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An outline of the \Rpackage{Ruuid} package and its required
functionality. A uuid 
is a 16 byte (128 bit) unsigned char. There is also a 36 byte string 
representation. As I read the spec neither is NULL terminated. I
propose representing a uuid in R as an S4 class. Instances have two
slots, \Rfunction{uuid} and \Rfunction{string}; both of which will be
length one character vectors. Each will contain a \Rfunction{CHAR} SXP
which will be NULL terminated.

The R interface will consist of four functions that mimic the
underlying C structure.

\begin{description}
\item[getuuid] Return one object of class \Rfunction{uuid}.
\item[str2uuid] Take a string and return the relevant uuid (as a
  length one character vector).
\item[uuid2str] Take a uuid and return a string.
\end{description}

Note that all three functions should probably be implemented using a
interface function. That is, R calls \verb+Ruuid_something+, that calls
the real C routine. This will allow us to share the second set of C
entry points with other libraries. It is very unlikely that much uuid
processing will happen at the R level, but it will happen at the C
level.

The windows interface is different from the Linux one.
There is an example at \url{http://www.codeproject.com/string/uniquestring.asp}
Here, rather than build Ts'o's library we should just link to the
built in one (\verb+rpcrt4.lib+).
This has (at least) one more function, \verb+UuidCreateSequential+
which we should probably provide and R interface for (for Unix just
make it the same as getuuid).

An interesting question is whether a uuid created under Windows (and
serialized via R's mechanism) will restore on Unix and will have the
same relationship between uuid and its string representation.
You might want to create two rda's (one with a Unix version and one
with a Windows version), then testing on any platform could be
designed to say whether string <-> uuid equality is preserved.


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