Re: Scheme identification in stream wrappers: (Partial) disambiguation?

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.