source: XMLF90/src/xpath/Developer.Guide @ 6

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1Developer Notes for the XPATH-lite API
3This API is built on top of the more fundamental SAX one. The basic
4idea is to have a set of programable handlers that communicate among
5themselves and with the parser via module variables.
7A new pseudo-handler, "signal_handler", has been added to the optional
8argument list of xml_parse(). In the current implementation it just
9checks whether a stop signal has been raised by the user side of the
10program (for example, after a "begin tag" event, or after going out
11of the scope of a parent element).
13Since the SAX parser is stream-oriented, and XPATH searches can be
14done in any order, there are new routines to rewind the XML file and
15to synchronize the physical file reader with a previously saved point
16in the XML tree.
18These tools, and the rather sophisticated path-matching routine
19provided (which allows for wildcards and the "//" construction) would
20be enough for standard use, as implemented in the routine
21"get_node". However, there is also the possibility of performing
22searches constrained to a given ancestor element ("context" searches)
23so that blocks of logically related information can be processed
24together. A context is implicitly created by a call to
25"mark_node". Contexts can be saved and "synched" to, allowing for
26repeated constrained searches (calls with relative paths). Contexts
27can even be passed to subroutines to package the parsing of common
28elements once and for all. (See for example Examples/xpath/pseudo.f90).
29This feature is nevertheless in need of a more rigorous specification:
31* What should be the behavior if a "mark_node" is followed by a
32  call to "get_node" with an absolute path?
33* Should there always be an "automatic rewind" to the beginning of the
34  context before any successive calls to "get_node"?
39The pcdata buffer provided by the user as a character variable could
40overflow.  Note that the parser itself uses a string of length
41MAX_PCDATA_SIZE (currently 65536) as a buffer to hold PCDATA. A
42warning is issued if there is not enough space (in the user or in the
43system buffer) to hold the data.
45Support for converting PCDATA characters to numerical arrays "on the
46fly" is planned for a forthcoming version.
49The coding style is that of the F subset of Fortran90. I strongly
50believe that it makes for better coding and fewer errors.
51Go to and get a feel for it. You can
52download free implementations for Linux and Windows, or get an
53inexpensive CD+Book combination to help support the project. Of course,
54F *is* Fortran, so you can always compile it with a Fortran compiler.
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