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/diff).

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 10
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 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

  # 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) click to toggle source

Returns a diff string based on a format.

# File lib/diff/lcs/hunk.rb, line 97
def diff(format)
  case format
  when :old
    old_diff
  when :unified
    unified_diff
  when :context
    context_diff
  when :ed
    self
  when :reverse_ed, :ed_finish
    ed_diff(format)
  else
    raise "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 77
def merge(hunk)
  if overlaps?(hunk)
    @start_old = hunk.start_old
    @start_new = hunk.start_new
    blocks.unshift(*hunk.blocks)
  else
    nil
  end
end
Also aliased as: unshift
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 91
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() click to toggle source
# File lib/diff/lcs/hunk.rb, line 171
def context_diff
  s = encode("***************\n")
  s << encode("*** #{context_range(:old)} ****\n")
  r = context_range(:new)

  # 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.select { |e| not e.remove.empty? }
  if removes
    outlist = @data_old[lo .. hi].map { |e| e.insert(0, encode(' ')) }

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

  s << encode("\n--- #{r} ----\n")
  lo, hi = @start_new, @end_new
  inserts = @blocks.select { |e| not e.insert.empty? }
  if inserts
    outlist = @data_new[lo .. hi].collect { |e| e.insert(0, encode(' ')) }
    inserts.each do |block|
      block.insert.each do |item|
        outlist[item.position - lo][0, 1] = encode(block.op) # + or !
      end
    end
    s << outlist.join("\n")
  end
  s
end
context_range(mode, op = ',') 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 227
def context_range(mode, op = ',')
  case mode
  when :old
    s, e = (@start_old + 1), (@end_old + 1)
  when :new
    s, e = (@start_new + 1), (@end_new + 1)
  end

  (s < e) ? "#{s}#{op}#{e}" : "#{e}"
end
ed_diff(format) click to toggle source
# File lib/diff/lcs/hunk.rb, line 207
def ed_diff(format)
  op_act = { "+" => 'a', "-" => 'd', "!" => "c" }
  warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1

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

  unless @blocks[0].insert.empty?
    @data_new[@start_new .. @end_new].each { |e| s << e + encode("\n") }
    s << encode(".\n")
  end
  s
end
encode(literal, target_encoding = @preferred_data_encoding) click to toggle source
# File lib/diff/lcs/hunk.rb, line 257
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 261
def encode_as(string, *args)
  args.map { |arg| arg.encode(string.encoding) }
end
old_diff() 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 116
def old_diff
  warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1
  op_act = { "+" => 'a', "-" => 'd', "!" => "c" }

  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)}#{op_act[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.
  @data_old[@start_old .. @end_old].each { |e| s << encode("< ") + e + encode("\n") } unless block.remove.empty?
  s << encode("---\n") if block.op == "!"
  @data_new[@start_new .. @end_new].each { |e| s << encode("> ") + e + encode("\n") } unless block.insert.empty?
  s
end
unified_diff() click to toggle source
# File lib/diff/lcs/hunk.rb, line 135
def unified_diff
  # Calculate item number range.
  s = encode("@@ -#{unified_range(:old)} +#{unified_range(:new)} @@\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| e.insert(0, encode(' ')) }

  @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
    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]
      num_added += 1
    end
  end

  s << outlist.join(encode("\n"))
end
unified_range(mode) 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 242
def unified_range(mode)
  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 + 1
  first = (length < 2) ? e : s # "strange, but correct"
  (length == 1) ? "#{first}" : "#{first},#{length}"
end