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Date: Thu, 07 Apr 2005 15:05:33 +1200
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Subject: Re: [PHP-DEV] Scheme identification in stream wrappers: (Partial)
	disambiguation?
From: packrat@nznet.gen.nz ("Morgan L. Owens")

If there's something that looks like a scheme (i.e., a well-formed 
sequence of
characters followed by ':'),
	see if it's registered;
	if it is,
		the appropriate wrapper should be used.
	Otherwise,
		on platforms where ':' has significance,
			try it again as a file path.
Otherwise, it fails due to an absent stream wrapper.

This limits problems to users who are trying to access a child directory 
of the
current path which happens to have the same name as a registered scheme. The
problems will consist of the stream failing because the URL it's 
receiving is
bogus. People in such a situation can use the file: scheme explicitly to
disambiguate (assuming they can't have a directory whose name starts with
a double slash!).

Alternately,
on problem platforms,
	if the string is ambiguous,
		see if it is well-formed as a file path.
		If it is,
			try it as such.
		If it's not, or it fails,
			see if it starts with a registered scheme name and if so,
				try that.

It would be easier to check if a string is a well-formed file path than 
it is to
check if it's a valid URL according to some arbitrary scheme (impossible in
general).

Assuming no-one tries to register a one-letter scheme, the Windows build 
can get
away with seeing if the "scheme" is only one letter long, and if it is, 
assume
that it's a drive letter.

I dunno; Windows users use '/' as the directory separator in file:// 
URLs, since
it's supposed to be up to the application to map a URL to the actual 
resource
('\' is frequently tolerated however) in whatever platform-specific 
manner is
appropriate; does the same hold for platforms that use ':' as the directory
separator in their file: URLs? Currently the standard for file URLs is still
RFC1738; this is supposed to be updated at some stage, however. It 
explicitly
gives the VMS example of mapping
      DISK$USER:[MY.NOTES]NOTE123456.TXT
on vms.host.edu to the URL
	file://vms.host.edu/disk$user/my/notes/note12345.txt
and noting that to refer to the local machine the host part can be either
'localhost' or the empty string.