| Overview |  |
Copyright © 2024 Fred Youhanaie
Version: 0.2.0
Authors: Fred Youhanaie (fyrlang@anydata.co.uk).
gen_xml is an Erlang behaviour module for processing eXtensible
Markup Language (XML) files.
To start the process of parsing the XML file, an application should
call the read/3 function. While read/3 is scanning the XML file
it will call the appropriate handler functions in the supplied
callback module.
read/3 can process plain and compressed files.
The callback module should export three functions for processing the individual XML elements:
handle_begin(Tag, Attr, State), is called whenever a new tag
is encountered. It takes three arguments: Tag is an atom
corresponding to the element tag, Attrs is the list of
attributes from the startElement event, see xmerl_sax_parser
for further details. If required, the attributes can be converted
to a map of attribute name/value pairs using the
gen_xml:attr_map/1 function.
State, is explained below.
handle_end(Tag, State) corresponds to the endElement event,
which signals the </Tag> element. It can be used to finish off
any outstanding work for this element.
handle_text(Text, State) corresponds to the characters
event, which is the text within an element.
Associated with each callback module is a state variable maintained
by the gen_xml:read/3 function, and is initialized to the value
supplied to it during the call. The current contents of the state
variable is passed to the handler functions, which should return it,
optionally updated, for the future calls to the handlers.
The structure of the state variable is entirely dependent on the
callback module, for example the genxml_counter module will
maintain a map where the keys are the XML element tags and the
values are the cumulative counts of the corresponding tags.
Once read/3 has concluded processing the file, the final contents of the
state variable is returned to the caller.
A number of sample callback modules have been provided in the Examples/
directory of the git repo.
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