of the MD5 hash		o Set the clock_seq_hi_and_reserved field to octet eight of the MD5
			hash
	o Set octets 0-5 of the node field to octets 10-15 of the MD5 hash		o Set the two most significant bits (bits 6 and 7) of the
			clock_seq_hi_and_reserved to zero and one, respectively.
	o Set the 2 most significant bits (bits numbered 6 and 7) of the		o Set the clock_seq_low field to octet nine of the MD5 hash
	clock_seq_hi_and_reserved to 0 and 1, respectively.
	o Set the 4 most significant bits (bits numbered 12 to 15 inclusive)		o Set octets zero through five of the node field to octets then
	of the time_hi_and_version field to the 4-bit version number		through fifteen of the MD5 hash
	corresponding to the UUID version being created, as shown in the
	table above.
	o Convert the resulting UUID to local byte order.		o Convert the resulting UUID to local byte order.
	5. Algorithms for creating a UUID from truly random or pseudo-random		4.4 Algorithms for creating a UUID from truly random or pseudo-random
	numbers		numbers
	The version 4 UUID is meant for generating UUIDs from truly-random or		The version 4 UUID is meant for generating UUIDs from truly-random or
	pseudo-random numbers.		pseudo-random numbers.
	The algorithm is as follows:		The algorithm is as follows:
	o Set the 2 most significant bits (bits numbered 6 and 7) of the		o Set the two most significant bits (bits six and seven) of the
	clock_seq_hi_and_reserved to 0 and 1, respectively.		clock_seq_hi_and_reserved to zero and one, respectively.
	o Set the 4 most significant bits (bits numbered 12 to 15 inclusive)		o Set the four most significant bits (bits 12 through 15) of the
	of the time_hi_and_version field to the 4-bit version number		time_hi_and_version field to the four-bit version number from
	corresponding to the UUID version being created, as shown in the		Section 4.1.3.
	table above.
	o Set all the other bits to randomly (or pseudo-randomly) chosen		o Set all the other bits to randomly (or pseudo-randomly) chosen
	values.		values.
	Here are several possible ways to generate the random values:		See Section 4.5 for a discussion on random numbers.
	o Use a physical source of randomness: for example, a white noise
	generator, radioactive decay, or a lava lamp.
	o Use a cryptographic strength random number generator.
	6. Byte order of UUIDs
	UUIDs may be transmitted in many different forms, some of which may
	be dependent on the presentation or application protocol where the
	UUID may be used. In such cases, the order, sizes and byte orders of
	the UUIDs fields on the wire will depend on the relevant presentation
	or application protocol. However, it is strongly RECOMMENDED that
	the order of the fields conform with ordering set out in section 3.1
	above. Furthermore, the payload size of each field in the
	application or presentation protocol MUST be large enough that no
	information lost in the process of encoding them for transmission.
	In the absence of explicit application or presentation protocol
	specification to the contrary, a UUID is encoded as a 128-bit object,
	as follows: the fields are encoded as 16 octets, with the sizes and
	order of the fields defined in section 3.1, and with each field
	encoded with the Most Significant Byte first (also known as network
	byte order).
	0 1 2 3		4.5 Node IDs that do not identify the host
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| time_low |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| time_mid | time_hi_and_version |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|clk_seq_hi_res | clk_seq_low | node (0-1) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| node (2-5) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	7. Node IDs when no IEEE 802 network card is available		This section describes how to generate a version 1 UUID if an IEEE
			802 address is not available, or its use is not desired.
	If a system wants to generate UUIDs but has no IEE 802 compliant		One approach is to contact the IEEE and get a separate block of
	network card or other source of IEEE 802 addresses, then this section		addresses. At the time of writing, the application could be found at
	describes how to generate one.		[6], and the cost was US$550.
	The ideal solution is to obtain a 47 bit cryptographic quality random		A better solution is to obtain a 47-bit cryptographic quality random
	number, and use it as the low 47 bits of the node ID, with the most		number, and use it as the low 47 bits of the node ID, with the most
	significant bit of the first octet of the node ID set to 1. This bit		significant bit of the first octet of the node ID set to one. This
	is the unicast/multicast bit, which will never be set in IEEE 802		bit is the unicast/multicast bit, which will never be set in IEEE 802
	addresses obtained from network cards; hence, there can never be a		addresses obtained from network cards; hence, there can never be a
	conflict between UUIDs generated by machines with and without network		conflict between UUIDs generated by machines with and without network
	cards.		cards.
	If a system does not have a primitive to generate cryptographic		If a system does not have the capability to generate cryptographic
	quality random numbers, then in most systems there are usually a		quality random numbers, then in most systems there are usually a
	fairly large number of sources of randomness available from which one		fairly large number of sources of randomness available from which one
	can be generated. Such sources are system specific, but often		can be generated. Such sources are system specific, but often
	include:		include:
	o the percent of memory in use		o the percent of memory in use
	o the size of main memory in bytes		o the size of main memory in bytes
	o the amount of free main memory in bytes		o the amount of free main memory in bytes
	o the size of the paging or swap file in bytes		o the size of the paging or swap file in bytes
	skipping to change at page 18, line 4 ¶		skipping to change at page 16, line 22 ¶
	o the creation, last read, and modification times of files in		o the creation, last read, and modification times of files in
	various system directories		various system directories
	o the utilization factors of various system resources (heap, etc.)		o the utilization factors of various system resources (heap, etc.)
	o current mouse cursor position		o current mouse cursor position
	o current caret position		o current caret position
	o current number of running processes, threads		o current number of running processes, threads
	o handles or IDs of the desktop window and the active window		o handles or IDs of the desktop window and the active window
	o the value of stack pointer of the caller		o the value of stack pointer of the caller
	o the process and thread ID of caller		o the process and thread ID of caller
	o various processor architecture specific performance counters		o various processor architecture specific performance counters
	(instructions executed, cache misses, TLB misses)		(instructions executed, cache misses, TLB misses)
	(Note that it precisely the above kinds of sources of randomness that
	are used to seed cryptographic quality random number generators on
	systems without special hardware for their construction.)
	In addition, items such as the computer's name and the name of the		In addition, items such as the computer's name and the name of the
	operating system, while not strictly speaking random, will help		operating system, while not strictly speaking random, will help
	differentiate the results from those obtained by other systems.		differentiate the results from those obtained by other systems.
	The exact algorithm to generate a node ID using these data is system		The exact algorithm to generate a node ID using these data is system
	specific, because both the data available and the functions to obtain		specific, because both the data available and the functions to obtain
	them are often very system specific. However, assuming that one can		them are often very system specific. A generic approach, however is
	concatenate all the values from the randomness sources into a buffer,		to accumulate as many sources as possible into a buffer, and use a
	and that a cryptographic hash function such as MD5 [3] is available,		message digest such as MD5 [3], take an arbitrary six bytes from the
	then any 6 bytes of the MD5 hash of the buffer, with the multicast		hash value, and set the multicast bit as described above.
	bit (the high bit of the first byte) set will be an appropriately
	random node ID.
	Other hash functions, such as SHA-1 [5] , can also be used. The only		Other hash functions, such as SHA-1 [5], can also be used. The only
	requirement is that the result be suitably random _ in the sense that		requirement is that the result be suitably random in the sense that
	the outputs from a set uniformly distributed inputs are themselves		the outputs from a set uniformly distributed inputs are themselves
	uniformly distributed, and that a single bit change in the input can		uniformly distributed, and that a single bit change in the input can
	be expected to cause half of the output bits to change.		be expected to cause half of the output bits to change.
	8. Obtaining IEEE 802 addresses		5. Community Considerations
	At the time of writing, the following URL
	http://standards.ieee.org/regauth/oui/pilot-ind.html
	contains information on how to obtain an IEEE 802 address or
	"company_id" block. At the time of writing, the cost is $550 US.
	9. Community Considerations
	The use of UUIDs is extremely pervasive in computing. They comprise		The use of UUIDs is extremely pervasive in computing. They comprise
	the core identifier infrastructure for many operating systems		the core identifier infrastructure for many operating systems
	(Microsoft Windows) and applications (the Mozilla browser) and in		(Microsoft Windows) and applications (the Mozilla browser) and in
	many cases, become exposed to the web in many non-standard ways.		many cases, become exposed to the web in many non-standard ways. This
	This specification attempts to standardize that practice as openly as		specification attempts to standardize that practice as openly as
	possible and in a way that attempts to benefit the entire Internet.		possible and in a way that attempts to benefit the entire Internet.
	10. Security Considerations		6. Security Considerations
	It should not be assumed that UUIDs are hard to guess; they should		Do not assume that UUIDs are hard to guess; they should not be used
	not be used as capabilities. It should also not be assumed that it		as capabilities, for example.
	is easy to determine if a UUID has been slightly transposed in order
	to redirect a reference to another object. Humans do not have the
	ability to easily check the integrity of a UUID by simply glancing at
	it.
	11. Acknowledgements		Do not assume that it is easy to determine if a UUID has been
			slightly transposed in order to redirect a reference to another
			object. Humans do not have the ability to easily check the integrity
			of a UUID by simply glancing at it.
	Ninety-five percent of this document is original to Paul Leach and		7. Acknowledgments
	Rich Salz. The conversion to the format for registering a URN
	namespace was done by Michael Mealling who is indebted to them for
	providing a clear and extremely thorough document from which to
	start. The fact that their original document is still referenced
	even in draft form is a testament to a well done document that is
	timely and useful.
	This document draws heavily on the OSF DCE specification for UUIDs.		This document draws heavily on the OSF DCE specification for UUIDs.
	Ted Ts'o provided helpful comments, especially on the byte ordering		Ted Ts'o provided helpful comments, especially on the byte ordering
	section which we mostly plagiarized from a proposed wording he		section which we mostly plagiarized from a proposed wording he
	supplied (all errors in that section are our responsibility,		supplied (all errors in that section are our responsibility,
	however).		however).
	Normative References		Normative References
	[1] Zahn, L., Dineen, T. and P. Leach, "Network Computing		[1] Zahn, L., Dineen, T. and P. Leach, "Network Computing
	skipping to change at page 20, line 5 ¶		skipping to change at page 17, line 45 ¶
	[3] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April		[3] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
	1992.		1992.
	[4] Moats, R., "URN Syntax", RFC 2141, May 1997.		[4] Moats, R., "URN Syntax", RFC 2141, May 1997.
	[5] National Institute of Standards and Technology, "Secure Hash		[5] National Institute of Standards and Technology, "Secure Hash
	Standard", FIPS PUB 180-1, April 1995, <http://www.itl.nist.gov/		Standard", FIPS PUB 180-1, April 1995, <http://www.itl.nist.gov/
	fipspubs/fip180-1.htm>.		fipspubs/fip180-1.htm>.
	Authors' Addresses		[6] <http://standards.ieee.org/regauth/oui/pilot-ind.html>
	Michael Mealling
	VeriSign, Inc.
	21345 Ridgetop Circle
	Dulles, VA 21345
	US
	Phone: +1 770-717-0732		Authors' Addresses
	EMail: michael@neonym.net
	URI: http://www.verisignlabs.com
	Paul J. Leach		Paul J. Leach
	Microsoft		Microsoft
	1 Microsoft Way		1 Microsoft Way
	Redmond, WA 98052		Redmond, WA 98052
	US		US
	Phone: +1 425-882-8080		Phone: +1 425-882-8080
	EMail: paulle@microsoft.com		EMail: paulle@microsoft.com
			Michael Mealling
			VeriSign, Inc.
			21345 Ridgetop Circle
			Dulles, VA 21345
			US
			Phone: +1 678-581-9656
			URI: http://www.verisignlabs.com
	Rich Salz		Rich Salz
	Datapower Technology, Inc.		DataPower Technology, Inc.
	1 Alewife Center		1 Alewife Center
	Cambridge, MA 02142		Cambridge, MA 02142
	US		US
	Phone: +1 617-864-0455		Phone: +1 617-864-0455
	EMail: rsalz@datapower.com		EMail: rsalz@datapower.com
	URI: http://www.datapower.com		URI: http://www.datapower.com
	Appendix A. Appendix A - UUID Sample Implementation		Appendix A. Appendix A - Sample Implementation
	This implementation consists of 5 files: uuid.h, uuid.c, sysdep.h,		This implementation consists of 5 files: uuid.h, uuid.c, sysdep.h,
	sysdep.c and utest.c. The uuid.* files are the system independent		sysdep.c and utest.c. The uuid.* files are the system independent
	implementation of the UUID generation algorithms described above,		implementation of the UUID generation algorithms described above,
	with all the optimizations described above except efficient state		with all the optimizations described above except efficient state
	sharing across processes included. The code has been tested on Linux		sharing across processes included. The code has been tested on Linux
	(Red Hat 4.0) with GCC (2.7.2), and Windows NT 4.0 with VC++ 5.0.		(Red Hat 4.0) with GCC (2.7.2), and Windows NT 4.0 with VC++ 5.0. The
	The code assumes 64 bit integer support, which makes it a lot		code assumes 64-bit integer support, which makes it a lot clearer.
	clearer.
	All the following source files should be considered to have the		All the following source files should be considered to have the
	following copyright notice included:		following copyright notice included:
	copyrt.h		copyrt.h
	/*		/*
	** Copyright (c) 1990- 1993, 1996 Open Software Foundation, Inc.		** Copyright (c) 1990- 1993, 1996 Open Software Foundation, Inc.
	** Copyright (c) 1989 by Hewlett-Packard Company, Palo Alto, Ca. &		** Copyright (c) 1989 by Hewlett-Packard Company, Palo Alto, Ca. &
	** Digital Equipment Corporation, Maynard, Mass.		** Digital Equipment Corporation, Maynard, Mass.
	** Copyright (c) 1998 Microsoft.		** Copyright (c) 1998 Microsoft.
	** To anyone who acknowledges that this file is provided "AS IS"		** To anyone who acknowledges that this file is provided "AS IS"
	** without any express or implied warranty: permission to use, copy,		** without any express or implied warranty: permission to use, copy,
	** modify, and distribute this file for any purpose is hereby		** modify, and distribute this file for any purpose is hereby
	** granted without fee, provided that the above copyright notices and		** granted without fee, provided that the above copyright notices and
	** this notice appears in all source code copies, and that none of		** this notice appears in all source code copies, and that none of
	** the names of Open Software Foundation, Inc., Hewlett-Packard		** the names of Open Software Foundation, Inc., Hewlett-Packard
	** Company, or Digital Equipment Corporation be used in advertising		** Company, or Digital Equipment Corporation be used in advertising
	** or publicity pertaining to distribution of the software without		** or publicity pertaining to distribution of the software without
	** specific, written prior permission. Neither Open Software		** specific, written prior permission. Neither Open Software
	** Foundation, Inc., Hewlett-Packard Company, Microsoft, nor Digital		** Foundation, Inc., Hewlett-Packard Company, Microsoft, nor Digital
	Equipment		** Equipment Corporation makes any representations about the
	** Corporation makes any representations about the suitability of		suitability
	** this software for any purpose.		** of this software for any purpose.
	*/		*/
	uuid.h		uuid.h
	#include "copyrt.h"		#include "copyrt.h"
	#undef uuid_t		#undef uuid_t
	typedef struct _uuid_t {		typedef struct {
	unsigned32 time_low;		unsigned32 time_low;
	unsigned16 time_mid;		unsigned16 time_mid;
	unsigned16 time_hi_and_version;		unsigned16 time_hi_and_version;
	unsigned8 clock_seq_hi_and_reserved;		unsigned8 clock_seq_hi_and_reserved;
	unsigned8 clock_seq_low;		unsigned8 clock_seq_low;
	byte node[6];		byte node[6];
	} uuid_t;		} uuid_t;
	/* uuid_create -- generate a UUID */		/* uuid_create -- generate a UUID */
	int uuid_create(uuid_t * uuid);		int uuid_create(uuid_t * uuid);
	/* uuid_create_from_name -- create a UUID using a "name"		/* uuid_create_from_name -- create a UUID using a "name"
	from a "name space" */		from a "name space" */
	void uuid_create_from_name(		void uuid_create_from_name(
	uuid_t * uuid, /* resulting UUID */		uuid_t *uuid, /* resulting UUID */
	uuid_t nsid, /* UUID to serve as context, so identical		uuid_t nsid, /* UUID of the namespace */
	names from different name spaces generate		void *name, /* the name from which to generate a UUID
	different UUIDs */		*/
	void * name, /* the name from which to generate a UUID */
	int namelen /* the length of the name */		int namelen /* the length of the name */
			);
	);		/* uuid_compare -- Compare two UUID's "lexically" and return
			-1 u1 is lexically before u2
	/* uuid_compare -- Compare two UUID's "lexically" and return		0 u1 is equal to u2
	-1 u1 is lexically before u2		1 u1 is lexically after u2
	0 u1 is equal to u2
	1 u1 is lexically after u2
	Note: lexical ordering is not temporal ordering!
	*/
	int uuid_compare(uuid_t *u1, uuid_t *u2);
	uuid.c		Note that lexical ordering is not temporal ordering!
			*/
			int uuid_compare(uuid_t *u1, uuid_t *u2);
	#include "copyrt.h"		uuid.c
	#include <string.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <time.h>
	#include "sysdep.h"
	#include "uuid.h"
	/* various forward declarations */		#include "copyrt.h"
	static int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,		#include <string.h>
	uuid_node_t * node);		#include <stdio.h>
	static void write_state(unsigned16 clockseq, uuid_time_t timestamp,		#include <stdlib.h>
	uuid_node_t node);		#include <time.h>
	static void format_uuid_v1(uuid_t * uuid, unsigned16 clockseq,		#include "sysdep.h"
	uuid_time_t timestamp, uuid_node_t node);		#include "uuid.h"
	static void format_uuid_v3(uuid_t * uuid, unsigned char hash[16]);
	static void get_current_time(uuid_time_t * timestamp);
	static unsigned16 true_random(void);
	/* uuid_create -- generator a UUID */		/* various forward declarations */
	int uuid_create(uuid_t * uuid) {		static int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,
	uuid_time_t timestamp, last_time;		uuid_node_t *node);
	unsigned16 clockseq;		static void write_state(unsigned16 clockseq, uuid_time_t timestamp,
	uuid_node_t node;		uuid_node_t node);
	uuid_node_t last_node;		static void format_uuid_v1(uuid_t *uuid, unsigned16 clockseq,
	int f;		uuid_time_t timestamp, uuid_node_t node);
			static void format_uuid_v3(uuid_t *uuid, unsigned char hash[16]);
			static void get_current_time(uuid_time_t *timestamp);
			static unsigned16 true_random(void);
	/* acquire system wide lock so we're alone */		/* uuid_create -- generator a UUID */
	LOCK;		int uuid_create(uuid_t *uuid)
			{
			uuid_time_t timestamp, last_time;
			unsigned16 clockseq;
			uuid_node_t node;
			uuid_node_t last_node;
			int f;
	/* get current time */		/* acquire system-wide lock so we're alone */
	get_current_time(&timestamp);		LOCK;
	/* get node ID */		/* get time, node ID, saved state from non-volatile storage */
	get_ieee_node_identifier(&node);		get_current_time(&timestamp);
	/* get saved state from NV storage */		get_ieee_node_identifier(&node);
	f = read_state(&clockseq, &last_time, &last_node);		f = read_state(&clockseq, &last_time, &last_node);
	/* if no NV state, or if clock went backwards, or node ID changed		/* if no NV state, or if clock went backwards, or node ID
	(e.g., net card swap) change clockseq */		changed
	if (!f || memcmp(&node, &last_node, sizeof(uuid_node_t)))		(e.g., new network card) change clockseq */
	clockseq = true_random();		if (!f || memcmp(&node, &last_node, sizeof node))
	else if (timestamp < last_time)		clockseq = true_random();
	clockseq++;		else if (timestamp < last_time)
			clockseq++;
	/* stuff fields into the UUID */		/* save the state for next time */
	format_uuid_v1(uuid, clockseq, timestamp, node);		write_state(clockseq, timestamp, node);
	/* save the state for next time */		UNLOCK;
	write_state(clockseq, timestamp, node);
	UNLOCK;		/* stuff fields into the UUID */
	return(1);		format_uuid_v1(uuid, clockseq, timestamp, node);
	};		return 1;
			}
	/* format_uuid_v1 -- make a UUID from the timestamp, clockseq,		/* format_uuid_v1 -- make a UUID from the timestamp, clockseq,
	and node ID */		and node ID */
	void format_uuid_v1(uuid_t * uuid, unsigned16 clock_seq, uuid_time_t		void format_uuid_v1(uuid_t* uuid, unsigned16 clock_seq,
	timestamp, uuid_node_t node) {		uuid_time_t timestamp, uuid_node_t node)
	/* Construct a version 1 uuid with the information we've gathered		{
	* plus a few constants. */		/* Construct a version 1 uuid with the information we've gathered
			plus a few constants. */
	uuid->time_low = (unsigned long)(timestamp & 0xFFFFFFFF);		uuid->time_low = (unsigned long)(timestamp & 0xFFFFFFFF);
	uuid->time_mid = (unsigned short)((timestamp >> 32) & 0xFFFF);		uuid->time_mid = (unsigned short)((timestamp >> 32) & 0xFFFF);
	uuid->time_hi_and_version = (unsigned short)((timestamp >> 48) &		uuid->time_hi_and_version =
	0x0FFF);		(unsigned short)((timestamp >> 48) & 0x0FFF);
	uuid->time_hi_and_version |= (1 << 12);		uuid->time_hi_and_version |= (1 << 12);
	uuid->clock_seq_low = clock_seq & 0xFF;		uuid->clock_seq_low = clock_seq & 0xFF;
	uuid->clock_seq_hi_and_reserved = (clock_seq & 0x3F00) >> 8;		uuid->clock_seq_hi_and_reserved = (clock_seq & 0x3F00) >> 8;
	uuid->clock_seq_hi_and_reserved |= 0x80;		uuid->clock_seq_hi_and_reserved |= 0x80;
	memcpy(&uuid->node, &node, sizeof uuid->node);		memcpy(&uuid->node, &node, sizeof uuid->node);
	};		}
	/* data type for UUID generator persistent state */		/* data type for UUID generator persistent state */
	typedef struct {		typedef struct {
	uuid_time_t ts; /* saved timestamp */		uuid_time_t ts; /* saved timestamp */
	uuid_node_t node; /* saved node ID */		uuid_node_t node; /* saved node ID */
	unsigned16 cs; /* saved clock sequence */		unsigned16 cs; /* saved clock sequence */
	} uuid_state;		} uuid_state;
	static uuid_state st;		static uuid_state st;
	/* read_state -- read UUID generator state from non-volatile store */		/* read_state -- read UUID generator state from non-volatile store */
	int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,		int read_state(unsigned16 *clockseq, uuid_time_t *timestamp,
	uuid_node_t *node) {		uuid_node_t *node)
	FILE * fd;		{
	static int inited = 0;		static int inited = 0;
			FILE *fp;
	/* only need to read state once per boot */		/* only need to read state once per boot */
	if (!inited) {		if (!inited) {
	fd = fopen("state", "rb");		fp = fopen("state", "rb");
	if (!fd)		if (fp == NULL)
	return (0);		return 0;
	fread(&st, sizeof(uuid_state), 1, fd);		fread(&st, sizeof st, 1, fp);
	fclose(fd);		fclose(fp);
	inited = 1;		inited = 1;
	};		}
	*clockseq = st.cs;		*clockseq = st.cs;
	*timestamp = st.ts;		*timestamp = st.ts;
	*node = st.node;		*node = st.node;
	return(1);		return 1;
	};		}
	/* write_state -- save UUID generator state back to non-volatile		/* write_state -- save UUID generator state back to non-volatile
	storage */		storage */
	void write_state(unsigned16 clockseq, uuid_time_t timestamp,		void write_state(unsigned16 clockseq, uuid_time_t timestamp,
	uuid_node_t node) {		uuid_node_t node)
	FILE * fd;		{
	static int inited = 0;		static int inited = 0;
	static uuid_time_t next_save;		static uuid_time_t next_save;
			FILE* fp;
	if (!inited) {		if (!inited) {
	next_save = timestamp;		next_save = timestamp;
	inited = 1;		inited = 1;
	};		}
	/* always save state to volatile shared state */		/* always save state to volatile shared state */
	st.cs = clockseq;		st.cs = clockseq;
	st.ts = timestamp;		st.ts = timestamp;
	st.node = node;		st.node = node;
	if (timestamp >= next_save) {		if (timestamp >= next_save) {
	fd = fopen("state", "wb");		fp = fopen("state", "wb");
	fwrite(&st, sizeof(uuid_state), 1, fd);		fwrite(&st, sizeof st, 1, fp);
	fclose(fd);		fclose(fp);
	/* schedule next save for 10 seconds from now */		/* schedule next save for 10 seconds from now */
	next_save = timestamp + (10 * 10 * 1000 * 1000);		next_save = timestamp + (10 * 10 * 1000 * 1000);
	};		}
	};		}
	/* get-current_time -- get time as 60 bit 100ns ticks since whenever.
	Compensate for the fact that real clock resolution is
	less than 100ns. */
	void get_current_time(uuid_time_t * timestamp) {
	uuid_time_t time_now;
	static uuid_time_t time_last;
	static unsigned16 uuids_this_tick;
	static int inited = 0;
			/* get-current_time -- get time as 60-bit 100ns ticks since UUID
			epoch.
			Compensate for the fact that real clock resolution is
			less than 100ns. */
			void get_current_time(uuid_time_t *timestamp)
			{
			static int inited = 0;
			static uuid_time_t time_last;
			static unsigned16 uuids_this_tick;
			uuid_time_t time_now;
	if (!inited) {		if (!inited) {
	get_system_time(&time_now);		get_system_time(&time_now);
	uuids_this_tick = UUIDS_PER_TICK;		uuids_this_tick = UUIDS_PER_TICK;
	inited = 1;		inited = 1;
	};		}
	while (1) {		for ( ; ; ) {
	get_system_time(&time_now);		get_system_time(&time_now);
	/* if clock reading changed since last UUID generated... */		/* if clock reading changed since last UUID generated, */
	if (time_last != time_now) {		if (time_last != time_now) {
	/* reset count of uuids gen'd with this clock reading */		/* reset count of uuids gen'd with this clock reading */
	uuids_this_tick = 0;		uuids_this_tick = 0;
	break;		break;
	};		}
	if (uuids_this_tick < UUIDS_PER_TICK) {		if (uuids_this_tick < UUIDS_PER_TICK) {
	uuids_this_tick++;		uuids_this_tick++;
	break;		break;
	};		}
	/* going too fast for our clock; spin */		/* going too fast for our clock; spin */
	};		}
	/* add the count of uuids to low order bits of the clock reading */		/* add the count of uuids to low order bits of the clock reading
			*/
	*timestamp = time_now + uuids_this_tick;		*timestamp = time_now + uuids_this_tick;
	};		}
	/* true_random -- generate a crypto-quality random number.		/* true_random -- generate a crypto-quality random number.
	This sample doesn't do that. */		**This sample doesn't do that.** */
	static unsigned16		static unsigned16 true_random(void)
	true_random(void)		{
	{
	static int inited = 0;		static int inited = 0;
	uuid_time_t time_now;		uuid_time_t time_now;
	if (!inited) {		if (!inited) {
	get_system_time(&time_now);		get_system_time(&time_now);
	time_now = time_now/UUIDS_PER_TICK;		time_now = time_now / UUIDS_PER_TICK;
	srand((unsigned int)(((time_now >> 32) ^ time_now)&0xffffffff));		srand((unsigned int)(((time_now >> 32) ^ time_now) &
			0xffffffff));
	inited = 1;		inited = 1;
	};		}
	return (rand());		return rand();
	}		}
	/* uuid_create_from_name -- create a UUID using a "name" from a "name
	space" */		/* uuid_create_from_name -- create a UUID using a "name" from a "name
	void uuid_create_from_name(		space" */
	uuid_t * uuid, /* resulting UUID */		void uuid_create_from_name(uuid_t *uuid, uuid_t nsid, void *name,
	uuid_t nsid, /* UUID to serve as context, so identical		int namelen)
	names from different name spaces generate		{
	different UUIDs */
	void * name, /* the name from which to generate a UUID */
	int namelen /* the length of the name */
	) {
	MD5_CTX c;		MD5_CTX c;
	unsigned char hash[16];		unsigned char hash[16];
	uuid_t net_nsid; /* context UUID in network byte order */		uuid_t net_nsid;
	/* put name space ID in network byte order so it hashes the same		/* put name space ID in network byte order so it hashes the same
	no matter what endian machine we're on */		no matter what endian machine we're on */
	net_nsid = nsid;		net_nsid = nsid;
	htonl(net_nsid.time_low);		htonl(net_nsid.time_low);
	htons(net_nsid.time_mid);		htons(net_nsid.time_mid);
	htons(net_nsid.time_hi_and_version);		htons(net_nsid.time_hi_and_version);
	MD5Init(&c);		MD5Init(&c);
	MD5Update(&c, &net_nsid, sizeof(uuid_t));		MD5Update(&c, &net_nsid, sizeof net_nsid);
	MD5Update(&c, name, namelen);		MD5Update(&c, name, namelen);
	MD5Final(hash, &c);		MD5Final(hash, &c);
	/* the hash is in network byte order at this point */		/* the hash is in network byte order at this point */
	format_uuid_v3(uuid, hash);		format_uuid_v3(uuid, hash);
	};		}
	/* format_uuid_v3 -- make a UUID from a (pseudo)random 128 bit number
	*/
	void format_uuid_v3(uuid_t * uuid, unsigned char hash[16]) {
	/* Construct a version 3 uuid with the (pseudo-)random number
	* plus a few constants. */
	memcpy(uuid, hash, sizeof(uuid_t));
			/* format_uuid_v3 -- make a UUID from a (pseudo)random 128-bit number
			*/
			void format_uuid_v3(uuid_t *uuid, unsigned char hash[16])
			{
	/* convert UUID to local byte order */		/* convert UUID to local byte order */
			memcpy(uuid, hash, sizeof *uuid);
	ntohl(uuid->time_low);		ntohl(uuid->time_low);
	ntohs(uuid->time_mid);		ntohs(uuid->time_mid);
	ntohs(uuid->time_hi_and_version);		ntohs(uuid->time_hi_and_version);
	/* put in the variant and version bits */		/* put in the variant and version bits */
	uuid->time_hi_and_version &= 0x0FFF;		uuid->time_hi_and_version &= 0x0FFF;
	uuid->time_hi_and_version |= (3 << 12);		uuid->time_hi_and_version |= (3 << 12);
	uuid->clock_seq_hi_and_reserved &= 0x3F;		uuid->clock_seq_hi_and_reserved &= 0x3F;
	uuid->clock_seq_hi_and_reserved |= 0x80;		uuid->clock_seq_hi_and_reserved |= 0x80;
			}
	};
	/* uuid_compare -- Compare two UUID's "lexically" and return		/* uuid_compare -- Compare two UUID's "lexically" and return */
	-1 u1 is lexically before u2		#define CHECK(f1, f2) if (f1 != f2) return f1 < f2 ? -1 : 1;
	0 u1 is equal to u2		int uuid_compare(uuid_t *u1, uuid_t *u2)
	1 u1 is lexically after u2		{
	Note: lexical ordering is not temporal ordering!
	*/
	int uuid_compare(uuid_t *u1, uuid_t *u2)
	{
	int i;		int i;
	#define CHECK(f1, f2) if (f1 != f2) return f1 < f2 ? -1 : 1;
	CHECK(u1->time_low, u2->time_low);		CHECK(u1->time_low, u2->time_low);
	CHECK(u1->time_mid, u2->time_mid);		CHECK(u1->time_mid, u2->time_mid);
	CHECK(u1->time_hi_and_version, u2->time_hi_and_version);		CHECK(u1->time_hi_and_version, u2->time_hi_and_version);
	CHECK(u1->clock_seq_hi_and_reserved, u2->clock_seq_hi_and_reserved);		CHECK(u1->clock_seq_hi_and_reserved,
			u2->clock_seq_hi_and_reserved);
	CHECK(u1->clock_seq_low, u2->clock_seq_low)		CHECK(u1->clock_seq_low, u2->clock_seq_low)
	for (i = 0; i < 6; i++) {		for (i = 0; i < 6; i++) {
	if (u1->node[i] < u2->node[i])		if (u1->node[i] < u2->node[i])
	return -1;		return -1;
	if (u1->node[i] > u2->node[i])		if (u1->node[i] > u2->node[i])
	return 1;		return 1;
	}		}
	return 0;		return 0;
	};		}
			#undef CHECK
	sysdep.h		sysdep.h
	#include "copyrt.h"		#include "copyrt.h"
	/* remove the following define if you aren't running WIN32 */		/* remove the following define if you aren't running WIN32 */
	#define WININC 0		#define WININC 0
	#ifdef WININC		#ifdef WININC
	#include <windows.h>		#include <windows.h>
	#else		#else
	#include <sys/types.h>		#include <sys/types.h>
	#include <sys/time.h>		#include <sys/time.h>
	#include <sys/sysinfo.h>		#include <sys/sysinfo.h>
	#endif		#endif
	/* change to point to where MD5 .h's live */		#include "global.h"
	/* get MD5 sample implementation from RFC 1321 */		/* change to point to where MD5 .h's live; RFC 1321 has sample
	#include "global.h"		implementation */
	#include "md5.h"		#include "md5.h"
	/* set the following to the number of 100ns ticks of the actual		/* set the following to the number of 100ns ticks of the actual
	resolution of		resolution of your system's clock */
	your system's clock */		#define UUIDS_PER_TICK 1024
	#define UUIDS_PER_TICK 1024
	/* Set the following to a call to acquire a system wide global lock		/* Set the following to a calls to get and release a global lock */
	*/		#define LOCK
	#define LOCK		#define UNLOCK
	#define UNLOCK
	typedef unsigned long unsigned32;		typedef unsigned long unsigned32;
	typedef unsigned short unsigned16;		typedef unsigned short unsigned16;
	typedef unsigned char unsigned8;		typedef unsigned char unsigned8;
	typedef unsigned char byte;		typedef unsigned char byte;
	/* Set this to what your compiler uses for 64 bit data type */		/* Set this to what your compiler uses for 64-bit data type */
	#ifdef WININC		#ifdef WININC
	#define unsigned64_t unsigned __int64		#define unsigned64_t unsigned __int64
	#define I64(C) C		#define I64(C) C
	#else		#else
	#define unsigned64_t unsigned long long		#define unsigned64_t unsigned long long
	#define I64(C) C##LL		#define I64(C) C##LL
	#endif		#endif
	typedef unsigned64_t uuid_time_t;		typedef unsigned64_t uuid_time_t;
	typedef struct {		typedef struct {
	char nodeID[6];		char nodeID[6];
	} uuid_node_t;		} uuid_node_t;
	void get_ieee_node_identifier(uuid_node_t *node);		void get_ieee_node_identifier(uuid_node_t *node);
	void get_system_time(uuid_time_t *uuid_time);		void get_system_time(uuid_time_t *uuid_time);
	void get_random_info(char seed[16]);		void get_random_info(char seed[16]);
	sysdep.c		sysdep.c
	#include "copyrt.h"		#include "copyrt.h"
	#include <stdio.h>		#include <stdio.h>
	#include "sysdep.h"		#include "sysdep.h"
	/* system dependent call to get IEEE node ID.		/* system dependent call to get IEEE node ID.
	This sample implementation generates a random node ID		This sample implementation generates a random node ID. */
	*/		void get_ieee_node_identifier(uuid_node_t *node)
	void get_ieee_node_identifier(uuid_node_t *node) {		{
	char seed[16];
	FILE * fd;
	static inited = 0;		static inited = 0;
	static uuid_node_t saved_node;		static uuid_node_t saved_node;
			char seed[16];
			FILE *fp;
	if (!inited) {		if (!inited) {
	fd = fopen("nodeid", "rb");		fp = fopen("nodeid", "rb");
	if (fd) {		if (fp) {
	fread(&saved_node, sizeof(uuid_node_t), 1, fd);		fread(&saved_node, sizeof saved_node, 1, fp);
	fclose(fd);		fclose(fp);
	}		}
	else {		else {
	get_random_info(seed);		get_random_info(seed);
	seed[0] |= 0x80;		seed[0] |= 0x80;
	memcpy(&saved_node, seed, sizeof(uuid_node_t));		memcpy(&saved_node, seed, sizeof saved_node);
	fd = fopen("nodeid", "wb");		fp = fopen("nodeid", "wb");
	if (fd) {		if (fp) {
	fwrite(&saved_node, sizeof(uuid_node_t), 1, fd);		fwrite(&saved_node, sizeof saved_node, 1, fp);
	fclose(fd);		fclose(fp);
	};		}
	};		}
	inited = 1;		inited = 1;
	};		}
	*node = saved_node;		*node = saved_node;
	};		}
			/* system dependent call to get the current system time. Returned as
	/* system dependent call to get the current system time.		100ns ticks since UUID epoch, but resolution may be less than
	Returned as 100ns ticks since Oct 15, 1582, but resolution may be		100ns. */
	less than 100ns.		#ifdef _WINDOWS_
	*/
	#ifdef _WINDOWS_
	void get_system_time(uuid_time_t *uuid_time) {		void get_system_time(uuid_time_t *uuid_time)
			{
	ULARGE_INTEGER time;		ULARGE_INTEGER time;
	GetSystemTimeAsFileTime((FILETIME *)&time);		/* NT keeps time in FILETIME format which is 100ns ticks since
			Jan 1, 1601. UUIDs use time in 100ns ticks since Oct 15, 1582.
	/* NT keeps time in FILETIME format which is 100ns ticks since
	Jan 1, 1601. UUIDs use time in 100ns ticks since Oct 15, 1582.
	The difference is 17 Days in Oct + 30 (Nov) + 31 (Dec)		The difference is 17 Days in Oct + 30 (Nov) + 31 (Dec)
	+ 18 years and 5 leap days.		+ 18 years and 5 leap days. */
	*/		GetSystemTimeAsFileTime((FILETIME *)&time);
			time.QuadPart +=
	time.QuadPart +=		(unsigned __int64) (1000*1000*10) // seconds
	(unsigned __int64) (1000*1000*10) // seconds		* (unsigned __int64) (60 * 60 * 24) // days
	* (unsigned __int64) (60 * 60 * 24) // days		* (unsigned __int64) (17+30+31+365*18+5); // # of days
	* (unsigned __int64) (17+30+31+365*18+5); // # of days
	*uuid_time = time.QuadPart;		*uuid_time = time.QuadPart;
			}
	};		void get_random_info(char seed[16])
	void get_random_info(char seed[16]) {		{
	MD5_CTX c;		MD5_CTX c;
	typedef struct {		struct {
	MEMORYSTATUS m;		MEMORYSTATUS m;
	SYSTEM_INFO s;		SYSTEM_INFO s;
	FILETIME t;		FILETIME t;
	LARGE_INTEGER pc;		LARGE_INTEGER pc;
	DWORD tc;		DWORD tc;
	DWORD l;		DWORD l;
	char hostname[MAX_COMPUTERNAME_LENGTH + 1];		char hostname[MAX_COMPUTERNAME_LENGTH + 1];
	} randomness;		} r;
	randomness r;
	MD5Init(&c);		MD5Init(&c);
	/* memory usage stats */
	GlobalMemoryStatus(&r.m);		GlobalMemoryStatus(&r.m);
	/* random system stats */
	GetSystemInfo(&r.s);		GetSystemInfo(&r.s);
	/* 100ns resolution (nominally) time of day */
	GetSystemTimeAsFileTime(&r.t);		GetSystemTimeAsFileTime(&r.t);
	/* high resolution performance counter */
	QueryPerformanceCounter(&r.pc);		QueryPerformanceCounter(&r.pc);
	/* milliseconds since last boot */
	r.tc = GetTickCount();		r.tc = GetTickCount();
	r.l = MAX_COMPUTERNAME_LENGTH + 1;		r.l = MAX_COMPUTERNAME_LENGTH + 1;
			GetComputerName(r.hostname, &r.l);
	GetComputerName(r.hostname, &r.l );		MD5Update(&c, &r, sizeof r);
	MD5Update(&c, &r, sizeof(randomness));
	MD5Final(seed, &c);		MD5Final(seed, &c);
	};		}
	#else
	void get_system_time(uuid_time_t *uuid_time)		#else
	{
	struct timeval tp;
	gettimeofday(&tp, (struct timezone *)0);		void get_system_time(uuid_time_t *uuid_time)
			{
			struct timeval tp;
	/* Offset between UUID formatted times and Unix formatted times.		gettimeofday(&tp, (struct timezone *)0);
	UUID UTC base time is October 15, 1582.
	Unix base time is January 1, 1970.
	*/
	*uuid_time = (tp.tv_sec * 10000000) + (tp.tv_usec * 10) +
	I64(0x01B21DD213814000);
	};
	void get_random_info(char seed[16]) {		/* Offset between UUID formatted times and Unix formatted times.
			UUID UTC base time is October 15, 1582.
			Unix base time is January 1, 1970.*/
			*uuid_time = (tp.tv_sec * 10000000) + (tp.tv_usec * 10)
			+ I64(0x01B21DD213814000);
			}
			void get_random_info(char seed[16])
			{
	MD5_CTX c;		MD5_CTX c;
	typedef struct {		struct {
	struct sysinfo s;		struct sysinfo s;
	struct timeval t;		struct timeval t;
	char hostname[257];		char hostname[257];
	} randomness;		} r;
	randomness r;
	MD5Init(&c);		MD5Init(&c);
	sysinfo(&r.s);		sysinfo(&r.s);
	gettimeofday(&r.t, (struct timezone *)0);		gettimeofday(&r.t, (struct timezone *)0);
	gethostname(r.hostname, 256);		gethostname(r.hostname, 256);
	MD5Update(&c, &r, sizeof(randomness));		MD5Update(&c, &r, sizeof r);
	MD5Final(seed, &c);		MD5Final(seed, &c);
	};		}
	#endif		#endif
	utest.c		utest.c
	#include "copyrt.h"		#include "copyrt.h"
	#include "sysdep.h"		#include "sysdep.h"
	#include <stdio.h>		#include <stdio.h>
	#include "uuid.h"		#include "uuid.h"
	uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */		uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */
	0x6ba7b810,		0x6ba7b810,
	0x9dad,		0x9dad,
	0x11d1,		0x11d1,
	0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8		0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
	};		};
	/* puid -- print a UUID */		/* puid -- print a UUID */
	void puid(uuid_t u);		void puid(uuid_t u)
			{
			int i;
	/* Simple driver for UUID generator */		printf("%8.8x-%4.4x-%4.4x-%2.2x%2.2x-", u.time_low, u.time_mid,
	void main(int argc, char **argv) {		u.time_hi_and_version, u.clock_seq_hi_and_reserved,
			u.clock_seq_low);
			for (i = 0; i < 6; i++)
			printf("%2.2x", u.node[i]);
			printf("\n");
			}
			/* Simple driver for UUID generator */
			void main(int argc, char **argv)
			{
	uuid_t u;		uuid_t u;
	int f;		int f;
	uuid_create(&u);		uuid_create(&u);
	printf("uuid_create() -> "); puid(u);		printf("uuid_create(): "); puid(u);
	f = uuid_compare(&u, &u);		f = uuid_compare(&u, &u);
	printf("uuid_compare(u,u): %d\n", f); /* should be 0 */		printf("uuid_compare(u,u): %d\n", f); /* should be 0 */
	f = uuid_compare(&u, &NameSpace_DNS);		f = uuid_compare(&u, &NameSpace_DNS);
	printf("uuid_compare(u, NameSpace_DNS): %d\n", f); /* s.b. 1 */		printf("uuid_compare(u, NameSpace_DNS): %d\n", f); /* s.b. 1 */
	f = uuid_compare(&NameSpace_DNS, &u);		f = uuid_compare(&NameSpace_DNS, &u);
	printf("uuid_compare(NameSpace_DNS, u): %d\n", f); /* s.b. -1 */		printf("uuid_compare(NameSpace_DNS, u): %d\n", f); /* s.b. -1 */
	uuid_create_from_name(&u, NameSpace_DNS, "www.widgets.com", 15);		uuid_create_from_name(&u, NameSpace_DNS, "www.widgets.com", 15);
	printf("uuid_create_from_name() -> "); puid(u);		printf("uuid_create_from_name(): "); puid(u);
	};		}
	void puid(uuid_t u) {
	int i;
	printf("%8.8x-%4.4x-%4.4x-%2.2x%2.2x-", u.time_low, u.time_mid,
	u.time_hi_and_version, u.clock_seq_hi_and_reserved,
	u.clock_seq_low);
	for (i = 0; i < 6; i++)
	printf("%2.2x", u.node[i]);
	printf("\n");
	};
	Appendix B. Appendix B - Sample output of utest		Appendix B. Appendix B - Sample output of utest
	uuid_create() -> 7d444840-9dc0-11d1-b245-5ffdce74fad2		uuid_create(): 7d444840-9dc0-11d1-b245-5ffdce74fad2
	uuid_compare(u,u): 0		uuid_compare(u,u): 0
	uuid_compare(u, NameSpace_DNS): 1		uuid_compare(u, NameSpace_DNS): 1
	uuid_compare(NameSpace_DNS, u): -1		uuid_compare(NameSpace_DNS, u): -1
	uuid_create_from_name() -> e902893a-9d22-3c7e-a7b8-d6e313b71d9f		uuid_create_from_name(): e902893a-9d22-3c7e-a7b8-d6e313b71d9f
	Appendix C. Appendix C - Some name space IDs		Appendix C. Appendix C - Some name space IDs
	This appendix lists the name space IDs for some potentially		This appendix lists the name space IDs for some potentially
	interesting name spaces, as initialized C structures and in the		interesting name spaces, as initialized C structures and in the
	string representation defined in section 3.5		string representation defined above.
	uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */
	0x6ba7b810,
	0x9dad,
	0x11d1,
	0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
	};
	uuid_t NameSpace_URL = { /* 6ba7b811-9dad-11d1-80b4-00c04fd430c8 */		/* Name string is a fully-qualified domain name */
	0x6ba7b811,		uuid_t NameSpace_DNS = { /* 6ba7b810-9dad-11d1-80b4-00c04fd430c8 */
	0x9dad,		0x6ba7b810,
	0x11d1,		0x9dad,
	0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8		0x11d1,
	};		0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
			};
	uuid_t NameSpace_OID = { /* 6ba7b812-9dad-11d1-80b4-00c04fd430c8 */		/* Name string is a URL */
	0x6ba7b812,		uuid_t NameSpace_URL = { /* 6ba7b811-9dad-11d1-80b4-00c04fd430c8 */
	0x9dad,		0x6ba7b811,
	0x11d1,		0x9dad,
	0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8		0x11d1,
	};		0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
			};
	uuid_t NameSpace_X500 = { /* 6ba7b814-9dad-11d1-80b4-00c04fd430c8 */		/* Name string is an ISO OID */
	0x6ba7b814,		uuid_t NameSpace_OID = { /* 6ba7b812-9dad-11d1-80b4-00c04fd430c8 */
	0x9dad,		0x6ba7b812,
	0x11d1,		0x9dad,
	0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8		0x11d1,
	};		0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
			};
			/* Name string is an X.500 DN (in DER or a text output format) */
			uuid_t NameSpace_X500 = { /* 6ba7b814-9dad-11d1-80b4-00c04fd430c8 */
			0x6ba7b814,
			0x9dad,
			0x11d1,
			0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8
			};
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End of changes. 260 change blocks.
	843 lines changed or deleted		781 lines changed or added
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