Class: Diff::LCS::Hunk

Inherits:
Object
  • Object
show all
Defined in:
lib/diff/lcs/hunk.rb

Overview

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).

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(data_old, data_new, piece, flag_context, file_length_difference) ⇒ Hunk

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



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# 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

Instance Attribute Details

#blocks ⇒ Object (readonly)

Returns the value of attribute blocks.



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# File 'lib/diff/lcs/hunk.rb', line 61

def blocks
  @blocks
end

#end_new ⇒ Object (readonly)

Returns the value of attribute end_new.



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# File 'lib/diff/lcs/hunk.rb', line 63

def end_new
  @end_new
end

#end_old ⇒ Object (readonly)

Returns the value of attribute end_old.



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# File 'lib/diff/lcs/hunk.rb', line 63

def end_old
  @end_old
end

#file_length_difference ⇒ Object (readonly)

Returns the value of attribute file_length_difference.



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# File 'lib/diff/lcs/hunk.rb', line 64

def file_length_difference
  @file_length_difference
end

#flag_context ⇒ Object

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



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# File 'lib/diff/lcs/hunk.rb', line 69

def flag_context
  @flag_context
end

#start_new ⇒ Object (readonly)

Returns the value of attribute start_new.



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# File 'lib/diff/lcs/hunk.rb', line 62

def start_new
  @start_new
end

#start_old ⇒ Object (readonly)

Returns the value of attribute start_old.



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# File 'lib/diff/lcs/hunk.rb', line 62

def start_old
  @start_old
end

Instance Method Details

#diff(format, last = false) ⇒ Object

Returns a diff string based on a format.



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# 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) ⇒ Object Also known as: unshift

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.



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# 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

#overlaps?(hunk) ⇒ Boolean

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.

Returns:



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# 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