class 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

blocks[R]
end_new[R]
end_old[R]
file_length_difference[R]
flag_context[RW]

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

start_new[R]
start_old[R]

Public Class Methods

new(data_old, data_new, piece, flag_context, file_length_difference) click to toggle source

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 16
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.new(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

  if String.method_defined?(:encoding)
    @preferred_data_encoding = data_old.fetch(0, data_new.fetch(0, '')).encoding
  end

  @data_old = data_old
  @data_new = data_new

  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 & 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) click to toggle source

Returns a diff string based on a format.

# File lib/diff/lcs/hunk.rb, line 116
def diff(format, last = false)
  case format
  when :old
    old_diff(last)
  when :unified
    unified_diff(last)
  when :context
    context_diff(last)
  when :ed
    self
  when :reverse_ed, :ed_finish
    ed_diff(format, last)
  else
    fail "Unknown diff format #{format}."
  end
end
merge(hunk) click to toggle source

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 98
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
missing_last_newline?(data) click to toggle source
# File lib/diff/lcs/hunk.rb, line 326
def missing_last_newline?(data)
  newline = encode("\n")

  if data[-2]
    data[-2].end_with?(newline) && !data[-1].end_with?(newline)
  elsif data[-1]
    !data[-1].end_with?(newline)
  else
    true
  end
end
overlaps?(hunk) click to toggle source

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 110
def overlaps?(hunk)
  hunk and (((@start_old - hunk.end_old) <= 1) or
            ((@start_new - hunk.end_new) <= 1))
end
unshift(hunk)
Alias for: merge

Private Instance Methods

context_diff(last = false) click to toggle source
# File lib/diff/lcs/hunk.rb, line 213
def context_diff(last = false)
  s = encode("***************\n")
  s << encode("*** #{context_range(:old, ',', last)} ****\n")
  r = context_range(:new, ',', last)

  if last
    old_missing_newline = missing_last_newline?(@data_old)
    new_missing_newline = missing_last_newline?(@data_new)
  end

  # Print out file 1 part for each block in context diff format if there
  # are any blocks that remove items
  lo, hi = @start_old, @end_old
  removes = @blocks.reject { |e| e.remove.empty? }

  unless removes.empty?
    outlist = @data_old[lo..hi].map { |e| String.new("#{encode('  ')}#{e.chomp}") }

    last_block = removes[-1]

    removes.each do |block|
      block.remove.each do |item|
        outlist[item.position - lo][0, 1] = encode(block.op) # - or !
      end

      if last && block == last_block && old_missing_newline
        outlist << encode('\\ No newline at end of file')
      end
    end

    s << outlist.join(encode("\n")) << encode("\n")
  end

  s << encode("--- #{r} ----\n")
  lo, hi = @start_new, @end_new
  inserts = @blocks.reject { |e| e.insert.empty? }

  unless inserts.empty?
    outlist = @data_new[lo..hi].map { |e| String.new("#{encode('  ')}#{e.chomp}") }

    last_block = inserts[-1]

    inserts.each do |block|
      block.insert.each do |item|
        outlist[item.position - lo][0, 1] = encode(block.op) # + or !
      end

      if last && block == last_block && new_missing_newline
        outlist << encode('\\ No newline at end of file')
      end
    end
    s << outlist.join(encode("\n"))
  end

  s
end
context_range(mode, op, last = false) click to toggle source

Generate a range of item numbers to print. Only print 1 number if the range has only one item in it. Otherwise, it’s ‘start,end’

# File lib/diff/lcs/hunk.rb, line 293
def context_range(mode, op, last = false)
  case mode
  when :old
    s, e = (@start_old + 1), (@end_old + 1)
  when :new
    s, e = (@start_new + 1), (@end_new + 1)
  end

  e -= 1 if last
  e = 1 if e.zero?

  s < e ? "#{s}#{op}#{e}" : e.to_s
end
ed_diff(format, _last = false) click to toggle source
# File lib/diff/lcs/hunk.rb, line 271
def ed_diff(format, _last = false)
  warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1

  s =
    if format == :reverse_ed
      encode("#{ED_DIFF_OP_ACTION[@blocks[0].op]}#{context_range(:old, ',')}\n")
    else
      encode("#{context_range(:old, ' ')}#{ED_DIFF_OP_ACTION[@blocks[0].op]}\n")
    end

  unless @blocks[0].insert.empty?
    @data_new[@start_new..@end_new].each do |e|
      s << e.chomp + encode("\n")
    end
    s << encode(".\n")
  end
  s
end
encode(literal, target_encoding = @preferred_data_encoding) click to toggle source
# File lib/diff/lcs/hunk.rb, line 339
def encode(literal, target_encoding = @preferred_data_encoding)
  literal.encode target_encoding
end
encode_as(string, *args) click to toggle source
# File lib/diff/lcs/hunk.rb, line 343
def encode_as(string, *args)
  args.map { |arg| arg.encode(string.encoding) }
end
old_diff(_last = false) click to toggle source

Note that an old diff can’t have any context. Therefore, we know that there’s only one block in the hunk.

# File lib/diff/lcs/hunk.rb, line 135
def old_diff(_last = false)
  warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1

  block = @blocks[0]

  # Calculate item number range. Old diff range is just like a context
  # diff range, except the ranges are on one line with the action between
  # them.
  s = encode("#{context_range(:old, ',')}#{OLD_DIFF_OP_ACTION[block.op]}#{context_range(:new, ',')}\n")
  # If removing anything, just print out all the remove lines in the hunk
  # which is just all the remove lines in the block.
  unless block.remove.empty?
    @data_old[@start_old..@end_old].each { |e| s << encode('< ') + e.chomp + encode("\n") }
  end

  s << encode("---\n") if block.op == '!'

  unless block.insert.empty?
    @data_new[@start_new..@end_new].each { |e| s << encode('> ') + e.chomp + encode("\n") }
  end

  s
end
unified_diff(last = false) click to toggle source
# File lib/diff/lcs/hunk.rb, line 160
def unified_diff(last = false)
  # Calculate item number range.
  s = encode("@@ -#{unified_range(:old, last)} +#{unified_range(:new, last)} @@\n")

  # Outlist starts containing the hunk of the old file. Removing an item
  # just means putting a '-' in front of it. Inserting an item requires
  # getting it from the new file and splicing it in. We splice in
  # +num_added+ items. Remove blocks use +num_added+ because splicing
  # changed the length of outlist.
  #
  # We remove +num_removed+ items. Insert blocks use +num_removed+
  # because their item numbers -- corresponding to positions in the NEW
  # file -- don't take removed items into account.
  lo, hi, num_added, num_removed = @start_old, @end_old, 0, 0

  outlist = @data_old[lo..hi].map { |e| String.new("#{encode(' ')}#{e.chomp}") }

  last_block = blocks[-1]

  if last
    old_missing_newline = missing_last_newline?(@data_old)
    new_missing_newline = missing_last_newline?(@data_new)
  end

  @blocks.each do |block|
    block.remove.each do |item|
      op     = item.action.to_s # -
      offset = item.position - lo + num_added
      outlist[offset][0, 1] = encode(op)
      num_removed += 1
    end

    if last && block == last_block && old_missing_newline && !new_missing_newline
      outlist << encode('\\ No newline at end of file')
      num_removed += 1
    end

    block.insert.each do |item|
      op     = item.action.to_s # +
      offset = item.position - @start_new + num_removed
      outlist[offset, 0] = encode(op) + @data_new[item.position].chomp
      num_added += 1
    end
  end

  outlist << encode('\\ No newline at end of file') if last && new_missing_newline

  s << outlist.join(encode("\n"))

  s
end
unified_range(mode, last) click to toggle source

Generate a range of item numbers to print for unified diff. Print number where block starts, followed by number of lines in the block (don’t print number of lines if it’s 1)

# File lib/diff/lcs/hunk.rb, line 311
def unified_range(mode, last)
  case mode
  when :old
    s, e = (@start_old + 1), (@end_old + 1)
  when :new
    s, e = (@start_new + 1), (@end_new + 1)
  end

  length = e - s + (last ? 0 : 1)

  first = length < 2 ? e : s # "strange, but correct"
  length <= 1 ? first.to_s : "#{first},#{length}"
end