##
##  OSSP uuid - Universally Unique Identifier
##  Copyright (c) 2004 Ralf S. Engelschall <rse@engelschall.com>
##  Copyright (c) 2004 The OSSP Project <http://www.ossp.org/>
##
##  This file is part of OSSP uuid, a library for the generation
##  of UUIDs which can found at http://www.ossp.org/pkg/lib/uuid/
##
##  Permission to use, copy, modify, and distribute this software for
##  any purpose with or without fee is hereby granted, provided that
##  the above copyright notice and this permission notice appear in all
##  copies.
##
##  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
##  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
##  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
##  IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
##  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
##  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
##  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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##  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
##  SUCH DAMAGE.
##
##  uuid.pod: manual page
##

=pod

=head1 NAME

B<OSSP uuid> - B<Universally Unique Identifier>

=head1 VERSION

OSSP uuid UUID_VERSION_STR

=head1 DESCRIPTION

B<OSSP uuid> is a ISO-C application programming interface (API) and
corresponding command line interface (CLI) for the generation of DCE
1.1 and ISO/IEC 11578:1996 compliant I<Universally Unique Identifier>
(UUID). It supports DCE 1.1 variant UUIDs of version 1 (time and node
based), version 3 (name based) and version 4 (random number based).

UUIDs are 128 bit numbers which are intended to have a high likelihood
of uniqueness over space and time and are computationally difficult
to guess. They are globally unique identifiers which can be locally
generated without contacting a global registration authority. UUIDs
are intended as unique identifiers for both mass tagging objects
with an extremely short lifetime and to reliably identifying very
persistent objects across a network.

This is the ISO-C application programming interface (API) of B<OSSP uuid>.

=head2 UUID Binary Representation

According to the DCE 1.1 and ISO/IEC 11578:1996 standards, a DCE 1.1
variant UUID is a 128 bit number defined out of 7 fields, each field a
multiple of an octet in size and stored in network byte order:

  0                   1                   2                   3
   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 0|                          time_low                             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 1|       time_mid                |         time_hi_and_version   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 2|clk_seq_hi_res |  clk_seq_low  |         node (0-1)            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 3|                         node (2-5)                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

An example of a UUID binary representation is the octet stream "C<0xEC
0xB9 0xF3 0x5F 0x44 0x2A 0x11 0xD8 0x8A 0x24 0x00 0x90 0x27 0x2F 0xF7
0x25>". The binary representation format is exactly what the B<OSSP uuid>
API functions B<uuid_pack>() and B<uuid_unpack>() deal with.

=head2 UUID ASCII String Representation

According to the DCE 1.1 and ISO/IEC 11578:1996 standards, a DCE
1.1 variant UUID is represented as an ASCII string consisting
of 8 hexadecimal digits followed by a hyphen, then three groups
of 4 hexadecimal digits each followed by a hyphen, then 12
hexadecimal digits. Formally, the string representation is defined by
the following grammar:

 uuid                   = <time_low> "-" <time_mid> "-"
                          <time_high_and_version> "-"
                          <clock_seq_and_reserved>
                          <clock_seq_low> "-" <node>
 time_low               = 4*<hex_octet>
 time_mid               = 2*<hex_octet>
 time_high_and_version  = 2*<hex_octet>
 clock_seq_and_reserved = <hex_octet>
 clock_seq_low          = <hex_octet>
 node                   = 6*<hex_octet>
 hex_octet              = <hex_digit> <hex_digit>
 hex_digit              = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"
                         |"a"|"b"|"c"|"d"|"e"|"f"
                         |"A"|"B"|"C"|"D"|"E"|"F"

An example of a UUID string representation is the ASCII string
"C<54531d28-402b-11d8-af12-0002a5094c23>". The string representation
format is exactly what the B<OSSP uuid> API functions B<uuid_parse>() and
B<uuid_format>() deal with.

=head2 UUID Variants and Versions

A UUID has a variant and version. The variant defines the layout of the
UUID. The version defines the content of the UUID. The UUID variant
supported in B<OSSP uuid> is the DCE 1.1 variant only. The DCE 1.1 UUID
variant versions supported in B<OSSP uuid> are version 1 (time and node
based), version 3 (name based) and version 4 (random data based).

=head2 UUID Uniqueness

Version 1 UUIDs are guaranteed to be unique through combinations of
hardware addresses, time stamps and random seeds. There is a reference
in the UUID to the hardware (MAC) address of the first network interface
card (NIC) on the host which generated the UUID -- this reference
is intended to ensure the UUID will be unique in space as the MAC
address of every network card is assigned by a single global authority
(IEEE) and is guaranteed to be unique. The next component in a UUID
is a timestamp which, as clock always (should) move forward, will
be unique in time. Just in case some part of the above goes wrong
(the hardware address cannot be determined or the clock moved steps
backward), there is a random clock sequence component placed into the
UUID as a "catch-all" for uniqueness.

Version 3 UUIDs are guaranteed to be inherently globally unique if the
combination of namespace and name used to generate them is unique.

Version 4 UUIDs are not guaranteed to be globally unique, because they
are generated out of locally gathered pseudo-random numbers only.
Nevertheless there is still a high likelihood of uniqueness over space
and time and that they are computationally difficult to guess.

=head2 Nil UUID

There is a special I<Nil> UUID consisting of all octets set to zero in
the binary representation. It can be used as a special UUID value which does
not conflict with real UUIDs.

=head1 APPLICATION PROGRAMMING INTERFACE

The ISO-C Application Programming Interface (API) of B<OSSP uuid>
consists of the following components.

=head2 CONSTANTS

The following constants are provided:

=over 4

=item B<UUID_LEN_BIN>, B<UUID_LEN_STR>

The number of octets of the UUID binary and string representations.
Notice that the lengths of the string representation does I<not> include
the necessary C<NUL> termination character.

=item B<UUID_VERSION1>, B<UUID_VERSION3>, B<UUID_VERSION4>, B<UUID_MCASTRND>

The I<mode> bits for use with B<uuid_generate>(). The
B<UUID_VERSION>I<N> specify which UUID version to generate. The
B<UUID_MCASTRND> forces the use of a random multi-cast MAC address
instead of the real physical MAC address in version 1 UUIDs.

=item B<UUID_RC_OK>, B<UUID_RC_ARG>, B<UUID_RC_MEM>, B<UUID_RC_SYS>, B<UUID_RC_INT>

The possible numerical return-codes of API functions.
Use B<uuid_error>() to translate them into string versions.

=back

=head2 FUNCTIONS

The following functions are provided:

=over 4

=item uuid_rc_t B<uuid_create>(uuid_t **I<uuid>);

Create a new UUID object and store a pointer to it in C<*>I<uuid>.
A UUID object consists of an internal representation of a UUID, the
internal PRNG and MD5 generator contexts, and cached MAC address and
timestamp information. The initial UUID is the I<Nil> UUID.

=item uuid_rc_t B<uuid_destroy>(uuid_t *I<uuid>);

Destroy UUID object I<uuid>.

=item uuid_rc_t B<uuid_nil>(uuid_t *I<uuid>);

Sets or resets the UUID in I<uuid> to the I<Nil> UUID.

=item uuid_rc_t B<uuid_isnil>(uuid_t *I<uuid>, int *I<result>);

Checks whether the UUID in I<uuid> is the I<Nil> UUID.
If this is the case, it returns I<true> in C<*>I<result>.
Else it returns I<false> in C<*>I<result>.

=item uuid_rc_t B<uuid_compare>(uuid_t *I<uuid>, uuid_t *I<uuid2>, int *I<result>);

Compares the order of the two UUIDs in I<uuid1> and I<uuid2>
and returns the result in C<*>I<result>: C<-1> if I<uuid1> is
smaller than I<uuid2>, C<0> if I<uuid1> is equal to I<uuid2>
and C<+1> if I<uuid1> is greater than I<uuid2>.

=item uuid_rc_t B<uuid_unpack>(uuid_t *I<uuid>, const void *I<buf>);

Imports the value of the UUID in I<uuid> by unpacking the binary
representation of length C<UUID_LEN_BIN> starting at I<buf>.

=item uuid_rc_t B<uuid_pack>(uuid_t *I<uuid>, void **I<buf>);

Exports the value of the UUID in I<uuid> by packing it into the
binary representation and storing it (with length C<UUID_LEN_BIN>)
at I<buf>. If I<buf> points to a C<NULL> pointer, a buffer of length
C<UUID_LEN_BIN> is allocated and stored into C<*>I<buf> first.

=item uuid_rc_t B<uuid_parse>(uuid_t  *I<uuid>, const char  *I<str>);

Imports the value of the UUID in I<uuid> by parsing the string
representation of length C<UUID_LEN_STR> starting at I<str>.

=item uuid_rc_t B<uuid_format>(uuid_t *I<uuid>, char **I<str>);

Exports the value of the UUID in I<uuid> by formatting it into the
C<NUL>-terminated string representation and storing it (with length
C<UUID_LEN_STR>+1) at I<str>. If I<str> points to a C<NULL> pointer,
a buffer of length C<UUID_LEN_STR>+1 is allocated and stored into
C<*>I<str> first.

=item uuid_rc_t B<uuid_generate>(uuid_t *I<uuid>, unsigned int I<mode>, ...);

Generates a new UUID in I<uuid> according to I<mode> and optional
arguments (dependent on I<mode>).

If I<mode> contains the C<UUID_VERSION1> bit, a DCE 1.1 variant UUID of
version 1 is generated. Then optionally the bit C<UUID_MCASTRND> forces
the use of random multi-cast MAC address instead of the real physical
MAC address (the default). The UUID is generated out of the 60-bit current
system time, a 12-bit clock sequence and the 48-bit MAC address.

If I<mode> contains the C<UUID_VERSION3> bit, a DCE 1.1 variant UUID
of version 3 is generated and two additional C<NUL>-terminated string
arguments of type "C<const char *>" are expected: first a namespace,
given as an internally pre-defined id (currently known are ids "C<DNS>",
"C<URL>", "C<OID>", and "C<X500>") or a UUID in string representation.
Second, a name string of arbitrary length. The UUID is generated out of
the 128-bit MD5 from the concatenated octet stream of namespace UUID and name
string.

If I<mode> contains the C<UUID_VERSION4> bit, a DCE 1.1 variant UUID
of version 4 is generated. The UUID is generated out of 128-bit random
data.

=item uuid_rc_t B<uuid_dump>(uuid_t *I<uuid>, char **I<str>);

FIXME

=item char *B<uuid_error>(uuid_rc_t I<rc>);

Returns a constant string representation corresponding to the
return-code I<rc> for use in displaying B<OSSP uuid> errors.

=back

=head1 SEE ALSO

See the following are references to more B<UUID> documentation and specifications:

=over 4

=item 

B<UUIDs and GUIDs>,
IETF Internet Draft (expired),
Paul J. Leach, Rich Salz,
February 1998, 27 pages,
http://www.opengroup.org/dce/info/draft-leach-uuids-guids-01.txt

=item 

B<DCE 1.1: Remote Procedure Call>,
appendix B<Universally Unique Identifier>,
Open Group Technical Standard
Document Number C706, August 1997, 737 pages,
(supersedes C309 DCE: Remote Procedure Call 8/1994,
which was basis for ISO/IEC 11578:1996 specification),
http://www.opengroup.org/publications/catalog/c706.htm 

=item 

B<Information technology -- Open Systems Interconnection (OSI) -- Remote Procedure Call (RPC)>,
ISO/IEC 11578:1996,
August 2001, 570 pages, (CHF 340,00),
http://www.iso.ch/cate/d2229.html

=item 

B<HTTP Extensions for Distributed Authoring (WebDAV)>,
section B<6.4.1 Node Field Generation Without the IEEE 802 Address>,
IETF RFC 2518,
February 1999, 94 pages,
http://www.ietf.org/rfc/rfc2518.txt

=item

B<A UUID URN Namespace>,
P. Leach, M. Mealling, R. Salz,
IETF Internet Draft draft-mealling-uuid-urn-01,
October 2003, 31 pages,
http://www.ietf.org/internet-drafts/draft-mealling-uuid-urn-01.txt

=item

B<DCE 1.1 compliant UUID functions>,
FreeBSD manual pages uuid(3) and uuidgen(2),
http://www.freebsd.org/cgi/man.cgi?query=uuid&manpath=FreeBSD+5.2-RELEASE

=back

=head1 HISTORY

B<OSSP uuid> was implemented in January 2004 by Ralf S. Engelschall
E<lt>rse@engelschall.comE<gt>. It was prompted by the use of UUIDs
in the B<OSSP as> and B<OpenPKG> projects. It is a clean room
implementation intended to be strictly standards compliant and maximum
portable.

=head1 SEE ALSO

uuid(1), uuid-config(1).

=cut