[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: SAX2: Interning names in namespaces
At 4:46 AM 2/5/00, Stefan Haustein wrote: >> >> PROPOSAL >> >> I suggest that parsers interns each name as a separate string in the >> namespace it belong to. This should guarantee that two equal names in the >> same namespace are identical, and that two equal names in different >> namespaces are unidentical. > >Sounds too complicated for broad acceptance [...] It is straight-forward to implement. Here is pseudo code for one possible implementation using hash tables: constant namespaces = make new hashtable with equality as test function internName (namestring, URI): namespace = namespaces.find(URI) if no namespace namespace = make new hashtable with equality as test namespaces.insert(URI, namespace) end if name = namespace.find(namestring) if no name name = namestring.copy namespace.insert(name, name) end if return name end function Parsers should of course be free to choose more complex implementations if they find it beneficial. A parser might for example avoid using hash tables but instead do the interning during reading time by navigating a structure based on each character read. > [...] and I must admit that I do not see the great benefit. One of several benefits is that it simplifies and speeds up determining whether two names are the same as defined by the namespace recommendation. If names are not interned, determining whether two names are the same involves testing both namespaces and names for equality. Two names are the same if: namespace1.equals(namespace2) && name1.equals(name2) If the names are interned globally, it only speeds up testing the two names while still requiring comparing the namespaces: namespace1.equals(namespace2) && name1 == name2 Given that names are interned in namespaces, one only have to test whether the two names are identical to determine whether the two names are the same: name1 == name2 Note that in the latter case, comparing namespaces are no longer required. This allows major simplifications of code as one no longer have to pass namespaces with names. -- Terje <terje@i...> | Media Design in*Progress Software for Mac Web Professionals at <http://www.in-progress.com> Take advantage of XML with Emile, the first XML editor for Mac!
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