class Diff::LCS::Hunk

A Hunk is a group of Blocks which overlap because of the context surrounding each block. (So if we’re not using context, every hunk will contain one block.) Used in the diff program (bin/ldiff).

Attributes

flag_context [R]

Change the “start” and “end” fields to note that context should be added to this hunk. :attr_accessor: :flag_context

Public Class Methods

new (data_old, data_new, piece, flag_context, file_length_difference)

Create a hunk using references to both the old and new data, as well as the piece of data.

# File lib/diff/lcs/hunk.rb, line 14
def initialize(data_old, data_new, piece, flag_context, file_length_difference)
  # At first, a hunk will have just one Block in it
  @blocks = [Diff::LCS::Block.from_chunk(piece)]

  if @blocks[0].remove.empty? && @blocks[0].insert.empty?
    fail "Cannot build a hunk from #{piece.inspect}; has no add or remove actions"
  end

  @preferred_data_encoding = data_old.fetch(0) { data_new.fetch(0) { "" } }.encoding
  @newline = "\n".encode(@preferred_data_encoding)
  @missing_newline = "\\ No newline at end of file".encode(@preferred_data_encoding)

  @data_old = data_old
  @data_new = data_new
  @old_empty = data_old.empty? || (data_old.size == 1 && data_old[0].empty?)
  @new_empty = data_new.empty? || (data_new.size == 1 && data_new[0].empty?)

  before = after = file_length_difference
  after += @blocks[0].diff_size
  @file_length_difference = after # The caller must get this manually
  @max_diff_size = @blocks.map { |e| e.diff_size.abs }.max

  # Save the start and end of each array. If the array doesn't exist (e.g., we're only
  # adding items in this block), then figure out the line number based on the line
  # number of the other file and the current difference in file lengths.
  if @blocks[0].remove.empty?
    a1 = a2 = nil
  else
    a1 = @blocks[0].remove[0].position
    a2 = @blocks[0].remove[-1].position
  end

  if @blocks[0].insert.empty?
    b1 = b2 = nil
  else
    b1 = @blocks[0].insert[0].position
    b2 = @blocks[0].insert[-1].position
  end

  @start_old = a1 || (b1 - before)
  @start_new = b1 || (a1 + before)
  @end_old = a2 || (b2 - after)
  @end_new = b2 || (a2 + after)

  self.flag_context = flag_context
end

Public Instance Methods

diff (format, last = false)

Returns a diff string based on a format.

# File lib/diff/lcs/hunk.rb, line 112
def diff(format, last = false)
  case format
  when :old
    old_diff(last)
  when :unified
    unified_diff(last)
  when :context
    context_diff(last)
  else
    fail "Unknown diff format #{format}."
  end
end
merge (hunk)

Merges this hunk and the provided hunk together if they overlap. Returns a truthy value so that if there is no overlap, you can know the merge was skipped.

# File lib/diff/lcs/hunk.rb, line 95
def merge(hunk)
  return unless overlaps?(hunk)

  @start_old = hunk.start_old
  @start_new = hunk.start_new
  blocks.unshift(*hunk.blocks)
end
Also aliased as: unshift
overlaps? (hunk)

Determines whether there is an overlap between this hunk and the provided hunk. This will be true if the difference between the two hunks start or end positions is within one position of each other.

# File lib/diff/lcs/hunk.rb, line 107
def overlaps?(hunk)
  hunk && (((@start_old - hunk.end_old) <= 1) || ((@start_new - hunk.end_new) <= 1))
end