[Alephmodular-devel] Fleshing out file types...

[Br'fin <br...@ma...>]

After getting initial iostreams working for files I decided to handle 
file types and creator codes before working on FileDescs proper. As I 
get my head around the creator codes better and write up the classes I 
thought I would revamp that portion of my file document.

-Jeremy Parsons


CFileType represents the type of a file
CFileSystemDesc is our friend and can use the protected virtual methods 
for getting type_code, type_extension and the type checking.

There are three special cases of CFileType
	CDirectoryType
		a plain old directories
		(a directory that was a bundle would be handled seperately)
	CUnknownType
		If we examine a CFileSystemDesc and it matches no known types,
		then CUnknownType is the tye used for the file
	CFamilyType
		A hierarchy of types for checking a file's type against. For
		instance, checking if a given specific type is a map or a M2 file.
		CCreatorFamilyType is a subset of the family type which also knows
		its creator code.

All others descend from CTypedFileType which has basic operations
A file type generally encapsulates the following:
	The file's creator: ala M2, Minf, or AlephModular)
	The four character code associated with a file on MAcintosh: aka TEXT
	The extension associated with the file on other systems: aka txt (as 
in README.txt)
	a test() method for checking whether or not a CFileSystemDesc matches 
the current type
	a test_contents() method for checking within a file for a type match

Testing CDirectoryType against file decriptions only matches type with 
directories
Testing CUnknownType against file descriptions is always false. It is 
only assigned when either nothing is known, or everything else fails to 
match.
Testing CFamilyType against file descriptions always fails.
Testing CTypedFileTypes against a file succeeds if type and creator 
match or if the extension matches. Subclasses may perform more 
complicated tests, such as inspecting the file's contents (by 
implementing test_contents(FileDesc*))

test_contents() is seperate from test() so that if a first pass by 
inspecting via test fails to locate a file's type, then that file can 
be checked over the available types by performing the content tests of 
the types.

FileTypes support a matches(FileType) method to tell if the type who's 
matching method is being called considers itself to be the type of the 
argument, or a logical element of that type's set.

	CMarathon2MapType.matches(CAlephModularMapType) == false
	CMarathon2MapType.matches(CMarathon2MapType) == true
	CMarathon2MapType.matches(CMapFamily) == true
	CMarathon2MapType.matches(CMarathon2Family) == true

	
I admit, on typing I'm trying to figure out if the class is 
C<whatever>Type and is essentially a singleton. What is a decent way of 
referring to one specific type or another?

A CFileTypeFactory that offers GetTypeFor("<whatever>") with a hash or 
dictionary within?