[wp-hackers] Accessing post content before it's split by page

[Mike Purvis]

Hi folks,

I'm new-ish to hacking WP, but I'm working on a plugin that needs to
be able to throw a 404. So I'm wondering if a) there's a global
mechanism for showing the default Wordpress error page, and b) how
late I can call it. Basically, is there any point before output starts
where I could run The Loop, check what I need to check, and then
rewind it for the real thing?

Obviously, I could do a simple one-off one within the plugin itself,
but it would be cleaner to tie into WP's one, as specified in the
theme.

Thanks,

Mike