lib/sax/helpers/sax_locator_impl.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # This file is free software, which comes along with NIT. This software is
   4 # distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
   5 # without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
   6 # PARTICULAR PURPOSE. You can modify it is you want, provided this header
   7 # is kept unaltered, and a notification of the changes is added.
   8 # You are allowed to redistribute it and sell it, alone or is a part of
   9 # another product.
  10
  11 # Provides an optional convenience implementation of `Locator`.
  12 module sax::helpers::sax_locator_impl
  13
  14 import sax::sax_locator
  15
  16 # Provides an optional convenience implementation of `Locator`.
  17 #
  18 # This class is available mainly for application writers, who
  19 # can use it to make a persistent snapshot of a locator at any
  20 # point during a document parse:
  21 #
  22 # ~~~nitish
  23 # import sax::helpers::sax_locator_impl
  24 # import sax::content_handler
  25 #
  26 # class Example super ContentHandler
  27 #     private var locator: SAXLocator
  28 #     private var start_loc: nullable SAXLocator = null
  29 #
  30 #     redef fun start_document do
  31 #         # save the location of the start of the document
  32 #         # for future use.
  33 #         start_loc = new SAXLocatorImpl.from(locator)
  34 #     end
  35 # end
  36 # ~~~
  37 #
  38 # Normally, parser writers will not use this class, since it
  39 # is more efficient to provide location information only when
  40 # requested, rather than constantly updating a `Locator` object.
  41 #
  42 # Note: The original source code and documentation of this class comes, in part,
  43 # from [SAX 2.0](http://www.saxproject.org).
  44 class SAXLocatorImpl super SAXLocator
  45         redef var public_id = null is writable
  46         redef var system_id = null is writable
  47         redef var line_number = -1 is writable
  48         redef var column_number = -1 is writable
  49
  50         # Zero-argument constructor.
  51         #
  52         # This will not normally be useful, since the main purpose
  53         # of this class is to make a snapshot of an existing Locator.
  54         init do
  55         end
  56
  57         # Copy constructor.
  58         #
  59         # Create a persistent copy of the current state of a locator.
  60         # When the original locator changes, this copy will still keep
  61         # the original values (and it can be used outside the scope of
  62         # `ContentHandler` methods).
  63         #
  64         # Parameters:
  65         #
  66         # * `locator`: locator to copy.
  67         init from(locator: SAXLocator) do
  68                 public_id = locator.public_id
  69                 system_id = locator.system_id
  70                 line_number = locator.line_number
  71                 column_number = locator.column_number
  72         end
  73 end