Method: Diff::LCS.patch

Defined in:
lib/gems/diff-lcs-1.1.2/lib/diff/lcs.rb

.patch(src, patchset, direction = nil) ⇒ Object

Given a patchset, convert the current version to the new version. If direction is not specified (must be :patch or :unpatch), then discovery of the direction of the patch will be attempted.



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# File 'lib/gems/diff-lcs-1.1.2/lib/diff/lcs.rb', line 697

def patch(src, patchset, direction = nil)
  string = src.kind_of?(String)
    # Start with a new empty type of the source's class
  res = src.class.new

    # Normalize the patchset.
  patchset = __normalize_patchset(patchset)

  direction ||= Diff::LCS.__diff_direction(src, patchset)
  direction ||= :patch

  ai = bj = 0

  patchset.each do |change|
      # Both Change and ContextChange support #action
    action = PATCH_MAP[direction][change.action]

    case change
    when Diff::LCS::ContextChange
      case direction
      when :patch
        el = change.new_element
        op = change.old_position
        np = change.new_position
      when :unpatch
        el = change.old_element
        op = change.new_position
        np = change.old_position
      end

      case action
      when '-' # Remove details from the old string
        while ai < op
          res << (string ? src[ai, 1] : src[ai])
          ai += 1
          bj += 1
        end
        ai += 1
      when '+'
        while bj < np
          res << (string ? src[ai, 1] : src[ai])
          ai += 1
          bj += 1
        end

        res << el
        bj += 1
      when '='
          # This only appears in sdiff output with the SDiff callback.
          # Therefore, we only need to worry about dealing with a single
          # element.
        res << el

        ai += 1
        bj += 1
      when '!'
        while ai < op
          res << (string ? src[ai, 1] : src[ai])
          ai += 1
          bj += 1
        end

        bj += 1
        ai += 1

        res << el
      end
    when Diff::LCS::Change
      case action
      when '-'
        while ai < change.position
          res << (string ? src[ai, 1] : src[ai])
          ai += 1
          bj += 1
        end
        ai += 1
      when '+'
        while bj < change.position
          res << (string ? src[ai, 1] : src[ai])
          ai += 1
          bj += 1
        end

        bj += 1

        res << change.element
      end
    end
  end

  while ai < src.size
    res << (string ? src[ai, 1] : src[ai])
    ai += 1
    bj += 1
  end

  res
end