SPCUUID: The rather complete UUID generation library

SPCUUID implements an API to generate RFC-4122 style UUIDs, which include 
the following UUID versions:

	1. the time based version (also uses a MAC address if found)
	2. not implemented/not described in RFC-4122
	3. name-based varsion which uses MD5 hashing
	4. a randomly generated UUID
	5. name-based version which uses SHA-1 hashing

This library also includes definitions for the following UUIDs (as
specificed in RFC-4122):

	1. DNS  UUID: 6ba7b810-9dad-11d1-80b4-00c04fd430c8
	2. URL  UUID: 6ba7b811-9dad-11d1-80b4-00c04fd430c8
	3. OID  UUID: 6ba7b812-9dad-11d1-80b4-00c04fd430c8
	4. X500 UUID: 6ba7b814-9dad-11d1-80b4-00c04fd430c8
	5. NULL UUID: 00000000-0000-0000-0000-000000000000

These are declared as:

	extern const uuid__t c_uuid_namespace_dns;
	extern const uuid__t c_uuid_namespace_url;
	extern const uuid__t c_uuid_namespace_oid;
	extern const uuid__t c_uuid_namespace_x500;
	extern const uuid__t c_uuid_null;

The following functions are defined:

	int uuidlib_cmp(const uuid__t *a,const uuid__t *b);

		This function compares two UUIDs and returns a negative
		value if a is less than b, 0 if a is equal to b, and a
		positive value if a is larger than b.  

	int uuidlib_parse(uuid__t *uuid,const char *text);

		This function will parse a text representation of a UUID. 
		It returns 0 on success, or an error suitable for use
		with strerror().

	int uuidlib_toa(const uuid__t *uuid,char *dest,size_t);

		This function will format a uuid__t for display purposes.
		It returns the number of characters written (36) on success,
		a negative value if there was an error.

	int uuidlib_v1(uuid__t *uuid,int clockseq);

		Generates a version 1 UUID, based off a MAC address and
		the current time.  If a MAC address cannot be found, a
		random MAC will be generated.  If clockseq is less than
		0, a random clock sequence value will be generated;
		otherwise, the value given will be used.

	int uuidlib_v2(uuid__t *uuid);

		Not implemented---returns ENOSYS.

	int uuidlib_v3(
		uuid__t       *uuid,
		const uuid__t *ns,
		const void    *data,
		const size_t   size
	);

		Generates a name-based UUID from the given UUID (ns) and
		data (data,size) using an MD5 hash.  Returns 0 if success.
		You must link to -lcrypto if you use this function.

	int uuidlib_v4(uuid__t *uuid);

		Generates a random UUID.  This function assumes that srand()
		has been called prior.  Returns 0 if success.

	int uuidlib_v5(
		uuid__t       *uuid,
		const uuid__t *ns,
		const void    *data,
		const size_t   size
	);
	
		Generates a name-based UUID from the given UUID (ns) and
		data (data,size) using an MD5 hash.  Returns 0 if success.
		You must link to -lcrypto if you use this function.

The Lua bindings:

	require "org.conman.uuid"

The predefined UUIDs are:

	org.conman.uuid.URL
	org.conman.uuid.DNS
	org.conman.uuid.X500
	org.conman.uuid.OID
	org.conman.uuid.NIL

Functions are:

	org.conman.uuid.parse(string)

		Parse a string into a UUID

	org.conman.uuid.breakout(uuid)

		Return a table with the UUID broken down into fields (only
		valid for a v1 UUID, but will break down any UUID)

	org.conman.uuid()

		Return a v4 UUID (random UUID)

	org.conman.uuid(n)

		Return a v1 UUID (MAC/time based UUID).  If n < 0, then
		the "clock sequence" portion of the UUID will be randomly
		generated; otherwise, the value of n is used.  n should
		increase with each call; if you really don't care manage
		this, passing in a -1 should be used.

	org.conman.uuid(uuid,string)
	
		Return a v5 UUID (SHA-1 name-based UUID)

	org.conman.uuid(uuid,string,true)

		Return a v3 UUID (MD5 name-based UUID)

UUIDs support the following metamethods:

	__tostring	- returns display format
	__eq		- compares two UUIDs
	__lt		- compares two UUIDs
	__le		- compares two UUIDs
	__len		- returns 16