Class: Contrast::Agent::Assess::Policy::Propagator::Next

Inherits:
Base
  • Object
show all
Defined in:
lib/contrast/agent/assess/policy/propagator/next.rb

Overview

Propagation that results in all the tags of the source being applied to the target. In those cases where overflow occurred, the overflow is tagged the same as the character which preceded it. The target’s preexisting tags are shifted to account for this.

Class Method Summary collapse

Methods inherited from Base

find_source, tracked_value?

Class Method Details

.propagate(propagation_node, preshift, target) ⇒ Object

String has some silly methods like next. Basically, this flips a character in a predictable manner



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# File 'lib/contrast/agent/assess/policy/propagator/next.rb', line 17

def propagate propagation_node, preshift, target
  return unless (properties = Contrast::Agent::Assess::Tracker.properties!(target))

  source = find_source(propagation_node.sources[0], preshift)
  properties.copy_from(source, target, 0, propagation_node.untags)

  # this means the char that was shifted overflowed and created new
  # chars (i.e 'z' "wraps" to create 'aa' )
  unless target.length == source.length
    properties.copy_from(source, target, 0, propagation_node.untags)

    first_difference = (0...source.length).find { |i| source[i] != target[i] } || source.length

    properties.tags_at(first_difference).each do |tag|
      tag.shift_end(target.length - source.length)
    end
  end

  properties.cleanup_tags
end