== What I know about the _patchdiag.xref_ format

The [[_patchdiag.xref_ file /blog/solaris/EasierPatchManagement]] is the
patch index file used by various tools, Sun and otherwise, such as the
marvelous [[pca /Software/pca]]. Here's what I've worked out about its
format, much of which comes from reading [[pca]]'s source code.

Any line starting with a '_#_' is a comment. In practice, they seem to come
only at the start of the file and start with '_##_', but I wouldn't count on
that.

Each patch is one line, with fields separated by '_|_', and *appears*
to be ordered by increasing patch number, although I wouldn't count on
that. The fields are, in order:

|_. _id_	| patch ID, usually a six-digit number
| _rev_		| the patch's revision, usually a two-digit number
| _date_	| the issue date of the patch, as Mon/DD/YY.
| _rflag_	| '_R_' if the patch is a recommended patch
| _sflag_	| '_S_' if the patch is a security patch
| _oflag_	| '_O_' if the patch is obsolete
| _byflag_	| The first character is '_Y_' if this is a Y2K patch.
		  The second character is '_B_' if this is a bad patch.
| _os_		| applicable operating system version, or '_Unbundled_' for
		  just stuff.
| _archs_	| the machine architectures that the patch is for, plus
		  prerequisite patches.
| _pkgs_	| the packages that this patch affects/requires, plus
		  incompatible patches.
| _synopsis_	| Human readable (hopefully) patch synopsis.

The _os_ field also sometimes bundles the architecture in, so you will
see things like an OS of '((8_x86))' for Solaris 8 on x86, versus just
'_8_' for Solaris 8 SPARC.

The _archs_ and _pkgs_ fields contains subvalues; each subvalue ends
with a '_;_', even if it is the last (or the only) subvalue in the
field. (This helpfully mucks up pretty much any language's 'split'
function; you get to split and then throw away the last element.)

Any prerequisite patches are encoded in the _archs_ field, as _id-rev_
values. Incompatible patches are slapped into the _pkgs_ field in the
same format.

If a patch has been obsoleted by something, its _synopsis_ says so.
There are a number of slightly varied formats that this information
can be in.

The subvalues in the _pkgs_ field (apart from incompatible patches)
are in the format 'PKG:REV', with REV in the same form that
'_pkginfo -x_' produces it (more or less, it looks like).

The subvalues in the _archs_ field (apart from prerequisite patches)
may be an architecture name ('sparc' or 'i386'), '_all_', or
'<arch>.<model>' such as 'sparc.sun4u'. [[Pca /Software/pca]]'s
matching code accepts a patch if any of the subvalues match, and you'll
frequently see 'redundant' _archs_ values like 'sparc;sparc.sun4u;'.